Should I bother with weather compensation on new boiler?

[m3jappa]

We need a new boiler, its never simple as its part of a bigger refurbishment so im trying to make the system the best it can be.

The plumber I am using doesn't know a lot about weather comp, he's a bit old school which tbh im ok with as he's very thorough, just not that up on all modern stuff. he's ok fitting it, its more a case of I personally want to know how to use it and is it easy to set up? I don't want some mentally complicated system which requires you to a gas engineer to turn it on

so between myself, the plumber and my own research I think I want a valiant boiler with weather comp.

Am I right in thinking this is what ill have :

valiant vrc700 fitted on or near to boiler (boiler is in its own little room).

tado thermostat for each zone.

day to day is controlled by the tado . if I want/need to adjust weather comp thats a separate entity on the vrc700

I understand the valiant sensocomfort is quite complicated as opposed to a tado, hence the tado choice.


Any input valued?

[Magic919]

Vaillant.

It’s a good choice of boiler. Weather comp also a good idea.

I’d probably stick with Vaillant controls.

I run WC with a Viessmann, but have no thermostats.

[POIDH]

I had a new boiler fitted. Plumber said not to fit weather compensation.
At the first service a different plumber, originally from Denmark, asked why we didn't have it. So he fitted it.

I compared the two years and there was 8% difference in cost.

We also noted that the house was better controlled in temperature as the boiler 'learned' to modulate output times.

[StreetDragster]

Also worth noting that tado has weather adaption built in and cannot be disabled

[AyBee]

Definitely get weather compensation - it's a no-brainer. My boiler is too old for it unfortunately, but I'd have it if I could.

[Trustmeimadoctor]

You dont run both tado and manufacturers controls at the same time either use vaillants trvs and room sensors or just dumb trv's of no trv's and just use pure weather comp

[Actual]

I installed Tado and it is OK but it doesn't work if my Internet service is down.

[OutInTheShed]

Weather compensation seems to come in different flavours.
I had a rubbish version of it about 10 years ago.
Going too far trying to control your heating based on the outdoor temperature can go badly.
The amount of heat my lounge needs is influenced by other things, like wind, rain and sun. It can be frosty outside but my lounge is warm because the sun is flooding in. My lounge can cool down because a lot of people have been in and out, opening doors.
We have 'load compensation' working fairly well, the boiler sets the flow temperature according to how far below 'target' the thermostat sensor is.
It's also varying the pump speed.

Ideally, I think you'd have all the parameters available to the controller, and control over the weightings of various factors. In reality, it's a lot of work to get things exactly right and it's easier to adjust some controls to suit major changes in the weather.

[Simpo Two]

AyBee said:

Definitely get weather compensation - it's a no-brainer. My boiler is too old for it unfortunately, but I'd have it if I could.

If it's cold outside my house gets colder so the thermostat switches the boiler on until it's back to where I want it.

What does 'weather compensation' bring to the party?

If it could make the weather warmer or stop it raining I might be interested!

[Trustmeimadoctor]

Indeed and that's why manufacturers controles work better. I you have full opentherm then your getting closer but 3rd party smart controls really don't cut the mustard


Also make sure the external sensor is positioned correctly or you will find it turning off as it thinks it's too warm

Weather comp with room compensation is the best solution really so you get it where it's needed.

But really the entire system needs properly planning and alot of heating engineers don't spend the time doing it as users don't want to pay for it "but boxt can do me a boiler for x, why are you charging more than double"

[Hoofy]

Simpo Two said:

AyBee said:

Definitely get weather compensation - it's a no-brainer. My boiler is too old for it unfortunately, but I'd have it if I could.

If it's cold outside my house gets colder so the thermostat switches the boiler on until it's back to where I want it.

What does 'weather compensation' bring to the party?

If it could make the weather warmer or stop it raining I might be interested!

That's what I wondered.

[Trustmeimadoctor]

It tries to stop it using more energy than necessary.
It's of most benefit with steady state heating but can benefit off and on

[Simpo Two]

Trustmeimadoctor said:

It tries to stop it using more energy than necessary.

I wonder which is greater, the cost of energy saved, or the cost of a more expensive boiler with more tech that will need replacing every so often?

[AyBee]

Hoofy said:

Simpo Two said:

AyBee said:

Definitely get weather compensation - it's a no-brainer. My boiler is too old for it unfortunately, but I'd have it if I could.

