New Boiler - Weather Compensator?
Discussion
EVening all.
The time has now arrived for me to get the boiler replaced, which is being done in a couple of weeks.
Now, at the moment i am running standard S plan, but this is being adapted so that we can zone upstairs and downstairs individually with separate programmable room stats.
However, the latest thing seems to be having the system weather compensated, with the appropriate sensor outside.
From my very basic understanding, is that if the system is WC, there is no need for room stats?
Thats great, but, on occasion there is sometimes the need to give the heating a 'boost', in which case, would be impossible as there is nothing to adjust.
Looking at the installation instructions, it does state that a room stat can be installed as well, but i am struggling to understand how this would work on a WC system?
My gas man who is installing it all is a good friend, but won't really say how it works or even which would be the best way to go.
An idiots guide to this type of set up would be most appreciated!
The time has now arrived for me to get the boiler replaced, which is being done in a couple of weeks.
Now, at the moment i am running standard S plan, but this is being adapted so that we can zone upstairs and downstairs individually with separate programmable room stats.
However, the latest thing seems to be having the system weather compensated, with the appropriate sensor outside.
From my very basic understanding, is that if the system is WC, there is no need for room stats?
Thats great, but, on occasion there is sometimes the need to give the heating a 'boost', in which case, would be impossible as there is nothing to adjust.
Looking at the installation instructions, it does state that a room stat can be installed as well, but i am struggling to understand how this would work on a WC system?
My gas man who is installing it all is a good friend, but won't really say how it works or even which would be the best way to go.
An idiots guide to this type of set up would be most appreciated!
Thanks for that.
Yes, thats what i thought but then i read that it seems that the heating is running all the time, with the radiators cooling and warming up depending on outside temp.
If thats the case, i'm not sure why a room stat is needed as the boiler theoretically would control the room temp?
Yes, thats what i thought but then i read that it seems that the heating is running all the time, with the radiators cooling and warming up depending on outside temp.
If thats the case, i'm not sure why a room stat is needed as the boiler theoretically would control the room temp?
vladcjelli said:
From a laymans point of view, I couldn't see the point of this when we had our boiler installed.
Surely, if the stat is saying it's cold, the boiler has to work harder. Then, if the water coming into the boiler is colder, the boiler has to work harder to get it up to the outgoing temp as specified on the boiler control?
So apart from telling the boiler to work harder, which it already knows due to temp, what does a compensator do?
I think the idea is the house is maintained at the required temp, but if the sensor picks up a drop in temp outside, it runs hotter to maintain the desired temp in the house.Surely, if the stat is saying it's cold, the boiler has to work harder. Then, if the water coming into the boiler is colder, the boiler has to work harder to get it up to the outgoing temp as specified on the boiler control?
So apart from telling the boiler to work harder, which it already knows due to temp, what does a compensator do?
What i don't get is why/how a room stat can work in conjunction with WC.
Just reading through the boiler user instructions again (Viessmann Vitodens 100W) and it says that the room temp can be adjusted via the boiler temp control knob if WC is installed.
That was my main concern really.
Also, as we are fitting the boiler to an existing two pipe system, the DHW will take priority over heating, which means i will have to time the hot water to come on and be done, an hour or so before we get up.
But, you can also connect room stats to the WC system, so i am assuming if a room stat calls for more heat, it will over ride WC mode and work normally until the room temp is achieved, and then revert back to WC to maintain the set temp.
My head hurts.
That was my main concern really.
Also, as we are fitting the boiler to an existing two pipe system, the DHW will take priority over heating, which means i will have to time the hot water to come on and be done, an hour or so before we get up.
But, you can also connect room stats to the WC system, so i am assuming if a room stat calls for more heat, it will over ride WC mode and work normally until the room temp is achieved, and then revert back to WC to maintain the set temp.
My head hurts.
Edited by Alucidnation on Sunday 25th May 10:56
Gingerbread Man said:
Alucidnation said:
Just reading through the boiler user instructions again (Viessmann Vitodens 100W) and it says that the room temp can be adjusted via the boiler temp control knob if WC is installed.
That was my main concern really.
Also, as we are fitting the boiler to an existing two pipe system, the DHW will take priority over heating, which means i will have to time the hot water to come on and be done, an hour or so before we get up.
But, you can also connect room stats to the WC system, so i am assuming if a room stat calls for more heat, it will over ride WC mode and work normally until the room temp is achieved, and then revert back to WC to maintain the set temp.
My head hurts.
You can cap off the two dedicated cylinder feeds and use a standard zone valve setup That was my main concern really.
Also, as we are fitting the boiler to an existing two pipe system, the DHW will take priority over heating, which means i will have to time the hot water to come on and be done, an hour or so before we get up.
But, you can also connect room stats to the WC system, so i am assuming if a room stat calls for more heat, it will over ride WC mode and work normally until the room temp is achieved, and then revert back to WC to maintain the set temp.
