Gas central heating on constant or timer?

mech_2

Andy_Hamilton wrote: »

I have tried turning off the heating for one of the coldest days earlier this year, it was raining and overcast so I know the sun had no/little influence. When I got in at 6pm the temperature was 16degrees, at 8:30 the temperature went up to 19degrees. In my house there was no heating, no cooking and no hot water on so I know the heat must have been coming from next doors. At the time the neighbours came around and told me that there house was freezing and they had their thermostat at the 30 mark (not achieving this though) Apparently it had been cold since they came in so they turned it up.
The houses are breezeblock with a couple of inches of insulation between)

Wow, crazy. I stand corrected. Construction and size of house may play a part here.

The original temperature sensor can be bought new on eBay for £5 delivered. The controller could be set to a temperature and this seemed to have around the 1.5 degrees on/off error but because the house has 10 large radiators and a powerful boiler it would overshoot around 4 degrees, when it cooled it would then drop 5 degrees before it kicked the boiler in to overheat the room again.

Ah, now I understand.

Can the boiler temperature be turned down any further?

Andy_Hamilton

The boiler can be turned down but as I'm just wanting to heat the air I don't want it to be on a cooler setting. It's all irrelivent now as the thermostat has effectivily calcultated the relationship with the boiler and room sizes.

mech_2

Andy_Hamilton wrote: »

The boiler can be turned down but as I'm just wanting to heat the air I don't want it to be on a cooler setting. It's all irrelivent now as the thermostat has effectivily calcultated the relationship with the boiler and room sizes.

I am of the opinion that lower boiler temperatures are better. I know this runs against popular opinion, but it broadly agrees with the whole idea behind weather compensation systems.

You can evidently solve the problem of overshoot with a new thermostat, but I'm not sure I can see an argument for having a return temperature above 60 degrees C even with a non-condensing boiler. Under-floor losses and losses through walls behind radiators will be greater at a higher water temperature (even if only by a small amount owing to insulation). Heat exchanger efficiency will go up as the temperature difference between the circulating water and the combustion gases will increase. Therefore flue losses will go down.

Obviously a condensing boiler would benefit most as it would condense more of the time. When condensation in the flue is a good thing, rather than something to avoid, you can turn the water temperature as low as is still able to heat the house and all the above effects will be greater.

paceinternet

So, do you think a system that had some "buffering" in it would be more energy efficient and create less temperature variation?
As in the thermal store systems?

mech_2

paceinternet wrote: »

So, do you think a system that had some "buffering" in it would be more energy efficient and create less temperature variation?
As in the thermal store systems?

I'm not sure any efficiency gain would justify the cost of the thermal store. I'm interested in finding the best way of running a conventional heating system rather than making it more elaborate. It's clear overshoot can be eliminated with a more sophisticated thermostat, but that must mean a non-modulating boiler will be cycling on and off more frequently which is less efficient. I've never seen figures saying how much less efficient, but I would guess that not overshooting the thermostat temperature is better than avoiding boiler cycling. Maybe a thermal store would help with that problem, but at the prices I've seen, it would be more cost effective just to fit a newer boiler which can vary its heat output.

I think the way to go is more sophisticated controls. Not just a roomstat that turns the heating on and off, but an integrated boiler management system with control over the flame size in the boiler. Ideally it would incorporate an outdoor temperature reading as well as an indoor one, so that the controller could learn the characteristics of the building as well as the radiators. It would turn the water temperature right up when fast response was needed (the heating has come on and the house is cold) and when the roomstat indicates the living space is close to the target temperature, the system would try and balance the burn rate with the heat loss of the building. No more boiler cycling, just a trickle of heat at just the right level.

Obviously easier said than done, but it would be better than my boiler which just modulates down progressively as it approaches a manually set water temperature and the roomstat is a totally separate on/off device.

HarryH_3

crockpot wrote: »

Hi

A bloke at work was told by heating engineer that it was better, ie cheaper to keep heating on all the time, I had heard this before, but the chap I asked said not!!

I have an old gas central heating boiler (potterton) which I am ashamed to admit I have not had serviced for 10 years!! since we moved in!!

I am into MSE and only put the central heating on when needed, I see no point it having it on in an am when most days we are out at work and school.

