Frost-Stat for Heating Boiler - changing froststart temperature

CrazyChemist_2

Hello :santa2:

I have had a central heating system updated with a new boiler, but initially in the cold weather it was on all the time so I had to call the installers back to do something about it. It turned out to be the froststat thermostat next to the boiler in the garage which was set too high. That was activating and explained why the heating was almost always on.

However I noticed that although last night was around -4C, it didn't activate itself so was wondering if I am able to actually check what temperature it will come on at, to prevent pipes freezing/cracking, etc.?

I tried to take the front circular bit off the front of the Frost Stat unit in the garage but it didn't come off and I don't particularly want to break anything just yet!! Basically it's just like a square thermostat you find in the house with a round plastic bit on it except instead of the round rotating dial with temperature marks on it. The only thing is that I'm not sure if it is possible to check this temperature threshold or not so if anyone knows about this I'd really appreciate the advice!

Cheers :snow_grin

CC :beer:

kevc_2

On these frost stats you normally insert a small screwdriver under the round plastic cover to lever it off and underneath a similar dial to the room stat will be found but with lower temperatures on it.If you test on a cold day then you can just turn the stat up till the boiler fires then you know the stat is O.K.

moneysavingplumber

Ideally frost stats should work in conjunction with a pipe stat , thereby only causing the boiler and pump to come on until the common return pipe on the heating has reached the required temperature, otherwise whenever the temperature in the garage is 5 degrees or lower the heating will stay on until it rises naturally (as the garage will only take residual heat from the boiler being on), which is totally unnecessary as it's the water in the boiler that is of concern, assuming the pipe work has been lagged correctly. Usually the front will need to come off of the frost stat to adjust it, and there is live electricity under there, so if in doubt, get an electrician (one with experience of domestic heating controls) in to advise you. They normally have a minimum setting of 5 degrees anyway so it definitely needs checking out by the sounds of it.

CrazyChemist_2

moneysavingplumber wrote:

Ideally frost stats should work in conjunction with a pipe stat , thereby only causing the boiler and pump to come on until the common return pipe on the heating has reached the required temperature, otherwise whenever the temperature in the garage is 5 degrees or lower the heating will stay on until it rises naturally (as the garage will only take residual heat from the boiler being on), which is totally unnecessary as it's the water in the boiler that is of concern, assuming the pipe work has been lagged correctly. Usually the front will need to come off of the frost stat to adjust it, and there is live electricity under there, so if in doubt, get an electrician (one with experience of domestic heating controls) in to advise you. They normally have a minimum setting of 5 degrees anyway so it definitely needs checking out by the sounds of it.

Thanks very much for that! It's a standalone unit which doesn't seem to be attached to any pipework. Previously it used to be on for a lot of the time which is when we called them back to readjust it.

Is there any way to check if it is working in conjunction wish a pipe stat?

moneysavingplumber

Not easily, although any pipe stat would also be in the garage on the return pipe to the boiler. It's possible they fitted one to solve the initial problem.

CrazyChemist_2

Grrrrr they're 'not in the office' till 5th January! :mad: The froststat did kick in this morning and managed to stay on for about 4 hours heating our house up to 25 degrees C!!

I reckon there isn't a pipe stat involved otherwise why would it have stayed on constant for that time even though it is set to be off on the control panel. I'm annoyed about the amount of gas it must be using, and wasting! :mad:

How much would it cost to get a pipe stat fitted to the system?? It may be worth it...

kevc_2

This should not happen as the room stat tells the system/motorised valve to close off the heating side but the heating has to be switched on(live to the motorised valve).Otherwise you possibly have valve which when off rests either heating open or in mid-position.At least your not feeling cold!

moneysavingplumber

A frost stat is usually wired to overide all other controls and (I think!) to open the mid-position or heating zone valve, with a view to circulating heat around the entire system until the return reaches the required temperature (when the pipe stat is fitted), thus protecting the entire property, not just the primary circuits.

moneysavingplumber

CrazyChemist wrote:

How much would it cost to get a pipe stat fitted to the system?? It may be worth it...

Depends on how far the electrician would have to run the cable to the wiring centre, best to get a quote first from someone experienced in these types of controls, not all electricians are that hot on domestic heating controls. The low-limit pipe stat shouldn't be more than £15.

CrazyChemist_2

Thanks again. It happened again today and it felt like Summer in our house I can tell you!! I went into the garage and just turned down the dial from Max to about half way between min and max. It then stopped firing and although the orange light was switched on on the room thermostat in teh house, th eheating did switch off for about 30 mins before powering up again.

It seems stupid to have the whole house heating up indefinitely every time the temperature falls. Could it be a fault with this valve then? I would have asked the nutters who installed it but they're on a 2 week break :rolleyes:

moneysavingplumber

CrazyChemist wrote:

Could it be a fault with this valve then? I would have asked the nutters who installed it but they're on a 2 week break :rolleyes:

No because I'm pretty sure your frost stat will be overriding the room stat and opening the valve, which is why you should have a pipe stat. Honeywell do actually sell a Frost Stat 'kit' that includes both wall and pipe stat.