Heating engineer advice? Most cost efficient temp to set boiler for central heating?

TomsMom

ValHaller wrote: »

Actually, TRVs are not an on-off switch. It is not all or nothing - they can modulate flow between 0% and 100% according to temperature.

OP, as you have TRVs, I suggest just running the boiler at maximum temperature. The TRVs will do the rest - as the rooms heat up, the TRVs will cut the flow quite substantially and the return water temperature will be quite low, which as already stated is helpful to run a condensing boiler at a low temperature.

Thanks. Just missed your post as I was typing mine. So is there any way of making it more cost effective? As I don't heat my house like a greenhouse and barely heat, if at all, over half the rooms, then I can't understand why my gas consumption seems to be a lot higher than other people.

Mr_Ted

TomsMom wrote: »

Thanks. Just missed your post as I was typing mine. So is there any way of making it more cost effective? As I don't heat my house like a greenhouse and barely heat, if at all, over half the rooms, then I can't understand why my gas consumption seems to be a lot higher than other people.

The Output from a radiator is only slightly lower than the input into it, therefore at a low temperature the output is low but the boiler will be on longer, as previousy suggested, to heat the room, so you will use gas at the boiler for a longer period!
The TRV's will still work exactly the same in either case according to there setting!
The general output setting for heating water temperature is 72 degree's, if its a modern condensing combi boiler it should modulate accordingly to the way the boiler is set to operate!
Radiator outputs, Kw or Btu, are rated with this temperature input, but the output of a radiator decreases on a sliding scale comparible to input, i.e. you cant get more out than you put in.

closed

TomsMom wrote: »

I can't understand why my gas consumption seems to be a lot higher than other people.

Probably because you have it on for 15 hours a day (at maybe 60p+/hour on a cold day), in a house without cavity wall insulation. half an hour before wakeup should take the chill off on cold mornings.

If you spend most of that time in one room, a gas fire or fan heater with thermostat might be cheaper than heating the whole house (if you close the doors).

The rads with no trv or a setting of 5 (wasteful) shouldn't just be warm, they should be hot.

TomsMom

Thanks both. I think I'm slowly getting my head around this.

Mr_Ted wrote: »

The Output from a radiator is only slightly lower than the input into it, therefore at a low temperature the output is low but the boiler will be on longer, as previousy suggested, to heat the room, so you will use gas at the boiler for a longer period!
The TRV's will still work exactly the same in either case according to there setting!
The general output setting for heating water temperature is 72 degree's, if its a modern condensing combi boiler it should modulate accordingly to the way the boiler is set to operate!
Radiator outputs, Kw or Btu, are rated with this temperature input, but the output of a radiator decreases on a sliding scale comparible to input, i.e. you cant get more out than you put in.

I'm experimenting today. My boiler's top temp is 75, I've set it at 70 last night. In the rooms not used the TRVs are now set either at 0.5 or 1 and the rads are not coming on. In the little used rooms (utility, downstairs WC, hall and landing) TRVs are set at 1.5 and are just coming on barely warm sometimes so keeping the chill off. Dining area is set at 2 and hasn't come on yet. Bedroom is set at 2, temp was 17C this morning and that's fine. I've set the living room and sun room TRVs at 3 and they are hot, can't keep hand on. Will continue to monitor and see what suits best and I'll keep a check on gas usage to see if it makes a difference.

Is it OK to keep the water temp at 70 or should I go to the max of 75?

closed wrote: »

Probably because you have it on for 15 hours a day (at maybe 60p+/hour on a cold day), in a house without cavity wall insulation. half an hour before wakeup should take the chill off on cold mornings.

If you spend most of that time in one room, a gas fire or fan heater with thermostat might be cheaper than heating the whole house (if you close the doors).

The rads with no trv or a setting of 5 (wasteful) shouldn't just be warm, they should be hot.

I can alter the time setting for the morning now I've increased the water temp and see how that goes.

The only rad without a TRV is the bathroom, from what I understand you have to have one rad without (I've forgotten the technicalities of why ), but it was much warmer in there this morning and the rad was hot rather than luke warm as it has been before.

I would say the longest I spend in one room is in the living room in the evening. No gas fire but there is an electric fire which isn't really used. I would rather not heat just one room during the winter, I want the house to be reasonably comfortable. Having spent my childhood during the late 1940s/50s with a coal fire in the living room, paraffin heater in the bedroom during the worst of the winter and ice on the inside of the windows, then a warm and comfortable home in retirement stays at the top of my list .

jayyar66

Ice on the inside of windows, and if it was REALLY cold a semi-solid hot water bottle on the floor at the foot of the bed! Oh yes, happy days indeed. . . . You just trying telling kids these days!! They don't know they're born!!

Mr_Ted

jayyar66 wrote: »

Ice on the inside of windows, and if it was REALLY cold a semi-solid hot water bottle on the floor at the foot of the bed! Oh yes, happy days indeed. . . . You just trying telling kids these days!! They don't know they're born!!

:eek: you had a bed, windows and a hot water bottle :eek:

:rotfl::rotfl::rotfl:

gas4you

If your rads are old and existing from before your Vaillant install, then set the heating temp to 65C or 70C.

Old systems were designed for a flow temp of 82C, whilst new systems are designed for around 60C.

At 65/70C you should still be getting a return temperature of around 55C which is below dew point so the boiler will be condensing.

Hot water is usually set for 55C on these, but this is up to you.

Mr_Ted

gas4you wrote: »

If your rads are old and existing from before your Vaillant install, then set the heating temp to 65C or 70C.
Old systems were designed for a flow temp of 82C, whilst new systems are designed for around 60C.
At 65/70C you should still be getting a return temperature of around 55C which is below dew point so the boiler will be condensing.
Hot water is usually set for 55C on these, but this is up to you.

:eek: Sorry totally disagree, 72C was the norm for designed temps, 82C would only be used for a commercial constant temp circuit feeding fan convectors that need higher design temp!
Or, "MAYBE" in extreme cold weather conditions?
82C would take the skin of your hands if you put it on a rad, 72C is also very hot and must be used with care these days especially around kids and the infirm, where LST rads should be used!

For info>>
http://www.engineeringtoolbox.com/heat-emission-radiators-d_272.html

Also "Dew Point" is not a fixed point it is variable dependant on humidity and air and surface temperature!
Working in the commercial, as well as the domestic, sector I know this but for info>>>
http://www.weatherquestions.com/What_is_dewpoint_temperature.htm

gas4you

Each to their own, but boiler manufacturers state 56c as the dew point for their products to condense.

Mr_Ted

gas4you wrote: »

Each to their own, but boiler manufacturers state 56c as the dew point for their products to condense.

:eek: Not each to their own AT ALL, its a scientific FACT :T