Vent-Axia HR400 User guide

HR320 & HR400
Whole House Ventilation System
With Heat Recovery
Installation and
Servicing Instructions
Please leave these instructions with the user
HR400
HR320

2

3
1.0Introduction 4
2.0Site Requirements 5
3.0Installation 7
4.0Electrical 17
5.0Commissioning 18
6.0Servicing 20
7.0Fault Finding 21
8.0Guarantee 22
Section Page
Contents

1.0 Introduction
4
1.1 Description
1. The HR320 and HR400 are a
range of whole house ventilation units
(Figs. 1 & 2).
The ventilation unit works in conjunction with a
duct system enabling air to be transferred
throughout the house.
The whole house system works by replacing
the warm stale moist air from the house, with
fresh air from outside. The fresh air passes
through a highly efficient heat exchanger and is
prewarmed by the heat which is recovered from
the extracted air. The heat exchanger recovers
up to 70% heat from the outgoing stale air.
1.2 Operation
1. The unit is designed to switch between trickle
and boost settings to give optimum
performance. This can be achieved manually
through a switch or pull cord, or automatically
using a remote humidity sensor.
Trickle is continuous low speed at which the air
in the property is changed approximately once
every two hours.
Boost increases the ventilation rate throughout
the property for manual control. Under
automatic control the unit changes to boost on
increase in relative humidity above a set point.
It reverts to trickle when the relative humidity
drops below the set point.
NOTE: The system is audible when
operating at boost speed.
2. Speed control of the unit is via a separate
transformer (VCON77) which is capable of
giving a range of six speeds (Fig. 3). Any two
speeds can be selected on installation to give
trickle and boost settings most appropriate to
the system.
With the units operating on boost setting the
electrical power consumption is;
HR320 - 200W
HR400 - 305W
NOTE: Refer to the VCON77 instructions for
information on installation and speed
selection.
Fig. 1
Fig. 2
Fig. 3
HR400
HR320
VCON77

2.1 Information
1. The fan unit is to be permanently connected
to the mains electrical supply and must be
installed by a suitably qualified person.
2. The fan unit must be sited and connected in
accordance with UK Building and IEE Wiring
Regulations (BS 7671) or regulations and /or
standards appropriate to the country of use.
3. Wiring to the fan unit in the UK must be via
a 3 Amp fused and switched connection unit
incorporating a double pole switch having a
contact separation not less than 3mm and
conforming to BS 5733 or BS 1363 Part 4. The
connection must be located outside of a fixed
bath, shower or wash hand basin. The wiring
should be suitably (BASEC or HAR) approved
cable of appropriate current carrying capacity.
4. The fan unit is Class 1 and must therefore be
earthed.
5. The fan unit must be connected to a trapped
drainage system to allow condensate to be
freely drained from the unit to the chosen
discharge point.
6. If the fan is installed in an unheated roof
void, or similar location, it should be insulated
together with any associated ducting within this
space.
7. The fan unit must be sited away from direct
sources of heat in excess of 40°C.
8. Do not position an internal extract valve/grille
in the vicinity of excessive levels of airborne oil
or grease i.e. above or close to a cooker.
9. If it is intended to fit an extract terminal/grille
in a room containing a fuel burning appliance,
the installer must ensure that provision for air
replacement is adequate for both appliances
and is in compliance with the requirements of
Part F of the current edition of the Building
Regulations.
2.0 Site Requirements
5

2.0 Site Requirements
6
2.1 Information (cont)
10. The external grilles/terminals for the system
must be sited at least 1m away from the flue of
a fuel burning appliance, in compliance with the
requirements of Local Authority, Building
Regulations and any other relevant Codes of
Practice.
11. All safety regulations and requirements must
be strictly followed to prevent hazards to life
and property both during and after installation
or servicing.
12. Ensure that the mains electrical supply is
switched off before commencing installation,
maintenance or servicing.
13. Fire compartmentation must be maintained
to comply with the requirements of the current
edition of the Building Regulations. Where
applicable fire dampers complying with the
recommendations of BS CP 5588: Part 9 will
require to be installed in the ducting installation.
14. Do not locate fittings (QTET, QTB90,
QTB45) closer than 2.5 diameters to each other
or to supply/extract terminal (SV100/EV100).
15. Never locate tees (QTET) directly over or
adjacent to a terminal housing otherwise noise
will be generated.

