Airflow AIROVENT MEV WH4B Operation manual

80001184 –Issue 1 02/22
Installation / Operation and Service
Guide
MEV WH4B & MEV WH6B
Part No`s: 90001495 & 90001496
Central Mechanical Extract Ventilation
Units
90001495
90001496
Page 1 of 23

Contents
Page 2 of 23
Page Nº Heading
3 Unit Dimensions
4 Unit Specifications
5 Transport and Storage
6 –7 Electrical Installation
8 Wiring Diagram
9 –10 Mechanical Installation
11 –14 Duct Connection
15 –16 Fan Performance Settings
17 Flow / Pressure Graph
18 –19 Service and Maintenance
20 Fan and Packaging Disposal
21 Assorted Accessories
22 –23 Warranty

Overall Unit Dimensions
Page 3 of 23

Unit Specifications
Voltage Required: 230V –50 / 60Hz –1Ph
Three Fan Speed Bands Available:
Band 1(Low) = Two speeds –87 and
123m³/h
Watts= 5 & 8
Band 2 (Medium) = Eight speeds –97 to 234
m³/h
Watts = 6 To 27
Band 3 (High) = Eight speeds –158 to 335
m³/h
Watts = 12 to 71
Weight: 3.5Kg
MEV WH4 = 3 x 125Ø ports from rooms &
1 x 125Ø to outside
MEV WH4B = 6 x 75Ø ports from rooms &
1 x 125Ø to outside
Page 4 of 23

Transport and Storage
Units should be stored in their original packaging in
a dry environment protected from the weather. If
palletised quantities are stored or transported, it is
recommended they are covered to protect against
particulate damage and contamination.
Suitable storage temperatures are between –10ºC
and +40ºC.
Care should be taken when re-packing any unit to
ensure the packaging is suitable for the required
form of transport. Damage due to improper
transportation, storage or installation is not covered
under warranty. Care should be taken when lifting.
Correct lifting techniques / apparatus should be
used when necessary. Dropping or sharp blows to
the fan can cause damage. Any damage to the fan
or packaging should be inspected by a suitably
qualified person or returned to Airflow
Developments Ltd for inspection before use.
Fans should not be lifted or carried by an electrical
lead, if fitted.
Page 5 of 23

Electrical Installation
All electrical installations must be carried out by an
approved electrician in accordance with the latest
IET BS7671 Requirements for Electrical Installation,
Low Voltage Directive 2014/35/EU, Machinery
Directive 89/392/CE or the appropriate regulations
in the country of installation. All fans require a 240V
50/60 Hz single phase supply. Electric circuit to be
used should be isolated before any work is carried
out.
All electrical connections and controls can be found
under the unit’s top protective cover held on with two
large screws. See fig.D page 10. The units electrical
supply cable must be fitted through the cable
retaining path moulded into the unit’s electrical
connection tray. As below.
Page 6 of 23

Electrical Installation contd.
All cables should be suitably retained and
enclosed where necessary to prevent damage
taking place. A 3 x pole lockable isolation switch with
a 3mm contact gap should be used on the mains
supply to the unit.
The unit should be protected by using a 3amp inline
fuse.
Before function testing the fan, ensure the impeller
runs freely. Function testing should be carried out by
switching the fan on for a short time. When the fan is
running, checks should be carried out for: impeller
rotation direction, undue noise or vibration and
power consumption. Immediately switch off the fan
should any problems be found, and contact Airflow
Developments Ltd. Fan motors used are suitable for
continuous running and have a rated duty type S1
(motor is suitable to this duty type and rating at which
the fan may be operated for an unlimited period).
Page 7 of 23

Wiring Diagram
230V –50 / 60Hz –1Ph
Airflow Developments fan speed switch,
Part number 90000541 should be used.
Page 8 of 23
L1 = High Speed
L2 = Medium Speed
L3 = Permanent Live
Page 8 of 23

Mechanical Installation
Mechanical installation should only be carried out
by a competent person. Fans are supplied ready for
installation. Care should be taken when removing
the fan from its packaging. Correct lifting
techniques / apparatus should be used where
necessary. Fans should be inspected for any
damage. If the fan is found to be damaged it should
be returned to the supplier immediately. Fans
should be installed to a sufficiently solid structure
giving adequate support. Fixings supplied with the
unit should be used. Alternatively, Airflow
Developments Rubber mount part number
90001294 (set of four) can be used to help protect
against mechanical noise transmission into the
mounting surface.
Units are mounted by using the 6mm clearance
holes provided in the extract duct connection box.
See fig A –B –C & D page 10.
Units can be mounted at any angle or position.
When mounting ensure there is no distortion to the
fan case.
Page 9 of 23

Mechanical Installation contd.
Air in
Air out
Page 10 of 23

Duct Connection
MEV WH4 (90001495)
This unit has three 125mm diameter ports moulded
on the extract duct connection box. These ports are
sealed off with a blanking membrane. This
membrane is put in place when the duct connection
box is moulded. Care should be taken when
removing the blanking membrane to ensure the
correct port / ports are opened and no excess force
is used which could cause irreputable damage. See
fig A page 10. Failure to remove the whole
membrane could causeexcess system pressure and
noise.
Air is expelled to outsidefrom the unit by the 125mm
diameter open port in the fan mounting case. See
fig.D page 10. If the ducting from this port is installed
vertically a condensation trap should be fitted
(Airflow part number: 90001242).
125mm diameter ridged ducting, or a ridged duct
with at least 90% free surface area of 125mm
diameter duct should be used. This isto keep system
pressures to a minimum.
Page 11 of 23

