Intermittent radiator

[stender]

I have one radiator in the house that works intermittently. it's the lowest rad in the house and has the drain plug on it. Today for example the heating is on in the house but this radiator is totally cold as are both pipes either side. We previously changed the try as it was intermittent getting hot but i assume that its not that as the pipe before it should be hot? any ideas? no air in the rad and system is full.

 

[denso13]

Turn all the other radiators off and see if this one heats up.

 

[stender]

lot of effort. what will that tell me? it does come on some times without me touching anything

 

[HERTS P&D]

Balancing issue, when the trv's on other rads reach temp, more water is pushed to this rad.

Andy

 

[denso13]

lot of effort. what will that tell me?

It'll point to what's wrong with it. It's just guesswork for now.

 

[denso13]

it does come on some times without me touching anything

Then the system needs balanced.

 

[stender]

I only have trv on a couple of radiators, most are just open and close valves and all open

 

[ChrisJP]

I only have trv on a couple of radiators, most are just open and close valves and all open

If all the radiator valves are fully open, that's your problem.
The hot water is flowing through the other radiators and by-passing the problem one.
As has been said, turn off completely all the lockshield valves on all the other radiators (but fully open the TRVs) and see if the problem radiator gets hot. If it does (which it almost certainly will) then progressively crack open the lockshield valves on the other radiators, one radiator at a time, until each one gets hot. Don't open any lockshield valve further than is needed to get the radiator hot, and wait for around 30 mins after each cracking open to see the effect on the radiator.

 

[ericmark]

My first water central heating system had no TRV heads, same with parents, but the central heating was never designed as the sole method to heat the home, we had coal, coke, or gas fires to heat the living rooms, the central heating was only designed as a back-up to take chill off the home before the main fires were lit.

Between 1980 and 1990 we moved to condensing boilers, which in turn needed a modulating boiler, and for the modulating boiler to work we need by-pass valves and TRV's.

I remember trying to balance radiators without TRV's, and it did not work. The problem was, there was nothing to compensate if a door left open or closed.

With a TRV we are told to set the differential between in and out at around 15°C, but without a TRV it would need the radiator in the same room as the wall thermostat set that way, and the rest set based on room temperature. I look at my house, and wonder how it would work. Today I see 20.4°C living room, 19°C in my bedroom,14.1°C flat under the main house, and 8.9°C in utility room. OK, utility room unheated, I look at the living room, 16°C, 20°C, 20.5°C TRV 1, TRV2, Wall thermostat. This is one room, how you control a whole house, I don't know.

 

[Harry Bloomfield]

I only have trv on a couple of radiators, most are just open and close valves and all open

Flowing water, in a network, always takes the easiest routes. The easiest routes, are via radiators, with wide open valves, you need to close those valves down, to about 1/4 open, to increase the resistance, and help distribute the flow to your problem radiator. It's working intermittently, at the moment, but only when the two TRV's close.

 

[stender]

which is the locksheild valve? they both have a white cap and brass valve i can open close using a spanner? odd that all are fully open (6 downstairs and 7 upstairs including 2 towel rails). All are fully open and only about 2 have trvs including the problem rad which we switched the trv as well. Aside from the main controller in airing cupboard we just have a thermostat on front room wall, so basically the heating is on in all rooms but set temp in front room. not ideal.

 

[denso13]

they both have a white cap and brass valve i can open close using a spanner?

One should be a wheelhead valve, that is a cap you can turn by hand. If they are both the same then use either one.

 

[Harry Bloomfield]

which is the locksheild valve? they both have a white cap and brass valve i can open close using a spanner?

Which ever one of the two you fancy adjusting. The other one, then becomes the on/off valve, for when you don't want the radiator on - usually you would make that, the easier, more convenient one to access, to turn it on/off.