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

malc_b

oldskoo1 wrote: »

For now is it better to run my old system boiler on max boiler temperature regardless of the time of year?

I've been running it mainly on setting 4 out of 6 which equates to roughly 72c

In the middle of winter at 0c to -10c i put it to 6.

But is it more efficient to have it cycling less and keep it on 6? It does not modulate the gas output

If it is non-condensing and not modulating then you are best to set the boiler to max. That way it is more likely to be the room thermostat that cuts the boiler out. If you set the boiler thermostat lower then that will cut the boiler out as well as the room stat so you are more likely to have short cycles which are a bit wasteful (short cycles on oil are more wasteful than those on gas though).

Cardew

This is the advice from the latest edition of the Energy Saving Trust(EST) newsletter.


Take control of your heating

Our recent Ipsos MORI survey of over 2,000 UK respondents has revealed that almost 80 per cent of the UK believe they understand their heating controls. However over half are using their thermostats and heating controls incorrectly. Make sure you’re avoiding some of the most common pitfalls.

1. Turning the heating up when it’s cold outside
   You shouldn't need to do this, as a thermostat is there to maintain a set temperature whatever the weather.
2. Turning up the thermostat to heat the room quicker
   35 per cent of people do this but it won’t heat up your room any quicker; it will only make it warmer when it does heat up!
3. Leaving the heating on constantly at a low temperature
   Turning your heating on and off as you need it is more energy efficient.
4. Believing that hot water runs out if you stop feeding the tank
   Leaving your water heating on all the time could be costing you far more on energy bills than necessary.
5. Keeping electric storage heaters on all the time
   Storage heaters are designed to take advantage of cheaper, night rate tariffs but some storage heaters also have in-built electric panel heaters. Leaving the heaters on all the time with incorrect settings could result in them using the panel heaters not the storage ones - costing you far more.

Viberduo

What I notice from experience with both gas heaters and things like fan or bar heaters is that gas heaters warm you up much faster but the initial drain is more extreme i.e for the first hour in my old 1 bedroom flat it used about £2(and this was 4 years ago) then having heating on in the 2 heaters in living room, 1 in bedroom, 1 ensuite, 1 seperate bathroom, 1 kitchen and 2 hallway used about 30p a hour after that, wheras at the time a 2kw heater running a hour cost me 10p and I didnt use one in hall or bathrooms(apart from when having a shower in winter due to it being so cold the steam would take a whole day to dissipate)

One time I ran heating for 6 days when away on lowish temp all day and it cost about £27 but the flat felt burning hot, so going by my own calculations it was £4.50 a day equalled just unde 19p a hour which overall would make it cost about the same as running a electric heater non stop(and safer)

Have no idea about running it for a few hours though, but assume its similar i.e £2 for 1st hour then 30p a hour after running for 4 hours total would be £2.90 to heat entire flat, but running electric heaters would of been about £1.60 for 4 hours

orrery

Cardew wrote: »

This is the advice from the latest edition of the Energy Saving Trust(EST) newsletter.

1. Turning the heating up when it’s cold outside
   You shouldn't need to do this, as a thermostat is there to maintain a set temperature whatever the weather.

This is a bit misleading, in that:

• you may need to turn up a thermostatic radiator valve slightly to achieve the same temperature, and
• you may need to turn up the boiler temperature to get the same heating effect.

Cardew

orrery wrote: »

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This is a bit misleading, in that:

• you may need to turn up a thermostatic radiator valve slightly to achieve the same temperature, and
• you may need to turn up the boiler temperature to get the same heating effect.

The TRV is still a 'thermostat' and the settings are calibrated to provide the same temperature regardless of it being 10C or -10C outside.


For instance the settings on my TRVs are 16/18/20/22/24C(marked 1/2/3/4/5). Set to '3' it should keep the room at 20C.


In very cold conditions, if the boiler water temperature is too low to maintain 20C, the water temperature will need to be increased.


However in those very cold conditions, without increasing the water temperature, turning up the TRV to any setting will have no effect as the radiator output will always be insufficient to keep the room at 20C.

orrery

Cardew wrote: »

The TRV is still a 'thermostat' and the settings are calibrated to provide the same temperature regardless of it being 10C or -10C outside.