3.0 Installation
7
3.1 Installing the Fan Unit
1. Check the diagrammatic ducting layout
drawing to ensure that the proposed duct
routes, fan unit and air terminal locations can
be accomodated. If in doubt refer to the
Technical Department.
2. The units are suitable for either vertical or
horizontal mounting. After noting the positions
of the electrical connector, duct spigots and
drainage connection on the unit, choose a
suitable installation site for the unit. The most
desirable location for the unit, in single and two
storey properties with a roof space, is in the
roof space.
3. Never locate the unit over a sleeping area -
above the landing or bathroom is always
preferred. The selected site must allow
adequate space around the unit for the removal
of the access panel and heat exchanger for
maintenance and servicing puposes.
Condensate Drainage
HR400
4. The condensate drain is supplied fitted to the
unit as shown (Fig. 4).
HR320
5. The unit is supplied with a 22mm diameter
condensate drain fitting, packed loose in the
box. The WH unit casing is moulded with two
22mm diameter drainage spigots in the bottom
corners. The casing of the unit can be set up for
right hand or left hand drainage by cropping the
domed end off either one of these spigots and
pushing on the condensate drain fitting (Fig. 5).
6. The units must be positioned so that the
condensate outlet can be trapped and the
condensate conveyed properly with a
continuous gradient to discharge through the
gable or to the eaves gutter in the selected
location. Parts ref. CP, CPC and CPE are
included with the kit. Connect the drainage
system using the parts provided, jointing the
PVC pipework and fittings using PVC cement to
form watertight joints.
NOTE: Trap should be charged/filled before
operating the system and should be
checked, especially in summer.
BEWARE: A blocked condensate outlet pipe
due to insufficient pipe run (gradient) will
quickly lead to water damage.
Condensate Drain
HR400
HR320
Condensate Drain
Fig. 4
Fig. 5

3.0 Installation
8
Top Cover
Fig. 7
Fig. 6
Heat Exchanger
Filter
Drain
Outlet
Condensate
Trap
Joists
Inclined
Platform
Acoustic Mat
Condensate
Drain
Mounting Pad
3.1 Installing the Fan Unit (cont)
Horizontal Mounting (Fig. 7)
7. Before installation of the fan unit, a wooden
platform must be provided to mount the unit on.
8. The platform should be constructed from
50mm x 100mm timber bearers with a 19mm
block board deck.
9. The platform should incline the unit to ensure
a fall to the drain outlet. An acoustic mat
(ACMW/HOUSE) can be fitted on top of the
board to minimise vibration.
10. Remove the top cover and withdraw the
heat exchanger from the casing. Carefully drill
four holes through the mounting pads.
11. Secure the casing to the platform deck
using four No.8 round head screws and large
pattern washers to dissipate the load (Fig. 6).

3.0 Installation
9
3.1 Installing the Fan Unit (cont)
Vertical Mounting HR400 (Fig. 8)
12. The HR400 can be mounted
vertically by securing with plugs and screws
through the casing (see horizontal mounting).
Vertical Mounting HR320
The HR320 is supplied with a wall mounting kit.
13. Hold the unit against the wall and mark the
horizontal base line.
14. Remove the unit and position the mounting
channel on the line.
15. Mark through the three holes and drill and
plug them (Fig. 11).
16. Secure the mounting channel to the wall
using the screws provided (Fig. 11).
17. Locate the unit’s lower mounting rib in the
channel and mark the position of the upper
slotted mounting lug. Drill and plug the wall
(Fig. 9).
18. Secure the unit to the wall ensuring a large
pattern washer is used on the fixing lug (Fig. 9).
HR400
HR320
Fig. 8
Fig. 9
Fig. 10
Fig. 11
Mounting Channel
Securing Screw
and Washer
Upper slotted
Mounting Lug