So which is cheaper, on all the time in winter I guess,rad`s all have thermos on so could turn them all down?

Thanks

Laws of physcis show that its better to heat intermittently than all the time. Additionally, if instead of using a timer, you press the +1 advance so you get heating for an hour, and press again after an hour if you need, then you will approximately halve your gas bill. All those times you stay late at work, go to the pub or gym and your house is being heated on the timer. Plus those weekends where you go away and forget to turn off the heating. it all adds up.

HarryH_3

X1GVC wrote: »

I have read the posts on this topic with some interest as a question that is often discussed with varying thoughts and ideas. The reference to physics is particularly interesting. The answer is of course to use timers.

The transfer of heat from our homes is a function of the driving force between the two bodies. To keep it simple let's say for arguments say that during the colder months the ambient outdoor temperature is a 6C. For the purpose of a house we can assume everything to be at uniform temperature as would be the case at steady state. The driving force for temperature change is the difference between the two bodies. The higher the difference the higher the rate of transfer.

Based on this a home at a constant 18C loses more energy to a 6C surrounding (outdoor temperature) than a home that is say 18C for 2hrs on the morining and perhaps 4hrs on an evening. During the times between the temperature of the home is either reducing or increasing based on the timer settings. At these times the loss of heat from the home is less than would be the case for a home at constant high temperature, therefore you save money on your fuel bill.

If you really want to save money then spend your efforts on reducing heat loss from your home as this directly reduces heat loss (waste) from your home.

good explanation.

the energy your heating system supplies is proportional to the difference between internal and external temperature. when your internal temperature goes down, you are using less energy.

vod

There are some very interesting points raised here, but I wonder if anyone might be able to answer my question please?

I live in a new three-storey detached house, built around 2 years ago. It's double glazed, insulated, cavity wall etc etc.

The two upper floors heat quickly and stay warm without problem, so we can have the radiators set at a very low temperature for those, but we have a huge open-plan kitchen/living room/dining room downstairs which is difficult to heat.

We're out at work all day, so it's only a question of having the heating on from around 6.30pm-11pm but I'm wondering which is the most economical way to use the heating:

1. Do we turn the heating on at a higher temperature 2 or 3 times during this timescale to give the house 'blasts' of heat; or

2. Is it best to keep the heating on for a longer period at a lower temperature to create an 'even' heat.

I suppose what I'm really asking is "is it more expensive to 'blast' heat into your house, rather than heating it slowly and gradually at a modest setting"?

Thanks in advance for your responses.

Andy_Hamilton

As you set upstairs low, you need to close the doors to make any difference. As the upstairs is effectively not warming up quickly most of the heat downstairs will dissapear upstairs to compensate (just like leaving an outside door open pulls the heat out of your house).

Blast of heat and warming slower will make little difference (blast will be very slightly less)

diamondirish

I have been running this experiment for more than 10 years now, in 3 different homes!

The proof is this simple - I have Gas bills at least 30% lower than anyone else I know in a similar property, and 70% lower than some.

I leave the central controls to 'on' for heating (not water) 24/7. I work at home, and my wife is a homemaker - the property is occupied most of the time, most days (and we still have much lower gas bills than families who are all out of their homes monday through friday from 8am until 6pm!!!)

The Thermostat downstairs is set to 19 or 20 degrees - upstairs never above 15 degrees. When we pop out, and when we go to bed, downstairs stat is also set to 15. (edit: Must say at this stage, on the boiler, both the water and radiator temperatiures are set right at the lowest end of the 'recommended' settings)

In the depths of winter (last year we had -19degrees, yes minus ninteen) the downstairs stat was set to 22 and upstairs still at 15.

When we go away for a number of days, all stats are set at 10-12 to stop the house becoming too cold to reheat (and keeping the cats from turning to ice).

As for Hot water, I have always used a timer - 20 minutes in the morning before we rise, and a ten minute boost around dinner time. We rarely (once every 2-3 months on the occassion when everyone wants a shower / bath at the same time) run out of hot water, and if we do I use the GCH boost - NEVER the immersion heater.

So, you can continue to use your laws of physics and gas company marketing jingo-jango - but using your termostats to manage your enery use is much more effective and efficient than letting the temperature yo-yo by 10-12 degres (at least ) 2 or 3 times a day.