McDonald Engineers UK THERMflow Technical Manual

Technical Manual

THERMflow

Boiler Model

McDonald Engineers UK

November 2017

THERM

flow

Boiler Model Technical Manual

HOT WATER SOLUTIONS SINCE 1945

1

Contents

Design .................................................................................................................. 2

Preface ................................................................................................................. 2

Handling & Storage .............................................................................................. 2

What is a thermal store? ..................................................................................... 3

Basics of the Thermal Store ................................................................................. 3

Mains Water Supply ............................................................................................ 4

Water Treatment ................................................................................................. 4

THERMflow Combination General Schematic ..................................................... 5

THERMflow Cylinder General Schematic ............................................................. 6

THERMflow Connection Heights.......................................................................... 7

THERMflow with External PHE ............................................................................ 8

THERMflow Combination with PHE General Schematic ...................................... 9

THERMflow Cylinder with PHE General Schematic ........................................... 10

Commissioning................................................................................................... 11

Commissioning Best Practice ............................................................................. 12

Troubleshooting................................................................................................. 13

Schematics ......................................................................................................... 15

Ancillary Descriptions ........................................................................................ 18

Installing a Gravity System................................................................................. 20

2

Design

An early adopter of the principal of domestic thermal stores, McDonald Engineers UK
first started manufacturing thermal stores in early 1990s. Manufactured by our trained
coppersmiths and designed based upon the experiences of our technical team. The
McDonald Engineers UK THERMflow provides the perfect solution to both mains
pressure hot water and space heating requirements.

Preface

The THERMflow Technical Manual should be read in conjunction with the installation
and servicing manuals issued by the manufacturer(s) of the heat source(s) used within
the thermal storage system, such as the boiler/solid fuel boiler, solar etc.

This information provided is intended to provide support with the installation of the
THERMflow storage system. Responsibility for selection and specification of our
equipment remains that of our customer and any experts or consultants concerned with
the installation(s). Our full Terms & Conditions of Sale are available on request.

The THERMflow thermal storage system is required to be fitted by a competent installer,
as defined by the relevant regulations e.g. Gas Safety Regulations. Please note that
while the THERMflow overcomes Part G Building Regulation discharge requirements
for unvented cylinders, the installation of the THERMflow may be notifiable to the
relevant building control.

Handling & Storage

It is important the THERMflow is handled with care and stored the correct way up in a
dry place at all times prior to, during and after installation. Any manual lifting will need
to comply with the requirements of the Manual Handling Operations Regulations issued
by the Health & Safety Executive. For installations on higher levels of properties such
as the 4th floor it is recommended as best practice for the THERMflow to be moved
vertically within a lift.

3

What is a thermal store?

Often used in conjunction with a variety of alternative energy sources such as solid fuel,
wood burning stoves and solar, a thermal store captures input energy from heat sources
to allow that energy to be converted into mains pressure hot water and space heating
at a later time when the demand is greater. Energy from a heat source is captured within
the primary water of an open vented cylinder at a temperature of up to 80°C.

Cold water at mains pressure then passes through a High Efficiency Coil, which is
specifically designed as a heat exchanger, to draw heat from the thermal store at mains
pressure.

This heated water is subsequently blended with cold mains water through a
Thermostatically Controlled Mixing Valve, to provide mains pressure water at 55°C to
the taps. In addition, the primary water captured within the store can also be circulated
around the heating system allowing the householder to enjoy the benefits of mains
pressure water and heating produced from alternative and renewable heat sources.

Basics of the Thermal Store

The THERMflow Boiler Model utilises open vented boilers and/or Electric Immersion
Heaters as its primary heat source/s, with options available for wood burning, AGA, solid
fuel boiler and underfloor connections amongst others.

The main benefit of the Open Vented Thermal Store configuration is the open vented
nature allows the full power (kW) output of the boiler directly into the thermal store, as
no heat exchanger is required thus reducing energy usage and running costs. Input
energy from the boiler(s) is circulated from the thermal store to the central heating
system while the High Efficiency Secondary Coil is specifically designed to provide high
performance blended mains pressure hot water to the taps at 55°C.

4

Mains Water Supply

The THERMflow’s performance is directly related to the cold water supply pressure and
volume incoming to the property. The THERMflow will operate with a minimum
incoming mains pressure of 1.0 Bar. A maximum incoming pressure of 3.0 Bar would be
the most optimal for performance. If the incoming mains pressure is higher than 3.0
Bar, a pressure reducing valve must be fitted downstream of where the incoming cold
supply enters the property at a lesser and appropriate pressure.

If the flow rate exceeds 20 Litres per minute at any tap, it should be restricted to
maintain the performance of the system as a whole.

Water Treatment

The THERMflow is part of the primary system and while it does not require any special
water treatment itself, the radiators and other parts of the primary circuit will require
the application of a protective scale and corrosion inhibitor such as Fernox to ensure
adequate protection. This should avoid having corrosive material in the primary system
and remove any build-up of sludge which can reduce the performance of the High
Efficiency Heat Exchanger Coil.

The volumes and concentration of inhibitor required should be calculated in accordance
with the manufacturer’s instructions. Please ensure that the thermal store volume is
also included as well as the radiator and pipework volume.

Please note that in all THERMflow models, the primary water within the thermal store
water is used as primary storage and the domestic hot water is heated instantaneously
by means of the High Efficiency Heat Exchanger Coil. Therefore, treating the primary
water will not have an effect on the domestic hot water supply.

5

THERM

flow

Combination General Schematic

Immersion Heater

22mm Boiler Flow

(Other Sizes Available)

28mm Solid Fuel Return

(Other Sizes Available)

3kW

⁰C

Thermometer

22mm Central

Heating Flow &

Return Connections

(Other Sizes Available)

15mm Drain

Cold Mains

Secondary Water c/w

Check Valve & Strainer

Hot Out

c/w Thermostatic

Mixing Valve

2 Litre

Expansion

Bottle

High Efficiency
Secondary Coil

Maintenance Free
Jetseal Ballvalve

High-Limit

Stat

Control Stat

@ 75⁰C

Overflow

(Not fitted as standard)

22mm Boiler Return

(Other Sizes Available)

28mm Solid Fuel Flow

(Other Sizes Available)

6

THERM

flow

Cylinder General Schematic

22mm Boiler Flow

(Other Sizes Available)

28mm Solid Fuel Return

(Other Sizes Available)

3kW

⁰C

Thermometer

22mm Vent

22mm Central Heating

Flow & Return

Connections

(Other Sizes Available)

15mm Drain

Immersion Heater

Cold Mains Secondary Water

c/w Check Valve & Strainer

Hot Out

c/w Thermostatic

Mixing Valve

22mm Cold Feed

2 Litre

Expansion

Bottle

Secondary Return

(Optional)

High Efficiency

Secondary Coil

High-Limit Stat

@ 90⁰C

Control Stat

@ 75⁰C

28mm Solid Fuel Flow

(Other Sizes Available)

22mm Boiler Return

(Other Sizes Available)