12 Special requirements for R32 units
Installation and operation manual
17
BS4~12A14AJV1B
VRV 5 branch selector unit
4P670163-1 – 2022.02
The information in the table below must be taken into account in
case a ventilated enclosure is used as a safety measure:
Ductwork
The evacuation ductwork MUST vent outside the
building.
Avoid that dirt, dust and small animals can enter
the ductwork and lead to an obstruction.
Example:
Install a non-return valve, grill, filter or other
component in the evacuation duct.
Extraction fan
The extraction fan must have a CE marking and
can not act as an ignition source during normal
operation.
Example:
Brushed DC motors cause
sparks and are not allowed.
Fan power must be lower than 2.5 kVA.
Replacement
air
Make sure that sufficient replacement air is
available for the extraction of a refrigerant leak.
The extraction airflow rate must be maintained for
at least 6.5 hours. This is achieved by providing a
sufficiently large air volume around the BS unit or
by providing sufficient replacement air around the
BS unit (e.g. natural openings or a dedicated
opening in the false ceiling).
Maintenance
A periodic inspection of the unit is required, where
the test run is repeated (see
Maintain the evacuation channel to avoid dust and
dirt from building up and obstructing the flow path
(see
"6.2 Periodic check of the ventilated
11]).
One BS unit – one extraction fan
In the most simple configuration, each BS unit in the system has its
own evacuation channel and its own extraction fan.
a
b
c
a
BS unit
b
Ductwork
c
Extraction fan
An extraction fan must be connected to the BS unit, see
In order to size the fan, a calculation has to be performed to find the
pressure capacity required. The total pressure drop in the
evacuation channel consists of multiple parts: the pressure drop
generated by the BS unit and the pressure drop generated by the
components of the ductwork.
Select an airflow rate for the evacuation that meets the legal
requirements. This means that the airflow rate is above the legally
required minimum, and generates sufficient pressure difference
inside the BS unit, when compared with the pressure of the
surroundings. The minimum required airflow rate (AFR
OUT
) is
18.8 m³/h, and the pressure drop generated by the BS unit should
lead to a pressure inside the BS unit (P
internal
) that is more than 20 Pa
below the pressure of the surroundings.
a
P
internal
AFR
OUT
a
BS unit
AFR
OUT
Airflow
P
internal
Internal pressure
It is advised to take a safety margin on these minimum values when
designing the evacuation channel in order to account for tolerances
on parts, dirt and dust building up in the evacuation channel over
time, etc.
Note:
The internal pressure of the BS unit should not be more than
350 Pa below the pressure of the surroundings.
With the selected airflow rate, note down the pressure drop
generated by all the components in the evacuation channel. For the
BS unit this means using the curve that gives the pressure at the
outlet (P
OUT
) in function of the airflow rate (AFR
OUT
). To find the
pressure drop curves of the BS unit, see the latest version of the
technical engineering data.
a
P
OUT
AFR
OUT
a
BS unit
AFR
OUT
Airflow
P
OUT
Outlet pressure
For the pressure drop caused by other components of the
evacuation channel (ducts, bends, etc.), use the curves of the
manufacturer.
Use the airflow rate and the sum of the pressure drops to select a
suitable fan.
Example
a
b
d
f
g
i
h
e
c
a
BS unit
b~h
Ductwork (duct, bend, reducer, expander, non-return
valve, wall grill, etc.)
i
Extraction fan
In this example we use a BS12A unit. Use the curve of the internal
pressure inside the BS unit (P
internal
) in function of the airflow rate
(AFR
OUT
). When an airflow rate of 115 m³/h is selected, the pressure
inside the BS unit is 42.9 Pa below the pressure of the surroundings.
So this airflow rate is above the required 18.8 m³/h, as well as the
pressure inside the BS unit is within the range of 20~350 Pa below
the pressure of the surroundings. We use this 115 m³/h airflow rate
for further calculations.
- 42.9
115
P
INTERNAL
[Pa]
-300
-250
-200
-150
-100
0
0
50
100
150
200
250
300
-50
AFR
OUT
[m³/h]
Note:
These curves are plotting the internal pressure of the BS unit
compared to an ambient pressure of 101325 Pa.
Use the curve of the outlet pressure (P
OUT
) in function of the airflow
rate (AFR
OUT
) for the BS unit. With an airflow rate of 115 m³/h, the
resulting pressure drop generated by the BS unit is 47.5 Pa.
-300
-250
-200
-150
-100
0
0
50
100
150
200
250
300
-50
P
OUT
[Pa]
AFR
OUT
[m³/h]
- 47.5
115
