The timed vs 24/7 heating question again

Wsb5tails

Forgive me, I've just spent the last 4 hours reading the arguments about leaving the gas Central heating on around the clock compared with timed on and off and I'm still looking for an answer.

I am concerned that our kWh hours usage is 34% higher for the November to Feb period this year compared with last. That seems at odds with my memory that winter 2013 was colder than winter 2014. I'm comparing usage not cost/price.

What's changed:
We had a new system condensing boiler fitted in October 2014 with a digital thermostat in the hall in the same place as the old one.
With the old boiler, we timed the heating 6am to 10pm.
The new boiler daytime temperature call was initially set at 22 degrees (14 overnight) but the thermometer would reach 25 degrees forcing us to turn the whole thing off.
We now have it set at 12 degrees overnight and 20 degrees from 6am to 9pm. The thermostat will still reach 21 degrees and above even though there's is no call on the system to reach that temp.
We have loft insulation above recommended level and cavity wall insulation in a modern home. We work from home and that hasn't changed to explain the variation in gas usage. All that has happened is the new boiler, thermostat and trusting the digital thermostat for control rather than the timer.

Do have any theories for the extra kWh

Cardew

so02see wrote: »

I am concerned that our kWh hours usage is 34% higher for the November to Feb period this year compared with last. That seems at odds with my memory that winter 2013 was colder than winter 2014. I'm comparing usage not cost/price.

Winter 2013/14 was extremely mild. Winter 2014/15 was colder in the period Nov to Feb that you were comparing.


Provisional graph of UK daily mean temperature for Winter 2013/14 (December, January and February)


http://www.metoffice.gov.uk/climate/uk/summaries/2014/winter


Provisional graph of UK daily mean temperature for Winter 2014/15 (December, January and February)

saveallmymoney

It sounds like your thermostat isn't working correctly.

Does it actually end up showing a temperature above its set point or are you measuring that somewhere else?

Your house is getting very hot, given that and the colder winter I think you've done well to only use 34% more gas!

Shrimply

The max temperatures reached are probably less important than the temperatures when the boiler switches off, and kicks back in again.

If the insulation is good and you have the water coming out the boiler very hot it doesn't surprise me that the temperature rises an extra 3C after the boiler switches off as the radiators cool down. Given the smaller max temp when the target temperature is lower it sounds to me like the thermostat is working just fine.
It's only a basic on/off thermostat at the end of the day, you can't expect perfectly constant temperatures.

I think turning down the boiler temperature might help, the rooms will take longer to heat but I'd have thought once the place was up to temperature it would remain more constant.

AndyPK

sounds like a programmable thermostat would help, where you can set different temperatures during the day. Or do you have one of them.

So

19/20 Deg evening
17 during day light till 15:30
8-10 overnight

Smiley_Dan

If you have a condensing boiler, is it in condensing mode, i.e. is the return temperature as expected?

Winter last year seemed milder than this winter. Stormier, but milder.

lstar337

I would say you need to turn your boiler output temperature down, for two reasons:

1. To even out the over-swings.
2. To keep the return flow temperature low enough to make the boiler condense.

Wsb5tails

AndyPK wrote: »

sounds like a programmable thermostat would help, where you can set different temperatures during the day. Or do you have one of them.

So

19/20 Deg evening
17 during day light till 15:30
8-10 overnight

Yes, we have a programmable thermostat perhaps we have it up too high but OH has been sitting in 3 layers of jumpers with the stat at 20 degrees complaining loudly since I became aware of the dramatic usage rate

Wsb5tails

Smiley_Dan wrote: »

If you have a condensing boiler, is it in condensing mode, i.e. is the return temperature as expected?

Winter last year seemed milder than this winter. Stormier, but milder.

Sorry, what do you mean by "return temp"?

Wsb5tails

saveallmymoney wrote: »

It sounds like your thermostat isn't working correctly.

Does it actually end up showing a temperature above its set point or are you measuring that somewhere else?

Your house is getting very hot, given that and the colder winter I think you've done well to only use 34% more gas!

That is what I wondered "stat not working correctly"
Yes it shows a temp way above the set point. It was unbearably hot for the first few days after installation till we turned it right down to the point that we often feel the chill in front of the TV in an evening. Daytime temps are fine while we're moving about.

lstar337

The return temp is the temperature of the water that returns to the boiler from the radiators. If it is below 55c then the boiler will condense and become ever so slightly more efficient.

If your stat is in the hall (and set correctly) and you are hot/cold in the lounge, then your system is not balanced right.

You need to set the radiator in the hall to maximum, as this is the largest space and the stat needs to be triggered to turn the boiler off. Once the radiator in the hall is set to maximum, you need to change all the other radiators to be a comfortable temperature in each of the rooms, when they reach this temperature turn the hall stat down until it clicks.

Leave the hall stat at that temperature, and then you know that when all your rooms have hit a temperature you like, the hall will reach temperature and the boiler will turn off.

It's all a bit of a balancing act, but once you have it set you shouldn't have to alter it much.