MEGAFLO Compact 2d, Compact 4d, Compact 8d, Compact 10d, Compact 2i User Manual

Important

Please read & understand all these instructions before commencing installation.

Please leave this manual with the customer for future reference

Megaflo Compact

Unvented Direct & Indirect

Hot Water Cylinders

2

Contents

1. Introduction 3

1.1 General 3

1.2 Symbols used 3

1.3 Abbreviations 3

1.4 Liabilities 3

2. Safety 4

2.1 General safety warnings 4

3. Technical specications 5

4. Description of the product 10

4.1 General description 10

4.2 Operation principle 10

4.3 Main components 10

4.4 Standard delivery 10

4.5 Storage and Handling 10

5. Before installation 12

5.1 Installation regulations 12

5.2 Installation requirements 12

5.3 Choice of location 12

6. Installation 13

6.1 General 13

6.2 Water connections 13

6.3 Electrical connections 19

6.4 Filling the installation 22

7. Commissioning 23

7.1 General 23

7.2 Checklist before commissioning 23

7.3 Commissioning procedure 23

7.4 Benchmark 23

8. Operation 24

8.1 General 24

9. Maintenance 25

9.1 General 25

9.2 Standard inspection & maintenance
operations 25

10. Troubleshooting 27

10.1 Fault nding 27

11. Decommissioning 28

11.1 Decommissioning procedure 28

12. Spare parts 29

12.1 Spare parts list 29

Benchmark checklist 34

Commissioning & service records 35

Warranty 36

Benchmarktm places responsibilities on both manufacturers and installers. The purpose is to ensure that
customers are provided with the correct equipment for their needs, that it is installed, commissioned and
serviced in accordance with the manufacturer’s instructions by competent persons and that it meets the

requirements of the appropriate Building Regulations and relevant electrical qualications. The Benchmarktm

Checklist can be used to demonstrate compliance with Building Regulations and should be provided to the
customer for future reference. Installers are required to carry out installation, commissioning and servicing
work in accordance with the Benchmarktm Code of Practice which is available from the Heating and Hotwater
Industry Council who manage and promote the Scheme. Visit www.centralheating.co.uk for more information.
IMPORTANT NOTE TO USER: PLEASE REFER TO THE COMMISSIONING SECTION, PAGE 23 FOR
IMPORTANT INFORMATION WITH RESPECT TO THE BENCHMARK SCHEME

3

1. Introduction

1.1 General

The following instructions are offered as a guide to the
user and installer.

The installation must be carried out by a competent
plumbing and electrical installer in accordance with
Building Regulation G3 (England and Wales), Technical
Standard P3 (Scotland) or Building Regulation P5
(Northern Ireland) and the Water Fitting Regulations
(England and Wales) or Water Byelaws (Scotland).

1.2 Symbols used

In these instructions, various risk levels are employed
to draw the user’s attention to particular information. In
doing so we wish to safeguard the user, avoid hazards
and guarantee the correct operation of the appliance.

DANGER

Risk of a dangerous situation causing serious
physical injury.

WARNING

Risk of dangerous situation causing slight
physical injury.

CAUTION

Risk of material damage.

 Signals important information.

1.3 Abbreviations

` T&P - Temperature & Pressure relief valve
` PRV - Pressure Reducing Valve
` ERV - Expansion relief valve

1.4 Liabilities

Manufacturers liability

Our products are manufactured in compliance with
the requirements of the various applicable European
Directives.

This appliance complies with the requirements of the
CE marking directive.

In the interest of UK customers, we are continuously
endeavouring to make improvements in product

quality. All the specications stated in this document

are therefore subject to change without notice.

Our liability as the manufacturer may not be invoked in
the following cases:

` Failure to abide by the instructions on using the

appliance.

` Faulty or insufcient maintenance of the

appliance.

` Failure to abide by the instructions on installing the

product.

Installer's liability

The installer is responsible for the installation and the
commissioning of the appliance. The installer must
respect the following instructions:

` Read and follow the instructions given in the

manuals provided with the appliance.

` Carry out installation in compliance with the

prevailing legislation and standards.

` Perform the initial start up and carry out any checks

necessary.
` Complete the commissioning checklist.
` Explain the installation to the user.
` If maintenance is necessary, warn the user of the

obligation to check the appliance and maintain it in

good working order.
` Give all the instruction manuals to the user.

Users liability

To guarantee optimum operation of the appliance, the
user must respect the following instructions:

` Read and follow the instructions given in the

manuals provided with the appliance.
` Call on qualied professionals to carry out

installation and initial start up.
` Get your installer to explain your installation to you.
` Have your required checks and services done.
` Keep the instruction manuals in good condition and

close to the appliance.



This appliance can be used by children aged

from 8 years and above and persons with
reduced physical sensory or mental capabilities
or lack of experience and knowledge if they
have been given supervision or instruction
concerning use of the appliance in a safe
way and understand the hazards involved.
Children shall not play with the appliance.
Cleaning and user maintenance shall not be
made by children without supervision.

Children must be supervised to ensure they
do not play with the appliance.

4

2. Safety

2.1 General safety warning



- Water may drip from the discharge pipe of the
pressure-relief device and this pipe must be left
open to the atmosphere; (see page 18 for more
details)

-the pressure-relief device is to be operated
regularly to remove lime deposits and to verify that
it is not blocked; (see page 18 for more details)

- How hot water can be drained. (see page 25 for
more details)

- The type or characteristics of the pressure-relief
device and how to connect it; (see Figure 4 page
9 )

- A discharge pipe connected to the pressure­relief device is to be installed in a continuously
downward direction and in frost free environment;
(see page 18 for details)

Details on how to set the temperature controls
for both immersion heaters and boiler controls
can be found in section “Installation Instructions,
page 20.

WARNING TO USER

` If this unvented water heater develops

a fault, such as a ow of water from

the discharge pipe, switch the heater
off and contact the installer.

` Do not remove or adjust any component

or part of this unvented water heater ;
contact installer

` DO NOT bypass the thermal cut-out(s)

in any circumstances.

WARNING

` Only competent persons having

received adequate training are
permitted to work on the appliance and
the installation.

` Do not tamper with any of the safety

valves or controls supplied with the
cylinder.

` Before any work, switch off the mains

supply to the appliance.

` Do not switch on if there is a possibility

that the water in the cylinder is frozen.

DANGER

This cylinder is unvented and as such
becomes pressurised when in operation. The
combination of pressurisation and hot water
could lead to serious physical injury if the safety
instructions in this manual are not adhered to.

CAUTION

Do not operate immersion heaters until the

cylinder has been lled with water.

WARNING

When handling the unit, take appropriate
precautions for the weight of the unit. Weights
can be found in section 3, Tables 1&2, pages
5&6.

CAUTION

Annual maintenance is recommended by a
competent person.

5

3. Technical specications

Table 1: Technical data - Indirect Cylinders

Notes:
1: at 3 bar water inlet pressure
2: at 80°C - +/- 2°C
3: Although the primary coil pressure rating is 1.0MPa (10bar) the 2 port zone valve and coil compression nuts supplied with

the cylinder are only rated at 0.86MPa (8.6 bar). If the cylinder is to be plumbed into a system delivering 1.0MPa (10 bar) a
suitable 2 port zone valve and the coil compression nuts will have to be sourced.

4:Tested to EN 12897:2016

2i

4i

6i

8i

10i

Max direct kW rating 3 3 3 3 3

Immersion heat up times
(Btm immersion, 3kW)

139 167 179 208 252

Coil surface area (m²) 0.51

Coil heat up times

15l/min 33.1 40.1 43.0 45.1 52.8

30l/min

26.9 30.2 34.8 37.7 46.7

45/min 25.0 28.8 32.3 34.2 41.7

Coil rating (kW) ²

15l/min 13.1 12.7 13.7 14.3 14.8

30l/min 16.3 16.3 17.1 17.3 17.4

45l/min 17.6 17.7 18.8 19.1 19.0

Pressure drop through

coil

15l/min 0.004 MPa (0.04 Bar)

30l/min 0.013 MPa (0.13 Bar)

45l/min 0.031 MPa (0.31 Bar)

Heat loss (kW/24hrs) 1.58 1.59 1.82 1.97 2.16

Weight empty (kg) 31 34 37 42 46

Weight full (kg) ¹

168 190 217 238 283

Volume (Litres) ¹

137 155 178 195 233

Mixed water delivery to 40°C

1

168 188 218 238 281

Max mains pressure 1.6 MPa (16 Bar)

Max design pressure 0.8 MPa (8 Bar)

Operating pressure/PRV set pressure

0.3 MPa (3 Bar)

Max primary pressure ³ 1.0 MPa (10 Bar)

Expansion relief valve setting 0.8 MPa (8 Bar)

