Downstairs radiators cold

[paulsexton50]

I have a 2 storey 3 bed house with 4 radiators upstairs and 4 downstairs. The system is about 15 years old and is a standard boiler downstairs with a hot water cylinder upstairs.

The upstairs rads all heat up as normal but the downstairs ones remain stone cold. We have attempted to balance the system which has had no real effect to the downstairs. The pipes going into the rads downstairs are hot but there appears to be no flow into the rads as they are still cold. I've removed 3 of the rads d'stairs and the water coming out has only a small amount of suspended black debris coming out. An inhibitor has been added which i picked up in B and Q which stopped the rads being stone cold but they are still not heating up - as if there is still no flow through them.

When i took the rads off i turned the TRVs on and there appears to be good flow coming from them which suggests to me that the pump is functioning and there is nothing wrong with the supply flow.

When i then put the rads back on and bled them to fill them up they got hot as they filled but cooled down soon after as if the water wasn't flowing out of the rads.

The only thing i can think is that there is a block somewhere in the return pipes.

Can anybody shed some light as the 3Kw heaters are getting expensive!!!

[F]

Try turning off all the radiators except one downstairs. Ensure that the valve at each end is fully on and then start up the heating. Give it a while and, with a bit of luck, anything that is reducing the flow, including air, will be shifted.

You might need to do this with each downstairs radiator in turn.

[Dave Plowman (News)]

Separate return pipe for each floor? Is the ground floor one very hot? If the rads ain't working it should be near the same temp as the feed.

Most likely thing is an airlock due to poor pipe runs. Try turning off all rads apart from one downstairs and see what happens.

[Roger Mills]

You could have an airlock in the return pipe which is preventing circulation from occurring.

Bleed each rad with only one of its valves open at a time - and bleed about a litre out for each side. This will ensure that *both* pipes are full. [If it's a vented system, make sure that the ballvalve on the F&E tank is working].

[If the system has been balanced, note the position of each lockshield (number of turns to close) so you can restore it when you've finished].

How are your downstairs rads fed? Is there a separate downstairs circuit under the floorboards, or does each rad have its own feed from above (as is typical with solid downstairs floors)? Is your system fully pumped - or is it gravity (convection) HW and pumped CH?

[Heliotrope Smith]

The fact that there is a good flow of water from the trv is no indication that the pump is working or not. If your pump has a large chrome screw then remove it see if the pump is turning by inserting a small screwdriver throuhg the hole and touching the end of the spindle. If it is not turning then try engaging the screwdriver in the slot on the spindle and turn in the direction of the arrow on the top of the pump.

[John]

Pity you didn't check to see if you had a good flow from the return pipe (tried without the pump running - the head of water on flow and return should be equal)

I have one with a poor flow in the return pipe. I haven't fixed it yet , but at least I have identified the problem.