Vent-Axia LoWatt HR204 User, Installation & Servicing Instructions

Please leave these instructions with the user

Whole House Ventilation System
with Heat Recovery

User, Installation & Servicing
Instructions

LoWatt HR204

ABC

2

Contents

Section

Page

1.0 Safety and Guidance Notes

2.0 User Information

3.0 General Layout

4.0 Technical Data

5.0 Appliance Operation

6.0 Installation Requirements

7.0 Installation

8.0 Wiring Diagrams

9.0 Commissioning

10.0 Maintenance

11.0 Changing Components

12.0 Fault Finding

13.0 Short Parts List

3

4

5

6

8

9

12

15

18

19

20

22

24

3

1.0 Safety and Guidance Notes

1. DO NOT install this product in areas where
the following may be present or occur:

-Excessive oil or a grease laden atmosphere.

-Corrosive or flammable gases, liquids or

vapours.

-Ambient temperatures higher than 40°C or
less than 5°C.

-Possible obstructions which would hinder the
access or removal of the product.

2. All wiring to be in accordance with the current

I.E.E. Regulations, or the appropriate standards
of your country and MUST be installed by a
suitably qualified person.

3. The LoWatt HR204 and accessories should

be provided with a local isolator switch capable
of disconnecting all poles, having a contact
separation of at least 3mm.

4. Ensure that the mains supply (voltage,

frequency, and phase) complies with the rating
label.

5. The LoWatt HR204 should only be used in

conjunction with the appropriate Vent-Axia
accessories.

6.When the LoWatt HR204 is used to remove air

from a room containing a fuel-burning
appliance, ensure that the air replacement is
adequate for both the LoWatt HR204 and the
fuel-burning appliance.

7. The LoWatt HR204 should not be fitted where

it is liable to be subject to direct water spray.

8. This appliance is not intended for use by

persons (including children) with reduced
physical, sensory or mental capabilities, or lack
of experience and knowledge, unless they have
been given supervision or instruction
concerning use of the appliance by a person
responsible for their safety.

9. Children should be supervised to ensure that

they do not play with the appliance.

10. The power supply to the unit and its

accessories should always be switched off
before removing the cover or ducting.

4

2.0 User Information

Read the instructions fully before installing
or using the appliance.

This appliance must be installed in
accordance with the manufacturer's
instructions and the regulations in force.

The LoWatt HR204 is a mechanical ventilation
with heat recovery (MVHR) unit. The unit
provides continuous extraction of stale air
from the dwelling, typically from the
bathroom and from the kitchen. The stale
air passes through the heat exchanger
before being ducted to outside.

Fresh air from the outside is continuously
drawn into the unit and passed through a
filter and then into the heat exchanger. In
the heat exchanger the fresh air is pre­warmed and ducted into the dwelling,
typically to living rooms / bedrooms.

Fig. 1

This product should not be disposed of with
household waste. Please recycle where
facilities exist. Check with your local
authority for recycling advice.

For cleaning and servicing instructions,
refer to section 9, page 19.

Exhaust

Out

Fresh Air

In

Hot Stale

Air In

Warm Air

Out

Applicable only to products installed and
used in the United Kingdom. For details of
the Guarantee outside of the United Kingdom
contact your local supplier.

Vent-Axia guarantees this product for two
years from the date of purchase against faulty
material or workmanship. In the event of any
part being found to be defective, the product
will be repaired, or at the Company's
discretion the product will be replaced
without charge, provided that the product:

1). Has been installed and used in

accordance with the instruction given with
each unit.

2). The electricity supply complies with the

rating label.

3). Has not been misused, neglected or

damaged.

4). Has not been modified or repaired by any

person not authorised to do so by Vent-Axia.
IF CLAIMING UNDER THE TERMS OF THE

GUARANTEE

Please return the complete product, carriage
paid to your original supplier by post or in
person. Please ensure that it is adequately
packed and accompanied by a letter clearly
marked 'Guarantee Claim' stating the nature
of the fault and providing proof of the date
and source of purchase.