T&P valve setting

90°C +/- 5°C/1.0 MPa (10 Bar)

T&P Part number

7034796

Immersion heater electrical rating 3.0 kW@240V/2.8kW@230V ~

ErP Data

Model(s) 2i 4i 6i 8i 10i

Energy efciency class C C C C C

Standing loss W 65.8 66.3 75.8 82.1 90.0

Storage volume V in Litres 137 155 178 195 233

Technical parameters in accordance with European Commission regulations 814/2013 and 812/2013

6

2d

4d

6d

8d

10d

Max direct kW rating 6 6 6 6 6

Immersion heat up times
(Btm immersion, 3kW)

139 175 193 205 267

Immersion heat up times
(Top immersion, 3 kW)

65 83 87 89 96

Immersion heat up times
(Both immersions, 6kW)

62 79 88 90 98

Heat loss (kW/24hrs) 1.53 1.59 1.80 1.97 2.22

Mixed water delivery to 40°C

1

168 188 218 238 281

Weight empty (kg) 25 31 34 38 46

Weight full (kg) ¹ 165 183 216 237 282

Volume (Litres) ¹ 140 152 182 199 236

Max mains pressure 1.6MPa (16 Bar)

Max design pressure

0.8 MPa (8 Bar)

Operating pressure/PRV set pressure 0.3 MPa (3 Bar)

Expansion relief valve setting 0.8 MPa (8 Bar)

T&P valve setting

90°C +/- 5°C/1.0 MPa (10 Bar)

T&P Part number

7034796

Immersion heater electrical rating 3.0 kW@240V/2.8kW@230V ~

ErP Data

Suppliers model identier 2d 4d 6d 8d 10d

Storage volume V in Litres 140 152 182 199 236

Mixed water at 40°C V40 in Litres 155 180 217 168 273

The declared load prole M L L L XL

The water heating energy efciency class of the model C C C C C

The water heating efciency in % 37 38 38 38 38

The annual electricity consumption in kWh

1397 2729 2697 2666 4379

Daily fuel consumption Q in kWh

6.52 12.66 12.47 12.29 20.20

The thermostat temperature settings of the water heater as
placed on the market by the supplier.

60°C

Specic precautions that shall be taken when the water

heater is assembled, installed or maintained and disposed
of at end of life.

See pages 3 to 39

Notes:
1: at 3 bar water inlet pressure
2:Tested to EN 60379:2004

3: Energy efciency tested to EN50440

Table 2: Technical data - Direct Cylinders

Technical parameters in accordance with European Commission regulations 814/2013 and 812/2013

7

General information:

Outer casing

White pre-coated corrosion protected steel body shell.
Polypropylene top and base mouldings. ABS electrical
controls housings and enclosures.

Water container

Duplex stainless steel. 100% pressure tested to 1.6MPa

(16 bar).

Connections

Pipe connections accept 22mm outside diameter pipe
(compression nuts and olives supplied). Thread rate is
3/4" BSP parallel to accept standard 3/4" BSP female

ttings if required.

Thermal insulation

CFC/HCFC free re retardant expanded polyurethane

foam with zero ozone depletion potential. It has a Global
Warming Potential (GWP) of 3.1.

Safety Features

Direct models: Manually re-settable thermal cut-out on

each immersion heater. Factory tted combined T&P and

Expansion Relief Valve.

Indirect models: Manually re-settable thermal cut-out on
immersion heater. Manually re-settable thermal cut-out for
primary heating - must be wired in conjunction with 2 port

motorised valve supplied. Factory tted T&P/Expansion

Relief Valve.

8

Figure 1: General dimensions - Direct models

Figure 2: General dimensions - Indirect models

Size DIMENSIONS

(mm)

A B C

2i N/A 728 1130

4i N/A 883 1256

6i N/A 1008 1413

8i 900 1084 1515

10i 1110 1309 1766

Table 3: Dimensions Direct Cylinders

Size DIMENSIONS

(mm)

A B C

2d 668 782 1130

4d 680 883 1256

6d 805 1008 1413

8d 900 1084 1515

10d 1110 1309 1766

424

394

316

355

A

B

C

47°

27°

32°

92

553

30°

355

394

A

B

C

553

32°

30°

92

Table 4: Dimensions Indirect Cylinders

9

Figure 3: Schematic installation details

TO HOT OUTLET

DISCHARGE PIPE

DRAIN COCK

TUNDISH

T&P and RELIEF VALVE

PRIMARY
FLOW

RETURN

PRIMARY

ELEMENT/CONTROLS
HOUSING

1/2” BSP SENSOR POCKET
ASSEMBLY LONG

BALANCED COLD WATER

CONNECTION (IF REQUIRED)

MAINS WATER

SUPPLY

3 BAR PRESSURE
REDUCING VALVE

STOP COCK (IF USED
IN THIS POSITION)

MIXING VALVE

Combination T&P/ERV

T&P = temperature and pressure

ERV = Expansion relief valve

Mains water

supply

90° Tundish

T&P

actuation knob

ERV

actuation knob

D2 Pipe

Figure 4: Combination T&P/ERV

10

4. Description of the product

4.1 General description

This appliance is a purpose designed unvented water
heater. The unit has a stainless steel inner vessel,
which ensures an excellent standard of corrosion
resistance. The outer casing is a combination of resilient
thermoplastic mouldings and pre-painetd corrosion
proofed steel. All products are insulated with CFC free
polyurethane foam to give good heat loss protection.

The appliance is supplied complete with all the
necessary safety and control devices needed to
allow connection to the cold water mains. All these
components are preset and should not be tampered
with.

4.2 Operation principle

The unvented cylinder is used to heat and store hot
water for use in domestic applications.

Depending on the model the water can be heated

directly using factory tted Immersion heater(s) or

indirectly through a coil in the unit using an indirect heat
source.

To provide pressure to the tap or shower an unvented
water heater uses the incoming mains water pressure.
To do this the water heater is sealed and not vented.
However, when the volume of water is heated it
expands and without any room for expansion could
cause the water heater to rupture and fail. The water
heater requires no separate expansion vessel to
accommodate this expansion as it incorporates an
internal air gap.

4.3 Main components

See Figure 3 on page 9

4.4 Standard delivery

The delivery includes:

` Cylinder incorporating factory tted immersion

heater(s) and thermal controls and factory tted

combination T&P/Expansion relief valve

` Instructions (inc benchmark commissioning

checklist & service record)

` Warranty card

` Cold water control pack

` Pressure reducing valve
` Isolation valve
` Mixer valve
` Mixer valve connection pipe
` Tundish
` Drain valve
` Nut and olive kit

` Immersion spanner
` 2 port zone valve (indirect only)
` Wiring centre (indirect only)

Check all components are supplied in the pack and
advise your supplier if any are missing

4.5 Storage and Handling

If the unit is to be stored before installation it must be
placed upright on a secure, level surface and be in a
dry, frost free environment. The support surface must
be capable of supporting the packaged weight of the
unit, the packaged weights are displayed on the carton
label.

Please take care when handling a packaged cylinder.
The units are heavy and must only be moved manually
using safe working practices. The package weights of
each unit are displayed on the carton label.
Take note of the unit weights when deciding on a safe

lifting method. DO NOT use the factory tted T&P/

Expansion Relief Valve to lift or manoeuvre the unit.

11

Figure 5: Typical system installation schematic (not to scale)

Balanced cold water

draw-off

Combined Temperature

and Pressure Relief valve

with Expansion Relief

Valve / Check Valve

0.3 Mpa/3 bar Pressure Reducing

Valve and Strainer.

(Stop cock can be fitted

here)

MCWS to Kitchen

(unbalanced cold

mains supply)

Mains Cold Water

Supply

KEY

MCWS = Mains Cold Water Supply

HWS = Hot Water Service

SC = Stop Cock / Isolating Valve

DOC = Drain Off Cock

Discharge pipe to atmosphere

(see page 18 “Discharge Pipework”)

Isolating / Regulating

Valves, as required

Mixed HWS supply

Balanced HWS and

MCWS to bathrooms,

showers, cloakrooms,

etc

DOC DOC

DOC

DOC

SC

SC

Tundish

Mixing valve

12

5. Before installation

WARNING

Installation of the appliance must be carried

out by a qualied engineer in accordance

with prevailing and national regulations as
listed below.

` Building Regulations G3
` The Building Standards (Scotland)
` The Building Regulations (Northern

Ireland)
` I.E.E Electrical Regs
` UK Water Regulations

5.2 Installation requirements

Water supply

In an unvented system the pressure and owrate is

directly related to the incoming water supply. For this
reason it is recommended that the maximum water
demand is assessed and the water supply checked to
ensure this demand can be satisfactorily met.

