COMBI boiler heating confusion - HELP!

brysonfire

I live in a rented house that has radiator panels, double glazing and good loft insulation BUT am end terrace and have lots of room-side outside walls. It gets VERY cold VERY quickly in my house when the heating is not on.

I'm at work during the day so am only in early morning/evening and at weekends. In our 'normal' winter temperatures, I'm still very much a 'heating on for a couple of hours in the morning and a few hours in the evening' sort of person. I always set my room thermostat no higher than 18C but usually 17-17.5C with the slight overshoot before the thermostat registers. I don't usually make use of TRVs and have my radiators on full - usually because my radiators in the bedrooms are not very big compared to the size of the rooms and they take a long time to heat up the rooms well with all the outside walls.

However, with the recent very cold weather (often -10C) and the fact that I have a young child I'm finding it's no longer possible to only have the heating on just when I'm in as it takes so long to heat up, it's not getting warm enough quick enough. I'm also worried about my pipes freezing if the heating's not on for an extended period (this has happpened to a few people I know), so would rather keep the house constantly comfortable.

So, how can I make it more efficient, while having the heating on constantly until things warm up enough for me to be able to go back to as-and-when-needed use?

How high should I set the radiator temperature on my combi boiler?

How high should the hot water setting be?

I intend to keep the room thermostat no higher than 18c, but should I set this lower during the day when I'm not in and at night OR should I leave the room thermostat and adjust the TRVs instead?

Any help appreciated. I'm sick of constantly fiddling with the controls and then feeling terrible guilt about how much energy I'm using! LOL

neilmcl

If you have a room thermostat and TRVs then its recommended that the boiler CH temp be set quite high, allowing the thermostat to control the heating. Set you hot water to as hot as you're comfortable with. I have mine set to a minimum of 14C at the moment when I'm not in (12C during the night) and around 19C-20C during the evening.

If you do a search there is a lot of debate as to whether keeping your thermostat set at around 17-18C all the time is more efficient but I have my doubts.

khampson

I am in the same boat, I am using another 3000 kwh of gas a month, my outside walls are really cold and even after the heating has been on, the outside rooms still feel cold, my property is also rented, I am not sure what my combination boiler setting temps should be, currently my water is set at 50 degrees and my heating set at 60 degrees, my thermstat is set at 18 degrees and low is 13 degrees

brysonfire

Thanks. I think the biggest confusing factor is what combi boiler radiator setting is classed as high? Mine will go up into the 70s. Is having it set to 60C high enough or does it need to be higher than that? Is there an optimal range?

fred7777

Basically as you have found there are 3 different temperature controls, the Room stat, the central heating water temperature and the thermostatic rad valves each does a different thing and it can be confusing!

The room stat switches the boiler on or off depending on the temperature it "feels", the heating water temperature is simply how hot the heating water is and the thermostatic rad valves reduce the flow of water into a radiator to lower the radiator temperature as the radiator is constantly cooled by the room.

So when you're in the house my advice is:

1. Set the rooms stat to the temperature you want that room to be.

2. If that room is to be the hottest in the house set the TRVs in that room to max and reduce the settings of the other TRVs in other rooms. Otherwise turn the TRV in the room with the room stat down and the others up and get a thermometer for the other rooms.

3. Set the heating water temperature to the lowest setting you can which will still get the house warm.

and when you're not in the house switch the heating off.

As an example in my house:

1. The rad valves are set to max in the lounge where the room stat is and much lower in the other rooms which I don't want as warm.

2. The central heating water temp is currently set at max otherwise the house doesn't get warm enough when its -?°C outside and i'll turn it down again when it gets warmer outside. Unless you have a modern Central heating system with under floor heating or oversize radiators the heating temperature will have to be toward the top of the range to get the house warm.

3. The rooms thermostat has a timer which runs it at 5°C during the day and 25°C in the evening.

brysonfire

FRED - In normal winter temps I would only have my heating on when I'm in. That's the problem. With the recent cold weather, I'm unable to just have my heating on for limited periods as with all my outside walls my house takes too long to warm up from freezing. It's just not comfortable for me or my 3-year old daughter. Plus I'm worried about possible burst pipes.

