Barely Warm Radiator

[Silver_Hawk]

I've read the Sticky

Moved into this large 1951 house about a year ago; it has had two extensions in 1959 and 1961. I'm not sure at what stage the CH was put it; it may have all been done at once or it may have been done in bits & pieces to tie in with the two extensions.

Most radiators are fine but one or two in the oldest part of the house barely get warm. The radiators look old. I've taken them off, flushed them through, checked the valves and TRVs, and the whole system has been drained recently to install new radiators in a new kitchen.

So is it poor design? The diagram below shows the rad arrangement in my 10yr daughter's bedroom (luckily she doesn't feel the cold ); this rad only ever get luke warm; the 15 mm pipes are also barely warm but the 22m pipes are nice and hot. I think the flow is from A to B but it could be the other way around. Valve and TRV are open, and there is no air in the rad.

Would a new, modern rad fix this problem, or is this layout never going to work? If not, what do I need to do?

Thanks for your help.

Paul

 

[Bahco]

Your rad is being supplied off the 22 mm pipes so should be ok.

What happens when you turn off all the others . It should get hot so try it.

Failing that, maybe your rad valves are not opening enough to allow circulation

 

[scaby]

your drawing looks like a one pipe system,i have read somewhere that the valves need to be low resistance to allow convection, i cant remember what type the valves are, perhaps someone else will know?

 

[TicklyT]

Is the TRV the right way round, or bi-directional?
Look for an arrow (or two) on the valve body. When the system starts, the 22mm flow will probably start to warm up a bit before the return does.

If it's a unidirectional valve the wrong way round, the water flow can close the TRV instead of assisting it to open.

Does it warm up if you it with the TRV head removed?

Is it a single pipe system? That could be another can of worms.....

 

[Silver_Hawk]

Thanks for the responses.

I turned off all other rads but it only got a little warmer

I think this oldest part of the house is a single pipe system; the room above also has a rad plumbed in the same way and suffers in a similar way --- both 15 mm tails connecting to the same 22mm main flow (as per diagram).

Not all our rads are like this though. Some do not appear to be on a single pipe system. Is that possible? Can you have mixed systems?

Ripping up the original parkay flooring is not an option (yet!), so what next? We live in a very hard water area, would renewing the valves and rad help? How else can I encourage the piping hot water in the 22mm main to enter the rad? Maybe some sort of adjustable valve on the 22mm pipe between pipe tails --- is that allowed?

Thanks

Paul

 

[Silver_Hawk]

It seems much of my system is a single pipe system...

...but some rads with same tail layout as in my diagram are getting very hot....so could this just be a case of fouled up valves preventing good flow into the rads?

Also would the design of modern rads help convection and therefore better flow into rads on a single pipe system?

I'm getting cold.

 

[ChrisR]

Start by taking the head off the TRV and making sure the pin is free to spring in and out. Leave it off to see if the rad warms up. Check other valve is fully open - ie several turns.

 

[Silver_Hawk]

Thanks for the reply. I did that sometime ago.

And I've had the rad off the wall to check the flow from the TRV and valve. The flow seemed OK, but who knows what its doing once the rad is back on...obviously not very much, since the rad stays cold. [/i]

 

[ChrisR]

Bin the TRV then. Some of them have very small holes, about 5mm diameter, which may be too resistive in your case.