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

orrery

the_devil_made_me_do_it wrote: »

Last year I moved into a small 2 bedroom bungalow. I rent it off a social landlord. Unfortunately they ain't the best when it comes to modernising their properties. It was bit in the early 90's, but still has the original patio door which has a metal frame and a hard wood front door with a small non double glazed window.

The metal frame and single glazed door will be a problem. The modern UPVC should be fine on all but the coldest nights.

You need ventilation and you need heat to stop the condensation forming - removing it is more difficult. I'd recommend you keep a window slightly open overnight and you run the heating for at least an hour before you go to bed.

The thermostat in your hallway is likely to control when the heating switches on and off by the temperature of the hallway. So, if the hall heats up too fast it may shut the heating off too quickly before the rest of the property has time to heat up. If that is the case, either turn the radiator in the hall down or the thermostat up.

The 0-5 is difficult, but the lounge should be around 3 or 4, and bedrooms 2 or 3.

If condensation is still a problem, then buy a de-humidifier (a proper one, not one of the smaller peltier effect machines, which are pretty ineffective).

r2015

And remember this is when outside temp is 0C, that's mid winter in UK.

Not in Scotland it's not, been -20 C a few years ago, even froze the cans of beer stored in the garage.

Cardew

malc_b wrote: »

I would appreciate maths based arguments as to where that is wrong. Arguing that physics says it is wrong when I'm using physics to prove it is a waste of your time and mine. I'm not saying you lose less heat, I'm saying heating efficiency can exceed the extra heat lost so less fuel is used.

Malc-B
You have conceded the principle that when heating is timed you use less fuel than having heating on 24/7 which was the point of this thread.

However you have simply 'plucked figures out of the ether' for heat loss for the hypothetical property.

Similarly you have 'plucked figures out of the ether' for the increased efficiency of a condensing boiler and how it applies to re-heating that hypothetical property.

I understand the point you are making, but with respect you are proving absolutely nothing. You are simply advancing a theory that there could be gains in the efficiency of a condensing boiler, running 24/7, that would offset the savings of having a boiler switched off for a set period.

It would be futile for me 'to pluck figures out of the ether' in an attempt to 'prove' you are wrong. That said I am(subjectively) very confident in a carefully controlled experiment that your theory would not hold up.

As an aside, I have contacted two manufacturers trying to determine how best to get condensing boilers into condensing mode for properties where the heating load will vary throughout the day; and quantify the potential gains. From the little I have gleaned I am not sure that your 'theory' of 24/7 running at a lower output will lead to any savings over a boiler running for 16 hours at a slightly higher output.

One last point. You state:

Hence it is quite probable that running in low power condensing mode 24/7 will use less fuel than 16/24 (in mid winter).

Yet later in the same paragraph you state:

So as the weather gets cold increase the heating hours rather than run not in condensing mode.

Not sure of the point you are making. Firstly run 24/7 and then increase the heating hours???

malc_b

No I haven't. What I have said is that it is

• TRUE - Having the heating on less means that over a day a house loses less heat.
• FALSE - Losing less heat is always the same as using less fuel aka less cost.

The simple case I used to show the maths was just that a simple case. Fixed inside and outside temperatures. It just shows the principles. From that can be inferred the rules.



To draw an analogy say you are driving to London and it is a trip of 100miles. Rolling resistance and air resistance decrease as speed decreases so the lowest energy for that trip will be a slowest speed. Therefore you should do the entire trip at 10mph if you want to save fuel right? Of course not, lowest energy is NOT the same as least fuel (which typically would be ~55mph, the lowest speed in 5th gear).


The difference in condensing mode and non condensing mode operation is a well know fact. AFAIR wikepedia says ~10%, or if you compare figures from SEDBUK for non-condensing and condensing boilers you get ~8% AFAIR. Similarly it's well known that you need cool return water for condensing to happen, 55C is the usual figure quoted. And it is also well known that radiators give less output at lower temperature.


