adding another pump to a combi heating system

[monymont]

I have a Worcester 30cdi combi system which is 15 moths old now, i have just added 3 new rads onto the system as a result of a new extension
12 rads complete in total, the new rads are not getting hot even with all the upstairs rads turned off at trv's and lockshields, the rest of the downstairs rads are really hot except in the new extension, they are getting fed properly as i have bled them all and there is no air locks in the system, any ideas ? I was thinking that the pump might be struggling to deliver the hot water to the new rads there is a total of 8 rads downstairs and 4 upstairs.

 

[seco services]

i wouldn't say its a pump issue.
as you have isolated the upstairs rads and still nothing at all on the downstairs new rads.
sounds more like a install fault.

have have you installed them to the mains flow/returns ?

 

[monymont]

Yes, The first rad in the extension is plumbed into the existing flow and return in the rest of the house, this rad gets nice and warm, the other 2 rads are not getting hot, the pipes are routed behind skirting and then they run up into loft space across and down the opposite wall to the other two rads, i have also had fitted two air blead valves in the loft space between the first and second rad.

 

[seco services]

thats a long way round.
so i take it the pipework going up into loft comes off the downstairs rad not the flow/return ?

if the first rad is hot how far along the pipework is the flow getting hot?
does the water flow ok from the rad valves on the new pipework that comes from the loft to the new rads ?

instead of taking it alround the house why didn't you tee off upstairs flow/return then just drop it down to new rads ?

 

[monymont]

I know it sounds daft but the route the new pipes have taken was far easier and with virtually no mess braeking through walls etc,,

The flow after the first new rad is still warm until the pipe elbows at 90 degrees and then runs up vertically, it then cools down half way up the vertical run, weird isn't it ?? pressure at rads is fine and no leaks

 

[seco services]

i would say air more than anything.
have you tried shutting the new one thats hot see what happens

or open the each valve into a bowl on the last rads make sure both pipes are circulating on the up/over pipework

 

[seco services]

delete