One cool rad ?

[joesoap13]

Hi Guys, need some advice please.
Posted this before a while ago, thought I solved it.
One rad of 15 is not getting hot, just warm, mostly at the top.
Told to turn All rads of and leave problem rad on.
Did, same result, still tepid, water just going round circs.
The inlet pipe to trv is very hot, but the rad at inlet point is cold, and top of rad tepid ?
Water is obviously getting through trv, so why is inlet point not hot as trv ?

I originally drained the rad to flush it, but water was clean ,so left it.
I suspected the trv must be faulty, blocked, so used last resort, Hammer, to clear it, pin is operating ok, didn’t,t open it when disconnected, which I should have to check flow!
opened lockshied when rad was empty, water coming out ok, so not blocked.
Used rubber mallet on rad to see if it was blocked, and try to loosen any crap.
I then re-balanced the lot, and it seemed to get a Lot hotter, thought, problem solved.
I have a long system due to shape the house, even the furthest rad which used to give me the same problem , is working ok now.

Now it’s the same, tepid.
Apart from the Trv, any suggestions of what to do next, apart from replacing it, and rad, but too cold to do that at present.
Don’t fancy trying changing it with system full, with my luck.
Don’t fancy draining system, and rad is not a standard size, it’s an old one, perhaps in spring will replace it, and a couple of other of same type.
Get the guy who services boiler to replace them.

Got me baffled I must admit,not hard
All other rads are fine now, even ones that were cool, after re-balancing, except this one.
It,s about third in the system from boiler.
Any hints at what I can try to get it hot, or just hotter ?
Does water in rads follow a route via the channels, or go throuhout to exit?

 

[denso13]

didn’t,t open it when disconnected, which I should have to check flow!

Perhaps should have tried this to rule out a faulty TRV. They are cheap as chips and might be worth replacing it just any case anyway.

 

[joesoap13]

Perhaps should have tried this to rule out a faulty TRV. They are cheap as chips and might be worth replacing it just any case anyway.

Yes,I should, hindsight is great, but that meant draining the system, if I had done that, I would have replaced the rad, and a couple of other older rads at the same time, which I will do come spring, hope it’s early like last lockdown, march!
The trv is red hot to touch now, but rad where connected to rad is cold, except the Chanel to top of rad, which is only slightly tepid ?
it did work after re-balancing, but then reverted to type.
If trv was not working, it would not get hot, pipe to it is red hot,so water is flowing through it.
If it was totally kaput,blocked, water would just bypass it in the circs, it can only get hot, if water is going through it.
It cannot get hot by conduction, as rad would be hot at point of inlet with conduction. Top of rad is warmer than the inlet point, but barely noticeable.

 

[denso13]

It could be passing very slightly letting a very small amount of hot water through.

Yes, but that meant drawing the system.

If it needs sorted then so be it. You seem to have tried everything else.

 

[joesoap13]

It could be passing very slightly letting a very small amount of hot water through.



If it needs sorted then so be it. You seem to have tried everything else.

In that case, engineers, and plumbers would just be fitters, replace the part, it’s cheaper.
As an ex engineer, I try and fix the problem first, I couldn’d just replace things , I had to solve it.

If I had a pound for things I have replaced that weren’t the problem ,I would be a bit better off.

If trv was not working, it would not get hot, pipe to it is red hot,so water is flowing through it.
If it was totally kaput,blocked, water would just bypass it in the circs, it can only get hot, if water is going through it.
It cannot get hot by conduction, as rad would be hot at point of inlet with conduction. Top of rad is warmer than the inlet point, but barely noticeable.

Read more: https://www.diynot.com/diy/threads/one-cool-rad.561115/#ixzz6ixY3nJXt

 

[denso13]

replace the part

Yes, replace the faulty part!! Sounds to me like the TRV is passing very slightly which would give you all the symptoms you have.

If you know better then I don't know why you asked for advice in the first place.

Good luck.

 

[joesoap13]

Yes, replace the faulty part!! Sounds to me like the TRV is passing very slightly which would give you all the symptoms you have.

If you know better then I don't know why you asked for advice in the first place.

Good luck.

Eliminate the possible, and what’s left is the probable.

Cheers.

 

[joesoap13]

Eliminate the possible, and what’s left is the probable.

Cheers.[

Eliminate the possible, and what’s left is the probable.

Cheers.

Is it me or am I losing my logic?

