boiler cycling

[CIB]

I've completed my new system.

The gas man conected it up and checked the boier on Friday.

Itr works fine except on DHW only. The boiler seems to cycle too much...30 seconds on, 1 minute off. This is with the pump on max speed

I Have updated an old system. The hot water used to be gravity feed with 28mm pipes. I have re used the cylinder. Could this be the cause of the problem? Could the indirect coil not have enough output to cope with the boiler? Maybe it is all lime-scaled up?

The system is a Halstead Hero 60 boiler, a mid position valve, and the old indirect cylinder.

On central heating only (with the room stat on max) it will run for 30 minutes from cold, then cycle 2 minutes on, two minutes off.

Any thoughts on the cycling appreciated

Thanks

Chris

 

[ChrisR]

It depends whether the old cylinder was a "BS" one or a "Medium duty",which were the cheapied with really short internal heat transfer coils. Yo can tell by the distance between the boiler 's primary connections.

They would only be 3kW at best, probably less. a 60.000 Btu/hr boiler produces 17.5 kW, so you might ony expect 20 seconds alight in 2 minutes!

 

[PEDANTICVINDICTIVEMAN]

Isn't the cylinder supposed to be upgraded anyway to comply with part l ? or is that a myth ?