Hi all, I have an Ideal Logic max 35 and have just connected my Nest thermostat via opentherm. The boiler modulates the water temp fine but as the heat reaches the the target temp on the thermostat, the boiler turns the flame off, keeps the pump running and then every 90-120seconds refires the flame for about 20 seconds before repeating this process for sometimes a few hours. During this time, the water temp is around 45 deg and drops down to 24/25 deg before relighting. Of note, it never did this when it was connected via on/off. Wondered if this is normal or if it’s actually bad for the boiler to constantly cycle so often. Many thanks.
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- Thread starter flyingsailor
- Start date
Do you have thermostatic rad valves throughout?
I guess either flow throught boiler is restricted by trvs or your heat demand is much lower than the boiler can modulate to so it cycles.
Shouldn't be a problem for the boiler tho.
I guess either flow throught boiler is restricted by trvs or your heat demand is much lower than the boiler can modulate to so it cycles.
Shouldn't be a problem for the boiler tho.
Hi Knappers, thanks for the reply! All rads have TRVs and are fully open. Is the boiler essentially ‘short cycling’ by doing this? I just don’t want it to reduce the lifespan of the boiler by constantly switching the burner on and off?
It's not going to break it but will add a bit of wear so not ideal. I'm not sure on the settings for the nest, if there's any advanced settings to change heat curve or anything but If there is then maybe have a look at that?
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Littlejack101
I have the exact same thing with the exact same setup - though some of my TRV's were shut some of the time which may have been my issue - testing now.
Be interested to see how you get on mate! Mines still doing it so I wonder if the boiler is indeed trying to modulate at too low a temp for my system or whether the nest is doing it to just keep a bit of residual heat pumping through to maintain the requested room temp.
Unfortunately I don’t think you can change the heat settings through nest which is frustrating
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Littlejack101
Still doing the same with all TRV's open...no idea whether this is working 'as designed' or an issue now!
How long have you had it running with this setup mate? I’ve had mine setup for about a week and a half and the last day or two, it’s done it a bit but not as much. It seems nest maybe ‘learning’ what water temp is required in order to maintain the temp of the thermostat. Rather than cycling as often it’s now holding around 48 deg flow temp as it approaches the target and then shuts off. I’ll keep an eye on it and let you know if it continues.
Firstly how many rads do you have ? The Ideal logic 35 kw max has a modulation rate from 8 - 24 kw in its heating mode , there must be a heat load loss through the boiler at all times we dont know how it's installed so let's say you need at least one decent size radiator with no trv fitted is this the case ?
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Littlejack101
I've had this setup for a week. No idea if the boiler behaved like this before as I was not really looking! I've messed around with the boilers 'Max flow temp' but that doesn't seem to make a difference.
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Littlejack101
I've got 10 rads & a couple heated towel rails. TRV's on all the rads but are fully open downstairs where the thermostat is located. The majority of the radiators are pretty old so would not surprise me if they not kicking out a huge amount of heat.
Opentherm should help stop the boiler cycling so much I am using it on my own system via a Nest thermostat , heating the system to a maximum of 60 °c over a longer period the boiler modulates to a very low output and condenses all the time , are you 100% sure you stat is operating in opentherm? it needs to be configured in the settings on the stat , you can then test it in the equipment setting. Kop
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Littlejack101
I was 100%, but your post prompted me to double check...I hadn't realised that the stat settings needed to be changed & was set up in on/off mode. Will see what happens now, but wanted to thank you Kop - I'd totally missed the stat set up part.
Can be a pita to configure sometimes you need to uninstall the app and start a fresh you should see something like this once your set up . Regards Kop
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Can be a pain to configure sometimes often it's better to uninstall the app and download it again , once your connected you should be able to see these
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Thanks King, I have 12 rads in the house, a couple are fairly large column ones and all TRVs are in the fully open position. I’ve balanced the system as best I can with an average differential between flow and return to the boiler between 13-15deg.
Hi kop, mine is setup exactly like this and does run for longer periods at lower temps but as the room temp reaches the target, the boiler doesn’t shut off, instead the pump runs and the flame ignites for a bit then goes out and repeats this continually. This maintains the target temp but wondered if it was normal or whether it should shut the boiler off and then restart it as the target temp drops a bit?
I don't think it should cycle so frequently even when it reaches its temperature set point mine doesn't Opentherm should modulate your boiler down to its lowest setting possible , review your settings on your Nest as my previous post , what boiler do you have ? it maybe possible to set a period of time your boiler heat between switchings ? Regards Kop
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