Also I'm just in a rented house, my landlord has fitted a very basic albeit modern combi boiler. I don't have any sophisticated timeable or boost settings that allow me to fine-tune my heating system depending on the time fo day or day of the week. It's just a basic dial-with-tappets system, so it's either on or off depending on the time. I can't change the temperature for different times of the day. That I have to do by hand on my room thermostat. So, if I set it to be at 13C when I'm out, that will be the temperature I come home to at the end of the day which is not ideal.

fred7777

brysonfire

If there is no timer on the boiler or anywhere else then you've got a bit of a problem.

An older system won't have oversize radiators or underfloor heating which will work with lower temperature central heating water available from newer boilers so you will need to have the central heating water around maximum (which will deliver the temperature water the heating system was set up for).

Also the higher the radiator temp the faster the room will warm up so set the rad valves to max in the room with the thermostat and high in other rooms you want to be warm.

I had a similar simple system in my previous flat where I could turn the thermostat down to around 10°C when I was out (stops freezing) to save money and come home to a cold flat or leave it turned up come home to a warm flat but spend a fortune on gas.:eek:

The solution I found worked well was turn the thermostat down whilst I was out turn it back up when I was in but run a fan heater for the first 5-10 minutes in the lounge of kitchen to warm the air whilst the heating got up to temperature.

The other problem you may have is most Combi boilers don't heat water and heating at the same time. Mine waits three minutes before switching the heat back on after I run the hot tap so running the hot tap in the kitchen sink 4-5 times during 1/2 an hour of cooking could mean 15 minutes of no central heating!

brysonfire

fred - I do have a timer but it's just a dial over 24 hours. It's a dial with tappets, not digital so I can time the heating to come on at different times of the day; I just can't adjust it to come on at different temps depending on the time of day. I suppose the only option I have like you say would be to have it set at say 14C or 15C when I'm out or at night and then turn it back up when I get in. At least then, it never gets too cold and won't take too long to warm up once I turn the thermostat up.

fred7777

how many tappets?

Instead of turning the thermostat up and down could you set it to the temperature you want in the morning and evening, set the timer so it was on when you were in then have it coming on for a couple of short bursts during the day. This would have a similar effect to having it running continuously at a low level.

brysonfire

FRED - It has 15 min tappets. Would doing that save me money? I have tried that already *sigh* I put my heating on for an hour halfway through the day and halfway through the night, then left it set to come on an hour before I returned from work in the evening, but it was still only 12C when I got back and too hours to warm up. It was a very cold day though (didn't get above -5C all day).

It takes so long to heat my house up from cold that I'd have to out my heating on for about 2 hours prior to my returm, not to mention that I'd want it on all evening after that. That's why I'm thinking I might need to turn the temperature on my boile thermostat up so that the radiators warm up quicker. Here I was feeling all proud because I didn't put my heating on till November, and then only for one hour in the morning and 2 hours in the evening. I always wear a jumper first.

It's not as cold tonight so I might just try blasting it for a bit instead.

fred7777

Putting it on for a couple of 15 min times during the day would ensure the system didn't freeze and stop you having to change the thermostat.

If it's taking 2 hours for the house to warm up then the radiator temp is definitely too low.

Heating systems used to be designed for 80°c/60°c where the water came out of the boiler at 80° and returned at around 60° some modern heating systems are designed for 60°/40° where the water comes out of the boiler at 60°c so new boilers have a large temperature range to suit different systems. If you have a new boiler with old radiators the boiler temp should be set high and wouldn't be unusual to set it at max. Try it at max and see how long the house takes to warm up.

Also try setting all the radiator valves to max and see how hot they actually get. Valves can easily stick at closed or partially closed and stop the radiator getting hot and whilst the system was not being used air may have got into it. Check the radiators are hot all over. A radiator which isn't as hot as the rest suggests a valve problem and a radiator which isn't hot all over suggests an airlock (both easy to fix).