New radiator put a gremlin in the system

27 Dec 2009
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United Kingdom
I added a new radiator to my system today and now Im left with a seemingly illogical problem....

I have a baxi combi boiler, 3 radiators on the 1st floor, one in the attic and two on the ground floor. The flow/return pipes go up from the boiler in the kitchen to the first floor, across under the floor boards, and then back down an understair cupboard wall, when they disappear through a wall into the other end of the kitchen to feed the kitchen and front room radiators.

I have just converted my under stair cupboard into a toilet, and have T'd off the flow/return pipes coming down the wall to fit a new radiator in the toilet room.

I have repressurised the system, and bled all the radiators, but my kitchen and front room radiators dont work anymore. The new radiator, which junctions off immediately before these two gets hot, but bizarrely, the return pipe only ever gets luke warm. The kitchen and lounge get less than luke warm, even thought the flow pipe which feeds them is red hot, that hot water never make it into the radiator. both have TRV's, and i've checked the pins on both and they aren't stuck.

Is it possible there's an airlock in the return pipe which goes back up the wall in the under stair cupboard, back under the 1st floor, and back down into the boiler?

All my upstairs radiators get red hot.

i'm stuck!!!

Any help much appreciated.

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You need to balance them, turn of the new rad a touch and all others that are hot untill hot water reaches the cold rads, (ie, the closest ones to the boiler get the least supply and as you go further from the boiler you open the rads more and more) The water in the heating curcuit is finding the easiest route and by-passing the rads.
I hope you understand I am not too good on the pc. :D
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thanks for the quick replies! I turned off all the hot radiators upstairs at the lockshields as they dont all have TRV's. Almost immediately, the new radiator and surrounding pipework started "gluggling", and behold, the previously cold radiators are now hot.
Thanks John506!

Homes, I'll now rebalance. I hadn't thought about it previously, but the two that were cold are at the end of the flow/return loop, and never really got as hot as the one in my bathroom which is immediately above the boiler in the kitchen, and the first radiator to T off.

Cheers guys :)

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