` We suggest the minimum supply requirements

should be 0.15MPa (1.5 bar) pressure and 20 litres

per minute ow rate. However, at these values
outlet ow rates may be poor if several outlets are

used simultaneously.

` A 22mm cold water supply is recommended,

however, if a smaller supply exists, which provides

sufcient ow, this may be used (although more
ow noise may be experienced).

` The higher the available pressure and ow rate the

better the system performance.

` See tables 1&2 on pages 5&6 for cylinder operating

pressures. This is controlled by the Pressure
Reducing valve (PRV)

Outlet/terminal ttings (taps, etc.)

` The appliance can be used with most types of

terminal ttings.

` Outlets situated higher than the appliance will give

outlet pressures lower than that at the appliance, a
10m height difference will result in a 1 bar pressure
reduction at the outlet.

` All ttings, pipework and connections must have a

rated pressure of at least 8 bar at 80°C.

Limitations

The appliance should not be used in association with
any of the following:

` Solid fuel boilers or any other boiler in which the

energy input is not under effective thermostatic
control, unless additional and appropriate safety
measures are installed.

` Ascending spray type bidets or any other class 1

back syphonage risk requiring that a type A air gap
be employed.

` Steam heating plants unless additional and

appropriate safety devices are installed.

` Situations where maintenance is likely to be

neglected or safety devices tampered with.

` Water supplies that have either inadequate

pressure or where the supply may be intermittent.

` Situations where it is not possible to safely pipe

away any discharge from the safety valves.

` In areas where the water consistently contains a

high proportion of solids, e.g. suspended matter
that could block the strainer, unless adequate

ltration can be ensured.

` In areas where the water supply contains chloride

levels that exceed 250mg/l.

5.3 Choice of location

The appliance must be vertically oor mounted.

Although location is not critical, the following points
should be considered:

` The appliance should be sited to ensure minimum

dead leg distances, particularly to the point of most
frequent use.

` Avoid siting where extreme cold temperatures will

be experienced. All exposed pipe work should be
insulated.

` The discharge pipework from the safety valves

must have minimum fall of 1:200 from the appliance
and terminate in a safe and visible position as per
G3 requirements

` Access to associated controls and immersion

heaters must be available for the servicing and
maintenance of the system. Where these controls
are installed against a wall a minimum distance of
250mm must be left (see Fig. 6).

` Note of the overall height of the appliance in relation

to the ceiling height and ensure that access and
space is available for piping/connections to the
outlet.

` Ensure that the oor area for the appliance is level

and capable of permanently supporting the weight
when full of water (see Tables 1&2, pages 5&6 for
weights).

` The tundish should be installed away from electrical

components.

Figure 6: Siting the appliance

WALL

Min 250mm

Min 250mm

5.1 Installation regulations

13

` The draining tap supplied should be installed in

the cold water supply to the cylinder between the
expansion valve and the heater at as low a level
as possible.

` It is recommended that the outlet point of the drain

pipework be at least 1 metre below the level of the
base of the appliance (this can be achieved by
attaching a hose to the drain tap outlet spigot).

` Hot water distribution pipework should be 22mm

pipe with short runs of 15mm pipe to terminal

ttings such as sinks and basins. Pipe sizes may

vary due to system design

Mixing valve

` The mixing valve should be installed at the hot

outlet point of the appliance using the copper tube

supplied. (see gure 7 below). The mixing valve will

reduce the hot water outlet temperature to approx
55°C, further temperature control will be required for

outlets such as showers and baths

` The mixing valve can be installed in any orientation

providing the pipe from the tank outlet to the H port
of the valve is no more than 500mm long and has no

other connections attached.

` Where the application dictates water to be

delivered at 60°C, a mixing valve pre-set at 60°C
is available as an accessory (see page 29) note the
overall mixed water volume would decrease

6. Installation

6.1 General

After reading the previous sections in this booklet and
choosing a suitable location for the appliance please
install, paying attention to the following water, electrical
and commissioning sections.

Boiler selection (Indirect units only)

` The boiler should have a control thermostat and non

self-resetting thermal cut-out and be compatible
with unvented storage water heaters.

` Where use of a boiler without a thermal cut-out

is unavoidable a “low head” open vented primary
circuit should be used. The feed and expansion
cistern head above the cylinder should not exceed

2.5m.

` Can be a sealed system or open vented type -

maximum primary pressure 10 bar.

` The boiler cannot be vented through the cylinder.

6.2 Water connections

WARNING

` Under no circumstances should the

factory fitted Temperature/Pressure/
Expansion Relief Valve be removed other
than by a competent person. To do so
will invalidate any warranty or claim.

` The cold water controls MUST be

fitted on the mains water supply to the
appliance.

` No control or safety valves should be

tampered with or used for any other
purpose.

` The discharge pipe should not be blocked

or used for any other purpose.

` The tundish should not be located

adjacent to any electrical components.

` The mixing valve supplied is factory pre-

set to give a water temperature of approx
55°C. Do not dismantle or attempt to
adjust

Refer to the installation schematic (Fig 3, page 9) for

details on the pipework layout. Specic details for the

discharge pipework layout is also provided in Figure 10
on page 18.

` All connections accept 22mm outside diameter

pipe (compression nuts and olives supplied). The
thread rate is 3/4" BSP Male parallel to accept

standard 3/4" BSP Female ttings if required.

` The Cold Water Inlet Control kit supplied

incorporates a full ow isolating valve which will

enable the appliance to be isolated from the mains
supply for maintenance or servicing.

` The location of the unit should allow access to the

Combination T&P/ERV to allow re-charging of the
internal air gap when necessary.

Hot water from

cylinder

Cold water from

Mains

Mixed water

Mixer Valve

Copper tube

H

M

C

Figure 7: Mixing valve layout

14

Cold water control pack

CAUTION

` Flush supply pipework before

connection to remove all ux and
debris prior to tting the inlet controls.

Failure to do this may result in
irreparable damage to the controls and
will invalidate any warranty.

` The cold water control pack can be connected

anywhere on the cold water cylinder supply.

` The Control pack incorporates the pressure

reducing valve and isolation valve
` The pressure setting is set to 0.3MPa/3.0 bar.
` The valve can be tted in any orientation to suit

the installation as long as the valve is installed with

the direction of ow arrows pointing in the correct

direction.

` The Expansion Relief has been incorporated into

the T&P valve for ease of installation

` No other valves should be placed between the cold

pressure reducing valve and the appliance.

Primary circuit control

` The 2 port motorised valve supplied with the

appliance MUST be tted on the primary ow to the

appliance heat exchanger and wired such that in
the event of the appliance overheating it will close
the primary circuit.

` Primary circulation to the appliance heat exchanger

must be pumped; gravity ow to the appliance heat

exchanger WILL NOT WORK.

` It is recommended that an air bleed or automatic

air vent is incorporated in the primary return pipe
work close to the unit.

` Boiler ow temperature should be set to 80°C

(peak temperature not to exceed 88°C)

Figure 9: Cold water controls

Isolation valve to be paired
with Reducing valve

3 bar Pressure

Reducing Valve

Isolation valve

Figure 8: Pressure Reducing Valve

Mains in

22mm compression connections

Outlet to Megao

Take note of ow

direction

Pressure reducing valve

cartridge (3 bar)

15

Secondary circulation

If secondary circulation is required it is recommended

that it be connected to the cylinder as shown (see g

10).

` The secondary return pipe should be in 15mm pipe

and incorporate a check valve to prevent backow.

` A suitable WRAS approved circulation pump will

be required.
` On large systems, due to the increase in system

water content, it may be necessary to t an

additional expansion vessel to the secondary

circuit. This should be done if the capacity of the

secondary circuit exceeds 10 litres.

Pipe capacity (copper):
15mm O.D. = 0.13 l/m (10 litres = 77m)
22mm O.D. = 0.38 l/m (10 litres = 26m)
28mm O.D. = 0.55 l/m (10 litres = 18m)

Note: Plastic pipe capacities may be reduced due to
thicker wall sections.



In direct electric installations where a secondary

circulation is required particular attention should be
paid by the installer to maintain the returning water
temperature (guidelines state that a minimum of 55°C
return temperature is advisable). Factors such as,

but not limited to, secondary circulation ow rates,

minimising heat loss of all secondary circuit pipework
and timed operation during periods of high demand
are critical to the correct operation and longevity of the
heating element(s) and thermostats.



Secondary circulation is not recommended for

direct electric units using off-peak tariffs where the
secondary circulation is not controlled in conjunction
with the heat source as performance can be affected.

