Rad not getting hot after new TRV

[Rmm]

I spent the afternoon fitting Drayton TRV4 rad valves to 3 bedroom radiators today.
Bedroom 1, closest to the boiler and bedroom 3 furthest from the boiler are operating as expected. The rad in bedroom 2, between the two is not getting hot.
The tail coming out of the trv into the rad is very hot but just an inch to the right the bottom corner of the rad is cold.
The tail doesn't go in in a straight line. For want of a better term there is a threaded 90 degree knuckle on the back of the rad .
I was wondering if I've screwed the tail so far in its jammed against the back of the 90 or could it be something else?

 

[terryplumb]

Something else !
Close every working rads TRV ,see if cold rad now heats up.

 

[Rmm]

Thanks Terry. I've done that and it is now warming up albeit very slowly. It's now at 35c after about 20 minutes.
What's the explanation?

 

[terryplumb]

There is a restriction on that rad,either one of the valves isn't open fully or the pipework is restricted. It should have heated fully ,and quickly ,once every other radiator was closed off. The pumps flow would have been concentrated through the problem rad and moved any air trapped in that rads pipes.
Did you alter the problem rads lockshield valve when changing TRV ? If not, remove the TRV's actuator head and check the pin in the centre of the body, it should move freely up and down a few millimetres. Leave the actuator head off and see if the rad performs any better.

 

[Rmm]

I replaced the lockshield valves on each of the 3 rads at the same time and have them fully open. The problem rad is now warm but it seems to have maxed out at 45c compared to 58c for the downstairs rads

 

[Rmm]

Forgot to say that the pin on the TRV is functioning properly.

 

[dilalio]

Did you do a full drain down?
If so what was the water like?
Is it a sealed system or open vent?

 

[Rmm]

I didn't do a full drain down though the rads are very long single panel types so by the time I'd emptied all 3 that's a lot of water drained.
The water was mucky but each of the rads was stood up vertically for a time and there wasn't gunk discharging just some dirty water.
It's a combi boiler

 

[Johntheo5]

I spent the afternoon fitting Drayton TRV4 rad valves to 3 bedroom radiators today.
Bedroom 1, closest to the boiler and bedroom 3 furthest from the boiler are operating as expected. The rad in bedroom 2, between the two is not getting hot.
The tail coming out of the trv into the rad is very hot but just an inch to the right the bottom corner of the rad is cold.
The tail doesn't go in in a straight line. For want of a better term there is a threaded 90 degree knuckle on the back of the rad .
I was wondering if I've screwed the tail so far in its jammed against the back of the 90 or could it be something else?

Might be worth removing the TRV tail and measuring it, in case it is, as you suggested above, too long.
As asked above, is it a seaed or OV system?.

 

[dilalio]

I would completely remove the trv head if you haven't already.

Put some x400 in the system and leave it cycling through just that rad for a few hours, then cycle it through all the other rads, one by one, then drain it out and refill with water. See if rad has improved then drain down again and refill with inhibitor.

 

[CountryFan]

I replaced the lockshield valves on each of the 3 rads at the same time and have them fully open.

Were they previously fully open?

 

[Rmm]

I don't know. Possibly a schoolboy error but I didn't check because I was replacing each of the lockshield valves.

 

[Rmm]

I would completely remove the trv head if you haven't already.

Put some x400 in the system and leave it cycling through just that rad for a few hours, then cycle it through all the other rads, one by one, then drain it out and refill with water. See if rad has improved then drain down again and refill with inhibitor.

Well that's another head scratcher for me because there's no obvious place in the system to dose with products.
There's no magna clean as an option and all of the rads only have a bleed screw threaded into the back of the rad.
It's a Greenstar combi so there's no braided filling loop that could be used either. It's a plastic thumbscrew under the boiler.
I'll be buying a towel rad soon so when it comes to fitting that I'll be able put system cleaner and inhibitor in.

 

[dilalio]

Well that's another head scratcher for me because there's no obvious place in the system to dose with products.
There's no magna clean as an option and all of the rads only have a bleed screw threaded into the back of the rad.
It's a Greenstar combi so there's no braided filling loop that could be used either. It's a plastic thumbscrew under the boiler.
I'll be buying a towel rad soon so when it comes to fitting that I'll be able put system cleaner and inhibitor in.

Sentinel X400 Sludge Remover

High performance cleaner, specifically designed for cleaning older central heating systems. A non-acid treatment which restores circulation to radiators and pipework. Ruthlessly efficient formula shifts built-up magnetite sludge, eliminating cold spots in radiators and restoring proper heat...

www.toolstation.com

Might be able to connect this to the rad air vent or, if not, undo the trv or lockshield from rad, swing it round and dose via that point or filling loop.
Might need a flexible hose as and adaptor if the kit doesn't use a male or female spigot!