Ideal Boiler Short Cycling

[matthewjamesruddock@]

Hi,

My Ideal Logic+ 2016 24kW boiler is short cycling in 2 scenarios and I'm wondering if anyone has idea why.

On central heating, the flow temp cant be less than 77 degrees or it short cycles. In other words I can never get it into condensing mode.
I have 1x double rad 80cm long, 1x single rad 80cm long, 1x single rad 40cm long, 1x single rad 110cm long and a 120cm tall towel rail.
I think the problem may be that the boiler cant dump heat quick enough on lower temps as its oversized for the amount of rads in my 1 bed house.

However the more annoying problem is when the rads and boiler is running fine on 77 flow temp for central heating , if I use the hot water for shower or tap etc and then it goes back to central heating it will then short cycle even on the 77 degree flow temp whereas before I used the hot water it was fine.

This scenario is much more annoying as it means I cant use the hot water while the heating is on or it will cycle on and off every 2 mins, and switch off and back on wasting gas.

If anyone knows why switching to hot water from central heating and then back to central heating upsets the boiler I would love to know to prevent/fix it.

Another weird thing that might help diagnose is that the radiator flow pipe under the boiler warms up when having a shower or using the hot water which im not sure is normal or not. Its happening now in summer with the boiler on summer mode.

I have a gas engineer coming in a few weeks


Thanks

 

[CountryFan]

Flow pipe warming up is generally a sign of the diverter valve failing, which could also be why it struggles at lower heating temps, unless it is not range rated.

 

[matthewjamesruddock@]

What is range rated? I might need to ask to get that done.

 

[CountryFan]

What is range rated? I might need to ask to get that done.

It is where you can set the output of the heating, but I’ve just looked and apologies, yours doesn’t seem to support this, so might just be the diverter.

 

[Justin Passing]

Could be sludge blocking flow, so the boiler heats up and has to turn off. Or a dud pump.

 

[matthewjamesruddock@]

Thank you. The hot water to central heating issue is much more annoying I hope its just a divertor or something simple rather than me needing to upgrade the rads to double panelled.

 

[denso13]

Thank you. The hot water to central heating issue is much more annoying I hope its just a divertor or something simple rather than me needing to upgrade the rads to double panelled.

Has it always been like this?

 

[matthewjamesruddock@]

I dont know I moved in my house in march and thats the first time the heating has been on since I've owned it.

The vendor didnt mention anything .

 

[drives]

Too much flow restriction in the system will lead to short cycling. I would start by opening up your lockshields/TRVs on all of your emitters and see how you get on.

The issue you describe with respect to change over from DHW to CH- when it does this the outlet flow temp is already high, so just exasperates the issue perhaps? That would be my guess.

As for the outlet flow to radiators getting warm- are you sure this isn't just conducted heat?

 

[matthewjamesruddock@]

thanks I will try opening them all. Do you turn them clockwise to open them with pliers?

The bedroom trv doesnt work. I tried setting it to the snowflake setting and the heating still came on full blast through it.

Yeah hot water to heating is what is the most annoying thing. The hot water temp is 50. I did speculate the boiler goes full power to the heat the water and the when it flicks back to heating it doesnt get chance to modulate back down and the ch flow temp gets too high.
I can live with the high central heating temps but this is the issue which makes it so i cant use hot water during winter with the heating on which is unrealistic

Could be conducted heat but its 3 foot down the pipe before it goes into the floor. The flow pipe feels hot all the way. Too hot to touch where the pipe enters the boiler

 

[drives]

thanks I will try opening them all. Do you turn them clockwise to open them with pliers?

Anti clockwise to open and you can use pliers. I normally use an adjustable wrench.

Yes- TRV sounds broken. I'd perhaps just remove the TRV heads from all your radiators and then go back to the boiler and see if it operates any better. I'm pretty sure it will if you open up both sides of each radiator. If one struggles to get warm then you can go back and adjust the lockshields accordingly to balance. On such a small system you probably won't need to. Just keep them all open.

TRVs should be used sparingly. A lot of people try to zone their houses with them, inadvertently restricting flow to the point where it becomes counter productive in terms of efficiency (due to the heat source short cycling). In a 1 bed house I might have one in the bedroom but that would probably be it.

Regarding the CH pipework getting hot I still wouldn't rule out conduction, assuming it's not too hot to touch all of the way down to floor level.