System balance issues

[joe plumber]

Hi there. Having a few issues getting the balance right on a large ish guest house. 18 rads and an unvented cylinder heated by a 28kw baxi system boiler located in the loft. I was called to the job last week after the painters had been in and removed some rads, after replacing the rads they found certain radiators were no longer getting hot. So after a few hours balancing i managed to get everything nice and hot again. Anyway 2 weeks later I receive a call saying the same the system is out of balance again! So I return and try to tweak the system again only this time it's a real struggle I can't seem to get the heat distributed evenly. When I close of the good radiators hoping to push the heat to the cold ones the boiler cycles. In wondering if perhaps tr system is blocked somewhere. Any thoughts would be great. As my patience is running low.

 

[SJB6]

Hi.

The fact that you managed to get the system balanced once leads me to believe that it's most likely some form of block, bare in mind some painters and other tradesmen can be reckless and I wouldn't be surprised if you said you found some paint lodged in the system. The fact that the boiler is in the loft and feeding a cylinder plus 18 rads means theres going to be many rises and falls within the pipework as well as some dead legs of pipework as well, air locks will always be a problem. Also consider that though the boiler may be powerful enough for the system there is no guarantee the pump is, a small pump at the end of the heating circuit on the return would suck heat through those dead runs providing heat to all rads.

 

[plumber0808]

Are the pipes sized correctly. If radiators have been added on and on the issue will never go away. Or pump not performing to its best