Weather compensation what does it do?

[ericmark]

If I feel warm at 20ºC that's the temperature I feel warm at, and it really does not matter what the weather outside is doing. I can see if going to be a warm day, better to allow home to remain cool in the morning so don't need AC latter in the day, but this is forecasting, not compensation, and yes smart thermostats may be able to forecast the weather.

I ask as I have a problem, with a hysteresis in room temperatures. This is likely due to three independent devices trying to control the room temperature, the boiler cycles on/off, the wall thermostat cycles on/off, and the TRV tries to modulate radiator output. So at the moment the wall thermostat has over shoot the mark

and until the hall has cooled the TRV can't possibly heat living room. It shows outside at 10ºC and raining

and yes found on warm days like today the wall thermostat works better if it raises by 0.5ºC every two hours, but on a cold day works better if it goes straight to 20ºC. But can't find any way to program in a different method depending on weather outside.

So all well and good the thermostat telling me it's raining, I could simply look out of the window, but what change does it make to the heating by knowing when it's raining?

 

[denso13]

https://www.hhic.org.uk/uploads/5A5F2F2C7D545.pdf

 

[MNW67]

But can't find any way to program in a different method depending on weather outside.

Weather compensation achieves something similar in a different way. It varies the boiler flow temperature depending on the outside temperature. So, you get gentler heating when it is warmer outside.

 

[ericmark]

Thank you both, so I should alter dial on boiler as we go into winter and into spring.

Not really sure how this helps, radiators will never get too hot as TRV will turn down heat. What it will do is reduce DHW temp.

But no harm giving it a go.

 

[MNW67]

The house will feel more comfortable if you do that. Certainly that's my experience. But you're not supposed to run cast iron boilers too cool as they say it can cause them to condense and that leads to corrosion. Can't remember what you have?

 

[ericmark]

I have a Worcester Bosch oil boiler, and this is the problem in the past use to a boiler which could modulate, but the oil boiler is 19 kW or nothing.

At least today when Smart meter fitted I now know it will still work when the grid power turned off, I had never tested to see if it would still work, now I know it will.

 

[Harry Bloomfield]

I have a Worcester Bosch oil boiler, and this is the problem in the past use to a boiler which could modulate, but the oil boiler is 19 kW or nothing.

At least today when Smart meter fitted I now know it will still work when the grid power turned off, I had never tested to see if it would still work, now I know it will.

I cannot see how it can work effectively, in a system which is unable to modulate, except by turning the boiler on and off (uneconomic short cycling).

 

[ericmark]

I will see tomorrow how the heating has worked, worth a try.

 

[ericmark]

I cannot see how it can work effectively, in a system which is unable to modulate, except by turning the boiler on and off (uneconomic short cycling).

I have been trying to get my head around this. So as the rooms warm up, the TRV's close down, causing first more water through those still open, and then lifting the by-pass valve, and this means the return water getting hotter and hotter, so the boiler reduces out put more and more until only way to reduce any more is to cycle off/on, and the algorithms in the boiler cause the output temperature to drop the more the boiler modulates, so there would be no reason to have weather compensation as this will naturally happen unless some external device turns off the boiler.

So only with a non modulating boiler would turning down output temperature make any sense. As to short cycling not actually measured, but temperature set low when we first moved in, and the boiler would fire for around 20 minutes to heat DHW, when I turned up the temperature there was very little change. The program was set for half hour, but it would always switch off before half hour, at around 20 minutes some times it would fire a second time, but rare.

Anyway this was today the missing bit was when smart meter fitted so route was off, but boiler still running. Heating now off so temperature will drop until 8 am when wall thermostat starts boiler again. The TRV will open at 7:30 am but clearly with boiler not running as unlikely hall will drop to 16ºC it will do nothing until 8 am. So tomorrow will post result.

 

[MNW67]

I would say the general principle here is that, at a lower flow temperature, everything heats up more slowly. The controls have more time to react and you get less lag and less overshoot.

 

[Johntheo5]

Oil boilers, because they have to cycle, still maintain a average boiler flow temperature within + or - 4C to 5C of the target temp, mine is set to 70C so cuts out at exactly 70C and back in at 62C so maintains average flow temp of 66C but the circ pump keeps running which works very well for my system with a combination of TRVs and one digital, (non TPI) roomstat which maintains the combined dining/lounge rooms at setroom temp to within 0.2C.
The main purpose of WC is to increase boiler efficiency by lowering to boiler flow temperature which in turn results in a lower rad/boiler return temperature and greater boiler efficiency.

 

[Andy165]

Weather compensation. You've been sold an idea that in theory will save you energy and improve heating efficiency. In practice, how well is your house insulated? How do each of the occupants react to cold ? Your looking at graphs and flow charts and trying for optimum improvements. Good luck with that. One persons comfort level is not the same as the next. Persevere and experiment until you get bored. Then get a different hobby.

 

[Harry Bloomfield]

I have been trying to get my head around this. So as the rooms warm up, the TRV's close down, causing first more water through those still open, and then lifting the by-pass valve, and this means the return water getting hotter and hotter, so the boiler reduces out put more and more until only way to reduce any more is to cycle off/on, and the algorithms in the boiler cause the output temperature to drop the more the boiler modulates, so there would be no reason to have weather compensation as this will naturally happen unless some external device turns off the boiler.

As the stat nears the desired temperature, the boiler modulates down, so it doesn't over shoot, thus generally avoiding the need to cycle on/off as much as possible. The boiler output, matches the heat losses. Gentle modulation, means a much steadier room temperature, for the occupants, than simple on/off switching, plus the creaking of pipes, as they expand and contract is almost completely eliminated.

WC, can directly control the flow temperature, to reduce it, when less heat is needed, again to limit overshoot, and long waits whilst the system/rooms cool down, before the need call for heat.

Heating which operates more accurately, and gently, becomes invisible/unnoticed by the occupants.

 

[Andy165]

If you leave the heating on all the time so the building fabric is maintained at that temperature aswell. Works better in some of the colder European countries as they have colder winters, better insulated homes, and have the heating on 24 hours a day. Uk housing stock is very poorly insulated, and playing catch up to standards due to under investment and "doing it to a price".

 

[ericmark]

Well today reducing flow temperature does not seem to have impacted on the heating of the hall it is still warming up as quick as when the flow temperature was higher, however it has made a big difference to heating of the Living room it is taking twice as long to reheat. Since only just got up, and not used the Living room yet today this is not a problem, but clearly not what I really want, so think boiler temperature will be going back up, but will leave it for now and see how it does. My bedroom outside temp 9.7ºC in room 21ºC so that room OK.