All night heating

FreeBear

givememoney said:

Yes I'm asking this as our new Vaillant boiler is costing us more than our old one. We are both retired so here a lot in the day. We've set the thermostat to 19.5° to come on at 6.50am then it takes hours to get up to 19.5°if it's cold to say maybe 10.30am. Again We've set the thermostat to go down to 16° at 10.30pm till the morning. Admittedly it is off for 8 hours 20 mins so not using gas, but then on for hours to reach 19.5°. Therefore I wondering if it would be more cost effective to leave it on constantly at maybe 19° and it would take less time to heat the house.

I've been messing around with boiler & thermostat settings over the last few months in an attempt to squeeze a bit more efficiency out of my boiler. A few random notes..

• Low flow temperature (50°C or less) - Takes a long while to heat the house up, but boiler efficiency is good (95% or more) at the expense of longer burns. Doesn't really save money.
• High flow temperature (60°C and higher) - House heats up quickly at the expense of lower efficiency (85-90%).
• Variable flow temperature depending on temperature differential - except for the first boost in the morning, flow temperature is around 40-45°C. Currently returning around 92-94% efficiency.

I'm fortunate that radiators have been oversized compared to what was originally fitted and I've strived to insulate & draught proof to the best of my ability. Also have full control over the boiler and the thermostat decides on flow temperature. Have also spent quite a bit of time balancing the radiators and matching the pump speed to suit.

Your Vaillant boiler should have the same ability, but not all thermostats are smart enough to talk to that particular boiler. You are probably reluctant to go fitting larger radiators and upgrading insulation (although loft insulation is relatively cheap and well worth increasing to 300mm if you are not already at that level). Draught proofing is often cheap and can return significant savings for little effort.

Look at your boiler temperature and set it to 60°C for a week or two if it is currently set lower. That will help to heat the house up a little quicker without dragging efficiency down too much. If the boiler is already set to 70°C (or higher) and it is still taking hours to heat the place, then larger radiators are called for (assuming the existing ones are properly balances).

Qyburn

givememoney said:

Yes I'm asking this as our new Vaillant boiler is costing us more than our old one. We are both retired so here a lot in the day. We've set the thermostat to 19.5° to come on at 6.50am then it takes hours to get up to 19.5°if it's cold to say maybe 10.30am. .

This is where optimised start comes in. You set the time at which you want the place to be up to temperature and the system decides how far in advance to fire the heating up. The function has been around for decades, I've seen mechanical and pneumatic optimisers that predate electronic let alone microprocessor controls.

Unfortunately it's been slow to make it into domestic systems, partly to the total shutdown of the whole energy saving industry in the later 1980s. But also I suspect because it's not easy to explain or to make it sound beneficial.

You can create the function with some fiddly configuration if you have a system that allows lots of different time/temperature ranges.

HumberFlyer

I've experimented with this many time. Ours is on 12 hours 9am -9pm at 20/21 degrees then set to 18 deg through the night.. it seems to cost approx 40p per 24 hours dearer than if I was to switch off till 9am and get up to a 16 deg house

Spoonie_Turtle

We didn't consciously experiment, it was just the default as the installers left it set to 24/7, we set the thermostat to 18℃, and our heat pump has no setback temperature.  We were finding the heating was coming on at night when we didn't need it, so set the heating to be off overnight and it definitely used less electricity after that. 

We set the heating to come back on around 5am as the eldest family member was getting up around 6-7am and we didn't want him to be getting up to a cold house.  (He had enough years of that before the heat pump was installed.)

moneysaver1978

We too have been experimenting the temperature and timings.

We found that on/off didn’t work well for us - taking too long to heat up the house and/or generally not comfortable. This might be due to the fact that we have no wall insulation (although we have obviously added insulation to the loft and draught proofing).

I think we have “cracked” it for our specific needs:

We both work from home 4 days a week.