2 cold rads

[Smurf]

Hi all

I've got a problem with my heating system. All except 2 of the rads get hot. If I turn all the other rads off the two will get hot. I've taken the two rads off, run a power washer through them both. I've connected a hose pipe to the pipework going to the two rads and let them flush themselves out so I know the pipe work leading to the rads is fine (15 mm pipes). I've changed the pump (had a spare Grundfoss UPS15 50x18). Most, but not all, of the working rads have TRVs on them, the outlet valves have been turned down to restrict flow to them to hopefully get flow to the non working ones. I'm now at a loss. I was hoping the new pump would fix everything but it didn't. Any suggestions????

 

[gasmarc]

if you can get these to rads hot then is sounds like a balancing issue ,good luck

 

[Smurf]

I've tried balancing them but the ONLY way to get them to work is to shut off all the others.

 

[Smurf]

I've just read the Grundfoss leaflet and taken my boiler apart and 'think' I may have found a problem. The manual says the pump, if mounted vertically, should pump upwards. Mine pumps downwards. Looking at the layout of the pipes this will then pump through the boiler. The water comes out of the Baxi and splits into 2. One for the water tank, one for the heating. Water is going to take the easiest route and miss out the rads and get pumped through the path of least resistance - the hot water system. It looks to me That the original pump was put in upside down by whoever installed it (been here 3 years and never had decent heating) a long time ago.

Does this sound right to you or am I barking up the wrong tree????

 

[gasmarc]

wow far play if you sussed that out and you are correct happy days ,good luck

 

[Smurf]

Well, turning the pump around has fixed the heating. It must have been that way since it was installed well before we moved in as the power cable wouldn't reach once the pump was mounted the correct way. Now that I've balanced the rads, loosened a sticky pin in a TRV everything is working fine

 

[gasmarc]

Nice one its great when thing work out well , happy days lol

 

[wallacengrommet]

I have this exact same problem - 2 upstairs rads running cold, pump is Grundfos and the flow is also going downwards towards the boiler ! I really hope this is all it is. I have tried flush rad outside, replaced TRV with lockshield, balanced, bled , poured in Sentinel x400 cleaner. all no good, the rads will only get hot if I turn all the others off. ......I would have thought the heating wouldn't work at all if the pump was fitted the wrong way round ???