Duct Connection contd.
MEV WH4 (90001495) cont.
Final connections can be made with a short length
of flexible ducting (Airflow part number: 52641009)
and the correct sealing clamps (Airflow part number:
51849403). The use of excessive amounts of flexible
ducting will result in high system pressures and a
noisy system. Ridged duct connections should be
sealed with a non-hardening sealant (Airflow part
number: 90000356).
MEV WH6B (90001496)
This unit has six ports moulded on the extract duct
box which are designed for Airflow Developments,
AirflexPro Round duct system. This is a highly
efficient, easily fitted, and quiet ducting system. Any
of the six ports that are not being used should be
blanked off byusingthe red caps, (4 off supplied with
the unit). See fig.E page 14.
Page 12 of 23

Duct Connection contd.
When connecting AirflexPro duct to the unit it should
be sealed into the extract duct box port using one of
the soft “O” Ring type seals (6off supplied with the
unit). See fig F. page 14. Each AirflexPro duct being
connected to the unit it should be cut square on its
end and to a length so that it is not under tension
when fitted and able to enter straight into the port by
20 to 30mm. AirflexPro round ducting should be held
in place using the correct clips (Airflow part number:
90000352). A soft “O” Ring should then be
positioned in the first full groove of the duct. See fig
G page 14. When this is done, use gentle pressure
to push the duct, with seal attached, into the relevant
port. See fig H page 14. This is a floating fit;
therefore, the seal may move around when carrying
out this process. This type of sealing will tolerate a
slight angle of the duct to the port and still maintain
the seal. See fig I page 14.
Air is expelled to outside from the unit by the 125mm
diameter open port in the fan mounting case. See
fig.D page 10. If the ducting from this port is installed
vertically a condensation trap should be fitted
Page 13 of 23

Duct Connection contd.
(Number: 90001242). Ridged duct should be used
wherever possible, as previously stated for the MEV
WH4 unit.
Fig.E
Fig.F
Fig. I
Fig. G
Fig. H
Page 14 of 23

Fan Performance Settings
The airflow requirements of a dwelling should be
calculated and conform to Building Regulations Part
F, Volume 1.
The performance of the unit is broken down into
three bands, low, medium, and high. Each band has
a number of fan speeds, which can be set by
adjusting the dip-switch settings. The dip-switch can
be found under the unit’s top protective cover held
on with two large screws. See fig D page 10. Choice
of appropriate band speed the fan runs at is by using
a three-position switch (Airflow part number:
90000541). See page 8 –Wiring Diagram.
Picture of dip-switch
Page 15 of 23

Fan Performance Settings contd.
Page 16 of 23

Flow / Pressure Graph
Service and Maintenance
Page 17 of 23

Safety first: Always isolate the fan unit from the
power supply before carrying out any work on
the fan. All electrical and mechanical installation
guidelines stated in these instructions should be
followed. Only competent qualified persons should
embark on service and maintenance of these fan
units.
All central extract systems should be serviced on a
planned / regular basis to stop excess build-up of
dirt, grease, and dust etc. The system should be
inspected initially by a competent person on a six-
monthly basis. After several inspections the
competent person will be able to adjust the
frequency of the service to suite. The frequency of
service will be dependent on a number of things,
lifestyle and where the property is positioned etc.
Failure to do so causes excess system pressure
which will reduce the systems airflow, make the
system noisier and ultimately lead to fan unit failure.
Cleaning the fan unit can be achieved by firstly
disconnecting the duct from the fan mounting case.
Page 18 of 23

Service and Maintenance Contd.
When complete - turn the fan mounting case anti-
clockwise 45º (leaving the extract duct connection
box in its fixed position). See fig C. Cleaning of fan
units’ parts should be carried out with a damp cloth
or soft brush.
The use of aggressive cleaning agents or high-
pressure cleaning techniques / equipment is not
recommended and can cause permanent damage
and loss of fan performance.
Things to check when the unit is split in two: Is the
extract duct connection box securely fixed. Does the
fan impeller rotate freely and quietly? Is there any
visible damage? When the service is complete, refit
the fan mounting case to the extract duct connection
box and the duct to the fan mounting case carrying
the exhaust air. After re-connecting the electrical
supply, the unit should be switched on. If there is any
undue noise switch the unit off immediately and
rectify the fault. If the fault cannot be found contact
Airflow Developments Ltd for advice at
[email protected]m. Tele:[phone].
Page 19 of 23

Fan and Packaging Disposal
These fan units consist mainly of steel, iron,
aluminium, copper, electrical insulation materials,
cables, wires, and plastic.
Complete fans and parts that are at end of life due
to wear and tear, corrosion, fatigue and or other
effects that can not be discerned must be disposed
of in the correct manner conforming to local and / or
international guidelines and regulations. Intended or
unintended further use of worn parts, e.g., impellers
and bearings etc. can result in danger to persons,
the environment and fan unit.
Packaging materials should be disposed of in the
correct manner conforming to local and / or
international guidelines and regulations. Some
packaging can be re-cycled. In this case seek
advice from a qualified waste management
company.
Page 20 of 23