Combi boiler frost stat...help !!!

webrits

We're in a dilemma with our combi-boiler / frost stat.
Basically, we've only been in the house a few months and the previous owners installed combi central heating in what was the outside WC outbuilding (lean-to). It's fitted with a frost stat (also in this outhouse). The problem is, the frost stat turns on the heating throughout the house whenever the temperature in the outhouse drops below a preset temp (~5°C) to prevent the boiler from freezing. As the only heat in the outhouse comes from the boiler itself, it can take an age for the stat to reach the temp to turn the heating off and therefore we have BIG gas bills. The heating also comes on when we are at work etc, even though the programmable stat in the house is set to "OFF". This is because the frost stat will overide any other stat to prevent freezing. Anyone know what the best remedy is?
We don't want to disable the stat in case the boiler freezes. (Not good!)
We 'could' turn off all the radiators in the house so the boiler is doing less work (pain in the ***).
Insulating the outhouse so it doesn't get as cold? Or my favorite... Installing a small radiator in the outhouse, so that when the heating comes on it should only take several minutes to be warm enough the knock the stat off again....

Any ideas or help on this greatly appreciated........

Thanks
Paul

beefster

Put an alternative heat source in the outhouse. A small electric heater working off a frost stat will suffice..... bit risky letting it go as low as minus 5et it nearer zero.
We use tubular heaters at our football club to prevent the showers freezing up. You will need a control box as the frost stat will probably not be rated high enough for the heater. I built one but they are probably commercially avialable. basically a slave contactor will be needed. IE the frost sta operates the contactor that feeds the heater. You should be able to feed the whole lot from a fused spur outlet rated at 13 amps. Its not as difficult as it sounds but get an electrician to do it for you to be covered by the new Part p legislation.

Tubular heaters are available via screwfix at less than £20 each

jos22

Think about an electric greenhouse heater available from DIY store. Has a thermostat built in.

webrits

Thanks for the repllies, I'll look out for a tubular / greenhouse heater.
BTW When I put ~5°c, the ~ meant "in the region of" not a minus (-) sign. Sorry for the confusion.

Are these greenhouse heaters cheap to run?

jennifernil

You can buy a pipe stat that you fix to the return to the boiler. This measures the returning water temperature and will turn off the boiler once the water temp reaches what you have set. This overrides the frost stat. We have one in our Guide Hall, but , sorry, I can't remember the make. It is specifically designed to be used in situations like yours.

roswell

I would go with insulating the outhouse as you must be loosing heat from it anyway, you can get insulation boards for around £15 for 20M2 that you just need to glue to the walls Plaster board over if you dont like the look of them :-) (Think its called dry walling ?? )

I think there equivilant to 65mm polystyrene we used them under our wood flooring and they work great.

Nile

Hello jos22


Welcome to the MSE site.:wave:

ariba10

webrits wrote:

Are these greenhouse heaters cheap to run?

You can leave them on all the year and they will only switch on when the air temp falls below what you have set it at and when the boiler is working in the cold weather the boiler room will be warm anyway.