upstairs hot,downstairs cold.help!

[Matt h]

I recently installed a heat only boiler and new pump and initially everything seemed to work ok. Now though its not getting downstairs. Its an s plan plus,one zone valve for upstairs one for downstairs.I had a spare zone valve so i replaced the downstairs one but its still not getting down.I've drained it down a couple of times and re-filled thinking it could be an airlock and thats not cured it.Could it be sludge/blockage? Should i try the pump on its lowest setting? I don't think its a wiring problem,the stats seem to be working ok with the zone valves. I'd be grateful for any more ideas. Like i said earlier theres a new pump so i'm sure its not a faulty pump as is usually the case with downstairs not getting warm!

 

[dontknowitall]

Hot upstairs and cold downstairs is a classic sympton of the pump not working. Is pump bled? Is pump big/powerful enough for the installation?

 

[fuzzy]

sounds like the pump

 

[Matt h]

Hot upstairs and cold downstairs is a classic sympton of the pump not working. Is pump bled? Is pump big/powerful enough for the installation?

I seem to recall the pump i replaced was a bit bigger and its on 28mm gate valves.Its a fairly big house,10 rads.DO you think i should swap for a bigger pump? It worked downstairs initially though?

 

[dontknowitall]

Standard pump (I assume you have one of these) should be fine for 10 radiators. Have you tried bleeding it?

 

[Matt h]

Yes the pump has been bled and ran on all 3 settings.

 

[Matt h]

The pump felt pretty hot to touch.I'm guessing it shouldn't be red hot.

 

[Matt h]

it was a standard circulating pump from Plumb Center,about £40.Not a recognisable brand like Grundfos.Have fit them in the past with no problems.

 

[tamz]

If the valves are opening it will be air.
How did you split the zones?