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8.4 Mains Supply Cable
All Grant Aerona Heat Pumps contain a
3kW immersion element as a boost
heat source. This element will energise
under either one or two conditions :
1. When the external ambient air
temperature drops between -5ºC
and +5ºC. This figure is variable and
adjustable at the ATC.
2. When the heat pump has not seen
a temperature rise of 1ºC or more in
the Return water from the heating
system, in a 20 minute period.
The cable sizing to the heat pump
must include for this additional 3kW
load.
For Bivalent systems where a Gas,
Oil or Wood Pellet boiler is switched
from the heat pump the immersion
heater is disconnected. Refer to
Section 8.8.
If the boiler is to be used with the
3kW immersion heater still
connected, the additional load must
be taken into account and the
maximum demand must be
determined for each heat pump.
8.5 Voltage Drop
Where a weak power supply is
encountered (usually in rural locations),
the starting current on any compressor
may result in a significant drop in
voltage. This voltage drop will reduce
the starting torque of the compressor.
This could affect the whole of the
electrical installation in the property by
reducing the voltage to the lighting
circuit, ring circuit, etc. This reduction
would last typically for 300 to 400
milliseconds and could cause lights to
dim. This voltage drop is caused by
inadequate power supplies and does
not signify a fault with the heat
pump.
Always assume maximum possible
load when considering cable sizing.
The cable supplying power from the
consumer unit to the heat pump must
be connected via an external 2 pole
isolator. This allows the service engineer
to isolate the power supply before
working on the heat pump in safety.
Electrical installation requirements
Heat
Max. Running
Pump
Current
Rating
Model
(A)*
(A)
HPAW65
23
32
HPAW85
27
32
HPAW110
28
32
HPAW130
30
40
HPAW155
36
40
*Includes 3kW immersion heater.
Heat
Max. Running
Pump
Current
Rating
Model
(A)*
(A)
HPAW130
43
50
HPAW155
49
63
*Includes 6kW immersion heater.
IMPORTANT
The above tables of cable sizes are based on the following:
1. Cable is surface mounted (clipped to masonry) - Method C as Table
4A2 of BS7671:2008 (17th edition Wiring Regs). For any other cable
installation method the cable size MUST be recalculated in
accordance with BS7671:2008.
2. Earth loop impedence value does not exceed 0.36Ω for a type
D MCB.
Red
Figure 8-6: Mains supply cable connections
MCB
Length of Cable Run (m)
Type
and Cable Size (mm
5
10
D
6
6
D
6
6
D
6
6
D
10
10
D
10
10
MCB
Length of Cable Run (m)
Type
and Cable Size (mm
5
10
D
10
10
D
10
10
Blue
Earth
2
)
15
20
30
6
6
6
6
6
6
6
6
6
10
10
10
10
10
10
2
)
15
20
30
10
10
10
10
10
10
19
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