Different boiler but the Vaillant VRT392 does exactly that. See my thread here if you want to know the detail. Don't think it would work with the OP's boiler but I 'assume' the OpenTherm controls work in a similar way to the VRT392 (Without Weather Compensation).
Modulating Boiler Controls
- Thread starter df55555
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Different boiler but the Vaillant VRT392 does exactly that. See my thread here if you want to know the detail. Don't think it would work with the OP's boiler but I 'assume' the OpenTherm controls work in a similar way to the VRT392 (Without Weather Compensation).
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The old boiler was a biasi riva 28s compact it worked quite well with the honeywell controller, which seems to be a decent controller in it's own right.
The new boiler is over sized in relation to the amount of radiators, but was chosen for the water flow rate - which was poor with the biasi boiler.
The radiators all get hot at the same rate - so I assume that they are balanced correctly. In fact when I mentioned it to the installers they said that they haven't changed anything, if it was fine before theres no reason to change it. The pipes & radiators were replaced when we moved in about 2 years ago - we just didn't replace the boiler as well at that time, just fitted the honeywell stat.
Whatever the cycling from the stat or the boiler trying to sort it's own flow rate & temp - the radiators are mostly cold. Although the air temperature is at the desired level we start to get cold spots in the house.
I'm guessing as the old boiler worked harder to achieve the desired temperature the radiators weren't getting as hot & staying warm for longer periods to keep the temperature up. Having more latent heat coming off of the radiators for longer periods meant these cold spaots didn't exist.
As I said I'm making a poorly educated guess here - but we do seem to have a problem, which is a pity really as we have essentialy upgraded the system.
The new boiler is over sized in relation to the amount of radiators, but was chosen for the water flow rate - which was poor with the biasi boiler.
The radiators all get hot at the same rate - so I assume that they are balanced correctly. In fact when I mentioned it to the installers they said that they haven't changed anything, if it was fine before theres no reason to change it. The pipes & radiators were replaced when we moved in about 2 years ago - we just didn't replace the boiler as well at that time, just fitted the honeywell stat.
Whatever the cycling from the stat or the boiler trying to sort it's own flow rate & temp - the radiators are mostly cold. Although the air temperature is at the desired level we start to get cold spots in the house.
I'm guessing as the old boiler worked harder to achieve the desired temperature the radiators weren't getting as hot & staying warm for longer periods to keep the temperature up. Having more latent heat coming off of the radiators for longer periods meant these cold spaots didn't exist.
As I said I'm making a poorly educated guess here - but we do seem to have a problem, which is a pity really as we have essentialy upgraded the system.
the radiators probably do need balancing. It was a lazy guess to assume that they were correct. You can do it yourself, it's not difficult but it takes time.
It is also possible that your old radiators and pipes have sludge and sediment in them if the system was not cleaned properly
You did not say what is the power rating of the radiators you are using or answer my other questions.
It is also possible that your old radiators and pipes have sludge and sediment in them if the system was not cleaned properly
You did not say what is the power rating of the radiators you are using or answer my other questions.
Its a very one sided senario when someone asks for advice but will not give us the information which we need to consider the situation.
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Sorry guys I'm at work at the moment & haven't worked out exactly the radiator output. But roughly theres five doubles, two singles and a full height towel rail.
When the system was powered up they checked that all the radiators heated up equally - I'm not sure if this constitutes acceptable balancing.
The system was power flushed prior to installing the boiler. I did pick an installer based on recommendations from here - he seemed to be the most honest & knowledgeable. However two other guys installed the boiler & he came round after to check & sign off all the paperwork. I've had them back to reposition the flue as there was water pooling in it.
When the system was powered up they checked that all the radiators heated up equally - I'm not sure if this constitutes acceptable balancing.
The system was power flushed prior to installing the boiler. I did pick an installer based on recommendations from here - he seemed to be the most honest & knowledgeable. However two other guys installed the boiler & he came round after to check & sign off all the paperwork. I've had them back to reposition the flue as there was water pooling in it.
It is possible to buy the Remeha iSense from suppliers in Holland. See //www.diynot.com/forums/viewtopic.php?p=1926824#1926824 and read the following posts.
If you old boiler was running at an 80C flow temperature and now is running at a 70C flow temperature, the radiators will no be chucking out less heat.
Do a bit of research, as follows:
1. Find out what your heating requirement is by using the Boiler Size Calculator. You need to deduct 2kW from the answer as you have a combi boiler.
2. Find the total output of your rads using the data in the Stelrad Elite Catalogue.
Then post the results.
The boiler size calculator gives me a figure of 5.77 or 6.77 depending on whether I consider one outside wall against an insulated garage or not.
So a figure of 4.77 taking the larger requirement and deducting the 2kw.
Fortunately my brother is at my house dropping something off, so he was able to go around and give me some figures for radiator sizes.
I got to a figure of over 9Kw without factoring in the towel rail.
We didn't have a problem with keeping the house heated or warm even with the previous boiler.
So a figure of 4.77 taking the larger requirement and deducting the 2kw.
Fortunately my brother is at my house dropping something off, so he was able to go around and give me some figures for radiator sizes.
I got to a figure of over 9Kw without factoring in the towel rail.
We didn't have a problem with keeping the house heated or warm even with the previous boiler.
It seems its yet another who gets cheaper unregistered people to do the installation then comes and signs it all off!
Thats not in the spirit of gas registration and I dont think the Gas Safe Register would aprove of it either!
That does seem on the low side but, assuming your calculations are correct, it is below the lowest modulation level of your Remeha boiler, which is 6kW. This means the boiler will be running in on/off mode all the time.
Lets say 10kW.
So if you really need 5kW and have 10kW of rads, they will be able to heat the house when the flow temp is 55C and the return is 45C.
So reducing the max flow temperature setting on the boiler is what is being suggested ?
I can see that would effectively take longer to warm the house than the current default temp of, 75 I think. Therefore keeping the boiler running lower output for longer periods of time to maintain the room temp.
Am I right in thinking that.
I can see that would effectively take longer to warm the house than the current default temp of, 75 I think. Therefore keeping the boiler running lower output for longer periods of time to maintain the room temp.
Am I right in thinking that.
How do you know they are unregistered Tony, maybe they are his emloyees, don't just assume
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