Figure 10: Secondary circulation schematic

Cold Water
Inlet

T

o Hot

Outlets

Check Valve

Swept Tee

Secondary
Return

Secondary

Circulation Pump

16

Discharge

It is a requirement of Building Regulation G3 that any
discharge from an unvented system is conveyed to
where it is visible, but will not cause danger to persons in
or about the building. The tundish and discharge pipes

should be tted in accordance with the requirements

and guidance notes of Building Regulation G3. The G3
Requirements and Guidance section 3.50 - 3.63 are
reproduced in the following sections of this manual.
For discharge pipe arrangements not covered by G3
Guidance advice should be sought from your local

Building Control Ofcer. Any discharge pipe connected

to the pressure relief devices (expansion valve and
temperature/pressure relief valve) must be installed in
a continuously downward direction and in a frost free
environment.

Water may drip from the discharge pipe of the
pressure relief device. This pipe must be left open to
the atmosphere. The pressure relief device is to be
operated regularly to remove lime deposits and to
verify that it is not blocked.

G3 REQUIREMENT

“...there shall be precautions...to ensure that the
hot water discharged from safety devices is safely
conveyed to where it is visible but will not cause danger
to persons in or about the building.”

The following extract is taken from the latest G3
Regulations

Discharge pipes from safety devices

Discharge pipe D1

3.50 Each of the temperature relief valves or combined

temperature and pressure relief valves specied in

3.13 or 3.17 should discharge either directly or by way
of a manifold via a short length of metal pipe (D1) to a
tundish.

3.51 The diameter of discharge pipe (D1) should be
not less than the nominal outlet size of the temperature
relief valve.

3.52 Where a manifold is used it should be sized to
accept and discharge the total discharge from the
discharge pipes connected to it.

3.53 Where valves other than the temperature and
pressure relief valve from a single unvented hot water
system discharge by way of the same manifold that
is used by the safety devices, the manifold should be

factory tted as part of the hot water storage system

unit or package.

Tundish

3.54 The tundish should be vertical, located in the
same space as the unvented hot water storage system

and be tted as close as possible to, and lower than,

the valve, with no more than 600mm of pipe between
the valve outlet and the tundish (see Fig 11, page 18).

Note: To comply with the Water Supply (Water Fittings)
Regulations, the tundish should incorporate a suitable
air gap.

3.55 Any discharge should be visible at the tundish. In
addition, where discharges from safety devices may
not be apparent, e.g. in dwellings occupied by people
with impaired vision or mobility, consideration should
be given to the installation of a suitable safety device
to warn when discharge takes place, e.g. electronically
operated.

Discharge pipe D2

3.56 The discharge pipe (D2) from the tundish should:

(a) have a vertical section of pipe at least 300mm
long below the tundish before any elbows or bends in

the pipework (see g. 11); and

(b) be installed with a continuous fall thereafter of at
least 1 in 200.

3.57 The discharge pipe (D2) should be made of:

(a) metal; or

(b) other material that has been demonstrated to be
capable of safely withstanding temperatures of the water
discharged and is clearly and permanently marked to
identify the product and performance standard (e.g. as

specied in the relevant part of BS 7291).

3.58 The discharge pipe (D2) should be at least one
pipe size larger than the nominal outlet size of the safety
device unless its total equivalent hydraulic resistance

exceeds that of a straight pipe 9m long, i.e. for discharge
pipes between 9m and 18m the equivalent resistance

length should be at least two sizes larger than the

nominal outlet size of the safety device; between 18
and 27m at least 3 sizes larger, and so on; bends must
be taken into account in calculating the ow resistance.

See Fig 11, Table 6 and the worked example.

Note: An alternative approach for sizing discharge

pipes would be to follow Annex D, section D.2 of BS
6700:2006 Specication for design, installation, testing

and maintenance of services supplying water for
domestic use within buildings and their curtilages.

3.59 Where a single common discharge pipe serves

more than one system, it should be at least one pipe
size larger than the largest individual discharge pipe
(D2) to be connected.

3.60 The discharge pipe should not be connected to a
soil discharge stack unless it can be demonstrated that
the soil discharge stack is capable of safely withstanding
temperatures of the water discharged, in which case, it
should:

(a) contain a mechanical seal, not incorporating a
water trap, which allows water into the branch pipe
without allowing foul air from the drain to be ventilated

through the tundish;

(b) be a separate branch pipe with no sanitary

appliances connected to it;

17

Worked example of discharge pipe sizing

Fig. 11: shows a G1/2 temperature relief valve with a
discharge pipe (D2) having 4 No. elbows and length of
7m from the tundish to the point of discharge.

From Table 6:
Maximum resistance allowed for a straight length of
22mm copper discharge pipe (D2) from a G1/2
temperature relief valve is 9.0m.

Subtract the resistance for 4 No. 22mm elbows at 0.8m
each = 3.2m

Therefore the permitted length equates to: 5.8m

5.8m is less than the actual length of 7m therefore
calculate the next largest size.

Maximum resistance allowed for a straight length of
28mm pipe (D2) from a G1/2 temperature relief valves
equates to 18m.

Subtract the resistance of 4 No. 28mm elbows at 1.0m
each = 4.0m

Therefore the maximum permitted length equates to:
14m

As the actual length is 7m, a 28mm (D2) copper pipe
will be satisfactory.

(c) if plastic pipes are used as branch pipes carrying
discharge from a safety device they should be either

polybutylene (PB) to Class S of BS 7291-2:2006 or
cross linked polyethylene (PE-X) to Class S of BS
7291-3:2006; and

(d) be continuously marked with a warning that no
sanitary appliances should be connected to the pipe.

Note:

1. Plastic pipes should be joined and assembled with

ttings appropriate to the circumstances in which they
are used as set out in BS EN ISO 1043-1.

2. Where pipes cannot be connected to the stack it
may be possible to route a dedicated pipe alongside or
in close proximity to the discharge stack.

Termination of discharge pipe

3.61 The discharge pipe (D2) from the tundish should
terminate in a safe place where there is no risk to
persons in the vicinity of the discharge.

3.62 Examples of acceptable discharge arrangements
are:

(a) to a trapped gully with the end of the pipe below a

xed grating and above the water seal;
(b) downward discharges at low level; i.e. up to

100mm above external surfaces such as car parks,
hard standings, grassed areas etc. are acceptable
providing that a wire cage or similar guard is positioned

to prevent contact, whilst maintaining visibility; and

(c) discharges at high level: e.g. into a metal hopper
and metal downpipe with the end of the discharge pipe
clearly visible or onto a roof capable of withstanding
high temperature discharges of water and 3m from
any plastic guttering system that would collect such
discharges.

3.63 The discharge would consist of high temperature

water and steam. Asphalt, roong felt and non-

metallic rainwater goods may be damaged by such
discharges.

18

Valve

Outlet Size

Minimum Size Of

Discharge Pipe

D1

Minimum Size Of

Discharge Pipe D2

From Tundish

Maximum Resistance

Allowed, Expressed As A

Length Of Straight Pipe

(I.E. No Elbows Or Bends)

Resistance

Created By Each

Elbow Or Bend

G1/2 15mm

22mm
28mm
35mm

up to 9m
up to 18m
up to 27m

0.8m

1.0m

1.4m

G3/4 22mm

28mm
35mm
42mm

up to 9m
up to 18m
up to 27m

1.0m

1.4m

1.7m

G1 28mm

35mm
42mm
54mm

up to 9m
up to 18m
up to 27m

1.4m

1.7m

2.3m

Table 5: Sizing of copper discharge pipe (D2) for common temperature relief valve outlet sizes

Safety device

(e.g. Temperature

relief valve)

Metal discharge pipe (D1) from

Temperature relief valve to tundish

Tundish

Discharge below

fixed grating

(Building Regulation

G3 section 3.61 gives

alternative points

of discharge)

Fixed grating

Trapped

gully

600mm maximum

300mm

minimum

Discharge pipe (D2) from tundish,

with continuous fall. See Building

Regulation G3 section 3.56,

Table 1 and worked example

Figure 11: Typical discharge pipe arrangement (extract from Building Regulation G3 Guidance Section 3.50)

19

6.3 Electrical connections

In case of difculty contact service support; contact

details are available on page 40 of this booklet.

WARNING

` Disconnect from the mains electrical

supply before removing any covers.

` Never attempt to replace the

immersion heater(s) other than with the
recommended immersion heater(s).

` DO NOT bypass the thermal cut-out(s)

in any circumstances.

` All electrical wiring should be carried

out by a competent electrician and
be in accordance with the latest I.E.E
Wiring Regulations.

` Each circuit must be protected by a

suitable fuse and double pole isolating
switch with a contact separation of at
least 3mm in both poles.

` DO NOT operate the immersion

heaters until the appliance has been

lled with water.

DIRECT models

` The immersion heater and controls are accessed

by removing the Control Cover (see Fig 12).

` Unscrew the large screw on the cover using a at

ended screwdriver.

` Lift from the bottom of the cover at the point

indicated on Fig 12 until cover comes away freely.

