Grant Products HPAW155 - Manual (Page 31)

Domestic Hot W
a
ter
27
NB. Setting this override switch to OFF
does not stop the automatic operation
of the immersion element.
The required relay, manual override
switch and enclosure are available from
Grant Engineering UK Ltd as a kit. For
details of this Automatic Domestic Hot
Water Boost Kit (Grant Ref.
HPDHWBK1) refer to Section 15 of
these instructions.
When fitted, this kit interrupts the
electrical supply between the existing
immersion heater and the fused
immersion switch. Refer to Figures 9-1
and 9-2 for electrical connection details.
With the cylinder thermostat set to
45°C, when the heat pump raises the
DHW cylinder to this temperature, the
cylinder thermostat switches to the
‘satisfied’ position. The resulting
switched live from the auxiliary (normally
open) contact of the cylinder thermostat
operates the relay in the booster kit and
energises the existing immersion
element in the cylinder, controller and
protected by its internal thermostat and
limit thermostat.
The immersion heater thermostat
should be set to 60°C
When hot water is drawn off, if the
temperature falls below 45°C the
cylinder thermostat will detect the drop
in cylinder temperature, creating a
demand for the heat pump to operate
to re-heat the cylinder. The switched
live to the boost kit relay will cease and
the immersion element is de-energised.
If the temperature detected by the
cylinder thermostat does not fall to
45°C the immersion element will
continue to operate, via the relay, to
re-heat the cylinder.
Supply from cylinder
thermostat auxiliary contact
Immersion
element
Fused
Immersion
switch
NB:
No connection to
Load N terminal is
required
L
Supply
Load
N
L
N
Relay Override
switch
A1 A2
L N
L N
L1 T2
Figure 9-3: DHW booster kit with cover removed to show relay
Figure 9-2: Connection of immersion element using DHW booster kit
IMPORTANT
This domestic hot water
booster pack is optional and is
only used if the customer
wants the most efficient form
of heating their hot water. If
not, then the BTC can be
programmed to deliver hot
water up to 60ºC with no
additional wiring.
IMPORTANT
For this system to operate the
existing immersion switch must
be left set permanently to ON.
To totally prevent operation of
the immersion element the
existing immersion switch must
be set to OFF.
Earth connections
between fused immersion
switch, override switch
and immersion element
not shown.
Two separate power supplies are
connected to the DHW boost kit. Do
not install or work on this kit, or
remove the switch or cover, without
ensuring that BOTH supplies are
isolated.
! WARNING