2. 2 The Vent-Axia Guarantee

2. 1 General

5

3.0 General Layout

LoWatt HR 204

Exhaust

out to

atmosphere

Fresh air

in from

atmosphere

N

L

1
2

1 234

5

6

7

8

Normal

Boost

1 234

5

4

5

6

ON

FRONT

UP

Hot stale air

extracted

in from

wet rooms

Warmed fresh

air supplied

out to

dry rooms

1

2

810

911

15

67

14

4

13

5

12

Fig. 2

3

1. Heat exchanger

2. Fan (fresh air in)

3. Rating label

4. Fuse

5. Speed select PCB

6. Accessory switch connection

7. Dip switch for speed selection

8. Lower fixing hole

9. Alternative outlet for condensate (bottom)

10. Condensate drain (Ø15mm)

11 Condensate tray

12 Alternative outlet for condensate (side)

13 Fan (extraction)

14. Air filter

15. Duct connections (4 off)

6

4.0 Technical Data

Dimensions (mm)
Height
Width
Depth

Minimum clearances (mm)
Both sides
Above casing
Below casing
Front for servicing
Front in operation

Lift weight (kg)

Power consumption @ 0Pa (watts)

Suitable for Ø100mm circular ducts.
Suitable for Ø15mm pipe.

220-240V ~50Hz
3 Amps

3.15 Amps

EU2

412
552
285

5
200
100
250

None

17

Speed 1
Speed 2
Speed 3
Speed 4
Speed 5
Speed 6

10
13
21
35
56
75

Duct connections
Condensate connection

Electrical supply
External fuse rating
Internal fuse rating

Filtration

Appliance must be connected to an earthed supply

Fig. 4

SAP Appendix Q Test Results

As tested and published by BRE (Building Research Establishment).
www.sap-appendixq.org.uk

Exhaust
terminal
configuration

Fan speed
setting

Total flow
supply rate (l/s)

Total exhaust
flow rate (l/s)

Specific fan
power (W/l/s)

Heat recovery
efficiency (%)

Kitchen + 1
additional wet
room

Kitchen + 2
additional wet
rooms

2

3

15.0

21.0

15.0

21.1

0.81

0.95

63

57

Fig. 3

7

4.0 Technical Data

412

552

Mounting

Brackets

Side View

Ø98

100

280

285

4

Lower

Fixing Hole

Exhaust

Out

Fresh Air

In

Hot Stale

Air In

Warm Air

Out

Air Flow System

Clean Air

Stale Air

Front View

Fig. 6

Flow Rate Vs Pressure Chart

Fig. 5

The unit has six speeds. One of the lowest five can be selected for normal speed. One of the top 3 can be
selected for boost speed. The performance curve chart gives the ventilation rates at each fan speed compared
to the pressure drop of the system.

102

100Pa @
100m³/h

0

50

100

150

200

250

300

350

400

0 20 40 60 80 100 120 140 160 180 200

Pressure (Pa)

0 5 10 15 20 25 30 35 40 45 50

Volume (l/s)

55

Volume (m³/h)

Extract

Supply

1

2

3

4

5

6

8

5.0 Appliance Operation

On normal running the fans run at the speed
set during commissioning (speed 1, 2, 3, 4 or 5).

If the external controls call for boost operation
the fans automatically run at the boost speed &

increase the air movement of both exhaust &
inlet air.

Optional Extras.

External Controls.

Normal/boost

Switch
NBSW

N

m

o

r

al

B

o tos

Humidity Sensor

HS6

Normal/boost

Pull Cord Switch

PCSW

CMSM control

TIM2 timer

The LoWatt HR204 can only be connected to
external controls with an uncommitted relay.

If the fans become jammed, then the
electronics will sense the reduction in speed
(rpm) and stop the electrical supply to the
motors to prevent overheating. The unit will
check the ability of the fan to rotate every
couple of seconds.

Air is then moved through the unit (see Fig 6).

Humidity Sensor

Ecotronic

9

6.0 Installation Requirements

6.1 Location and Site Requirements

All dimensions

in mm

Total required

(including clearances)

Height - 692

Width - 562
Depth - 530

Minimum top

clearance

for servicing

200

Minimum

side

clearance

5

Minimum

side

clearance

5

Minimum bottom

clearance

100

Minimum front

clearance

for servicing

250

Fig. 7

Clearances

1. Read the instructions fully before installing or
using the appliance.

2. The installation must be carried out in
accordance with the manufacturer's instructions
by a competent person and comply with the
relevant Building Regulations and the current
I.E.E Wiring Regulations.

3. Duct systems should be installed in
accordance with BRE Digest 398 and CIBSE
guides.

4. Consideration must be given to the position
of the ductwork connections, the electrical
connection and the condensate pipe
connection.

