Ideal boiler cycling with Nest & Opentherm

[flyingsailor]

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.

 

[Knappers]

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.

 

[flyingsailor]

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?

 

[Knappers]

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?

 

[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.

 

[flyingsailor]

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.

 

[flyingsailor]

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?

Unfortunately I don’t think you can change the heat settings through nest which is frustrating

 

[Littlejack101]

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.

Still doing the same with all TRV's open...no idea whether this is working 'as designed' or an issue now!

 

[flyingsailor]

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.

 

[king of pipes]

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 ?