So for condensing mode you set say 65C as boiler output expecting 55C return. Radiators are at ~60C so 60% of rated power. In a typical house in mid-winter that would really struggle to balance the heat loss even on 24/7.



The point that the maths shows it that the saving in energy loss between 24/7 or not is quite small. And more over you can estimate this by seeing how much the temperature in the house falls overnight which is pretty easy to measure. Basically the heating rule is to run in condensing mode as much as possible, even if that means running longer hours.


It's similar to the car analogy, it is better to be just in 5th gear speed range even if that means going faster (using more energy but less fuel).

So the answer to the question is it cheaper to have the heating on 24/7 is "it depends". It is not just "No". That's too simple.

the_devil_made_me_do_it

cyberman..I have to be concerned about condensation. I have asthma and it gets worse in damp conditions due to mould growth and other issues relating to condensation. Although I don't sleep with a window open, I do have my bedroom well vented.


orrery.. I will give your advice a try. Although I have noticed that the radiator in the hall doesn't have a thermostat, so I can't turn it down. Although it isn't close to the thermostat on the wall.

orrery

the_devil_made_me_do_it wrote: »

orrery.. I will give your advice a try. Although I have noticed that the radiator in the hall doesn't have a thermostat, so I can't turn it down. Although it isn't close to the thermostat on the wall.

You should be able to turn it down - the valves on the end of the radiator should be simple taps. To set the hall radiator:
- start from cold
- turn the hall stat to max
- turn hall rad to off (tap fully clockwise)
- set all other rads to '5'
- turn the hall rad up slowly until you get some flow, then down very very slightly to just choke it off
- turn all the other rad valves down to off - '0'
- the hall rad should now get full flow
- return hall and all radiator thermostats to normal setting

The result of this should be that all the individual rooms should come up to temperature with the hall remaining cold. As all the rooms approach their set temperature the hall rad will then come up to temperature and the heating system will shut down. You may need to increase the hall rad flow a little from that setting if it never gets hot.

Remember to keep all doors closed.

As a fellow sufferer, I'd recommend increasing the blankets on the bed and opening a window at night.

Richie-from-the-Boro

increasing the blankets on the bed and opening a window at night

- the simple act of putting a cheepo duvet 1 - 15 tog under the bottom sheet
- will raise body temp considerably without the extra weight on the top

Thicker duvets doesn't necessarily mean warmer, its the filling materials capacity to trap air versus weight that counts. Your brain and therefore body feels cold along the spine, insulate that spine [duvet underneath, as well as on top] and you will have an instant warmer bed for £10.

malc_b

orrery wrote: »

You should be able to turn it down - the valves on the end of the radiator should be simple taps. To set the hall radiator:
- start from cold
- turn the hall stat to max
- turn hall rad to off (tap fully clockwise)
- set all other rads to '5'
- turn the hall rad up slowly until you get some flow, then down very very slightly to just choke it off
- turn all the other rad valves down to off - '0'
- the hall rad should now get full flow
- return hall and all radiator thermostats to normal setting

This sounds like you are trying to balance the radiators. That is making sure all the radiators get their fair share of the water from the boiler. Only this is not the way to balance the radiators. Google balance radiators to get loads of pages on the correct method.

O for a quick and dirty fix turn on radiators on full if you have thermostatic valves turn on heating and they run round feeling which radiators warm up first. Turn down the lockshield on those and turn up the lockshield on the ones that are colder than average. Do say 1/2 turn at a time, or less. And after making one adjustment leave it and repeat when starting from cold again (e.g. do one check/adjust per day).

orrery

malc_b wrote: »

This sounds like you are trying to balance the radiators.

Nope, simply trying to make sure that the hall radiator isn't shutting down the heating before the rooms are up to whatever setting the OP has set.

the_devil_made_me_do_it

orrery..I have been putting the heating on as directed an hour before going to bed and it does appear to have reduced the condensation quite well so far. I haven't implemented your other suggestions yet, however, I will certainly give it a try and let you know