5. The exhaust duct must pass through an
outside wall or roof and discharge to
atmosphere in a suitable position. The clean air
inlet duct must pass through an outside wall or
roof and be suitably positioned to provide an
adequate fresh air supply from atmosphere.

6. The ventilation for any open flued appliance
must always be considered before siting the
extract and inlet vents. The vents must also be
sited away from other flue terminals, ventilators
etc. on the outside of the dwelling. In addition,
there shall be adequate ventilation of the kitchen
when a cooker hood is used at the same time as
appliances burning gas or other fuel. The
exhaust air duct must not be discharged into a
flue which is used for exhausting fumes from
appliances burning gas or other fuels. Refer to
the relevant current British Standard Codes of
Practice, Part J of the Building Regulations
(England and Wales) and, in Scotland, OFTEC
Technical Information Sheet TI/112.

7. The LoWatt HR204 is not suitable for
installation above any cooking appliance or with
any extraction system servicing a cooking
appliance.

8. If the unit is fitted in a room containing a bath
or shower then reference should be made to the
current I.E.E Wiring Regulations.

9. A flat vertical area 692mm high x 562mm wide
is required for installation.

10. It is important that any door or cupboard
front covering the LoWatt HR204 is easily
removable by the user as access for regular
cleaning is required.

11. Check that the information on the rating
label is compatible with the supply. See Fig 2.

12. The addition of anything that may interfere
with the normal operation of the appliance could
invalidate the appliance warranty and infringe
regulations.

Note: Clearances do not take into
account any acoustic mat that may
be fitted between the unit and the
wall.

10

6.0 Installation Requirements

6.2 General

1. The LoWatt HR204 has a choice of 5 normal
speed settings and 3 boost speed settings. The
performance curve chart (Section 4, Fig.5)
gives the ventilation rates at each fan speed
setting compared to the pressure drop of the
system.

2. The transmission of noise along ducts should
be reduced by fitting noise attenuation ducts.

(FS100. Part No 370426.)

6. 3 Ducting

1. The outside exhaust duct and outside air
intake duct should be sited a minimum of 2
metres apart to minimise the risk of exhaust
air being drawn back into the house.

2. The duct work system should be sized and
installed to minimise the pressure loss along it.

3. Using larger diameter pipes and keeping the
number of bends and fittings used to a minimum
will reduce the pressure drop and allow the unit
to be set at a lower fan speed.

5. Ducting should be insulated in cold areas to
minimise heat losses. All duct joints should be
suitably taped to ensure an air tight seal.

Exhaust out

Fresh air in

Hot stale air in

Warm air out

Examples of different ducting & fittings

Bathroom

Living room or
bedroom

Terminals

minimum

2m apart

Outside

Wall

LoWatt HR204

Fig. 8

or kitchen

4. Bend radii for flexible ducting, measured to

the inside of bends, should be kept to at least
1x the duct diameter.

11

6.0 Installation Requirements

N

L

1
2

1 234

5

6

7

8

Normal

Boost

1 234

5

4

5

6

ON

Remove bottom cover panel

to access the fan speed

settings & condensate connection.

The condensate

outlets

are marked

on the

wall template.

Wall template

Mains

lead

Cable

clamp &

grommet

for

mains

lead

Fuse

Fit fused double

pole isolator

Fit

3 Amp

fuse

Rear exit for

condensate

Cable clips for

accessories lead

FRONT

UP

Knock out

for side exit

condensate

Wall template HR204 &

HR205

(with cooker hood)

Whole House Ventilation System

Exhaust

Out

Fresh AirInHot Stale

Air In

Warm Air

Out

Minimum

Top

Clearance

200mm

Part No. 372706

98mm

Cooker Hood

Bottom of
MVHR Unit

Bottom of

Cooker Hood

Top of
MVHR

Unit

Bottom of

Mounting
Brackets

4 Fixing Holes

(Key Holes)

Use one

hole each side

Bottom

Fixing Hole

Back Case

Condensate Hole

Side Case Knock

Out Condensate Hole

Minimum Side

Clearance 1mm

Minimum Side

Clearance 1mm

Bottom Condensate

Pipe Exit (HR204 Only)

Minimum Bottom Clearance

100mm

(HR204 Model)

Minimum Side

Clearance

24mm

(HR205c)

Minimum Side

Clearance

5mm

(HR204)

MVHR

Side

Minimum Side

Clearance

24mm

(HR205c)

Minimum Side

Clearance

5mm

(HR204)

