Boiler cycling issue

[Burger]

Hello,

Just wanted some assistance if I may? I have been to a job whereby the heating gets to temperature, stays off for approx 90 seconds then fires up again. The room stat is in the hallway, and may be the culprit (it’s a Honeywell t6360 with no neutral, just a live in and switched out). All rads getting hot and have tried to balance by closing lockshields down to minimum.

Boiler is a Vaillant ecotec pro 28, in a flat, x4 rads drop fed in microbore, with TRVs except where room stat is located. The temp has approx 6 degrees between flow and return, so was thinking along lines of possible blockage?

Thanks in advance.

 

[Last Plumber]

Have you tried range rating the Boiler?
Measure the heat output from the system and reduce the output to what's required. It is a modulating Boiler so it will adapt itself but sometimes on small systems range rating is required.
If this is the same post as on EF, the answers are right. If the room stat has a neutral, it allows the live feed to the stat to heat an anticipator which improves the accuracy of the stat. The issue it normally presents is a noticeable delay in operation so the user will notice a drop in temperature prior to the heating coming back on.

What exactly is the complaint? Is the heating getting to temp and staying off on the anti-cycling delay or is it that the stat opens and the delay in it closing again is too long?

 

[Burger]

Have you tried range rating the Boiler?
Measure the heat output from the system and reduce the output to what's required. It is a modulating Boiler so it will adapt itself but sometimes on small systems range rating is required.
If this is the same post as on EF, the answers are right. If the room stat has a neutral, it allows the live feed to the stat to heat an anticipator which improves the accuracy of the stat. The issue it normally presents is a noticeable delay in operation so the user will notice a drop in temperature prior to the heating coming back on.

What exactly is the complaint? Is the heating getting to temp and staying off on the anti-cycling delay or is it that the stat opens and the delay in it closing again is too long?

Haven't seen post on EF. I have lowered the range down to I think 10kw . The complaint is the heating is heating up initially, and don't think anti cycling is kicking in. Basically he's noted heats up to approx 75 degrees on boiler display, then drops to approx 62, then heats up, and so on all in about 2 min intervals.

 

[Last Plumber]

Haven't seen post on EF

My apologies for being presumptuous. There is a post on the Electrician forum regarding a similar issue. I think it's the same stat and a Pro 28. Ignore that bit then.

When you altered the lock shields, did it make any difference?
What is the heat temp set to?
Are there any other issues that brought this to the customers attention or were they just 'watching'?

 

[Burger]

Didn't make any difference, the room stat about 21 & boiler stat is on max - 75. I turned it down to 62 which seemed to be better, but coz he was watching, he said it worked ok before. I've also changed the pump head as got 2 different resistance readings below what is on vaillant website.

Nothing else alerted him, other than it was ok a few weeks ago.

 

[Last Plumber]

Didn't make any difference, the room stat about 21 & boiler stat is on max - 75. I turned it down to 62 which seemed to be better, but coz he was watching, he said it worked ok before. I've also changed the pump head as got 2 different resistance readings below what is on vaillant website.

Nothing else alerted him, other than it was ok a few weeks ago.

More often than not I leave Boilers set around the 60 mark (checking the rad are suited). If that works OK, I'd leave it there. If it's on 75 the chances are it will not be in condensing state and therefore running less efficiently.

 

[Burger]

More often than not I leave Boilers set around the 60 mark (checking the rad are suited). If that works OK, I'd leave it there. If it's on 75 the chances are it will not be in condensing state and therefore running less efficiently.

Thanks for your help.