3.0 Installation
10
3.2 Installing the Ducting System
1. Cut off the closed ends of the duct spigots
that are to be connected to the duct system.
Ensure that no cutting debris falls into, or
remains in the unit as this could damage the
balanced impellers and cause excessive noise
and vibration.
2. A shell bit is recommended for drilling holes
in the ceiling to accomodate the housings for
supply and extract air terminals (SV100 and
EV100). Make sure that you are not drilling into
structural members, water or gas pipes or
electrical cables and that there is room behind
the plaster board for duct access and securing
ring. Ceiling terminals should preferably be
fitted equidistant from adjacent walls bearing in
mind that coving may already be fitted or may
be fitted at a later date.
3. Place the terminal housing in the hole in the
ceiling and secure to the back ring with the four
screws provided.
4. For two storey new build properties it is
recommended that the ground floor terminal
housings are secured in position in advance of
the plasterboard panels being fixed, by
obtaining a sheet of plasterboard of the type
and thickness to be used. Cut a square of the
sheet to just span two joists in the corner where
the terminal is to be fitted. Remember that the
edge of the sheet on the inner joist should only
rest on half of the joist thickness. This allows a
fixing surface for the next sheet of plasterboard
to be secured to when it is fitted. Tack up the
plasterboard in position on the ceiling and
connect up and seal the duct and fittings
(Fig 12).
5. For two storey existing properties it is
necessary to lift the floor coverings at first floor
level above the terminal positions to gain
access to the terminal housings to secure and
seal the duct and fittings.
6. Fix in position all vertical supply and extract
air ducting being conveyed between ground
floor ceiling level and the loft space (Fig 13).
Terminal Housing
Plaster Board
Securing Ring / Back Plate
(for fire valves)
Securing Screw
Terminal
Supply and Extract Air Terminals SV100 / EV100
Typical Installation
QT3
Joist
RD040
Floor Boards
Joist Direction
Terminal Housing
Plaster Board
EV100/SV100
RD015
Fig. 12
Fig. 13

3.0 Installation
11
3.2 Installing the Ducting System (cont)
7. The external grilles for intake and exhaust air
should be positioned so that the exhaust air is
not drawn in again.
8. If the grilles are fitted in the same gable at the
same height, a minimum of 1m between grilles is
recommended.
9. If the grilles are positioned above one another
the distance apart should be at least 1m with the
exhaust grille at the top.
10. Roof ventilators placed on the same roof
surface should be positioned at the same
distances as the grilles.
11. Always ensure that all exhaust grilles/roof
ventilators are placed higher than the top edge of
the highest window and at a distance of at least
1m from the nearest window.
12. External grilles placed in the soffit should be
positioned at the same distances as indicated for
gables.
13. The Quicktube Rigid UPVC duct system
permits fast, easy assembly whilst ensuring
pressure-proof system sealing.
14. The ducts are delivered in lengths of 3m and
are easily shortened as required with a duct saw
or a similar fine toothed saw. We recommend
that you file the edges of the ducts after
shortening.
15. Assemble the duct and fittings, following as
closely as possible the diagrammatic ducting
layout. Ensure that the duct is raised above joist
level to allow for thermal insulation of the
ducting.
16. Each straight length of duct is assembled
using a flexible connector (QTC) to join the two
ends, whilst 90°and 45°diversions and
branches are accomplished with flexible fittings
(QTB90, QTB45 and QTET). The duct is a push
fit into the socket of the connector and fittings.
17. Once assembled the joints are secured with
duct tape (DT30) to provide an airtight seal.
Ensure that the tape is secured over the
complete joint area to provide an airtight seal.

3.0 Installation
12
3.2 Installing the Ducting System (cont)
18. The quantity and location of flexible silencers
(FS100), if required, will depend upon total
airflow rate. If in doubt check with the Technical
Department. These should be installed between
the unit and the first supply/extract terminal on
the duct system, to reduce the noise from the
unit, which would otherwise be transmitted
through the duct system and into the home.
19. If the loft space is unheated the unit and
ducting will require to be thermally insulated to
preclude condensation occuring and to minimise
heat loss. This requirement must be observed in
the planning and routing of the duct system.
20. The insulation recommended comprises of
3mm thick polyethylene bubble sheet laminated
on the external surface with aluminium foil
protected by a thin polythene film. The product is
CFC and HFC free and has a surface spread of
flame of Class 1 tested to BS476 Part 7/971. It
should, however, be protected from open flames
or sparks and stored apart from highly flammable
materials.
21. The material provides resistance to heat loss
from the distribution ducting and a highly
effective vapour barrier when all joints are sealed
with metallised tape. It is light but robust, not
easily damaged in storage or during construction
and is rot proof, water and vapour resistent,
durable and can be expected to remain an
effective insulant for the normal life span of a
building.
22. The insulation is supplied in 1.5m long
preformed sections for application to the ducting
at the time of installation. All joints should be
secured using the metalised tape (DTA30)
provided to ensure that a continuous vapour seal
is maintained.
23. A purpose made insulating jacket is provided
to enclose the heat recovery unit. Simply cut out
the material for ducting connections to ensure a
snug fit.
24. The use of flexible ducting should be limited
to an absolute minimum. If used it should be fully
stretched in order to minimse pressure loss.