MVHR

Side

All dimensions

in mm

Minimum Top

Clearance

for servicing

200

Minimum

Side

Clearance

5

Minimum

Side

Clearance

5

Clearances

HR204

Minimum Bottom

Clearance

100

Minimum

Front

Clearance

for

servicing

250

280

Clearances

HR205

Minimum

Side

Clearance

(MVHR)

24

Minimum

Side

Clearance

(MVHR)
24

Minimum
Top Clearance
for servicing

200

300

Minimum

Front
Clearance
for servicing

250

Minimum Bottom

Clearance from Hob

700

Minimum

Side
Clearance
(C.Hood)

1

Measure Minimum
Bottom Clearance

700mm

From Hob
(HR205c Model)

Mains
Cable
Outlet

Top view of unit

Fig. 9

6.4 System controls

6.5 Electrical supply

1. External wiring must be correctly earthed ,
polarised and in accordance with the current
I.E.E. Regulations.

2. The mains supply must be 220-240V ~ 50Hz
fused at 3 Amps.

6.6 Condensate drain

1. The condensate pipe should have a
continuous fall of 10° (1 in 6) with as much of the
condensate pipe as possible run inside the
property to avoid freezing. The pipe should also
incorporate a trap with a minimum height of
75mm or similar device to prevent a return of

foul air from the waste pipe. See Fig. .11

The LoWatt HR204 has three condensate outlet

positions; rear, bottom and left hand side.

Cable

clamp &

grommet

for

accessories

lead

See page 8 for a list of optional controls.
These are used to switch the LoWatt HR204
from normal speed to boost speed.

Note: The method of connection to the
mains supply must facilitate complete
electrical isolation of the appliance.
Connection may be via a fused double pole
isolator with a contact separation of at least
3mm in all poles and supplying the LoWatt
HR204 and its controls only. The LoWatt
HR204 is not designed to be fitted with a
plug.

N

L

1
2

1 234

5

6

7

8

Normal

Boost

1 234

5

4

5

6

ON

FRONT

UP

12

E

x

h

a

u

s

t

O

u

t

F

r

es

h

A

ir

In

H

o

t

St

a

el

A

ir

In

W

a

rm

A

ir

O

u

t

Example of a possible
understairs installation

Place unit on its back

& remove front cover

Remove electrical cover plate (3 screws)

Ground Floor

Stair Case

Mark position
of the
condensate
pipe. Ø15mm.
Drill where
required.

Mark position

of the

fixing holes.

2 top (minimum)

& 1 lower,

then drill & plug.

Wall templateHR204 &

HR205

(with cooker hood)

Whole House Ventilation System

Exhaust

Out

Fresh AirInHot Stale

Air In

Warm Air

Out

Minimum

Top

Clearance

200mm

Part No. 372706

98mm

Cooker Hood

Bottom of

MVHR Unit

Bottom of

Cooker Hood

Top of
MVHR

Unit

Bottom of

Mounting
Brackets

4 Fixing Holes

(Key Holes)

Use one

hole each side

Bottom

Fixing Hole

Back Case

Condensate Hole

Side Case Knock

Out Condensate Hole

Minimum Side

Clearance 1mm

Minimum Side

Clearance 1mm

Bottom Condensate

Pipe Exit (HR204 Only)

Minimum Bottom Clearance

100mm

(HR204 Model)

Minimum Side

Clearance

24mm

(HR205c)

Minimum Side

Clearance

5mm

(HR204)

MVHR

Side

Minimum Side

Clearance

24mm

(HR205c)

Minimum Side

Clearance

5mm

(HR204)

MVHR
Side

All dimensions

in mm

Minimum Top

Clearance

for servicing

200

Minimum

Side

Clearance

5

Minimum

Side

Clearance

5

Clearances

HR204

Minimum Bottom

Clearance

100

Minimum
Front

Clearance

for

servicing

250

280

Clearances

HR205c

Minimum

Side
Clearance
(MVHR)

24

Minimum

Side

Clearance

(MVHR)

24

Minimum
Top Clearance
for servicing

200

300

Minimum

Front

Clearance

for servicing

250

Minimum Bottom
Clearance from Hob

700

Minimum

Side
Clearance
(C.Hood)

1

Measure Minimum
Bottom Clearance

700mm
From Hob

(HR205c Model)

Mains
Cable
Outlet

7.0 Installation

7.1 Preparation

1. Check site requirements (Section 6) before
commencing.

2. Remove the fixing template from the carton.

3. After considering the site requirements,
position the template on the wall ensuring it is

4. Mark the positions of at least two top fixing
holes, the lower fixing hole and the condensate
outlet.

5. If required, mark off the positions of the four
duct connections.

6. Drill and plug the wall at the fixing points and
drill the condensate hole.

7. The top two screws should now be fitted
leaving enough space for the keyhole fixing slots
to engage.

6. Place the unit on its back (Fig.10). Release the
two screws from the front cover and remove it.

7. Remove the bottom electrical cover plate by
releasing the 3 screws, pulling the panel
forwards and disconnecting the earth lead to the
panel.