That isn't strictly true - it is too simplistic a view. A TRV is a 'soft' control device - it doesn't turn sharply on and off like a traditional thermostat.

You need to bear in mind that it controls water flow through the radiator i.e. a specific room temperature will result in a specific flow rate, which will approximately relate to a level of heat delivery into the room. Thus, on a freezing cold day the TRV will need setting a little higher to deliver an increased heating effect to maintain the same temperature and on a warm day it will require setting to a slightly lower level so that there is lower flow and lower heating effect. On mine, this could be about +/- half a graduation.

Alternatively, a similar correction could be made by adjusting the boiler temperature to deliver differing heat input to the room at the same flow.

matelodave

As Cardew says, the temperature of the radiator water and the size of the radiator must be adequate to heat the room

If those two criteria are correct then the thermostatic valve will control the room to the set temperature, assuming that it's not in a draught or in the sun.
It should also make the room warmer if you turn it up, but it won't make it warmer faster, the only way you can do that is by increasing the boiler temperature. You should not need to keep adjusting a TRV unless you want to increase or decrease the room temperature.

If the rad can't deliver enough heat because it's either not big enough or hot enough then turning the rad valve up to full won't heat the room - you need to increase the boiler temperature.

Ideally once the room is up to temperature the TRV will modulate the flow through the rad to balance the heat loss in the room. Most people expect the radiator to be red hot, but that should only be the case when it's heating the room from cold, it should then only be lukewarm to maintain the set temperature

Cardew

orrery wrote: »

That isn't strictly true - it is too simplistic a view. A TRV is a 'soft' control device - it doesn't turn sharply on and off like a traditional thermostat.

You need to bear in mind that it controls water flow through the radiator i.e. a specific room temperature will result in a specific flow rate, which will approximately relate to a level of heat delivery into the room. Thus, on a freezing cold day the TRV will need setting a little higher to deliver an increased heating effect to maintain the same temperature and on a warm day it will require setting to a slightly lower level so that there is lower flow and lower heating effect. On mine, this could be about +/- half a graduation.

Alternatively, a similar correction could be made by adjusting the boiler temperature to deliver differing heat input to the room at the same flow.

Sorry but don't agree!


Obviously the TRV is a 'soft control device' (as you term it) in that the water flow into the radiator decreases as the room approaches the temperature set on the TRV.


However the whole purpose of a TRV is to control the amount of hot water entering the radiator. Thus it will let in sufficient hot water to allow the radiator output to maintain the temperature set on the TRV.


So, as stated in my previous post, setting my TRV to '3'(20C) will maintain the room at 20C* regardless of the outside temperature. If I turn it up to '4' it will raise the temperature to 22C.


* If it cannot maintain 20C when set to '3' then it will not maintain 20C regardless of the TRV setting i.e. turning it to '4' or '5' will have no effect; the output of the radiator is insufficient. The solution as matelodave states is to get a bigger radiator or increase water temperature on boiler.

orrery

Cardew wrote: »

Sorry but don't agree!

OK. Let's follow this through. You need to look at the steady-state condition to understand how this behaves.

We initially set the TRV on a warm sunny day. Outside it is 19.5C.

To get the room to 20C, we set the TRV to 3 (the actual number printed on the dial is arbitrary). At 20C, the valve allows through only 5% of full flow - all that is required to maintain the small heat loss. So, the radiator is warm at the top, and the rest of it is cold - but that is all we need to get to 20C, so we're happy.

That evening, in blows an arctic gale at minus 20C - the heat loss is now very significant (the room has poor insulation) and the only way to keep the temperature of the room at 20C is to have the radiator on at 95% flow. The problem now is that, if the room is currently at 20C then the flow is only 5%, then the temperature of the room must fall. It will fall along the soft curve to the point required to increase the flow rate to 95% but this might only be at a temperature of 18C, so that is where the room will stabilise to.

If you have a soft response curve than this behaviour is inevitable.

Andy_WSM

I've never adjusted my TRVs and they maintain the temperatures perfectly in each of the rooms. The towel radiator in the bathroom is a bit noisy and when in there with the door closed you can hear the flow changing as the TRV adjusts itself up & down. It's not THAT slow responding to changing temperatures.