My head hurts.
Edited by Alucidnation on Sunday 25th May 10:56
I'm not sure i understand what you mean?
We currently have a standard S plan system in place.
eliot said:
I've also got a Viessmann Vitodens 100W and looked into the WC sensor. As someone above correctly says, the theory is keep the return water at a low enough temp to ensure the boiler stays in condensing mode. Being into automation I started tracking temperatures and gas consumption - which i can track to the nearest decilitre.
What I found is that keeping the water low enough to condense resulted in the boiler running for ages to heat the water tank (which I only heat to around 55'c with a weekly high temp boost to kill the bugs) and the radiators not really heating the rooms.
I found I consumed far less gas by turning the boiler up to level 6 (70'c) as it only needs about 30mins to heat my 250L tank and the house heats quickly.
So i decided not to bother with WC. Btw, I also sussed out which off the shelf thermistor they use for the outdoor sensor - they are only a few quid rather than the price Viessmann charge.
Ok thanks.What I found is that keeping the water low enough to condense resulted in the boiler running for ages to heat the water tank (which I only heat to around 55'c with a weekly high temp boost to kill the bugs) and the radiators not really heating the rooms.
I found I consumed far less gas by turning the boiler up to level 6 (70'c) as it only needs about 30mins to heat my 250L tank and the house heats quickly.
So i decided not to bother with WC. Btw, I also sussed out which off the shelf thermistor they use for the outdoor sensor - they are only a few quid rather than the price Viessmann charge.
With the WC kit, they supply a hot water demand box, which i believe, over rides the WC/Htg, to heat the water, at a higher temp and then reverts back to heating, a bit like a combi.
I am going to ring them on Tuesday and try and find out exactly how it works.
moles said:
If you haven't already purchased the Viessmann i would have a rethink, they are not one of the most reliable boilers out there!.
Interesting that you say that, as I haven't seen many complaints on the internet about them, and we all know how quick people are to post up problems, plus they offer a 5 yr warranty, and a 10yr warranty on the heat exchanger.WB and Vaillant seem to be the ones most people choose, but I have heard from several gas installers that they can be problematic when they are fitted to older systems, and can be quite picky when it comes to warranty claims.
What would you recommend?
To be honest, i have also been looking into the Vaillant, but it appears that even their basic OV HO boiler will not allow easy control of existing valves room stats etc, unless i purchase another load of their connection/control boxes, and even then, i would have to use their own room stats as they are all ebus.
I have also been thinking of maybe a 4 pipe system boiler and do away with the external pump.
I am a bit limited with pipe layout, boiler location as its in a kitchen cupboard, (and funds), and so i am trying to make this as easy as possible.
Whichever way i go, i would really like to introduce the WC if possible.
I have also been thinking of maybe a 4 pipe system boiler and do away with the external pump.
I am a bit limited with pipe layout, boiler location as its in a kitchen cupboard, (and funds), and so i am trying to make this as easy as possible.
Whichever way i go, i would really like to introduce the WC if possible.
Interesting you say that as I have a 3 zone system installed with a nest down stairs and up.
From trying to understand the Vaillant manual, the controls are ebus with no provision for 230v switching with a wc installed.
It's possible I have gone cross eyed and missed something as I have been studying this all weekend!
From trying to understand the Vaillant manual, the controls are ebus with no provision for 230v switching with a wc installed.
It's possible I have gone cross eyed and missed something as I have been studying this all weekend!
With the Viessman, from what i understand, the heating runs 24/7 and adjusts the flow temp to the rads, through heat loss and depending on outside temp. i.e. if it gets cold outside it ups the flow temp to the rads. If there is a call for DHW, the heating shuts off and the boiler ramps up the temp to heat the water, a bit like a combi. The heating curve can also be adjusted manually via the temp dial on the boiler.
With the other systems, its appears that the WC works along side internal controls, and adjusts the flow temp according to the outside temp. However, i think this stays the same, even when demand for hot water, which means it would take forever for the water to heat up.
This is all from what i can make out from the brochures and manuals, which to be honest, are not very good from any of the manufacturers.
With the other systems, its appears that the WC works along side internal controls, and adjusts the flow temp according to the outside temp. However, i think this stays the same, even when demand for hot water, which means it would take forever for the water to heat up.
This is all from what i can make out from the brochures and manuals, which to be honest, are not very good from any of the manufacturers.
Edited by Alucidnation on Monday 26th May 22:51
With the Viessman, from what i understand, the heating runs 24/7 and adjusts the flow temp to the rads, through heat loss and depending on outside temp. i.e. if it gets cold outside it ups the flow temp to the rads. If there is a call for DHW, the heating shuts off and the boiler ramps up the temp to heat the water, a bit like a combi. The heating curve can also be adjusted manually via the temp dial on the boiler.