Fig. 10

Make sure the wall
template is level

level.

Mark out the position
of the unit with the
wall template.

N

L

1
2

1 234

5

6

7

8

Normal

Boost

1 234

5

4

5

6

ON

FRONT

UP

13

7.3 Fitting the LoWatt HR204

1. Offer the unit to the wall and engage the
keyhole slots over the screws previously fitted.

2. Make sure the unit is level and tighten the top
screws before engaging the final screw.

7.4 Making the condensate connection

1. The condensate connector is suitable for

Ø15 mm pipe.

2. The condensate pipe should incorporate a
water trap or similar to prevent foul air being

drawn into the unit. The minimum height of a

trap should be 75 mm.

Note: To ensure the condensate pipe is
primed, slowly pour water into the
condensate tray until it discharges into
the drain.

Fig. 11

Remove bottom cover panel

to access the fan speed

settings & condensate connection.

Condensate

rear exit shown

Side View

Front Rear

Condensate

drain (15mm)

Rear exit for

condensate pipe

(with grommet)

Condensate tray

Knock out

for side exit

condensate

Rear exit for
condensate

(with grommet).

Knock out for

side exit

condensate.

10º fall (1 in 6)

Condensate

pipe (15mm)

A Trap must be fitted

75mm min height

7.0 Installation

7.2

Condensate outlet

1. If the condensate pipe is to exit the unit at the
left hand side, stand the unit up on its base.

2. Locate the semi-pierced hole and carefully
remove the metal disc.

3. Swap over the grommet used on the rear exit
hole and seal the rear hole with duct tape or
similar.

Note: The LoWatt HR204 has an extra
condensate outlet on the bottom panel.

N

L

1
2

1 234

5

6

7

8

Normal

Boost

1 234

5

4

5

6

ON

FRONT

UP

14

7.0 Installation

7.5 Making the duct connections

1. The unit has four duct connections suitable for
100mm round ducting.

1. Exhaust outlet to outside

2. Air inlet from outside

3. Stale air inlet from dwelling

4. Fresh air outlet to dwelling

Notes: It is essential that the duct system
is connected as indicated.
It is important that the duct system does
not interfere with the correct fitting of the
front cover and does not prevent the
correct operation of the unit.

7.6 Controls

1. The LoWatt HR204 requires external controls
to enable normal/boost switching. Otherwise it
will only run at its normal speed.

7.7 Making the electrical connection

Warning: This appliance must be earthed

Refit electrical cover plate.

Front cover

Fig. 12

1 2

3

4

5

6

7

8

N

L

1
2

Normal

Boost

1 2

3

4

5

4

5

6

ON

1. The unit must be set to the appropriate speed
as determined by air flow required and duct
system pressure (see page 7).

2. To change the speed settings of the fans,
change the position of the dip switches on the
PCB. The 5 switches on the left let you select
the normal speed from speeds 1 to 5. The
remaining 3 switches let you select the boost
speed from speeds 4 to 6.

3. Refit the electrical cover plate and its earth
lead.

4. Connect the flying lead to the mains supply ­see section 6.5.

5. Check the electrical installation for earth
continuity, short circuits, resistance to earth and
correct polarity.

Example shown
Normal speed = speed 2
Boost speed = speed 5

2. Drill a hole in the top grommet, (do not
slice), equal to half the diameter of the two
core cable to go through it.

3. Feed the lead into the unit through the top
grommet, down the side, through the lower
grommet and into the PCB area. Secure the
lead with the cable clips and clamps.

