Connecting A Remote Frost Thermostat - Grant Vortex Series Installation And Servicing Instructions

8.5 CONNECTING A REMOTE
FROST THERMOSTAT
The boiler is fitted with two forms of pre-set internal frost
protection, as follows:
Water temperature:
Should the central heating water temperature (detected by the
flow thermistor) fall to below 8°C this frost protection function will
be activated and will operate as follows to protect the boiler from
freezing:
• The heating circulating pump will run for a period of 15
minutes. If during this time the water temperature exceeds
15°C the pump will stop.
• If after the 15 minutes the temperature is less than 10°C the
burner will fire and continue to do so until the flow thermistor
detects a temperature of 30°C when the burner will stop.
The heating circulating pump will then run for a period of 2
minutes before also stopping.
Air temperature:
Should the air temperature around the boiler fall to below 5°C
this frost protection will be activated and will operate as follows to
protect the boiler from freezing:
• First the heating circulation pump will operate for a period
of 15 minutes. If after that time the air temperature sensed
exceeds 10°C the pump will stop.
• If after the 15 minutes the temperature is less than 10°C the
burner will fire and continue to do so until the flow thermistor
detects a temperature of 30°C when the burner will stop.
The heating circulating pump will then run for a period of 2
minutes before also stopping.
For additional protection of either the entire heating system,
or any exposed parts of the heating system (e.g. if the boiler
is installed in an external boiler house, un-heated garage,
attic or outdoors) a remote frost thermostat can be connected
to the boiler. This will operate in conjunction with the internal
frost protection and, when activated, the boiler will operate as
described at the start of Section 8.5.
This remote frost thermostat should be sited within the house in
such a place that any rise or fall in ambient air temperature can be
detected, i.e. in a room with a radiator.
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To connect a remote frost thermostat (for example, a Danfoss
Randall RET230F), proceed as follows:
1. Remove the boiler door, top casing panel and insulation from
boiler. (Refer to Section 4.7)
2. Remove the two screws at top of control panel (in cross
member). Hinge down control panel front.
3. From rear of control panel, carefully feed the cable from the
Frost thermostat through the upper grommet at the right hand
end of the rear of the control panel.
4. Slacken the upper cable clamp on the inside rear face of the
control panel. Feed the cable through the cable clamp.
5. Connect wires to terminals on control panel as follows:
• Frost thermostat Neutral (N) to terminal 21 on PCB
connector.
• Frost thermostat Live (L) to terminal 24 on PCB
connector.
• Frost thermostat Switched Live-ON (3) to terminal 23 on
PCB connector.
6. Refer to Figure 8-1 for typical connection of Remote Frost
Thermostat.
7. If an alternative Frost thermostat to the Danfoss Randall
RET230F is used, connect it in accordance with the frost
thermostat manufacturer's instructions.
8. Make the remaining required connections to the control
panel, as detailed in this section.
9. Secure the cable clamp.
10. Re-fit control panel front and secure using the two screws.
11. Replace boiler insulation, top panel and front casing door.
! NOTE !
This external frost thermostat will operate in parallel with
the internal frost thermostat.
! NOTE !
For total system protection against freezing, particularly
during extended periods without electrical power, Grant
recommend the use of a combined heating system
antifreeze and corrosion inhibitor, used in accordance with
the manufacturer's instructions.
Section 8: Electrical