Energy myth-busting: Is it cheaper to have heating on all day?

Cardew

orrery wrote: »

Thus, it is likely that a high boiler temperature will reach the target earlier and then enter proportional control, and very efficient running, earlier.

Quite honestly I don't know if your theory/practice in your property applies elsewhere. All I know it goes against the general advice(on condensing boilers) which is to run the water temperature as low as possible, commensurate with having the property warm enough. That theory holds that the boiler will stay longer in condensing mode.


If your theory/practice holds true, why would they have a selectable range of water temperatures for the Central Heating radiators?

orrery

Cardew wrote: »

Quite honestly I don't know if your theory/practice in your property applies elsewhere. All I know it goes against the general advice(on condensing boilers) which is to run the water temperature as low as possible, commensurate with having the property warm enough. That theory holds that the boiler will stay longer in condensing mode.

It is a tricky trade off. In the initial burn to heat the house to the target temperature, the TRVs will be wide open for most of the time with high flow rates. This means high differential between outgoing and return temperatures and hence reasonably efficient running. If you run the system continuously then TRVs start to close, flow rates fall, the boiler modulates back to low power - all this causes low differential between outgoing and return temperatures, so even if you have a low outgoing temperature set you may still have the return temperature rising close behind and hence low efficiency.

Ideally, you'd want proportional control to kick in well before the target temperature is reached and before the return temperature starts to rise too far - the Honeywell wireless stat I had previously was good at this (starting proportional control some 1.5C away from the target). At the time I couldn't see the wisdom in that, but I do now.

..why would they have a selectable range of water temperatures for the Central Heating radiators?

Loads of reasons. Low temperatures to heat water and still allow maximum solar contribution, high temperatures to get effective heating if the radiators are undersized, you may want to select the highest temperature you can in your system that doesn't cause kettling.

orrery

malc_b wrote: »

If you look it the other way round you need to feed a certain amount of energy into the house. That's a fixed amount for a particular time and day. If you do it inefficiently then you use more gas, even if you then go on to enter efficient mode. I'd agree that taking longer to warm the house up increases the loss slightly but not by the same as running inefficiently.

The real inefficiency is to avoid to boiler taking the control into its own hands - once mine gets to full temperature it will modulate down to minimum power, then the temperature eventually climbs above maximum and the boiler shuts down. It will then re-start and go though the same process but if the flow rate is very low (which it will be if the TRVs are nearly closed) then it will shut down almost immediately and continue with this 'short cycling' - much better to have a good room-stat and allow it to control using a managed proportional scheme.

Even better would be to use an intelligent thermostat that connects using the boilers own data bus so the controller knows exactly what the boiler is doing. My Tado system will do this but I can't use it as there is relay control from the h/w system.

Cardew

My reservations about room stats are that the room in which the stat is situated determines the heating for the whole house. If that room is up to temperature then the CH is off and there is no heat to other reception rooms, bedrooms etc.


I have now got a wireless stat which largely overcomes the problem.

alan74

There was a bit on the energy saving myths section about keeping a window open in a room where clothes are drying to prevent condensation. I agree in principle, you don't want to make an unhealthy environment or accelerate redecorating costs... or worse!
There are other options though:
Tumble driers use electricity - expensive, agreed.
An open window wastes heat - expensive on cold days, so what else?
A dehumidifier, but it uses electricity, so fairly expensive, plus cost of the machine, although it works well in a cupboard as the confined space, as long as there is sufficient circulation, concentrates the effect, but if you don't want to invest in a dehumidifier, or have a suitable cupboard, what else?
An electric fan directed toward the clothes - put the clothes near the open window in a small heated room, a fan has a small motor, not expensive to run. The clothes will dry more quickly and you will be able to pack away or wear your clothes and close that window sooner! Of course, drying outside is often the cheapest way where possible if weather conditions are suitable.

orrery

Cardew wrote: »

My reservations about room stats are that the room in which the stat is situated determines the heating for the whole house....I have now got a wireless stat which largely overcomes the problem.

With TRVs in all other rooms, and the system properly balanced, there shouldn't really be a problem. My room-stat is in the hall and the only thing that really upsets it is opening the door for periods if I'm loading or unloading the car. Still, the TRVs shut down in the rest of the house and everything returns to normal when I close the door.

I do have a log burning stove in the lounge, but it copes with that as long as I keep all the internal door open - I need to do that anyway if the stove is to heat the house.

Like you, my room-stat is wireless, so I can take it into the lounge if necessary but that is really only necessary if I'm lighting the fire early and don't want the c/h to come on at all.

Cardew

orrery wrote: »

With TRVs in all other rooms, and the system properly balanced, there shouldn't really be a problem. My room-stat is in the hall and the only thing that really upsets it is opening the door for periods if I'm loading or unloading the car. Still, the TRVs shut down in the rest of the house and everything returns to normal when I close the door.

I do have a log burning stove in the lounge, but it copes with that as long as I keep all the internal door open - I need to do that anyway if the stove is to heat the house.

Like you, my room-stat is wireless, so I can take it into the lounge if necessary but that is really only necessary if I'm lighting the fire early and don't want the c/h to come on at all.

You are missing my point. Balancing the system is fine if you want all the rooms heated at the same time as, say, the lounge.


However I don't heat my in-use bedrooms until, say, late afternoon. If the lounge is at the set temperature the CH is off and the bedrooms are not heated regardless of the TRV settings or balancing.

orrery

Cardew wrote: »

Y... I don't heat my in-use bedrooms until, say, late afternoon. If the lounge is at the set temperature the CH is off and the bedrooms are not heated regardless of the TRV settings or balancing.

I sounds like you need multi zone control, with x2 wireless room-stats.

Cardew

orrery wrote: »

I sounds like you need multi zone control, with x2 wireless room-stats.

Agreed! With hindsight, when I had my house built I would have had CH zones, but as far as I am aware such systems were not on offer, or at least I hadn't heard of them; also an open fire with back boiler incorporated into the gas CH system was a further complication.

malc_b

Just FYI it is possible to retrofit zone controls. Have a look at eq-3 max. These are individual heads that replace the TRV heads. They can be just programmable heads or more usefully they can be wireless and then link to a max cube on you home lan. With a cube, then from a PC you can set up the individual valve head time/temperature settings. If you want to go further then look at "fhem" which is a flexible house control program that will run on many platforms, including a raspberry pi.