What is the correct setting for a frost stat?

[patagonia]

We have a frost stat on the garage wall just above the boiler, which is a Potterton Prima. It is set to -9 degrees C. My son in law says it should be above 0 degrees. Can anyone tell me what is the correct setting? Also, if the frost stat does turn on the boiler, will it also circulate the hot water round the heating system if the progammer is switched off? There is no room stat anywhere, just thermostatic rad. valves.

 

[Rico99]

Hi there,

I think it should be set at around 5c and yes it will circultae the water even if programmer is set to off.

Rico

 

[ColJack]

frost stats should be set at between +5°C and +10°C.. ( depending on the differential of the stat.. )..

 

[patagonia]

Many thanks to both. I will turn it up.

 

[D_Hailsham]

I don't know of any frost stats which have negative temperatures. Which make frost stat do you have?

You should also have a pipe stat.

The frost stat turns the boiler on when the temperature drops to the set temperature (about 5-10C). The pipe stat then turns the boiler off when the temperature has risen enough (about 15-20C). If you don't have the pipe stat, the boiler temperature will continue rising until the boiler stat turns it off. You will then find that the rads and/or cylinder will heat up.

 

[patagonia]

It's a Sunvic stat; no pipe stat so far as I can see. No instructions left by previous owners.

 

[D_Hailsham]

It's a Sunvic stat; no pipe stat so far as I can see. No instructions left by previous owners.

OK. Sunvics are the exception, they do go negative!

You might get away without a pipe stat, it all depends on how much the frost stat raises the temperature before the boiler turns off.

You can find this out by finding the temperatures at which it clicks on and off. Provided they are not too far apart (e.g On at 5C, Off at 10-15C) yu should be OK.

The pipe stat is a belt and braces, in case the frost stat sticks on.

 

[patagonia]

Thanks. Will try to keep an eye on it, though as we need it on all day at present it will be difficult to assess. We were snowbound away from home for 3 nights unexpectedly (had turned everything off) and are relieved to find no burst pipes which had been worrying me. Presumably, at the setting it was at it hadn't fired at all while we were away. Certainly the house was icy and is taking a long time to get to comfort heat. What is the correct setting for a boiler? Years ago an architect told us that it was most efficient to run the boiler at 180 degrees F., letting the roomstat and rad. stats control the room temperatures, and at that time our boiler was marked in degrees. However, this boiler only has numbers and I don't know what temperatures they are supposed to represent.

We also have a gas fire which we turned on as soon as we got home. However, sitting close to it I was aware of a very cold draught round my ankles and found this was coming from an airbrick (approx. 6 " x 6") located behind the radiator cabinet which is a lot larger than the radiator. I presume this is required for the gas fire but it rather defeats the object. An icy gale was coming in through it. Would it be unsafe to block off some of the louvres with a bit of cardboard? How much incoming air does a gas fire really need?

I am tempted to leave the heating on all night. Does anyone know the comparative economics of doing so, as opposed to turning it off at bedtime and starting from a low temperature in the morning? It would certainly be more comfortable to do the former as some of the rads seem rather undersized. We have recently added another couple of radiator cabinets. Should one set the rad. stats. higher, e.g. at 5? The valves are not easily accessible for adjustment; it means lifting the cover right off. 4 would normally be an acceptable room temperature but there seemed to be little heat coming out today on that setting.

 

[D_Hailsham]

What is the correct setting for a boiler? Years ago an architect told us that it was most efficient to run the boiler at 180 degrees F., letting the roomstat and rad. stats control the room temperatures, and at that time our boiler was marked in degrees. However, this boiler only has numbers and I don't know what temperatures they are supposed to represent.

The architect was right. Just set your boiler to the highest setting, which is 82C (about 180F) and leave the room stat to control everything.

We also have a gas fire which we turned on as soon as we got home. ... How much incoming air does a gas fire really need?

A gas fire uses more air than you realize. If you know what the output, it is possible to calculate the size of air vent is. Otherwise, leave well alone. If the fire does not get enough oxygen it produces carbon monoxide ... RIP!

I am tempted to leave the heating on all night. Does anyone know the comparative economics of doing so, as opposed to turning it off at bedtime and starting from a low temperature in the morning?

It all depends on how much heat is lost overnight and how quickly it heats up. All you can do is experiment. Do 24 hours set on continually then 24 hours with it off at night. Take gas meter readings at start and end of each period and compare.

Also, instead of turning right off at night, why not set it to a lower overnight temperature, e.g 15 degrees. Depending on how quickly the house cools down, the boiler will either stay off or come on. You could even experiment with this for 24 hours.

Having bedrooms at 20 or 21C is not a good idea.

It would certainly be more comfortable to do the former as some of the rads seem rather undersized. We have recently added another couple of radiator cabinets. Should one set the rad. stats. higher, e.g. at 5? The valves are not easily accessible for adjustment; it means lifting the cover right off. 4 would normally be an acceptable room temperature but there seemed to be little heat coming out today on that setting.

There is no point adding more radiators than the boiler can handle. If you have a 15kW boiler, all you can have is a total of 15kW radiators. If you add any more, each one will give off less heat, so the output still totals 15kW.

Setting the TRV to 5 instead of 4 should mean a warmer room. If you have to set it to 5 to give a temperature of about 20C, the radiator is either undersized or not giving off the correct amount of heat.

It would be a good idea to use the EST online boiler calculator to find out what size boiler your house needs; and to use the info in the Stelrad Elite Catalogue to find out the total KW output of your rads.

Which model Potterton Prima do you have?

