New rads added - last one cold

[nickrumble]

Hi - I'm a reasonably experienced DIY plumber but just can't work out why the last new rad I've installed is cold - would really appreciate your help please.

I've extended an existing 'run' of radiators - the last one on the run ( in downstairs kitchen) is cold.

The first rad added is upstairs in a bedroom - extended from a rad in an adjacent bedroom. Seems to work fine. I've put the TRV on the flow side and the locksheild on the return side.

The last new rad is located downstairs. I've had to run the pipework from this first new rad on the first floor - into an adjacent kitchen roofspace, then down into the kitchen.

To get into the kitchen roofspace - I've had to run the pipework about 18 inches vertically off the first floor (due to different ceiling heights on the ground floor - kitchen is higher that the other downstairs rooms).

The noticeable symptom is that hot water is not flowing beyond the tee to the TRV on the rad added to the bedroom on the first floor. I've tried closing the TRV and locksheild valve to this rad - has no effect.

I've bled both new rads, opened the locksheild valve on the last (kitchen) rad fully and closed down the preceding two rads (almost completely) to try to balance.

Is my problem that I just can't run a flow pipe vertically then down again between the last two rads or maybe just a balancing problem ( almost all existing rads at ground and first floor level run off a set of pipes on the first floor - perhaps I've got to balance all radiators on this circuit ?) ?

Thanks in advance

 

[Basher]

Not sure I've fully understood the layout, but might you have an airlock in the horizontal section of pipe in the kitchen roof space? You could need bleed valves in the flow and return at their highest point?

 

[nickrumble]

Not sure I've fully understood the layout, but might you have an airlock in the horizontal section of pipe in the kitchen roof space? You could need bleed valves in the flow and return at their highest point?

Thanks Basher - hadn't considered that. I could certainly try. Is there any way to tell those horizontal sections have air in them without opening up?

And on a wider question - is what I've done ( a section of pipework that raises up, then down ) fundamentally flawed or actually should be ok ( if not 'best practice' )? Just trying to understand if I'm flogging a dead horse!!

Thanks
Nick

 

[Basher]

Thanks Basher - hadn't considered that. I could certainly try. Is there any way to tell those horizontal sections have air in them without opening up?

I don't know of one!

And on a wider question - is what I've done ( a section of pipework that raises up, then down ) fundamentally flawed or actually should be ok ( if not 'best practice' )? Just trying to understand if I'm flogging a dead horse!!

I'm not a professional plumber so I can't say. My previous property had a similar scenario but was fitted with a bleed valve.
Where I've seen such fitted, they normally have a tee at the highest point, with a small upstand of pipe (which gives a little reservoir for the air), say 10cm tall and a manual bleed valve or an auto vent on top (the latter at your peril!)

 

[nickrumble]

I don't know of one!

I'm not a professional plumber so I can't say. My previous property had a similar scenario but was fitted with a bleed valve.
Where I've seen such fitted, they normally have a tee at the highest point, with a small upstand of pipe (which gives a little reservoir for the air), say 10cm tall and a manual bleed valve or an auto vent on top (the latter at your peril!)

Thanks - I can imagine the type of setup you mean - I'll give it a go.

 

[Dave Moore]

If it’s on a Trv check if the Trv is actually working. My step daughter had a problem with her heating and the index radiator had a faulty Trv even though it was new.
regards,
Dave

 

[nickrumble]

If it’s on a Trv check if the Trv is actually working. My step daughter had a problem with her heating and the index radiator had a faulty Trv even though it was new.
regards,
Dave

Thanks Dave - it was an air blockage in the highest point of the pipework. I happened to have some 'tails' hanging off the flow and return - so was able to bleed most of the air out. I then shield-locked off all the other radiators and it flushed the air through. Now working a treat. Thanks to everyone for.your help!

 

[Zippymark]

You seem to have got it sorted, but for future reference, try just turning ALL other rads off, and put heating only on if it's a conventional system, just put the heating on if it's a combi, and so the full force of the pump is pushing through that one rad, that should hopefully clear any air into the radiator where it can be bled.