If it's cold outside my house gets colder so the thermostat switches the boiler on until it's back to where I want it.

What does 'weather compensation' bring to the party?

If it could make the weather warmer or stop it raining I might be interested!

That's what I wondered.

Weather compensation governs how hard your boiler works. Right now, mine is either on or off, so it will heat up on full blast, then turn off, then cool down and turn back on again on full blast. If I had weather compensation, it would modulate itself to maintain a steady temperature inside which is more efficient for the boiler (therefore cheaper) and makes more sense in terms of maintaining a constant indoor temperature.

[OutInTheShed]

AyBee said:

Weather compensation governs how hard your boiler works. Right now, mine is either on or off, so it will heat up on full blast, then turn off, then cool down and turn back on again on full blast. If I had weather compensation, it would modulate itself to maintain a steady temperature inside which is more efficient for the boiler (therefore cheaper) and makes more sense in terms of maintaining a constant indoor temperature.

Lots of boilers without weather comp modulate in various ways.
The last boiler I scrapped was made in about 1996 and would modulate to keep a constant flow temperature (set on a dial), within limits.
Even a weather comp boiler will cycle on/off when the demand is really low.

There is a danger of chasing fractions of a % efficiency, as measured under test conditions which may not reflect how you live in your house.

[Trustmeimadoctor]

Simpo Two said:

Trustmeimadoctor said:

It tries to stop it using more energy than necessary.

I wonder which is greater, the cost of energy saved, or the cost of a more expensive boiler with more tech that will need replacing every so often?

It doesn't need to cost alot to do WC and the part is really cheap usually.

If it's worth it for you it's hard to say but if your replacing the boiler anyway you might as well

[Trustmeimadoctor]

OutInTheShed said:

AyBee said:

Weather compensation governs how hard your boiler works. Right now, mine is either on or off, so it will heat up on full blast, then turn off, then cool down and turn back on again on full blast. If I had weather compensation, it would modulate itself to maintain a steady temperature inside which is more efficient for the boiler (therefore cheaper) and makes more sense in terms of maintaining a constant indoor temperature.

Lots of boilers without weather comp modulate in various ways.
The last boiler I scrapped was made in about 1996 and would modulate to keep a constant flow temperature (set on a dial), within limits.
Even a weather comp boiler will cycle on/off when the demand is really low.

There is a danger of chasing fractions of a % efficiency, as measured under test conditions which may not reflect how you live in your house.

Modulate yes but as you know WC isn't about modulation it's adjusting flow temp, just it will modulate to get the flow temp down so the better the modulation the better.

It still all really depends how you heat your house though low and slow or fast and on and off

[OutInTheShed]

Trustmeimadoctor said:

Modulate yes but as you know WC isn't about modulation it's adjusting flow temp, just it will modulate to get the flow temp down so the better the modulation the better.

It still all really depends how you heat your house though low and slow or fast and on and off

Weather comp is another layer on top of modulation.

The boiler modulates the flame, or even turns it on/off, to keep the flow temp within a window.
Weather comp decides what the flow temp should be, according to the weather.
You can have a lot of modulation and a narrow window without weather comp, or you can have weather comp and not much modulation. A wider 'window' will make the boiler cycle on/off less often.

You can also blend other control schemes, like demand comp, to turn the radiators up a bit if your house is cooler than it should be despite it not being very cold out.

Some boilers at least are also taking other things into account, like the return temperature and rates of change of inputs.
There is a lot of code in there.

[Hoofy]

AyBee said:

Weather compensation governs how hard your boiler works. Right now, mine is either on or off, so it will heat up on full blast, then turn off, then cool down and turn back on again on full blast. If I had weather compensation, it would modulate itself to maintain a steady temperature inside which is more efficient for the boiler (therefore cheaper) and makes more sense in terms of maintaining a constant indoor temperature.

Ah, I can see the theory behind it then. Is there any research to prove that it is cheaper to run?

(It wouldn't work for me - even in winter, I only do an hour in the morning, then maintain 8C through the day until May!)

[OutInTheShed]

it's probably cheaper to run if it helps you run a lower water temperature more often.
Or if it stops temperatures overshooting.
It's not the only way of achieving these things.

If it means you run your boiler more often, it may cost you more to run.

Cost differences are probably quite small, it's more about running the heating the way you like it.