` The immersion heater thermostat is factory set at

57oC. This is set for eco mode. To maximise water
availability the thermostat should be set to maximum
during commissioning (see Fig 14). Should this
require adjustment see Fig 14 for details of how
to adjust the temperature setting. Each immersion
heater has its own individual thermostatic control.
The thermostat incorporates a thermal cut-out that
will switch off the immersion heater in the event
of a thermostat failure. The thermal cut-out reset
button position is also shown on Fig 14.

` Replace the Control Cover(s) before operating.

To do this tilt the cover and align the top two lugs
with the holes in the housing as indicated on Fig

12. Hinge the cover downwards and rmly press

the cover until it "snaps" back into place. Secure

by tightening the screw on the cover using a at

ended screwdriver. DO NOT OVER TIGHTEN

` Where the Megao's are tted with two immersion

heaters. Each immersion heater is rated 3kW at
240V ~ 1ph

` The immersion heater(s) should be wired in

accordance with Fig 13. The immersion heater(s)
MUST be earthed. The supply cable should be a
minimum 1.5mm² 3 core HO5 VV-F sheathed cable
and must be routed through the cable entry ports

provided with the outer sheath of the cable rmly

secured using the cable securing bar provided.

Figure 12: Immersion heater cover removal and
replacement

Figure 13: Wiring schematic - DIRECT models

N

L

Direct Wiring Layout

1.5mm² 3 Core
HO5 VV-F sheathed
cable

LIFT OFF

REPLACE

LIFT FROM THIS POINT

LUGS

20

` The immersion heater and indirect controls MUST

be earthed. The supply cable for the immersion
heater should be a minimum 1.5mm² 3 core HO5
VV-F sheathed cable and must be routed through
the right hand cable entry port provided, with the

outer sheath of the cable rmly secured using the

cable securing bar provided. The cable connecting
the indirect control to the heating system must
be an appropriate size for the maximum load of
the heating controls and should be routed in the
controls housing through the left hand cable entry
port and secured using the cable securing bar
provided.

` The immersion heater and boiler control

thermostats are factory set at 57oC and 70°C . See
Fig 14 for details of how to adjust the temperature
setting. The immersion heater and indirect controls
each has its own individual thermostatic control.
The thermostats incorporate a thermal cut-out that
will switch off in the event of a thermostat failure.
The thermal cut-out reset button position is also
shown on Fig 14.

` Replace the Control Cover(s) before operating.

To do this tilt the cover and align the top two lugs
with the holes in the housing as indicated on Fig

12. Hinge the cover downwards and rmly press

the cover until it "snaps" back into place. Secure

by tightening the screw on the cover using a at

ended screwdriver. DO NOT OVER TIGHTEN

Space and heating systems controls

` The controls provided with the cylinder will ensure

the safe operation of the unit within the central
heating system. Other controls will be necessary to
control the space heating requirements and times
that the system is required to function.

` The cylinder is compatible with most heating

controls, examples of electrical circuits are shown
in Figures. 16 & 17. However, other systems may
be suitable, refer to the controls manufacturers
instructions, supplied with the controls selected, for

alternative system wiring schemes.

INDIRECT models

` The indirect controls and back-up immersion heater

are accessed by removing the Control Cover (see
Fig 12).

` Unscrew the large screw on the cover using a at

ended screwdriver.

` Lift from the bottom of the cover at the point

indicated on Fig 12 until cover comes away freely.

` The back up immersion heater should be wired

in accordance with the instructions given for
DIRECT models. The immersion heater cannot be
controlled by the boiler control or space heating
programmer, it must be connected with its own
dedicated electrical supply circuit.

` The immersion heater and indirect thermal controls

should be wired in accordance with Fig 15

Figure 15: Wiring schematic - INDIRECT models

Figure 14: Thermostat adjustment

L

N

1 2 3

Control Housing Details

Immersion connections

1.5mm² 3 Core HO5 VV-F
sheathed cable

Indirect control wiring

SPINDLE POSITIONS

= MINIMUM TEMP

= MAXIMUM TEMP 70°C

= APPROX 57 °C

ROTATE SPINDLE CLOCKWISE
FOR TEMPERATURE INCREASE
AND COUNTER CLOCKWISE
FOR TEMPERATURE DECREASE

TEMPERATURE ADJUSTING
SPINDLE

THERMAL CUT-OUT RESET BUTTON

21

Figure 16: Wiring schematic - 2 x 2 Port valve heating system

Figure 17: Wiring schematic - 2 Port valve in conjunction with 3 port mid-position valve heating system

L
N

N L

N L

G GY

1 2 3

L N

HTG

ON

DHW

ON

Pump

Boiler

Zone valve (HTG)

Megaflo (DHW)

zone valve

(Supplied)

Wiring centre

(Supplied)

Programmer

Megaflo indirect

thermal controls

(Supplied fitted)

1 3 2

Room stat

NOTES:

1. A DOUBLE POLE ISOLATING SWITCH MUST BE INSTALLED IN THE MAINS SUPPLY.

2. ALL EARTH CONNECTIONS MUST BE LINKED BACK TO THE MAINS EARTH SUPPLY.

3. USE COPPER LINKS SUPPLIED TO MAKE CONNECTIONS BETWEEN TERMINALS.

4. DO NOT MOUNT WIRING CENTRE ON CYLINDER.

5. THE ABOVE DIAGRAM IS FOR GUIDANCE ONLY, HEATRAE SADIA ACCEPT NO LIABILITY FOR ANY LOSS OR DAMAGE ARISING FROM ANY ERRORS OR OMISSIONS.
THAT MAY BE INADVERTENTLY CONTAINED WITHIN THIS DIAGRAM. THE VARIOUS EQUIPMENT MANUFACTURERS SHOULD BE CONSULTED TO CONFIRM THE
CORRECT OPERATION OF THEIR PRODUCTS WITHIN THE SYSTEM.

KEY
Bl BLUE
Br BROWN
G GREY
O ORANGE
GY GREEN/YELLOW
DHW DOMESTIC HOT WATER
HTG HEATING

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Bl Br O

G GYBl Br O

L
N

N L

N L

Bl W G O GY

1 2 3

L N

HTG

ON

DHW

ON

Pump

Boiler

3-Port mid position valve

Megaflo (DHW) 2-Port

valve (Supplied)

Wiring centre

(Supplied)

Programmer

Megaflo Indirect

thermal controls
(Supplied fitted)

1 3 2

Room sta

NOTES:

1. A DOUBLE POLE ISOLATING SWITCH MUST BE INSTALLED IN THE MAINS SUPPLY.

2. ALL EARTH CONNECTIONS MUST BE LINKED BACK TO THE MAINS EARTH SUPPLY.

3. ASSUMES BASIC BOILER WITH EXTERNAL PUMP.

4. USE COPPER LINKS SUPPLIED TO MAKE CONNECTIONS BETWEEN TERMINALS.

5. DO NOT MOUNT WIRING CENTRE ON CYLINDER.

6. THE ABOVE DIAGRAM IS FOR GUIDANCE ONLY, HEATRAE SADIA ACCEPT NO LIABILITY FOR ANY LOSS OR DAMAGE ARISING FROM ANY ERRORS OR OMISSIONS.
THAT MAY BE INADVER TENTLY CONTAINED WITHIN THIS DIAGRAM. THE VARIOUS EQUIPMENT MANUFACTURERS SHOULD BE CONSULTED TO CONFIRM THE
CORRECT OPERATION OF THEIR PRODUCTS WITHIN THE SYSTEM.

KEY
Bl BLUE
Br BROWN
G GREY
O ORANGE
GY GREEN/YELLOW
DHW DOMESTIC HOT WATER
HTG HEATING

W WHITE

DHW

OFF

1

2 3 4 5 6 7

8

9

10

11 12

13 14

15

16

Bl

Br

G

O GY

22

6.4 Filling the appliance

` Ensure the drain cock is CLOSED.
` Open a hot tap furthest from the appliance.
` Open the mains stop cock.
` Open the isolating valve by turning the blue handle

so it is parallel with the direction of ow. It should

be fully opened, partial opening will restrict the inlet

ow rate.

` Allow the appliance to ll. When water ows from

the tap, allow to run for a few minutes to thoroughly

ush through any residue, dirt or swarf, then close

the tap.

` Open successive hot taps to purge the system of

air.

` Check all connections and system pipes for water

tightness.

