Cold radiator

[nc265]

I hope somebody can advise. I have a 5 bed house with 13 radiators and a Vaillant Ecofit Pure 835 combi. 15mm pipe work. All radiators get very hot, except our main bedroom. The top half of the radiator is warm, the bottom cold. The lockshield pipe is cold, the TRV pipe is quite hot. Is this likely to be a balancing issue, sludge in the radiator, a blockage or could it be something else? I was going to remove the radiator, flush it and see if that helps, but before I do I thought I would see if anybody has any ideas what it could be or a process of elimination. Thank you.

 

[Highway Man]

I hope somebody can advise. I have a 5 bed house with 13 radiators and a Vaillant Ecofit Pure 835 combi. All radiators get very hot, except our main bedroom. The top half of the radiator is warm, the bottom cold. The lockshield pipe is cold, the TRV pipe is hot. Is this likely to be a balancing issue, sludge in the radiator, a blockage or could it be something else? I was going to remove yhe radiator, flush it and see if that helps, but before i do i thought I would see if anybody has any ideas. Thank you.

I am no plumber a mere spark but it sounds like sludge to me.

 

[mitch66]

Check the Trv isn't stuck first You tube might help you.

 

[nc265]

Thank you. I did have a quick look. The pin doesnt appear stuck, but I'll have another look.

 

[Justin Passing]

Not sludge, the return pipe would be hot - the water goes over the top assuming you've bled the radiator, so check that.
(If there's air coming out, check the boiler pressure after.)

Check the lockshield isn't shut - it only needs to be open a small amount like half a turn, usually. If not that then yes TRV pin stuck. Push down & it should go down and come back up. If it's solid it's stuck, a 16oz hammer bounced from a few inches/10cm might get it going. You may have to bounce the hammer a lot until it's free - rubber bit sticks on the valve seat.. TOO hard will break it.

 

[ericmark]

If balancing is the problem, it is likely the other radiators in the house, not the one which is not working at fault. As with @Highway Man I am an electrician, and it is all well and good reading books that tell me how to use a differential thermometer and set each radiator to 15ºC, but I have misplaced my sensors, so I needed some other method.

So what I did, starting as close to the boiler as I could, I closed the lock shield valve, and then opened 1/4 turn at a time until one pipe got a little warm, then to the next, and it did sort of work.

The fitting of electronic heads, gave me current and target temperatures, and using them I could slowly close the lock shield even more, so that current never exceeded the target, this worked well with a modulating boiler, but failed with the old on/off oil boiler I have now.

The eQ-3 head does not show current, only target, but does have an auto fault-finding,

so I know if the pin is stuck. I have Energenie, Kasa, eQ-3 and Wiser TRV heads, each has some plus and minus points. Turning the wall thermostat up so that the TRV's do the room control, even if the lock shield is wide open, as each TRV closes it forces water through the next valve which is still open, assuming they are set to around 20ºC to start with. And once done once and water has gone through each valve, it tends to keep flowing.

I found with a modulating boiler, radiators may get stinking hot when heating first switched on, but once rooms are up to temperature, then the radiators just stay warm.

The problem is TRV's unless linked, with not turn boiler on/off, so we tend to try a balance wall thermostats and TRV's to work in harmony, If the radiator in on the inside wall, then the linked TRV works well, but if on the outside wall, they will turn on the heating too early as cooled by the wall. So the wall thermostat on an inside wall needs to start the boiler, but the TRV still controls the radiator once heating is running.

Today if the first day this season the boiler has run the app shows the temperture and when boiler was switched on by Wiser.