3.0 Installation
13
3.2 Installing the Ducting System (cont)
25. A pack of pre-insulated flexible ducting
(IFD100) is included with the kit together with
worm drive clips (FC180). The flexible ducting is
intended for use in making the final connection
between the rigid ducting and the external
wall/soffit grilles or roof ventilators.
26. Remove the controller (VCON77) from the
packaging, unscrew the cover retaining screws
and remove the cover.
27. Offer the base assembly to the selected
mounting surface and mark the fixing hole
positions. Fix the base assembly to the mounting
surface using suitable woodscrews and if
required, wall plugs.
28. Install the manual control switch (NBSW and
MBB), or pull cord switch (PCSW) in accordance
with the instructions supplied with it. Alternatively
install the automatic control option - a humidistat
(HS6).
29. Before wiring the fan unit, controller and
control switch, ensure that the mains electrical
supply is switched off.
30. Cut to length, strip and connect suitable
cables between the fan unit, controller and
control switch in accordance with the wiring
arrangements.
31. When using surface wiring, which is not
contained in conduit, anchor the cables to the
mounting surface along their length and
particularly adjacent to the connection to the unit,
controller and control switch.
32. Replace the controller cover and tighten the
retaining screws while ensuring that no wiring is
trapped between the base and the cover.
33. Locate the control switch on its mounting box
and tighten its retaining screws (NBSW or
PCSW).
34. Switch on the mains electrical supply and
test for satisfactory operation of the fan unit and
duct system. Operate the system with the
manual control switch (NBSW or PCSW) set to
boost speed, or with the humidistat (HS6) set at
minimum and the cores of all the air valves
removed. The system will be noisy, this is to be
expected. Operate the unit and system at boost
speed for approximately 15 minutes to ensure
that any dust and debris which has accumulated
during installation is ejected.

3.0 Installation
14
3.2 Installing the Ducting System (cont)
35. The rectangular system of ducting, white rigid
UPVC, permits fast, easy assembly and is
normally used in flatted accomodation. This
ducting can be surface mounted internally where
a ceiling void is not available, fitted between
ceiling and floor between joists, or when a ceiling
void is not accessible or too small to work in.
36. The ducting (RD015), which has external
dimensions of 54mm x 110mm x 1.5m long, can
be mounted horizontally with the long side
against the ceiling or vertically with the long side
against a wall.
37. This is done by drilling a 25mm dia hole in
the underside or exposed vertical side of the
ducting and then drilling a pilot screw hole on the
hidden side of the duct i.e. ceiling/wall side of the
duct, through the 25mm dia hole. Corresponding
fixing holes are drilled in the ceiling/wall and wall
plugs fitted as required. Using a screwdriver
through the 25mm hole fix the ducting with an
appropriate size and length of screw through the
pilot hole into the ceiling/wall. The 25mm dia hole
is then sealed using an appropriate sized plug
(PDPLUG) (Fig. 14).
38. A variety of push fit white rigid UPVC fittings
are available.
39. Duct runs longer than 1.5m can be built up
by the use of straight connector pieces (RD020),
changes in direction horizontally by 90°bends
(RD050) and vertically by 90°bends (RD060),
branches are obtained by the use of tee pieces
(RD080).
40. Changes in section from the rectangular to
circular to accomodate the use of quicktube or
flexible ducting (PFD100 etc.) can be obtained
with bent adaptors i.e. 90°elbow joints (RD040),
and straight adaptors (RD070). Note that the
RD070 is an eccentric fitting which allows both
the rectangular and circular ducting to be
installed flush to the wall/ceiling.
41. As the fittings are push fit over the outside of
the straight duct (RD015 - 110mm x 54mm) a
small gap, 2mm wide, will occur at the
wall/ceiling due to the thickness of the fitting.
This can be filled by the use of a white silicon
sealant.
Push Fit Grommet
Fig. 14