5. Wire to terminals 1 and 2. See wiring
diagrams in section 8.0.

Mains

lead

Optional

controls cable

Cable clips

on inside

1

2

3

4

Upper grommet

Lower grommet

15

8.0 Wiring Diagrams

Fig. 13

LoWatt HR204 Wiring

Manual Normal /Boost

Switch NBSW or

Pull Switch PCSW

Common

Boost

Normal

L

Fan

(air out)

Fan

(air in)

SPEED SELECT

1

2

L

N

1 2

3

4

5

6

7

8

Normal

Boost

1 2

3

4

5

4

5

6

ON

MOTOR

CONTROL

A B

MOTOR
SUPPLY

A B

220-240V 50Hz

MOTOR B

CONTROL P.C.B

MOTOR A

CONTROL P.C.B

CHASSIS

3A

N

L

Fan

(air out)

Fan

(air in)

SPEED SELECT

1

2

L

N

1 2

3

4

5

6

7

8

Normal

Boost

1 2

3

4

5

4

5

6

ON

MOTOR

CONTROL

A B

MOTOR

SUPPLY

A B

220-240V 50Hz

MOTOR B

CONTROL P.C.B

MOTOR A

CONTROL P.C.B

CHASSIS

N

16

8.0 Wiring Diagrams

Fig. 14

LoWatt HR204 Wiring & CMSM controller

CMSM Controller

L
N
L

Live in

Neutral in

Live to relay

N
E

Neutral out

Earth

N.O

C

N.C

Live out to fan

Live out

Common

Important: Remove
live link in wire

S1 S2

3A

17

HS6 Humidistat

0
2
1

Common

Boost

Ordinary

N
L

LoWatt HR204 with optional humidistats

8.0 Wiring Diagrams

1

2

Fig. 15

L

Fan

(air out)

Fan

(air in)

SPEED SELECT

1

2

L

N

1 2

3

4

5

6

7

8

Normal

Boost

1 2

3

4

5

4

5

6

ON

MOTOR

CONTROL

A B

MOTOR

SUPPLY

A B

220-240V 50Hz

MOTOR B

CONTROL P.C.B

MOTOR A

CONTROL P.C.B

CHASSIS

N

Ecotronic Humidistat

5
4
3
L
N

1

2

L N

Alternative
humidistat

3A

18

9.2 Balancing the system

It is important that a suitable anemometer
is used to balance the system to give the
required ventilation rates to each room.

1. Set the appliance running on normal speed.

2. Make a preliminary adjustment of all the duct
inlet and outlet louvres.

Note: The supply air terminal is directional
and incorporates a deflector plate. Ensure
that the deflector plate is correctly
positioned so that the active part of the
terminal is discharging to the room.

3. Check the flow rate and adjust if necessary
the extract valve furthest from the appliance.

4. Check the flow rates and adjust if necessary
the remaining extract valves.

5. Repeat the flow checks and adjust until the
extract system is balanced.

6. Check the flow rate and adjust if necessary
the inlet valve furthest from the appliance.

7. Check the flow rate and adjust if necessary
the remaining inlet valves.

8. Repeat the checks and adjust until the system
is correctly balanced.

Note: If the flow rates have been achieved
with all the louvres nearly closed, it may
be possible to reduce the fan speed and
re-adjust the louvre settings.

9.3 Instruct the user

Instruct the user in the operation of the
appliance. Hand over these instructions, giving
advice on the necessity for regular servicing of
the filters and heat exchanger.

SV100

Adjust ceiling supply valve for living room etc.

EV100

Adjust ceiling extract valve for bathroom etc

Inside view of

extract valve

Locking nut

to lock

the valve

in position

Inside view of

supply valve

Locking nut

to lock

the valve

in position

Air direction

Air deflector

plate

Air
direction
indicator

Fig. 16

9.0 Commissioning

9.1

Prepare for commissioning

1. Refit the front cover by hooking it over the
top lip of the appliance and swinging down.
Tighten the two case screws.

2. Check the external controls are set to normal
running.

3. Turn on the electrical supply. The unit will now
start running at the normal ventilation speed.

4. Set the external control to boost. The unit will
now switch to boost speed.

N

L

1
2

1 234

5

6

7

8

Normal

Boost

1 234

5

4

5

6

ON

FRONT

UP

WiringService

19

10.0 Maintenance

Important: Before servicing ensure that the
appliance is isolated from the electrical
supply. After isolating from the electrical
supply, allow one minute for the fans to stop
rotating before servicing the appliance.

