Frost Stat Wiring

[Hazzy]

I have just moved into a house thats fitted with a Greenstar 25Si central heating boiler thats about 5 years old. I'd like to fit a frost stat because I'm away for weeks at a time and like to bring the heating on automatically when the temperatures tumble. The diagram for the boiler shows a very simple 2 connection circuit, ha ha thats easy I thought so went out and bought a Tower RFS Frost Stat from my local supplier. But when I opened it up, it has a small circuit and seems to need both live and neutral. T1 is live, T3 and T4 are nuetral connections. T3 shows an M inside a circle. T3 and T4 has a neon lamp across them. Have I bought the wrong stat, or can I still use it ? Advice on how to wire it will be greatly appreciated.

 

[Taylortwocities]

The TFS has an Integral accelerator heater so you'll need 3-core and earth cable to provide
live
neutral and the switched live back to the wiring centre.

 

[Hazzy]

hey thanks TTC, your right about the accelerator heater. But still can't see how to wire the terminals. The boiler has FR and FS allocated for the frost stat so I assume one of them is live (FS ?). With there being only 3 terminals on the stat I can't see how to supply the heater and make the switched return as its showing T3 and T4 as neutral ?

Hangin on !

 

[stem]

T1 is live, T3 and T4 are nuetral connections.

No there aren't 2 neutral connections, T1 is live, T3 is the live return, and T4 is neutral.
Not all frost stats have have an accelerator or lamp that require a neutral, so the Greenstar manual may not show the neutral connection for it.

Based on the information you have given, I would expect at the boiler connections that FS is "frost supply" and FR is "frost return". If so the wiring would be as follows:

FS (frost supply)-----------Live------------- T1
FR (frost return)------Heating Output---- T3

N----------------------------Neutral---------- T4

Frost Stat Wiring

• stem
• 23 Oct 2009
• 1

Terminal T1 is the live supply, when the thermostat calls for heat, it makes T3 live that goes back to the boiler switching it on, and also puts a live on the lamp (x), the other side of which is connected to neutral.