After reading it a bit more, I think there might be a second level you need to access to get some of the settings.
EDIT: d.17 seems to be in here
Last edited:
Vaillant boiler cycling when using Underfloor Heating
- Thread starter windsortg
- Start date
After reading it a bit more, I think there might be a second level you need to access to get some of the settings.
EDIT: d.17 seems to be in here
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thanks @JonathanM. I would like to give your suggestion a go by changing the d.17 setting. However, since I do not have a d.17 status on my boiler, I need to scroll through to d.97 as you mention. If I scroll to d.97, you mention about a password. I am not clear on what you mean by this?
Currently, when I scroll to d.97 and press the "i" button, it displays the value 0
Currently, when I scroll to d.97 and press the "i" button, it displays the value 0
I think you have to enter "17" as the password. I don't know how that is done! It seems to be saying before pressing the i button.
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I copied the instructions from page 41 of the manual, below. There is more detail there about the whole process. This is the manual for 438. It says open vent, but I've been told before on here that it can be installed as a sealed system, which I think you said your is.
https://www.mrcentralheating.co.uk/media/catalog/product/ecotec_open_vent_install.pdf
EDIT: I think it means go to d.97, press i, press "+" to get 17, then press i again.
https://www.mrcentralheating.co.uk/media/catalog/product/ecotec_open_vent_install.pdf
EDIT: I think it means go to d.97, press i, press "+" to get 17, then press i again.
You will have to set a return temperature, rather than a flow temperature!
Do you know what value you might use for return temperature? The table in the manual seems to suggest to set that at d.5, but I don't know if it can also be done directly from the main display.
Do you know what value you might use for return temperature? The table in the manual seems to suggest to set that at d.5, but I don't know if it can also be done directly from the main display.
I've just thought it's probably a good idea if I restate what I said in my original reply! I don't actually have any experience of underfloor heating. I don't know if doing this might cause a problem, or damage your system. It may be, for instance, that the flow temperature will go a lot higher than its current set point, and I don't know what that would mean for your UFH system. As I said originally, I was really hoping that somebody with experience would advise.
If I were doing this, I would be keeping a close eye on both the flow and return temperatures (d.40 and d.41). And as I'm super cautious, I would probably monitor them first, using the current settings, to get an idea of what to expect.
no problem @JonathanM.
Am I experiencing this problem because I have a Vailllant boiler or would I have the same issue regardless of the boiler make/type? I am happy to change the boiler to either a Vaillant ecoTEC plus 637 (recommended by an engineer) or an alternative boiler if gets round the problem I am facing with the continuous boiler cycling when the UFH is ON without CH.
Am I experiencing this problem because I have a Vailllant boiler or would I have the same issue regardless of the boiler make/type? I am happy to change the boiler to either a Vaillant ecoTEC plus 637 (recommended by an engineer) or an alternative boiler if gets round the problem I am facing with the continuous boiler cycling when the UFH is ON without CH.
When you use UFH by itself, the boiler output is being used to heat just one large room. But the output should drop to 6.3KW under full modulation. I'm a bit surprised that it's cutting out after just two minutes and whilst the pipes are still quite cold. It might be worthwhile doing some basic diagnostics first, to try to confirm what the problem is. I've learnt from this forum, that boilers will usually cut out when the flow temperature reaches 5 degrees above its set point. Most likely, it is simply that the flow temperature from the boiler is reaching that SP+5. But there could feasibly be other reasons. If you haven't already, I would watch the flow temperature during those first few minutes, to see what temperature it reaches, before it cuts out. You can also watch the return temperature using d.41. And do the same when it's using both radiators and UFH for comparison.
It seems a lot of money, to spend £2.5K+ for a new boiler, unless you are sure it will fix the problem. Some new boilers will modulate lower, and there is potentially a problem, discussed above, with some Vaillants doing a long burn at full power before modulating. I personally wouldn't be worrying about the cycling damaging the boiler. I don't think two minutes is too bad. But if the orangery isn't getting warm, then that is more of a concern - and a puzzle.
I've not been following the thread, but might this problem be due to poor flow/restriction/isolation tap partially closed? Not enough flow, though UFH and boiler, so boiler quickly hits it's limit and shuts down?
I just noticed on the UFH manifold pump (see attached) that the green light is displayed on the first light which has the symbol of a 'radiator'. The second light, which is not lit, appears to show the symbol of an UFH system. Should the pump setting be on the 'UFH' symbol instead of the 'radiator' symbol?
The UFH manifold pump is also on the setting III - would this be the right setting?
The UFH manifold pump is also on the setting III - would this be the right setting?
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