Plumbing question: awkward radiators

[Nice But Dim]

I have recently moved into a new home and am trying to work out why two of the radiators in the property only get tepid at best.

The 2 rads are both fed by 15mm copper pipe into double panel radiators which are around 10 years old with TRVs and lockshields (but no drainage points) the diagram below shows the layout. As you can see the rads take a direct feed from the pump and then bizarrely go upwards into the ceiling and across the lounge and down.

So far I have removed Radiator 2 and flushed it thoroughly - there was some sludge but not a huge amount that would significantly restrict the flow. Checked that both the TRV and the lockshield are not blocked- refitted, filled and bled and its made no difference.

I was hoping that the rads would be full of sludge and hence restrict the flow into no getting hot but this does not seem to be the case. There is no drainage point currently fitted. I have tried to balance the system - but not made any difference. I have turned off all other rads in the house in an attempt to direct all the flow into these 2 rads - again they only get warm at best and not roasting like all the others in the house. Digital thermometer shown other house rads at 45 deg C - these at best hit 30 C

What diagnosis would you provide ? is it possible that all the return pipes are sludged up and restricting flow ?

[2lefthands]

Could do with seeing rest of the system in a diagram, but if you've jetted it in the garden and won't heat when all others off, your branches need replacing. That, or st TRVs? A new one to test isn't going to break the bank. Don't know what the sheds are charging but I buy Honeywell TRV + LS at £14 roughly, though fit a fair few through the year.

If you've got a digital thermometer, I'd be pointing it at pipework every metre and seeing where the drop starts.

[pmanson]

Is the thermostat too close to one of the rads? Maybe it's getting up to temperature ad shutting of the call to the boiler before the hot water has made it all the way through the system?

[blondini]

I would suspect that air is trapped in the pipe run above the ceiling.

[Unbusy]

blondini said:

I would suspect that air is trapped in the pipe run above the ceiling.

Also the pipe may have been crimped, restricting the flow. Either the feed or return.

[dirkgently]

I would suspect air at the high point, are there any air vents apparent?

[g7jtk]

dirkgently said:

I would suspect air at the high point, are there any air vents apparent?

I agree. Partially airlocked

[Nice But Dim]

Thanks for your help so far.... Just been to check the pipes in the ceiling and apart from a pair of very old what I presume are isolation values there are no air vents.

If this is the case I should install some bottle valves to try and remove the air ?

g7jtk said:

I agree. Partially airlocked

[finlo]

Nice But Dim said:

Thanks for your help so far.... Just been to check the pipes in the ceiling and apart from a pair of very old what I presume are isolation values there are no air vents.

If this is the case I should install some bottle valves to try and remove the air ?

g7jtk said:

I agree. Partially airlocked

They look more like bleed valves to me.

[Dogwatch]

finlo said:

They look more like bleed valves to me.

Yup. Just where you need them!

[Nice But Dim]

Every day is a school day

So what is the bleeding etiquette ? With CH pump on or off ?

Dogwatch said:

Yup. Just where you need them!

[CambsBill]

Nice But Dim said:

Every day is a school day

So what is the bleeding etiquette ? With CH pump on or off ?

Dogwatch said:

Yup. Just where you need them!

Oi, no need to swear

IANAP but if it's a sealed system I'd assume you just need to open the tap to the mains & then do the bleeding using the mains pressure to push any air out of the valves..

[blondini]

Just proceed as if you were bleeding a radiator.
I would start out with the pump off and see how that goes.

[Nice But Dim]

UPDATE : sadly opening the bleed valves shown in the picture released no air and only water in both inlet and outlet.

one thing I did not mention before - after flushing the rad and then refitiing and subsequent bleeding it did get as hot as the other rads in the house so clearly enough flow was at that time getting to the radiator whilt the lockshield end was off. However once the rad was full and the lockshield end opened it only ever returned to warm as before.

So either there is insufficent flow to the radiators or the return pipe is gunked up and inhibiting flow ?

[anonymous-user]

Nice But Dim said:

UPDATE : sadly opening the bleed valves shown in the picture released no air and only water in both inlet and outlet.

one thing I did not mention before - after flushing the rad and then refitiing and subsequent bleeding it did get as hot as the other rads in the house so clearly enough flow was at that time getting to the radiator whilt the lockshield end was off. However once the rad was full and the lockshield end opened it only ever returned to warm as before.

So either there is insufficent flow to the radiators or the return pipe is gunked up and inhibiting flow ?

You need to balance the lockshield to the rest of the system, close them down halfway and check the rest of the lockshields in the house to see what they're on.

[g7jtk]

Try turning all other rads off and see what happens. If it works thes start opening the other rad valves.

[Nice But Dim]

Update: thanks to all those who kindly replied

I balanced the whole system properly and now we have hot radiators everywhere - thank you

[Fore Left]

Nice But Dim said:

I looked at that picture and thought "why does he have a radiator 7 feet off the ground"

[S6PNJ]

Nice But Dim said:

I balanced the whole system properly and now we have hot radiators everywhere

Would you mind detailing YOUR method please? I realise I can Google how to balance radiators but first hand working experience is better than a myriad of random websites.