Intermittent heating from rads on ground floor - no issues with 1st floor

[tomatotomato]

Hope it's permissible to request some input here...

I live in a rented flat in London. We have two floors, ground and 1st, with radiator heating. The boiler is working fine (I believe) and we have plenty of hot water (radiator temp set at and hold at 73C). Four rads on the 1st floor are merrily putting out plenty of heat. Three of those four have TRVs on them, the other is "normal/manual" valve. On the ground floor we have two rads. One is TRV, the other is manual. The boiler is also on the ground floor.

We have always had issues with the rad in the dining room (manual). Until we turned the system down to leave for Xmas, the rad in the living room seemed fine. When I returned from Xmas, neither of the two were working. Again, 1st floor all fine. I called in the property agent's plumber yesterday, who indicated he adjusted one rad. Unfortunately I was at work so I don't know what exactly he did. When I got home, both rads were working.

This morning, once again, neither are working, and the air temp on ground floor is 14C (upstairs probably >20C). I can feel that the hot water line-in on both is cold. On the one in the living room, I can feel that it is at least warm about 7-8 ft from the rad, gradually growing cooler. I cannot do the same check for the one in the dining room as the line runs under the floor.

The valves on both are wide open (TRV on dining room is set to max/6). All I can guess is that something is preventing hot water from entering these rads. Obviously what the plumber did yesterday worked, but only temporarily.

What could this issue be caused by?

 

[tomatotomato]

The only thing you could do. Is turn all the others off and run just that one for a couple of hours then turn the others back on one at a time until they start getting hot?

To be clear, with the isolation/lockshield valves, right? Some have "innie" slot/blade screwdriver-style, not nibs/nipples like what I'm seeing on Youtube (I assume the newer style). I assume it's still a right to close, left to open thing. (Dumb questions but don't want to be mucking this thing up more.)

I should clarify that I come from a country where forced air heating is much more common than hot water... so these systems are pretty new to me.

 

[Harvest Fields]

Can you post another picture of what you mean

 

[ShaunCorbs]

sounds like iso valves

 

[tomatotomato]

Yup. Two pics of the isolator, one with cap, one without, plus one of the TRV, so you know what's on the other end. This is the one in the living room (working fine today). Several upstairs are similar. No nipples to twist.

 

[Harvest Fields]

How many Honeywell ones do you have?

 

[tomatotomato]

One. I also have a Drayton TRV, a Regis TRV, and a 4th that looks like the Honeywell but I'm not sure because it's somewhat hard to see (behind a chest of drawers).

Six rads total in the house. Four TRV. Two manual.

 

[Harvest Fields]

Turn the 4 trv off and leave the other two on.

 

[tomatotomato]

So before you made your last post, I went around and turned down, although not off, several of the TRVs. Lo and behold, it worked. The previously-cold rad is now putting out at least some heat. I am going to go and turn down the manual valve upstairs as well, since it's plenty warm up there.

Does this mean, basically, the boiler isn't of sufficient size, or the water flow through the house isn't efficient enough, to heat everything at once, so the hot water stalls in the system before reaching the badly-performing rad?

 

[Pickwickpick]

So before you made your last post, I went around and turned down, although not off, several of the TRVs. Lo and behold, it worked. The previously-cold rad is now putting out at least some heat. I am going to go and turn down the manual valve upstairs as well, since it's plenty warm up there.

Does this mean, basically, the boiler isn't of sufficient size, or the water flow through the house isn't efficient enough, to heat everything at once, so the hot water stalls in the system before reaching the badly-performing rad?

Sounds more like a balancing issue, so some rads are taking out too much heat and not leaving enough heat in the water for your problem rad. By balancing (i.e. in this case reducing) the flow through the other radiators your problem rad has heated up. With a bit more tweaking you should be able to get this to work properly.

 

[Pickwickpick]

There's a good guide to balance central heating here:

Croppie's Balancing Thread.

 

[tomatotomato]

Okay. Many thanks to all who provided constructive assistance in this thread! It is much appreciated.

 

[Pickwickpick]

Let us know how it goes.