I have a Firebird oil-burner boiler (with Megaflow for hot water) providing central heating to a farmhouse over 3 floors. There are 2 rads on top floor; 8 on middle; 11 on ground floor (mixture of new and old). Total floor area is approx. 7000 sq. ft. So far so good and no problems here at all.
However I have recently had an extension added to the lower 2 floors (to replace an old single storey extension)with a further 3 rads on ground floor and 5 on upper (middle relative to rest of house) floor. Flow/return to these rads is from previously installed tee-ed flow/return pipes (all 15mm) to pipework in the ground floor ceiling feeding rads directly on the floor above and via downpipes in the room corners for the ground floor (this echoes the set-up elsewhere in the house).
My problem is that I am not getting hot radiators (or indeed pipework) anywhere in the ground floor. The upper floor is fine. I have checked for airlocks by installing bleed valves in the corners of the highest points in the ceiling floor. Can it be that the pump simply doesn't have enough "umph" to cope with the additional capacity and the round trip down the corners and back up again? (I did have this design OKed by my heating engineer who installed the boiler a couple of years ago). If so - can I add an additional pump just for this part of the circuit or do I need to get a single bigger pump?
Yes of course the pump could bee too small for the extended system, but as you give no details about the pump or indeed only sparse info about what system you have, it's nigh on impossible to offer a positive answer to your question.
Have you tried balancing the radiators on the whole system? This may solve the problem.
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