WARNING

Should the Megaflo be used in conjunction
with a boiler or external controls that
control the water temperature via a sensor
connected to the cylinder, it should be noted
that the factory fitted indirect thermostat and
thermal cut-out MUST NOT be disconnected
or bypassed. To do so would invalidate the
product approvals and warranty and it
would not comply with Building Regulations.
Should this method of control be adopted
the Megaflo Indirect thermostat should be
set at maximum and the cylinder control
temperature set at 68oC to avoid the
thermostat over-riding the boiler control.
Where the boiler or external controls do not
directly power the 2 Port Motorised Valve
supplied with the Megaflo, the wiring should
ensure that in the event of the thermal
cut-out on the Megaflo Indirect controls
operating power will be interrupted to the 2
Port Motorised Valve such that it closes and
prevents flow of the primary heating fluid
around the Megaflo primary heat exchanger
coil.
For further details of wiring the boiler, or
external controls consult the manufacturer’s
installation instructions.

23

7. Commissioning

7.1 General

After lling the installation with water in the previous

section please follow the following steps to complete
the installation of the unit.

7.2 Checklist before commissioning

` Check all water connections for leaks and rectify

as necessary.
` Turn off mains water supply.
` Remove the pressure reducing valve head work to

access the strainer mesh, clean and re-t.

` Turn the water supply back on.
` Manually open, for a few seconds, each relief valve

in turn, checking that water is discharged and runs

freely through the tundish and out at the discharge

point.
` Ensure that the valve(s) reseat satisfactorily.

7.3 Commissioning procedure

Direct units

` Switch on electrical supply to the immersion

heater(s) and allow the water heater to heat up to

normal working temperature, factory set to 57°C

but for maximum hot water availability reset to

70°C (see Fig 14, page 20).
` Adjust the temperature by inserting a at bladed

screwdriver in the adjustment spindle on front of the

immersion heater (ELEMENT) control thermostat

and rotating (see Fig. 14 page, 20 for details

of how to adjust). The adjustment represents a

temperature range of 10°C to 70°C.
` Check the operation of thermostat(s) and that no

water has issued from the Expansion Relief Valve

or Temperature/Pressure Relief Valve during the

heating cycle.
` The mixing valve tted to the hot water outlet will

reduce the outlet temperature to approx 55°C. It is
not adjustable

Indirect units

` Fill the indirect (primary) circuit following the boiler

manufacturer’s commissioning instructions.

` To ensure the cylinder primary heat exchanger is

lled, the 2 port motorised valve (supplied) should

be manually opened by moving the lever on the
motor housing to the MANUAL setting. When
the primary circuit is full return the lever to the
AUTOMATIC position.

` Switch on the boiler, ensure the programmer is set

to Hot Water and allow the cylinder to heat up to a
normal working temperature, 70°C.

` If necessary adjust the temperature by inserting a

at bladed screwdriver in the adjustment spindle

on front of the indirect (BOILER) thermostat and
rotating (see Fig. 14, page 20 for details of how to
adjust). The adjustment represents a temperature
range of 10°C to 70°C, setting less than 70°C will
reduce the amount of available hot water.

` Check the operation of thermostat(s) and that no

water has issued from the Expansion Relief Valve
or Temperature/Pressure Relief Valve during the
heating cycle.

` The mixing valve tted to the hot water outlet will

reduce the outlet temperature to approx 55°C. It is
not adjustable

7.4 Benchmark

The appliance is covered by the Benchmark Scheme
which aims to improve the standards of installation
and commissioning of domestic heating and hot water
systems in the UK and to encourage regular servicing

to optimise safety, efciency and performance.

Benchmark is managed and promoted by the Heating
and Hotwater Industry Council. For more information
visit www.centralheating.co.uk.

Please ensure that the installer has fully completed the
Benchmark Checklist (see page 34) of this manual and
that you have signed it to say that you have received a
full and clear explanation of its operation. The installer is
legally required to complete a commissioning checklist
as a means of complying with the appropriate Building
Regulations (England & Wales).

All installations must be notied to Local Area Building

Control either directly or through a Competent
Persons Scheme. A Building Regulations Compliance

Certicate will then be issued to the customer who
should, on receipt, write the Notication Number on the

Benchmark Checklist.

This product should be serviced regularly to optimise

its safety, efciency and performance. The service

engineer should complete the relevant Service Record
on the Benchmark Checklist after each service. The
Benchmark Checklist may be required in the event of
any warranty work.

WARNING

` If the unit is to be left unused following

installation and commissioning e.g.
unocupied properties, the water heater

should be drained or regularly ushed

through with fresh mains water once a
week.

` When placing the unit into service,

the procedure for lling the unit and

the system checks below should be
observed.

WARNING

DO NOT operate the immersion heaters or
primary circuit until the appliance has been
filled with water.

24

8.1 General

8. Operation

Temperature controls – direct units immersion

heater(s)

` A combined thermostat and thermal cut-out is

provided for each immersion heater tted. The

thermostat is factory set to give a water storage
temperature of approx. 57oC, however it can be set
to control between 10oC and 70oC. For maximum
hot water availabilty its advisable to set the
thermostat to 70°C during commissioning.

` To access the thermostat open the controls housing

cover (see Fig 12, page 19)- DISCONNECT THE
ELECTRICAL SUPPLY BEFORE OPENING THE
COVER(S).

` Temperature adjustment is made by rotating the

adjustment spindle on the top of the thermostat.
The adjustment represents a temperature range of
10°C to 70°C (see page 20, Fig 14 for method of
adjustment).

` Maximum working temperature is 70°C.

DO NOT bypass the thermal cut-out(s) in any
circumstances.

Temperature controls - indirect units

` A combined thermostat and thermal cut-out is

provided for the control of the external boiler. The
thermostat is factory set to give a water storage
temperature of approx. 70oC, however it can be set
to control between 10oC and 70oC. Adjustments
can only be made by opening the controls covers.

` To access the thermostat open the controls housing

cover (see Fig 12, page 19)- DISCONNECT THE
ELECTRICAL SUPPLY BEFORE OPENING THE
COVER(S).

WARNING

` If water discharges from the Temperature

& Pressure relief valve on the cylinder
shut down the heat source and/or switch
off the immersion heater(s). DO NOT
turn off the water supply. Contact a
competent installer for unvented water
heaters to check the system.

` DO NOT tamper with any of the safety

valves tted to the system. If a fault is

suspected contact a competent installer.

` Disconnect from the mains electrical

supply before removing any covers.

` DO NOT bypass the thermal cut-out(s)

in any circumstances.

` All electrical wiring should be carried

out by a competent electrician and be in
accordance with the latest I.E.E Wiring
Regulations.

` Temperature adjustment is made by rotating the

adjustment spindle on the top of the thermostat.
The adjustment represents a temperature range of
10°C to 70°C (see page 20, Fig 14 for method of

adjustment).
` Maximum working temperature is 70°C.
` The boiler thermostat and thermal cut-out must

be wired in series with the 2 port motorised zone

valve supplied to interrupt the ow of primary water

around the heat exchanger coil when the control

temperature has been reached.
` The controls tted to the cylinder will affect the

temperature of the stored water only, other

controls will be provided in the system for time

and temperature control of the space heating

requirements. Consult the instructions provided

with those controls for details of adjustments.

DO NOT bypass the thermal cut-out(s) in any
circumstances.

Mixing Valve

The hot water outlet is tted with a factory pre-set

mixing valve which limits the temperature of the hot
water to approx 55°C. Scalding can still occur at this
temperature so further temperature control may be
required at shower and bath outlets

Flow performance

When initially opening hot outlets a small surge in

ow may be noticed as pressures stabilise. This is

quite normal with unvented systems. In some areas
cloudiness may be noticed in the hot water. This is due
to aeration of the water, is quite normal and will quickly
clear.

Operational faults

Operational faults and their possible causes are
detailed in the Fault Finding section (page 27) of this
book. It is recommended that faults should be checked
by a competent installer

25

9. Maintenance

9.1 General

Maintenance requirements

Unvented hot water systems have a continuing
maintenance requirement in order to ensure safe
working and optimum performance. It is essential
that the relief valve(s) are periodically inspected and
manually opened to ensure no blockage has occurred
in the valves or discharge pipework.

Similarly cleaning of the strainer element and
replacement of the air in the internal expansion volume
will help to prevent possible operational faults.

The maintenance checks described below should be
performed by a competent person on a regular basis,
e.g. annually to coincide with boiler maintenance.

After any maintenance, please complete the relevant
Service Interval Record section of the Benchmark

Checklist on page 35 of this document.

9.2 Standard inspection & maintenance
operations

Inspection

The immersion heater boss can be used as an access
for inspecting the cylinder internally.

Safety valve operation

CAUTION

Water discharged may be very hot!

