Heating on/off or just on?

katgirlie

I currently rent a small flat in a large converted Victorian house. At the back of the flat we have double glazed patio doors leading to a double glazed conservatory. At the front (north-facing) is a large, single-glazed bay window. We have gas central heating and a combi boiler but no thermostat, so at the moment we control the temperature by having the radiators on full blast and to come on and off for short spells throughout the day and night - often for just 15 mins at a time. This seems to keep us cosy enough, albeit with a little fluctuation, and we are quite happy to snuggle up with a blanket in the evening. The flat is also warmed quickly by the sun coming through the conservatory (or the rare occasion we see the sun these days!!), or having the oven on for any longer than half an hour.
We do have a bit of a condensation problem on the front window, which has caused mould on the lining of the curtains. When I'm home during the day and it's not raining I open the sash windows for a couple of hours and this clears it, but it isn't always possible, and I'm not always home during the day.

(Sorry this is turning out so long!!)

My question is, is it better to have the radiatiors on 24 hours a day on a low setting, or have them come on for a short time, blast the heat out and then turn off for a while? Which would be cheaper to run throughout the winter? Would having constant heat have any effect on the condensation problem? I know with hot water tanks it's better and cheaper to have it on continuously, but I was under the impression that this wasn't the case with a combi boiler, and that coming on and off wasn't too expensive, until someone suggested otherwise to me recently.

Any helpful advice would be gratefully received!

jennifernil

You say you have no thermostat, but also talk of having the radiators on "on a low setting".

Could you explain how you would do this? Just to get a better picture of what controls you do have.

The single glazed window will attract the condensation as it is the coldest surface. To reduce condensation you need to reduce the moisture in the air, either by not creating as much moisture or by removing it via an extractor or a dehumidifier.

More ventilation and a more even warmth will help too.

The type of boiler (combi or conventional) will not affect the CH costs, but lack of controls will. It is also more expensive to run the heating all the time than just to heat when you need to.

katgirlie

Thanks Jennifer. The radiators have their own dials to control how hot they are but we don't have a thermostat on the wall anywhere in the flat to switch on/off the heating when the ambient temperature drops above/below a certain level. So if the heating is on at the boiler and the radiators are on full the flat will just get hotter and hotter until we turn it off again!

I realise that the condensation is caused by moisture in the air, and we do run the extractors in the bathroom and kitchen when in use, and ventilate as much/often as possible. I was just wondering whether the heating being more constant rather than fluctuating throughout the day and night might reduce the problem. But not if it will cost me lots more on my heating bills!

macman

It is a ventilation problem, not a heating one. More heating just masks the problem, because warmer air holds more moisture than cooler air.
A wireless room 'stat or (preferably) programmer is an easy addition.

katgirlie

Thank you for your reply macman. I wasn't just asking about the condensation though, I realise I can't fix it just by turning the heating up. Whether it might reduce it was more of an aside, although I realise now that it didn't come across that way in my original post. It was more about whether in general it's better to have the heating on low all the time or on full every now and again in terms of heating the flat and keeping costs down. Does it cost more to fire up the boiler and blast the heat than having it running continuously?

iamcornholio

IMO, I would say have an electronic programmable thermostat fitted which you can set to different temperatures for different parts of the day or week - eg 19 degrees for when you get up, 15 degrees for if you are at work, and then 20 degrees for when you get home etc.

And then have thermostatic radiator valves fitted to control the heat in individual rooms

There are many threads about whether to have heating on all the time or just for set periods.

macman

katgirlie wrote: »

Thank you for your reply macman. I wasn't just asking about the condensation though, I realise I can't fix it just by turning the heating up. Whether it might reduce it was more of an aside, although I realise now that it didn't come across that way in my original post. It was more about whether in general it's better to have the heating on low all the time or on full every now and again in terms of heating the flat and keeping costs down. Does it cost more to fire up the boiler and blast the heat than having it running continuously?

No. The longer it's on, the more it will cost. You can't 'blast' it-it heats at exactly the same rate whether you set it high or low. The only thing you can alter is the temp at which it calls for heat, by altering the room 'stat, or the temp of the water circulating, at the boiler.
There are dozens of threads on this theme, but the answer is always the same.

Ectophile

macman wrote: »

No. The longer it's on, the more it will cost. You can't 'blast' it-it heats at exactly the same rate whether you set it high or low. The only thing you can alter is the temp at which it calls for heat, by altering the room 'stat, or the temp of the water circulating, at the boiler.
There are dozens of threads on this theme, but the answer is always the same.

If it's a modern boiler, then it may well have a variable power burner. In that case, it will be possible to have the boiler running constantly at a low power.

Condensing boilers are more efficient when running at a lower water temperature, rather than flat out.

macman

Even if modulating, it will still cost more to run it for longer, even at a lower temp.

jennifernil

katgirlie wrote: »

Thanks Jennifer. The radiators have their own dials to control how hot they are but we don't have a thermostat on the wall anywhere in the flat to switch on/off the heating when the ambient temperature drops above/below a certain level. So if the heating is on at the boiler and the radiators are on full the flat will just get hotter and hotter until we turn it off again!

When you say "dials", do you mean valves on the radiators with numbers on them?

If so, you seem to have thermostatic valves on the radiators. These should be set to the level you need in each room. You would need to try various settings, but we find on ours that a setting between 3 and 4 is comfortable for lounge and bathroom (dial goes up to 5), while bedrooms need a max of 1, or even fully off, and hall is set on 2-3.

You also need to set the water temperature on the boiler, we use something approaching max on ours, yours may be better at a lower setting, bit of trial and error.

With this system a room stat is not essential, possibly desirable, but not essential. When the rooms reach their desired temperature the valves close. The temperature of the water returning to the boiler will increase and the boiler stat will shut down the boiler until the temperature of the circulating water drops below the level set on the boiler.

You should of course also use your time clock to set the times you need the flat to be heated.

katgirlie

jennifernil wrote: »

When you say "dials", do you mean valves on the radiators with numbers on them?

...

When the rooms reach their desired temperature the valves close. The temperature of the water returning to the boiler will increase and the boiler stat will shut down the boiler until the temperature of the circulating water drops below the level set on the boiler.

Thanks, again, although whilst we do have what you describe, valves with numbers on them, they don't seem to do as you say above. They control how hot the radiator is, but the boiler doesn't shut off, ever, even when the room is really, really warm. And with ref to macman's comment about not being able to 'blast' it, I was referring to the radiators - having them on full means that they run much much hotter - if I have them hot for 15 mins this will warm the room faster than having them on warm for 15 mins, no?

But thanks to all who have replied; unfortunately fitting any kind of thermostat doo-dah isn't an option, as we rent the flat, so I'll just stick to having the radiators come on hot hot hot for short periods on and off throughout the day and night!