1. Lift off the front cover by releasing the two
screws and lifting upwards.

2. Remove the air inlet filter by pulling forwards.

3. Taking note of the offset sliders, carefully remove
the heat exchanger by gently pulling forwards.

4. Check both fans and fan compartments for
deposits. Clean as necessary, making sure that you

5. Remove the condensate tray by pulling forwards.
Check and clean if necessary.

6. Check the condition of the four heat exchanger
sealing strips and front cover seal. Replace seals as
necessary.

Note: Ensure the heat exchanger is located
correctly in the offset sliders.

Pull forward & remove
the cover.

Remove screws

Pull out & clean the
Condensate Tray

Air inlet
filter. Pull
out, brush
& vacuum
clean.

11. Re-assemble in reverse order and re-fit the
front cover ensuring it makes a good seal.

Fig. 17

The following cleaning and disinfection routine
should be conducted every 6 months to maintain
the efficiency and hygiene of the unit. It should be
carried out by a suitably qualified person.

Care should be taken when using sterilising
solutions. Gloves and eye protection are the
minimum levels of personal protective equipment
required. Do not spill the cleaning solution on any
other surfaces, especially fabric as bleaching
damage could occur.

The sterilising solution used should be a 'Milton'
type solution diluted 1 to 20, or 'Instachlor PR1000'
tablets (or similar), these will then give a 1,000
ppm available Chlorine solution.

7. Carefully wash the heat exchanger, making sure
that the solution penetrates the cell plates. Take
care not to loosen the plates. Dry thoroughly before
refitting.

8.Drain and clean the condensate pipe using a
bottlebrush, or similar, soaked in the sterilising
solution.

9. Wipe down all parts showing signs of fungal /
mould growth with the sterilising solution.

10. All parts should be well rinsed with clean water
and dried after cleaning.

F

R N

T

O

U

P

Use strap to pull
out heat
exchanger.

12. Check the condition of the ductwork system,
the soundness of all joints and repair if necessary.

Carefully vacuum the filter. Replace if necessary.

do not disturb any cables or connections.

N

L

1
2

1 234

5

6

7

8

Normal

Boost

1 234

5

4

5

6

ON

FRONT

UP

N

L

1
2

1 234

5

6

7

8

Normal

Boost

1 234

5

4

5

6

ON

20

11.0 Changing Components

11.3 Speed select & motor control PCBs

1. Remove the front cover by releasing the two
screws and lifting the cover up and forwards.

2. Remove the bottom electrical cover plate by
releasing the 3 screws, pulling the plate
forwards and disconnecting the earth lead to the

it. Make a note of the speed settings of the

dip switch and the wiring arrangement for the
PCBs.

3. Remove the two screw securing the PCB
chassis to the bulkhead. Pull the chassis

forward and down.

7. Re-assemble in reverse order. Make sure rear

tab of PCB chassis locates in slot. Check the

installation for earth continuity, short circuits,
resistance to earth and correct polarity.

IMPORTANT: ISOLATE FROM THE
ELECTRICAL SUPPLY BEFORE STARTING
ANY WORK ON THE APPLIANCE.

Fig. 18

4. Make a note of the connections between
PCBs and motors.

5. Disconnect the motor cables, mains cable
and boost switch cable. Remove chassis and
PCBs completely.

6. Replace PCBs as necessary.

Remove electrical cover plate.

Example shown
Normal speed = speed 1
Boost speed = speed 4

11.1 Heat exchanger

1. Lift off the front cover by releasing the two
screws and lifting upwards.

2. Gently remove the heat exchanger by pulling
the strap forwards.

3. Re-assemble in reverse order taking care not
to damage the heat exchanger seals.

11.2 Heat exchanger seals

1. Remove the heat exchanger (see 11.1).

2. Remove the four heat exchanger seals taking
care to remove all the old adhesive backing.

3. Fit the new seals ensuring they make good
contact with the location channel.

4. Re-assemble in reverse order taking care not
to damage the heat exchanger seals.

F

R

O

N

T

U

P

Re-fit new

heat

exchanger

1 3

2

4

Fit 4 new
self-adhesive
sealing strips

(see positions

1 to 4 below)

Fig. 18

1 2

3

4

5

6

7

8

N

L

1

2

Normal

Boost

1 234

5

4

5

6

ON

THE FANS MAY CONTINUE TO ROTATE
FOR A MINUTE AFTERWARDS.

21

11.4 Extract fan and input fan

1. Lift off the front cover by releasing the two
screws and lifting upwards.

2. Remove the PCB chassis by following the
instructions in 11.3. Disconnect the motor lead.

3. Slacken the two rear fan bracket screws.

4. Remove the two front fan bracket screws and
remove the fan assembly.
Note the position of the fan bracket relative to
the fan.

