5.3 immErSion HEAtEr SAfEtY
cUt-oUt
The immersion heater incorporates an in independent non self-
resetting over temperature cut-out device to prevent excessive
water temperatures.
In normal operation the reset pin positioned to the side of the
control knob and indicated by a triangle (with the word ‘safety’
below) will be approximately 2-3mm below the upper surface of
the thermostat cap.
Should the over temperature cut-out operate, the reset pin will be
pushed upwards to become level or slightly above the cover.
Wait until the temperature has fallen sufficiently. Then Investigate
and identify the cause of the cut-out operation and rectify the fault.
Then manually reset the cut-out by pressing in the reset pin to its
normal operating position using hand pressure only with a suitably
sized implement.
! cAUtion
!
Before removing the immersion heater covers to either
reset the safety cut-out or check/alter the thermostat
setting, ensure that the electrical supply is isolated.
Ensure the cover to the immersion heater cover is replaced
correctly and the retaining nut is fitted. Finally switch the mains
electricity supply back on.
5.4 dUAL tHErmoStAt
This is a combined cylinder control and high limit (overheat)
thermostat supplied with every Grant MonoWave cylinder with
buffer, to control the operation of the heat pump primary coil.
The cylinder control thermostat has an adjustment range between
25°C and 65°C. It is recommended that it is set to 60°C. The high
limit (overheat) thermostat will automatically operate at 90°C.
PrE-PLUmBEd cYLindErS
The Dual Thermostat is supplied factory fitted and connected to
the wiring centre on the cylinder. For details on the correct wiring
connections, refer to Figures 5-2, 5-3 or 5-6, as appropriate.
StAndArd cYLindErS
The Dual Thermostat is supplied separately in the unvented hot
water safety kit. It should be fitted into the stainless steel sensor
pocket in the cylinder and secured in place using the retaining
screws on the thermostat housing. Refer to Figures 2-3 or 2-4 for
sensor pocket position.
For details on the correct wiring connections, refer to Figures 5-4,
5-5 or 5-7, as appropriate.
5.5 2-Port VALVES
To comply with the regulations governing the installation of
indirect unvented hot water cylinders, a 2-port motorised valve
must be fitted in the primary flow to prevent gravity circulation
when the boiler switches off.
This acts as a positive energy cut-out should the high limit
(overheat) thermostat (in the dual thermostat) operate. If this
happens, the 2-port zone valve will operate and shut off the
primary flow to the cylinder.
When installed as part of an “S-plan” type of heating control
system, this motorised valve will also control the temperature of
the domestic stored water via the cylinder control thermostat,
(located in the dual thermostat).
This valve should be wired in accordance with the wiring diagrams
(Figures 5-2 to 5-7 as appropriate), to comply with current
legislation.
For other makes of air source heat pump, other than the Grant
Aerona³, consult the heat pump manufacturer for electrical
connection details.
5.6 PrE-PLUmBEd cYLindEr
WirinG
The Grant MonoWave ‘pre-plumbed’ HP cylinder with Buffer is
supplied with three factory-fitted 2-port zone valves, as follows:
•
2 x 2-port zone valves for space heating (for two separate
heating zones)
•
1 x 2-port zone valve for hot water heating
These are pre-wired to the factory-fitted wiring centre mounted on
the cylinder.
To independently control these three zones valves (two space
heating zones and one hot water zone) a three-channel
programmer will be required, with a room thermostat in each of
the two heating zones.
if the cylinder is to be used with a Grant Aerona³ air source
heat pump:
Refer to the wiring diagram Figure 5-2 or 5-3 as appropriate,
depending on whether the buffer or volumiser option is being
used.
A Grant EP002 heat pump interface box (supplied with the
cylinder) MUST be used to provide the voltage free switching for
the Aerona³ air source heat pump, as shown in Figure 5-2 and
5-3.
Refer to Section 5.8 for further details on the Grant EP002 heat
pump interface box.
if the cylinder is connected to a boiler:
Refer to the wiring diagram Figure 5-6. The Grant EP002 heat
pump interface box is NOT required in this case.
5.7 StAndArd cYLindEr WirinG
The Grant MonoWave ‘standard’ HP cylinder with Buffer is
supplied with a single 2-port zone valve is supplied separately in
the unvented hot water safety kit.
This valve MUST be fitted in the primary flow pipe to the cylinder
coil. It MUST be wired in accordance with the wiring appropriate
wiring diagram as detailed below.
if the cylinder is to be used with a Grant Aerona³ air source
heat pump:
Refer to the wiring diagrams Figure 5-4 or 5-5, depending on
whether the buffer or volumiser option is being used.
A Grant EP002 heat pump interface box (supplied with the
cylinder) will be required to provide the voltage free switching for
the Aerona³ air source heat pump, as shown in Figure 5-4 and
5-5.
Refer to Section 5.8 for further details on the Grant EP002 heat
pump interface box.
if the cylinder is connected to a boiler:
Refer to the wiring diagram Figure 5-7. The Grant EP002 heat
pump interface box is NOT required in this case.
5.8 HEAt PUmP intErfAcE Box
The Grant EP002 heat pump interface box (supplied with the
cylinder) designed to provide the voltage free switching for the
Aerona³ air source heat pump, using the space heating and hot
water switched live outputs from the control system wiring centre.
This box can be installed next to the heating system wiring centre.
Alternatively, it can be located nearer to the Aerona³ heat pump,
but NOT be installed externally.
This interface box is NOT required when the cylinder is used with
a Grant oil boiler.
Section 5: Electrical
Page 19