Discuss Weird, nonsensical radiator problem. Out of ideas... in the Plumbing Forum | Plumbing Advice area at PlumbersForums.net

Messages
5
Hoping somebody can help, So, in a nutshell…

Standard 90s Westbury home – condensing boiler, pump, wall thermostat, etc etc... Normal, common or garden, run-of-the-mill British housing estate CH setup.

Downstairs radiator, 1 of 2 in our living room, went cold one evening mid-November last year.

Opened bleed valve but no air, just cold water.

Assumed blockage somewhere, so closed TRV and lockshield valve, opened bleed valve and draincock and emptied rad.

Opened TRV – water flowed from draincock. Closed TRV

Opened lockshield – again, water flowed from draincock. Closed lockshield.

So, it appeared there was no blockage at either end of the rad.

Closed drain, opened valves, re-filled and, weirdly, rad is hot. Stays hot for rest of the evening (3-4 hours).

Next morning rad is cold, again, as are both supply and return pipes. Repeated process in the evening, rad is hot all evening.

Next morning – cold. Drain, refill – hot, and so on and so on, repeating same process every night and always getting same results for about 2 weeks (which I spend trying to avoid splashing out money on a plumber 😬)

Sometime around the beginning of December, when I was about to finally (maybe) call a plumber, rad is hot in the morning, and all evening. Next day the same.

“Great” I think – “problem solved”. How, I don't know, but - result! Continues this way right up to last night, and the rad was cold again this evening until I repeated the same process.

The most annoying thing isn’t actually having to drain and refill the rad to get it working – that’s just a pain in the a*se. It’s the fact that the problem makes no logical sense at all, and my solution to it, as far as I can see, shouldn’t even work!

Why is not hot water getting to the rad when there is no apparent blockage?

Why would it suddenly start going cold again after working fine for 2 months?

How can simply draining and refilling the radiator somehow allow it to heat up again, and stay hot until the heating shuts off?

And why is it cold again the next day, after being off for only 5-6 hours?

I just don’t get it! 😖😖😖

If anybody can make any sense at all of what’s happening, and has any idea how to fix it, please tell me!

Thanks!
 
Each time it again gets cold, if you shut off both TRV & L/shield and open the vent and then open the TRV (say first), do you get any pressure/flow from the vent and ditto with the TRV closed and L/shield open, do you get any pressure/flow from the vent?,.
Is it a open vent or sealed system and is it a heat only boiler with a external pump?
 
Each time it again gets cold, if you shut off both TRV & L/shield and open the vent and then open the TRV (say first), do you get any pressure/flow from the vent and ditto with the TRV closed and L/shield open, do you get any pressure/flow from the vent?,.
Is it a open vent or sealed system and is it a heat only boiler with a external pump?
Each time it again gets cold, if you shut off both TRV & L/shield and open the vent and then open the TRV (say first), do you get any pressure/flow from the vent and ditto with the TRV closed and L/shield open, do you get any pressure/flow from the vent?,.
Is it a open vent or sealed system and is it a heat only boiler with a external pump?
 
Hi John,

Thanks for replying. It’s an open vent system, with a heat only boiler and 3 speed pump. And yeh water sprayed out of the bleed valve when I opened it and opened the TRV or the lock shield! 😬😆

Cheers,

John
 
Weird is the word, possibly air building up somewhere,

Is it a Y or S plan system?
is the F&E cistern clean?
What is the arrangement of vent & cold feed?,
Is the pump pumping from the boiler flow?

Also assume the other rad in the room stayed hot and if you shut it off, the problem rad still stayed cold?.
Is the pump just a three speed without proportional pressure control and what speed is it on and what make/model/head is it?

Try??
Renew the TRV complete with body in case something loose inside.
Remove the pump head and prove ports clear by backflushing in both directions, check impeller vanes by pushing a tie wrap through them.
 
Sorry for not replying earlier,

It's a Y plan system. The tank is fine, full of clean water and covered, and the system was flushed and inhibitor added just before the autumn. The vent and cold feed are, I presume, pretty standard; header tank in the attic above the airing cupboard, and the vent empties into this.

The pump is downstream from the boiler flow. It's a Grundfoss UPS 18-60, 3 speed, and set to speed 2.

Will give your ideas a go, time permitting!

Thanks again for your reply
 
A 18-60 Grundfoss?, must be older than yourself?.
Ha I wish! We've been here 9 years and the house is 35 years old - as far as I know it's not been changed. Still has the paint splashes from where the pipes were painted. Still going strong though!
 
Will be a 15-60 then prob ups2

Green lights ?
 

Reply to Weird, nonsensical radiator problem. Out of ideas... in the Plumbing Forum | Plumbing Advice area at PlumbersForums.net

Creating content since 2001. Untold Media.

New Threads

Some Stats

Threads
98,776
Messages
1,073,090
Members
25,567
Latest member
FSTumi
Back
Top