5. Remove the bracket and re-fit to the new fan.

6. Re-assemble with the new fan in reverse
order ensuring the cable does not foul the fan
motor. Check the electrical installation for

earth continuity, short circuits, resistance to
earth and correct polarity.

11.0 Changing Components

Removal

of the

left hand

fan

(right hand

fan similiar)

FRONT

UP

Push fan
assenbly
to the left

and pull

away from

unit

Slacken

the 2 rear

securing

screws

Fan support

bracket

Fan support

bracket

Fan

Fan securing

nuts & washers

Remove

the 2 front

securing

screws

Fig. 19

22

12.0 Fault Finding

START

YES

NO

Check mains

supply.

Is there

mains voltage

across terminals

A1 & A2?

YES

NO

Investigate cause

and

rectify fault

Is the

fuse on the

speed select PCB

O.K?

Replace speed

NO

Is there low

voltage between

B1 and B2?

YES

NO

Check external

control wiring.

Reconnect wires

to terminals

B1 & B2.

Replace external

controls

Check

external

control,

rectify or

replace

as

necessary.

NO

Do the

external controls

have/require a mains

supply?

Are both fans

operating?

YES YES

Replace fuse

Before starting FAULT FINDING

carry out preliminary electrical systems checks

i.e. Earth Continuity, Polarity, Short Circuit

and Resistance to Earth.

Ensure all external controls are operating
and are set to normal running. Ensure that
a mains electrical supply is available to the
unit.

Refer to diagrams below to
identify terminals on components
(e.g. A1, B2 etc).

FINISH

NO

YES

Did this solve
the problem?

NO

YES

Did this solve
the problem?

YES

NO

NO

Clean filter &

heat exchanger

(section 10). Check

duct system and

terminals for

blockages or

damage. Ensure

terminals are

adjusted correctly.

Is there
adequate airflow
at the appliance

inlets and

outlets

Do external

controls switch

the unit to boost?

NO

Correct speed

settings

Is the

boost speed set

higher than the normal

speed on dip

switch C?

NO

YES

Did this solve
the problem?

YES

A2

A1

B2

B1

C

FUSE

SPEED SELECT PCB

YES

Fig. 20

1 2

3

4

5

6

7

8

N

L

1

2

Normal

Boost

1 234

5

4

5

6

ON

select PCB.

23

Replace fan

(section 11.4)

YES

Re-align

fan

either fan rotate
when powered?

Replace speed

select PCB.

NO

NO

NO

Are fans

free to

rotate?

Is the

fan fouling

on inlet

ring?

YES

Note

NO

YES

Did this solve
the problem?

YES

Does

Swap the problem
fan's connection to
the drive PCB with

the other fan's drive

PCB.

YES

NO

Does the

same fan fail to

run?

Replace

Replace problem

drive PCB

Replace fan
drive PCBs.

NO

YES

Did this solve
the problem?

Replace fans

FINISH

If the either fan does not rotate, check the entire
system and unit for correct installation. Check all
ducting outside and terminals for blockages.

The drive PCB can sense if the fan is not rotating.
When this happens, it will shut off the power to the
motor to prevent overheating. It will try powering the
motor again every few seconds until the problem is
resolved. This is characterised by the impeller jerking
every few seconds.

problem fan

12.0 Fault Finding

24

13.0 Short Parts List

1 2

3

4

5

6

10

7

8

12

N

rmo

a

l

B

o

ost

11

FR

O T

N

U

P

Fig. 21

Key No. Spares Part No. Description

1 436373 DC motor/impeller assembly

436374 Motor Drive PCB

372735 Inlet duct filter

372736 Heat exchanger
372737 Heat exchanger seals (4 off)

372739 Outer door/cover assembly

Optional extras

370254 Humidity sensor HS6

370495 Normal/boost switch NBSW
370278 Normal/boost pull cord switch PCSW

2
3
4
5
6
7

8

9
10
11
12
13

436375 Speed Select PCB

7

6

5

4

3

2

1

NLE

TAC

N/A

PWM

0 v

+V

370346
435960

TIM2 timer
CMSM controller

13

436224B - 0807

1 234

5

6

7

8

N

L

1
2

Normal

Boost

1 234

5

4

5

6

ON

9

563532 Ecotronic humidity sensor