` Manually operate the Temperature/Pressure Relief

Valve for a few seconds (Fig. 4 page 9)

` Check water is discharged and that it ows freely

through the tundish and discharge pipework.
` Check valve reseats correctly when released.
` Repeat the above procedure for the Expansion

Relief Valve. (Fig. 4 page 9)

Strainer

` Turn off the isolating valve prior to the Pressure

Reducing Valve or the main stop cock to the

system.
` Open the lowest hot tap in the system to relieve the

system pressure.
` Using a spanner unscrew the Pressure Reducing

Valve cartridge and remove the housing. The

strainer will be removed with the cartridge. (see Fig

18 page 30)
` Wash any particulate matter from the strainer

under clean running water.
` Replace the strainer and screw the Pressure

Reducing Valve cartridge into the moulded housing.
` Close hot tap, turn on isolating valve or main stop

cock to the system. Check for leaks.

Descaling immersion heater(s)

CAUTION

DO NOT use a sharp implement as damage
to the element surface could be caused.

Turn off the mains water supply, isolate the electrical
supply and turn off boiler

` Attach a hosepipe to the drain cock having sufcient

length to take water to a suitable discharge point
below the level of the unit.

` Open a hot tap close to the unit and open drain

cock to drain unit.

` Open the cover(s) to the immersion heater

housing(s) and disconnect wiring from immersion
heater(s) thermostat(s).

` Unscrew the immersion heater backnut using the tool

supplied and withdraw the immersion heater from the
cylinder. Take care when removing the immersion
heater from the cylinder and work within safe working
practices.

` Carefully remove any scale from the surface of the

element(s).

` Ensure sealing surfaces are clean and seals are

undamaged, if in doubt t a new gasket (spare part

number 7035165)

` Replace immersion heater(s), making sure the

gasket is correctly tted and does not become

displaced as the immersion heater is replaced.

` Rewire, check, close and secure immersion heater

housing cover(s).

Re-commissioning

` Check all electrical and plumbing connections are

secure. Close the drain cock.

` With a hot tap open, turn on the cold water supply

and allow appliance to rell.

` DO NOT switch on the immersion heater(s) or

boiler until the appliance is full.

` When water ows from the hot tap allow to ow

for a short while to purge air and ush through any

disturbed particles.

` Close hot tap and then open successive hot taps in

system to purge any air.

` When completely full and purged check system for

leaks.

` The heating source (immersion heater(s) or boiler)

can then be switched on.

26

Expansion volume re-charge

The air volume within the product will periodically
require recharging to ensure expanded water is
accommodated within the system. A discharge of
water INTERMITTENTLY from the expansion valve will
indicate the air volume has reduced to a point where it
can no longer accommodate the expansion.

To recharge the air volume:-

` Turn off the heat source to the cylinder via

programmers / immersion isolation switch(es).
` Turn off the water supply to the cylinder by turning

off the isolating valve on the 3 bar pressure

reducing valve if tted at this point. Turn the handle

so that it lies at 90° to the direction of ow.

` Open the lowest hot tap.
` Hold open the temperature / pressure relief valve

until water ceases to run from the tap and gurgling

noise at the valve stops, (see g 4, page 9)

` Close the temperature / pressure relief valve.
` Turn on the isolating valve at the cold water

combination valve by turning the handle so it lies

parallel to the direction of ow, when water ows

from the hot tap, close tap.
` The air volume will be automatically recharged

as the unit rells. If after following the above

actions water still discharges from the expansion

relief valve, further advice should be sought from

a competent installer or the Megao service

department.



http://www.baxi.co.uk/information-and-advice/how-to­videos.htm

27

10. Troubleshooting

` After servicing, complete the relevant Service

Interval Record section of the Benchmark Checklist

located on page 35 of this document.
` Any spare parts used MUST be authorised parts.
` Disconnect the electrical supply before removing

any electrical equipment covers.
` NEVER bypass any thermal controls or operate

system without the necessary safety valves.

The fault nding chart (table 6, below) will enable
operational faults to be identied and their possible
causes rectied. Any work carried out on the unvented

appliance and its associated controls MUST be carried
out by a competent installer for unvented water heating
systems. In case of doubt contact service support. (see

page 40 for details)

Spare Parts

A full range of spare parts are available for the cylinder
range (Table 7, page 29). Refer to the technical data
label on the unit to identify the model installed and
ensure the correct part is ordered. You will need to
quote the serial number, which is printed on the data
label.

Table 6: Fault nding chart

WARNING

Do not tamper with any of the safety valves
or controls supplied with the cylinder as this
will invalidate any warranty.
Water contained in the cylinder may be
very hot, especially following a thermal
control failure. Caution must be taken
when drawing water from the unit.

NEVER bypass any thermal controls or
operate system without the necessary
safety valves.

10.1 Fault nding

Important

` Servicing should only be carried out by competent

persons in the installation and maintenance of
unvented water heating systems.

Fault Possible cause Remedy

No hot water 1. Mains water supply off. 1. Check and open stop cock.

2. Strainer blocked. 2. Turn off water supply. Remove strainer and clean ( see
page 25 for details).

3. Pressure reducing valve

incorrectly tted.

3. Check and ret as required.

Water from hot taps
is cold

1. Immersion heater not switched

on.

1. Check and switch on.

2. Immersion heater thermal cut-

out has tripped.

2. Check. Reset by pushing button (Figure 14, page 20).

3. Indirect programmer set to

central heating only.

3. Check. Set programmer to a hot water programme.

4. Indirect boiler not working. 4. Check boiler operation. If fault is suspected consult boiler
manufacturers instructions.

5. Indirect thermal cut-out has

tripped.

5. Check. Reset by pushing button. Check operation of
indirect thermostat (Figure 15, page 20).

6. Indirect motorised valve not

connected correctly.

6. Check wiring and/or plumbing connections to motorised
valve (see Figures 16 & 17, page 21).

Water discharges
from expansion relief
valve

1. Intermittently. Air volume in the

cylinder has reduced

1. See page 26 for details on how to test and recharge.

2. Continually. 3 bar pressure

reducing valve is not working
correctly.

2. Check pressure from 3 bar Pressure Reducing Valve. If
greater than 3 bar replace Pressure Reducing Valve.

3. Continually. Expansion valve

seat damaged.

3. Replace combined T&P/Expansion relief valve assembly

Water discharges
from the T&P valve
intermittently

1. Air volume in the cylinder has

reduced

1. See page 26 for details on how to test and recharge.

2. 8 bar expansion relief valve

faulty.

2. Check valve and replace if necessary

Water discharges
from the T&P valve
continually

1. Thermal control failure. Note

water will be very hot.

1. Switch off power supply to immersion heater(s) and shut
down the boiler. DO NOT turn off the water supply. When
discharge stops check all thermal controls, replace if faulty.

Milky water 1 Oxygenated water. 1. Water from a pressurised system releases oxygen bubbles

when owing. The milkiness will disappear after a short

while.

28

11. Decommissioning

11.1 Decommissioning procedure

` Isolate electrical supplies and make safe
` Isolate the water supply
` Drain the appliance
` Drain the primary circuit (indirect only)
` Remove appliance
` Cap pipework

Environmental information

Products are manufactured from many recyclable
materials. At the end of their useful life they should be
disposed of at a Local Authority Recycling Centre in

order to realise the full environmental benets.

Insulation is by means of an approved CFC/HCFC free
polyurethane foam with an ozone depletion factor of
zero.

WEEE Declaration

Disposal of Waste Equipment by Users in Private
Households in the European Union.

This symbol on the product indicates that this product
must not be disposed of with your other household
waste. Instead, it is your responsibility to dispose of
your waste equipment by handing it over to a designated
collection point for the recycling of waste electrical
equipment. The separate collection and recycling of
your waste equipment at the time of disposal will help
to conserve natural resources and ensure that it is
recycled in a manner that protects human health and
the environment. For more information about where
you can drop off your waste equipment for recycling,

please contact your local city ofce, your household

waste disposal service or the company where this
product was purchased.

29

ITEM DESCRIPTION PART NUMBER

1 Cold water inlet control kit (NOT SHOWN) 70 347 97

2 3 bar Pressure reducing valve - Complete 95 605 886

3 Immersion heater gasket 70 351 65

4 Immersion heater key spanner (NOT SHOWN) 95 607 861

5 Immersion heater blanking plate (NOT SHOWN) 95 605 881

6 90° Tundish (NOT SHOWN) 70 342 07

7 T&P/ERV combination valve 70 347 96

8 Set of compression nuts and olives (NOT SHOWN) 95 607 838

9 Drain valve 1/4 turn (NOT SHOWN) 95 605 051

10 Swept tee joint (for secondary return) (NOT SHOWN) 95 605 812

11 Direct combined thermostat / thermal cut-out 70 316 88

12 Direct mounting plate 95 607 929

13 3 way terminal block 95 607 932

14 Element - Incoloy (Bent, lower) 95 606 984

15 Immersion heater backnut - Plastic (Black) 95 605 132

16 Indirect combined thermostat / thermal cut-out 70 316 89

17 Controls cover 70 316 73

18 Indirect mounting plate 95 607 931

19 6 way terminal block 95 607 933

20 2 port motorised valve (22mm compression connections)(NOT SHOWN) 95 605 819

21 1/2" BSP Sensor Pocket Assembly Long 70 325 79

22 Element - Incoloy (Straight, upper) 95 606 986

23 Mixer valve (55°C) - Standard 70 373 07

24 Mixer valve (60°C) - Accessory 70 373 06

12. Spare parts

Table 7: Spare parts list

12.1 Spare parts list

A full range of spare parts are available for the Megao Compact range. Refer to the Technical Data label on the unit

to identify the model installed and ensure the correct part is ordered.