To test the trv, as discussed, I closed both valves, drained the rad from either end to see if rad was blocked at either end.
Drained ok from both ends.
Now got empty rad, system still running ok.
Opened trv, plenty water coming out, with just a fraction of a turn, so it tells me it’s not blocked!
It has been operating without the thermostat top on , to eliminate that not operating.
If trv is open when turned open, a fraction, it should surely allow water through with top off .?
Did. Same with other end with the lock shield, that’s allowing plenty water through.
There does not seem much else to eliminate, so is there something I am missing, or am I going loopy !
Can it be back to balancing, which sorted it for a short while, or is it something else ?
BUT, why does it stay cool when it’s the only rad on ,eliminating balancing.
Some put me out of my misery, please

 

[denso13]

First you said you didn't open the TRV but you should have..

Hammer, to clear it, pin is operating ok, didn’t,t open it when disconnected, which I should have to check flow!

Now you are saying you did..

Opened trv, plenty water coming out, with just a fraction of a turn, so it tells me it’s not blocked!

My tuppence worth for the last time. You have said water runs freely from both valves and the radiator is clean. When this one is left open but all the others shut off it still doesn't work.

You say the pipe to the TRV gets hot but the the tail is cold and only slight heat at the top of the radiator.

You say you had previous problems with the TRV and had to hit it with a hammer to get it to work

I think the TRV is causing problems again and only letting through very little hot water. This would give you all the symptoms you are describing. TRV's are cheap and I would change it, not to throw parts at it, but to start ruling things out. Theorising will only get you so far.

 

[Terrywookfit]

The problem is lack of flow.
A TRV has a very small orifice so any restriction will really fook things up.
Suggest you drain rad and run each valve into a bucket to check flow. What size pipes are they?

 

[joesoap13]

First you said you didn't open the TRV but you should have.

First you said you didn't open the TRV but you should have..
Sorry denso, you are right, my fault entirely.
I didn,t turn the trv on first time, but have just done so, it gushed out at first, then just trickles, spring must be shutting it,
I thought default was open.
So it is a new trv.year
She weather is a bit better.
My most humble appologies.
Told you I was going loopy.!
Thanks Terry also, that,s just what
I have done, and should have done in first case, except rebalancing seemed to remedy it?
Cheers. Both
happy New year


Now you are saying you did..



My tuppence worth for the last time. You have said water runs freely from both valves and the radiator is clean. When this one is left open but all the others shut off it still doesn't work.

You say the pipe to the TRV gets hot but the the tail is cold and only slight heat at the top of the radiator.

You say you had previous problems with the TRV and had to hit it with a hammer to get it to work

I think the TRV is causing problems again and only letting through very little hot water. This would give you all the symptoms you are describing. TRV's are cheap and I would change it, not to throw parts at it, but to start ruling things out. Theorising will only get you so far.

Now you are saying you did..



My tuppence worth for the last time. You have said water runs freely from both valves and the radiator is clean. When this one is left open but all the others shut off it still doesn't work.

You say the pipe to the TRV gets hot but the the tail is cold and only slight heat at the top of the radiator.

You say you had previous problems with the TRV and had to hit it with a hammer to get it to work

I think the TRV is causing problems again and only letting through very little hot water. This would give you all the symptoms you are describing. TRV's are cheap and I would change it, not to throw parts at it, but to start ruling things out. Theorising will only get you so far.

The problem is lack of flow.
A TRV has a very small orifice so any restriction will really fook things up.
Suggest you drain rad and run each valve into a bucket to check flow. What size pipes are they?

The problem is lack of flow.
A TRV has a very small orifice so any restriction will really fook things up.
Suggest you drain rad and run each valve into a bucket to check flow. What size pipes are they?

 

[joesoap13]

Hi, just done that and the although letting it gush out at first, closed and just trickles.
I refilled it via tr v first time so assumed it was ok.
Why it,s closed again I know not.

so denso was correct.
my apologies to denso.
said
I was going loopy
New trv when weather warms up to drain system.
Cheers both and a happy New year.

 

[joesoap13]

Hi, just done that and the although letting it gush out at first, closed and just trickles.
I refilled it via tr v first time so assumed it was ok.
Why it,s closed again I know not.

so denso was correct.
my apologies to denso.
said
I was going loopy
New trv when weather warms up to drain system.
Cheers both and a happy New year.

Ps.Are tr v s interchangeable without altering pipework, using same but fittings on the the rad and pipes ?

 

[Terrywookfit]

Usually yes 1/2" bspt.

 

[denso13]

I was going loopy

No problem, that's plumbing for you!

As above should be a standard fitting but we could confirm if you can upload a photo.