 

[kirkgas]

[q
A gas fire uses more air than you realize. If you know what the output, it is possible to calculate the size of air vent is. Otherwise, leave well alone. If the fire does not get enough oxygen it produces carbon monoxide ... RIP!

i'm sure it is a typo from DH, but just in case, can i clarify that we use INPUT of the fire to calculate ventilation requirement

 

[patagonia]

Many thanks for taking so much trouble to answer my queries. I am afraid I don't know the output of our Prima boiler. It's in the garage and I shall have to get some tall steps tomorrow and see if I can find a model number. As I mentioned before, there is no room stat to turn down at night; I could only turn down the rad. stats which involves taking off the covers in most cases, although I could turn down bedroom and bathroom as there are no cabinets there. I'll turn up the boiler tomorrow if I can get at it (in my seventies and not too agile) and experiment as you suggest. Actually, it's all rather more complicated than I have so far explained. We have a bungalow which was extended around l5 yrs ago and is now quite large. I don't know whether it was for simplicity or as an insurance against total breakdown, but our predecessors here had a completely new system (small bore pipes) with another boiler and a second h.w. cylinder put in the new bit. The older part of the house has a Worcester Bosch boiler in the loft at that end and is the normal sized pipework. Again I don't know how high the boiler is set or what the output is; will get up into the loft tomorrow to find out. There was no rad. in the hall so we had one put in when we moved in but it doesn't seem to be making much impression, though I have turned up the rad stat to max. and I note that the return pipe is not very hot; I can easily keep my hand on it. I could open the lockshield valve a bit but maybe I should turn the boiler up first. There is a roomstat in the hall at that end but the temperature, after switching the heating on at about 11.30 this mornng when we got back home, hasn't reached anything like 20 and it's now nearly 11pm. I don't think that can be lack of boiler power as the rad stats in the rooms down that end are turned quite low as we are not using them on a regular basis, apart from a bathroom, also not very warm, and the hall, and the kitchen has no heating as the kickspace heater didn't work and has been disconnected. Another problem to solve.

The house seems to cool off quite quickly. I don't think the wall insulation requirements were very high l5 yrs ago and there is nothing one can do ti improve that. However, I have been waiting for some months for a firm to come to top up the loft insulation which is only about 3 inches.

I can't see the point in gas fires if they have to let in so much cold air. Maybe I'll block the vent and use an elec. fire instead if we can't manage with just the rads. I presume the same applies to gas cookers; we have another freezing gale coming in there but I have to light the ovens to warm up the kitchen till I can get some heating sorted out there which won't be this winter.

I don't know why heating engineers don't set the boilers and frost stats at the optimum setting. IIRC the instructions for the new boiler we had in our previous house didn't spell out what it should be set at so one is in their hands.

I'll try to follow up your refs. and do some calculations, which will take me some time. Again, many thanks.

 

[D_Hailsham]

As I mentioned before, there is no room stat to turn down at night; I could only turn down the rad. stats which involves taking off the covers in most cases, although I could turn down bedroom and bathroom as there are no cabinets there.

A room thermostat would be a good idea.

I'll turn up the boiler tomorrow if I can get at it (in my seventies and not too agile) and experiment as you suggest.

There are much younger people than you who have posted problems on here who give up before you. I seem to remember your name from previous posts - always had a go.

The house seems to cool off quite quickly. I don't think the wall insulation requirements were very high 15 yrs ago and there is nothing one can do to improve that. However, I have been waiting for some months for a firm to come to top up the loft insulation which is only about 3 inches.

The 15 year old extension will have cavity walls, so you would be able to have it cavity insulated. What about the rest of the house - are they cavity walls? If so they can also be insulated.

Did you know that all people over 70 can get free loft and cavity insulation from a government scheme?

I can't see the point in gas fires if they have to let in so much cold air. Maybe I'll block the vent and use an elec. fire instead if we can't manage with just the rads. I presume the same applies to gas cookers; we have another freezing gale coming in there but I have to light the ovens to warm up the kitchen till I can get some heating sorted out there which won't be this winter.

You certainly need to get the rads sorted out.

Gas cookers are slightly different as they are not normally running all the time and are a lower output than a gas fire. If you are using the oven to warm up the kitchen, make sure there is some ventilation.

 

[patagonia]

Thanks for reply. I thought I had typed a response a week ago but it doesn't seem to be here, which is why I haven't had a reply to my latest question. The house has warmed up nicely, apart from the kitchen area, having turned up the boilers, though we found one boiler didn't come on when we turned the programmer on one morning so we had to go into the garage and press a button which got it going again. Don't know what caused that.

So far as insulation is concerned, the old part of the house is up to current standards, having had insulation pumped into the walls and the loft topped up some years ago. The newer bit has some short of sheet insulation in the walls which wouldn't be as good as currently required but can't be added to. I tried to get Warmfront and various others to top up the lofts in the new bit on the free to the elderly scheme but they wouldn't do it because half the house had already been done. Finally Tesco surveyed it and agreed to top of and insulate the pipes for free but that was many weeks ago and I am still waiting. I shall have to chase them.

My latest query is re Lifestyle thermostatic rad valves, which I don't think can be very good quality. Now the weather is warmer and things have warmed up, we would like to be able to turn them down as I see it is 75 degrees tonight but the accessible ones don't seem to be working and stay hot even when turned low or off. I presume the pins have stuck. Could you, or someone else, please remind me whether you should have the valve set to max or off before taking off the head? I have fixed a stuck Satchwell valve in our other house but the Lifestyle is different though I presume the principle is the same.

I shall certainly get a roomstat before next Winter, or now if it can be fitted without the heating being off too long and if I can get anybody to do it. I was thinking of a wireless one to avoid spoiling decorations. As mentioned before, the programmer at that end of the house is only working on manual anyway so perhaps I can get something which would serve both purposes. Are there any snags with these?