3.0 Installation
15
3.2 Installing the Ducting System (cont)
42. Rectangular ducting can be concealed in a
suspended ceiling having a minimum clearance
of 76mm (double battening) between the ceiling
and the plasterboard. This allows the use of
ceiling mounted supply (SV100) and extract
(EV100) valves utilising the 90°rectangular to
circular elbow joint (RD040). The spigot of the
RD040 may have to be trimmed to facilitate this.
43. The system can be used with a variety of
wall louvres, grilles and terminals. The RD501 is
an internal brick sized grille in white, 200mm x
55mm, and can be used in conjunction with an
adaptor (RD077) to convert to 110mm x 54mm.
This permits connection to rectangular ducting.
The RD501 grille can be used directly onto the
rectangular ducting either on the 54mm side or
the 110mm. This is done by cutting a hole,
50mm x 100mm, in the duct, cutting off the
sleeve at the rear of the RD501 to leave the
grille which can then be attached to the hole in
the duct by solvent or by a white silicon sealant.
44. Wall louvres such as the RD104 and the
ESG100 can also be used by converting to
circular with either a straight adaptor (RD070) or
a bent adaptor (RD040). It is important to
remember that the spigot on the RD104 is
concentric, which is difficult to use if the
rectangular ducting is hard against the ceiling or
wall or both. In this use an ESG100 which has
an eccentric spigot.
45. Squareduct 100 is designed to provide a
smooth bore ducting system which can be
surface mounted in areas where concealment or
boxing-in is difficult or undesirable. The ducting
(SD3) comes in 3m lengths or (SD1.5) in 1.5m
lengths and with clean butt joints and concealed
fixing, Squareduct can be fitted along the top of
a wall providing a clean edge between wall and
ceiling.
46. All fittings are supplied with a matching push
fit grommet (PDPLUG) on one side. This is
removable to allow the fitting to be drilled and
screwed through the hidden duct wall to either
ceiling or wall. Removal of the grommet provides
a 25mm diameter hole for access. This
procedure is very similar to that used for
rectangular ducting. After fixing, the 25mm dia
hole is then sealed using the grommet
(PDPLUG) (Fig. 15).
Push Fit Grommet
Fig. 15

3.0 Installation
16
3.2 Installing the Ducting System (cont)
47. A variety of push fit white rigid UPVC fittings
are available.
48. Integral grilles and louvres provide attractive
extract and supply for low cost installations. Tube
and fittings are manufactured in flame retardant
plastics to DIN4102/B1.
49. A square to round adaptor (AD100) allows for
simple connection to the Quicktube (QT3)
system and the use of all ancillary equipment.
Wall louvres such as the RD104 and the
ESG100 can be used by converting to circular
with the straight adaptor (AD100). It is important
to remember that the spigot on the RD104 is
concentric which is difficult to use if the
Squareduct is hard against the ceiling or wall or
both. In this case use an ESG100 which has an
eccentric spigot.

4.0 Electrical
17
Mains Via 3A
Fused Spur
Normal/Boost
Switch
CN
B
L
N
L
N
O
B
To
HRV
Unit
VCON77
C
Mains Via 3A
Fused Spur
Mains Via 3A
Fused Spur
Normal/Boost
Switch
CN
B
L
N
L
N
O
B
To
HRV
Unit
0
2
1
N
L
HS6
VCON77
C
VCON7 and NBSW / VCON100 Manual Normal to Boost Speed Control
Select appropriate VCON77 tapping for NORMAL speed setting
VCON7 and HS6 Automatic Normal to Boost Speed Switching
Select appropriate VCON77 tapping for NORMAL speed setting
4.1 Wiring Options

