The myth about leaving your heating on all day-Martin Lewis

[Argyll]

Apparently leaving your heating on all day isn't the best way.

[Razor]

Total Bullspit!

It depends entirely on your house construction and exposure together with the type and levels of insulation and your type of heat source and usage patterns.

By way of example...

A had a client that wanted a bigger boiler and rads because she worked long hours - often picking up extra shifts and the house was always cold when she got home.

When she was out with the heating off for 12 hours plus a day in winter the internal temp of the house would drop to around 12 degrees. She would get in, put the heating on and by the time she went to bed a couple of hours later the house was only at 17 degrees.

I fitted a setback thermostat so the temp didn't drop below 15 during the day. It used some fuel but not much as heat loss increases with temp but when she got in it didn;t take long to bring the house up to a decent temp and te boiler wasn't working flat out during the recovery period.

Subsequently she was one of the first clients I fitted a smartphone controllable stat for. They are perfect for this.

If you have a modern well insulated house then having a setback temp during the day works really well and does not impact on your bills but if you have a drafty, poorly insulated property then you need lots of horsepower and rads to recover heat quickly when you need it and it's not worth having it on when you don't.

[dewaltdisney]

I have done this for years and as my home is well insulated and my house is always warm and comfortable. As I am on blood thinners I feel the cold. My gas costs are actually lower than when we did morning and evening heating only.

DWD

[Rorschach]

It's never as simple as do X or Y as Razor says, it all depends on your property. In general though leaving your heating on all the time is going to cost more than heating when you need it as most housing stock is not well insulated enough and most people don't know how to use a thermostat and TRV's properly.

[Argyll]

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[ericmark]

My old house had a standard 4 kW radiator, a Myson fan assisted 3.5 kW radiator and a 4.5 kW gas fire in the living room, 15 minutes and room was warm, no need for geofencing.

First house tried geofencing was mothers house, the TRV heads had the option, however the anti hysteresis software was OTT, so moved to simple time, so 7 am set to 22ºC then 8 am back to 20ºC other wise 10 am before it reached 20ºC.

But her house had a modulating boiler, which could extract the latent heat from flue gases if the return water temperature was low enough. So controlling room temperatures with electronic TRV heads the boiler did not switch off, but turned down, and ran in an economic way, as long as no silly wall thermostats turned boiler off/on, if the wall thermostat turned off boiler, any heat in boiler lost out of flue, and when it restated it did so flat out, so did not extract the latent heat and started a hysteresis. Unfortunately a Worcester Bosch so not Open Therm enabled.

However the main thing as @Rorschach says is setting the TRV and lock shield valves, and having TRV heads with *123456 does not help, we are told should set the lock shield so around 15ºC drop across the radiator, but differential thermometers are not standard items found in the DIY tool bag, so it means some other method has to be used.

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With electronic TRV heads you often get both current and target, and one can use this to set the lock shield valve, if it overshoots close the lock shield a tad, I found if TRV on supply it works far better than when on return, the make I used had two sensors one for air temperature and one for water, the latter compensated for the TRV being so close to radiator, found on return not as much lee way as on feed.

This house however does not have a modulating boiler, so switching it on/off does not matter in the same way, but a 18 kW boiler with three story house re-heat times are slow, it can maintain the temperature, it is the reheating where problem lies, however a sequence can get around that problem, when I return home we cook, eat, then sit watching TV then retire to bedrooms, so same with heating, first heat kitchen, then dinning room, then living room, then bedrooms.

A 10 minute delay between rooms is all one needs, so kitchen radiator gets hot first, then dinning room, then living room. However since the TRV heads not linked to wall thermostat, two hours before bed time the wall thermostat drops 0.5ºC then an hour before bedtime it goes back up 0.5ºC and the bedroom TRV's are set for temperature increase. This ensures the boiler is running when the TRV's change temperature, this was not required with the gas modulating boiler, as it did not turn off only down.

With a gas modulating boiler as warm weather comes it can't turn down any more, so starts to cycle, but left to own devices it would cycle all summer, so needs a wall thermostat set higher than the TRV in same room which is normally kept cool to turn off heating on warm days, it is not to set room temperature, the TRV does that.

Not quite the same with oil, but general idea is a wall thermostat turns off boiler in warm weather, and the TRV sets the room temperatures.