With the other systems, its appears that the WC works along side internal controls, and adjusts the flow temp according to the outside temp. However, i think this stays the same, even when demand for hot water, which means it would take forever for the water to heat up.
This is all from what i can make out from the brochures and manuals, which to be honest, are not very good from any of the manufacturers.
With the other systems, its appears that the WC works along side internal controls, and adjusts the flow temp according to the outside temp. However, i think this stays the same, even when demand for hot water, which means it would take forever for the water to heat up.
This is all from what i can make out from the brochures and manuals, which to be honest, are not very good from any of the manufacturers.
Edited by Alucidnation on Monday 26th May 23:01
I agree, however, i think the idea is that the house doesn't cool down at all with it on 24/7 as the system maintains a set temp, rather than being off for long periods, and then having to work harder to get back up to temp when required.
The WC sees the temp changes before the inside of the house does, so alters the boiler output accordingly so that the occupants don't feel the change.
Its a bit like climate in a car i guess.
Disclaimer: This is all a guess on my basic understanding and will be calling the manufacturers for specific details today.
The WC sees the temp changes before the inside of the house does, so alters the boiler output accordingly so that the occupants don't feel the change.
Its a bit like climate in a car i guess.
Disclaimer: This is all a guess on my basic understanding and will be calling the manufacturers for specific details today.
FiF said:
I can't see the point in setting the output lower unless it's to match the output better to the demand for a small house /oversized boiler and thus avoid boiler cycling. That issue is automatically dealt with if the boiler has a fully modulating burner surely?
Pass 
As i said, i am going to give them all a call today and try and get some more detailed info.
I think WC is not really used a lot in a domestic situation, and the tech is still in its infancy.
Well, had the wc system in for over a week now and works quite well as far as I can tell, as it's not exactly been cold!
A few issues with the existing system to start with, as in all the zone valves needed replacing but as things go, it was fairly painless. All the trvs were changed for Danfoss liquid filled and seem responsive, more so than the traditional wax type, although I see that they now do gas filled which should be even better.
The room stats still give overall total control over the system, but I think at some point they will be removed.
The viessman boiler is extremely quite once it has settled down and the display gives the flow temp through the boiler.
This alters as the external temps change and increases as it gets colder.
So, all in all, looking good so far, although I'll still reserve judgement until the winter!
A few issues with the existing system to start with, as in all the zone valves needed replacing but as things go, it was fairly painless. All the trvs were changed for Danfoss liquid filled and seem responsive, more so than the traditional wax type, although I see that they now do gas filled which should be even better.
The room stats still give overall total control over the system, but I think at some point they will be removed.
The viessman boiler is extremely quite once it has settled down and the display gives the flow temp through the boiler.
This alters as the external temps change and increases as it gets colder.
So, all in all, looking good so far, although I'll still reserve judgement until the winter!
Quick update!
After now having the heating on for a few days now the evenings are getting a bit colder, i have left it running 24/7 on the factory set curve.
The house is now an even temperature throughout after having tweaked the TRV's for each room, using some basic thermometers bought from Amazon to get a rough idea. All rooms are around the 20-21C and very comfortable. Its nice getting up in the night for a pee in to a warmer house.
For the last few days i have been in and out at various times and the temp has been very stable with the boiler adjusting well to the changes in external temps.
It was a bit of a faff to set up but, in my opinion and experience, well worth it!!
Over and out.
After now having the heating on for a few days now the evenings are getting a bit colder, i have left it running 24/7 on the factory set curve.
The house is now an even temperature throughout after having tweaked the TRV's for each room, using some basic thermometers bought from Amazon to get a rough idea. All rooms are around the 20-21C and very comfortable. Its nice getting up in the night for a pee in to a warmer house.
For the last few days i have been in and out at various times and the temp has been very stable with the boiler adjusting well to the changes in external temps.
It was a bit of a faff to set up but, in my opinion and experience, well worth it!!
Over and out.
herewego said:
What a ridiculous waste of fuel to heat your house 24 hours a day.
What experience of a weather compensated system do you have?I chose this particular system as the house is occupied most days, and from after having used it for a while, find that it keeps the internal temperature very stable, regardless of outside temps.
We like a warm environment, but hated using a room stat as they were so unreliable and to be honest, i am very surprised at how well it all works.
As for cost, well, I'm reckoning that it will cost the same, if not a bit less to run, than the old system.
eliot said:
Alucidnation said:
Christ forgot all about this thread.
Anyhoo, as an update, the WC system has been working fantastically and has reduced our gas bills by quite a bit.
Would recommend.
Ok then, how many sq ft is your house and what is your gas bill for nov,dec,jan,feb?Anyhoo, as an update, the WC system has been working fantastically and has reduced our gas bills by quite a bit.
Would recommend.
And is your house occupied during the day?
Edited by eliot on Sunday 10th March 19:01
Is it that your are going to try and tell me it’s too expensive, house is too big, inefficient insulation Etc etc
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