5.0 Commissioning
18
5.1 Commissioning the System
Before starting to commission the system check
that the crossflow heat exchanger and the filter
panel (if ordered) are properly and securely in
place (Fig. 16). Check that all sockets are
correctly engaged, that the wiring is secure and
properly mounted and that the unit cover is
secured.
The scope of the commissioning procedure
comprises:
1. Balancing the two airflows to achieve
maximum heat exchanger efficiency.
2. Adjusting the two airflows to obtain the
overall airflow rates and the individual terminal
air flow rates as specified on the air change
schedule.
3. Adjusting the fan speed controller (VCON77)
by increasing or decreasing the voltage setting
to obtain the most economical running costs
and the lowest noise levels attainable within the
parameters of the design concept as specified
on the air change schedule. The 230V tapping
is for BOOST speed operation only. At this
setting, the system will be audible.
4. An airflow meter must be used to set the
correct airflows.
5. Check that there are air gaps under all
internal doors to provide the transfer route of air
from the “living”areas to the “wet”rooms. Close
all windows, outside doors and all fresh air
terminals in windows and walls except the
necessary openings for gas oil heaters and
stoves etc. Fit the cores of the air valves,
ensuring that the correct type of supply and
extract terminal device is used.
NOTE: The supply air terminal device is
directional and incorporates a deflector plate.
Ensure that the deflector plate is correctly
positioned so that the active part of the
terminal device is discharging to the room.
6. Set the control switch (NBSW or PCSW)
(Figs. 17 & 18) to normal speed or set the
humidistat (HS6) (Fig. 19) at maximum and
check that air is flowing in the correct direction
at each terminal point. At this stage it will save
time if all the terminals are fitted and opened to
approximately half way.
7. Commence with the extract system at the
terminal nearest to the fan unit. Adjust and
measure until the airflow for that particular
terminal is achieved at the value indicated on
the air change schedule.
Fig. 16
Cover
Filter (optional)
Electrical Plug
Heat Exchanger
Fig. 17
NORMAL
BOOST
NBSW
NBSW
Fig. 18
PCSW
Fig. 19
HS6

5.0 Commissioning
19
5.1 Commissioning the System (cont)
8. Standard ceiling terminals type EV100 and
SV100 are adjusted by turning the central
screw and are locked in the “set”position by the
locknut.
9. Move to the next terminal down the line and
adjust as before. Repeat until all extracts have
been adjusted. Recheck the first terminal and
adjust, followed by the second, third etc., until
all individual extract air flow rates are within
approximately +/-10% of the design air flow
rates.
10. If each terminal has to be almost closed to
achieve the air flow rates, it is likely that the
VCON77 “normal”voltage setting is too high.
Change to the next lowest voltage setting and
remeasure the individual air flow rates.
11. Conversely, if the airflows cannot be
achieved with the terminals fully open it will be
necessary to increse the VCON77 “normal”
voltage setting by one step and to remeasure
the individual air flow rates.
12. When satisfied with all the extract air flow
rates, repeat the procedure stated above for all
supply air terminals. In this case it is important
that excessively high air velocities do not create
draughts and undue noise. It may be necessary
to install a volume control damper in the main
fresh air inlet ducting to increase system
resistance and hence induce the fan to move
down its curve (refer to the Technical
Department should this circumstance prevail).
13. Louvered terminals type RD104 and RD501
are adjusted by restricting the airflow using
acetate paper or similar, cut to the size required
to achieve design air flow rates. If the internal
louvered wall terminals (RD104 and RD501)
are used for supply air then the terminals
should be fitted at high level and the louvres
should direct the air upwards. Ensure that the
flyscreen is removed from the RD104 louvred
wall terminal and that the non-return flap is
removed from the RD501 wall terminal.

6.0 Servicing
20
6.1 Annual Servicing
1. As well as providing fresh pre-warmed air the
system also removes odours, moisture,
excessive heat and airborne impurities such as
dust, dirt and grease. These impurities
gradually build up and detract from the
efficiency of the heat exchanger.
2. It is recommended that the system is
serviced annually. Servicing must be carried out
by a competent person.
3. Switch off the mains electrical supply to the
unit.
4. Undo the captive retaining screws and
remove the cover (Fig. 20).
5. Withdraw the heat exchanger (Fig. 21).
6. Wash the heat exchanger in warm water
using a mild detergent and subsequently dry it
thoroughly.
7. Remove filter, if fitted, and replace with new
filter media (Fig. 21).
8. Clean the interior of the unit with a vacuum
cleaner if necessary and lightly brush the fan
impellors.
9. Disinfect the unit interior using a proprietary
product, noting and observing the
manufacturer’s instructions.
10. Check the drainage system for integrity of
joints and ensure that water flows freely and
that the trap is charged.
11. Replace the heat exchanger.
12. Replace the access panel and tighten the
captive retaining screws.
13. Switch on the mains electrical supply and
check for satisfactory operation.
Fig. 20
Cover
Fig. 21
Heat Exchanger
Filter (optional)