30

Pressure Reducing

Valve Cartridge (3 Bar)

Strainer Mesh

3 Bar Pressure Reducing Valve - Complete

2

Figure 18: Pressure Reducing Valve exploded view

Figure 19: Mixing valve assembly

Hot water from

cylinder

Cold water from

Mains

Mixed water

Mixer Valve

23

24

31

14

15

19

11

16

7

17

3

21

18

Figure 20: Indirect controls - exploded view

32

11

13

13

11

7

15

3

22

15

3

14

17

17

12

12

Figure 21: Direct controls - exploded view

33

Spares Stockists

Advanced Water Co.Ltd.
Unit D5 Enterprise Way
Vale Park, Evesham
Worcs WR11 1GS
Tel: [phone]
Fax: [phone]

Electric Water Heating Co.
2 Horsecroft Place
Pinnacles
Harlow
Essex CM19 5BT
Tel: [phone]
E-Mail: [e-mail]

SPD
Special Product Division
Units 9 & 10
Hexagon Business Centre

Springeld Road

Hayes
Middlesex UB4 0TY
Tel: [phone]

Parts Center
Tel: [phone]
www.partscenter.co.uk

Newey & Eyre
Unit 3-5 Wassage Way
Hampton Lovett Ind. Estate
Droitwich, Worcestershire WR9 0NX
Tel: [phone]
Fax: [phone]

UK Spares Ltd
Unit 1155
Aztec West
Almondsbury
Bristol BS32 4TF
Tel: [phone]

William Wilson Ltd
Unit 3A
780 South Street
Whiteinch
Glasgow G14 0SY
Tel: [phone]

Alternatively contact your local supplying merchant or
wholesale branch

34

Benchmark checklist

35

Commissioning &

service records

36

Warranty

The Megao Compact Warranty provides unrivalled levels

of customer support and peace of mind in the unlikely
event that a problem arises from a manufacturing defect.
It is supported by a large nationwide team of company-

employed eld-based engineers and our own call centre,

which is open 363 days a year.

The Megao Compact Warranty covers Megao Compact

cylinders against corrosion for 25 years from date of
original purchase.

The cold water inlet valve (and expansion vessel, where

supplied) is covered by a ve year warranty from the date
of purchase of the Megao Compact product, that includes

both parts and labour. All other components, including any

other valves, ttings and controls supplied with the Megao

Compact are covered by a two year warranty from the

date of purchase of the Megao Compact product, that

includes both parts and labour.

In the case of the Megao Compact Systemready, Megao
Compact Systemt appliances, the supplied pumps and
motorized valves ( where tted ) are also covered by this

two year warranty.

Incoloy immersion heaters ( where tted ) are covered by a

two year warranty.

Outside of the UK

These warranties are valid for installations within the United
Kingdom.

For installation in the Republic of Ireland please contact
Baxi Potterton Myson (Ireland) Limited on
00353 (0) 1 4590870

For installations outside of the United Kingdom and the

Republic of Ireland, please telephone Megao Export on

[phone] for further details of the warranty terms
and conditions applicable.

This warranty is valid provided that:

• The Megao Compact product has been installed by

a competent installer in accordance with the instructions
contained in the installation instructions and in compliance
with all relevant laws, guidance, codes of practice and
regulations in force at the time of installation.

• The Megao Compact product has not been modied or

tampered with in any way, other than by a Heatrae Sadia or
Baxi Customer Support approved engineer.

• The Megao Compact product has not been subject to

damage by scale.

• The Megao Compact product and any part or parts of
the Megao product (whether factory tted or otherwise)

have not been repaired or replaced other than by a Baxi
Customer Support approved engineer and any replacement

parts used on the Megao Compact product are authorised
Megao Compact spare parts.

• The factory tted Temperature /Pressure & Expansion

Relief Valve has not been tampered with or removed.

• The Megao Compact product has not been subject to

misuse or neglect.

• The Megao Compact product has only been used for

the storage of wholesome water. Should another substance
be put through the product, the warranty will be invalid
unless it is part of a disinfectant procedure carried out in
accordance with BS EN 806.

• The Megao Compact product has not been subjected to

frost or freezing temperatures.

• The Benchmark™ commissioning checklist service

record, included in the Megao Compact installation

instructions has been completed.

• Regular maintenance has been carried in accordance
with the requirements set out in the maintenance section
of the installation instructions, by a competent person, an
approved engineer from Heatrae Sadia or any other part
of the Baxi Groups Customer Support approved engineer
ing team.

• Access is available, at reasonable times and upon

reasonable notice, to the Megao Compact product to allow

for any inspection repair or replacement.

• The product is registered within 60 days of purchase.
This can be done by telephone, online or by using the
registration form provided with the product.

• Evidence of purchase (for example a receipt or delivery
note) and date of supply is submitted when making a claim.

• The Megao Compact product has not been affected

by any cause beyond our reasonable control including,

without limitation: an act of God, explosion, ood, re or

accident; war or civil disturbance; strike, industrial action or
stoppages of work; any form of government intervention;
a third party act or omission including theft or malicious
damage; failure by you to give us a correct delivery address
or notify us of any change of address.

.

If any of the following situations occur, the Megao

Compact Warranty will NOT apply:

• Any wilful or accidental damage caused by your
negligence

• Damage caused as a result of scale.

• Installation not in line with the installer and user manuals
provided,

• Failure to comply with installation instructions (whether
oral or in writing),

• Misuse of the Megao Compact product or alteration
of the Megao product not in accordance with the

requirements set out above.

• Defects which are reported to us outside of the warranty

period on 0344 8711535 or Mega[e-mail]

37

• Any third party repair or replacement costs unless those
costs have been agreed and authorised by Baxi Customer
Support or Heatrae Sadia in writing prior to incurring the
costs.

Claims

Defects should be reported to us as soon as you are aware
of them. Please report defect to us by contacting

0344 871 1535 or Mega[e-mail] .

Notes
Heatrae Sadia accepts no liability for any third party

damage.
These warranties do not affect your statutory rights and

remedies in relation to the Megao Compact products.

Annual service

Annual services are available from Baxi Customer Support,
the service division of Heatrae Sadia.

Please contact Baxi Customer Support on 0344 871 1535
for details.

Megao Compact 25 year warranty is the period during
which the rst owner of the Megao Compact or a new

build home continues to own the property. Should the
property be sold, the new owner and any subsequent
owners will receive a 25 year warranty from the date the

original owner purchased the Megao Compact or a new
home with a Megao Compact installed.

The Megao Compact warranty is conditional on the

installation being carried out in accordance with the
installation instructions supplied with the product. These
warranties do not affect your statutory rights. Full terms
and conditions of these warranty packages are available on

request or via www.heatraesadia.com/Megao

Megao may introduce modications to their products

from time to time. Consequentially the details given in this
brochure are subject to alteration without notice.

Contacts

Specication Advice Hotline

T: 01603 420220
F: 01603 420229

E: speci[e-mail]

www.heatraesadia.com

Heatrae Sadia*, Hurricane Way, Norwich, Norfolk, NR6
6EA

* Heatrae Sadia is a trading name of Baxi Heating UK
Limited, Brooks House, Coventry Road, Warwick, CV34
4LL

38

NOTES:

39

NOTES:

40

Customer service

Telephone: [phone]

Facsimile: 0344 8711528

E-mail: mega[e-mail]

Megao

Hurricane Way
Norwich
Norfolk
NR6 6EA

Important notice to installations outside of the UK.

References to legislation, legal requirements, regulations, building regulations benchmark, spares stockists, guarantees and warranty are ONLY APPLICABLE WITHIN THE UK.

For local legislation, legal requirements, regulations, building regulations outside of the UK, contact your local Authority.

For spares stockists, guarantees and warranty outside the UK, contact your local supplier or,

Export Sales

T: [phone]

F: [phone]

E: [e-mail]

7034800_issue _1

The HWA Charter’s Code of Practice requires that all members adhere to the following:

• Tosupplytforpurposeproductsclearlyandhonestlydescribed

• To supply products that meet, or exceed appropriate standards and building and water regulations

• To provide pre and post sales technical support

• To provide clear and concise warranty details to customers

© 2016