One of the radiators doesn't work

[MoonMan2]

This is a house I know very little about, other than it is 10 years old.

Just had central heating engineer out to check that my system is working correctly.

He said the boiler is in perfect working condition and switched the system on full. When I checked the radiators all were producing heat to varying levels of satisfaction. When I say that, the Kitchen radiator was not a hot as I would have expected, but in one of the bedrooms it was scorching hot, the rest were somewhere inbetween.

However the newest radiator which is in the extension of the house built 5 years ago has an issue. This is the only radiator in the house to have a thermostatic valve (ie settings 1 to 5, and operates by pin being pushed in and out). Heat could be felt from one of the pipes that fed up to it but the other one was stone cold. Of course this meant the radiator would not heat up. The engineer said "there was a blockage in the radiator". When I asked if he could fix it, he said there is no gurantees but any one of the following could do it:

1) Replace valve on radiator (on the pipe where it is cold) - approx £65

2) Replace radiator - approx £170

3) Flush entire system - approx £450 (takes all day)

After he left, I switched off the central heating at which point a tiny bit of heat was felt at the top of this 'cold radiator' - odd

I really need the entire system to work.

Advice please...

 

[Red_Man]

Turn one side of all of your radiators off, see if it gets warm.

If it does, it's a balancing issue.

Try it and get back to us.

Worth a try before spending money. May well be the valve though.

 

[ianniann]

When I say that, the Kitchen radiator was not a hot as I would have expected, but in one of the bedrooms it was scorching hot, the rest were somewhere inbetween.

Hopefully the boiler is set to produce "scorching hot" water, but all the radiators should reach more or less the same temperature. If they are ideally balanced they should come to temperature more or less at the same time. How long did you wait for the majority of the radiators to warm up? Do they ever reach the same temperature as the bedroom radiator? Is the bedroom radiator the "first" radiator, that is closest to the boiler as the pipes are run? Is the kitchen radiator at the end of the line? Or at the end of one branch of pipework?

 

[MoonMan2]

I tried what you suggested Red_Man, nothing happened, no warmth in any of the radiators. I then opened both valves fully on the radiator in question(suspected faulty one), once again nothing happened, in fact the boiler deactivated but when I touched the boiler it was very hot.

So, having read a few internet sites on balancing, I opened the valves on ONE side only of all the radiators that were working(standard I will call these) by 20%, leaving the other sides open 100%. I of course left the valves both open by 100% on the problematic radiator. The result, after about 5-10mins heat came through standard radiators as normal, but with the one in question it took about 30-35 mins before it felt hot. Of the two pipes that lead to the suspected radiator only one was hot, the non-valve side. After about 50mins the valve side started to become very warm. At this stage of course all the standard radiators were burning hot with both pipes leading to them also burning hot.

This is of course an improvement on what the engineer managed earlier today, in that he couldn't get a peep of heat from the suspected radiator. He insisted on always having all valves open 100% on all radiators and controlling temp using thermostat on wall.

The thermostat on the wall was set at maximum temperature. The radiator in question is on the bottom floor in an extension part of the house. As for the order of the radiators, ie start and finish line I do not know.

I do have another question, of the two pipes going into the radiator, how do you tell which is the inlet and outlet, and which valve is better at controlling individual room temperature?

 

[tincup]

Hi

Too late now but you should have left all radiators open and just removed TRV head on faulty rad. The pin can stick down and sometimes needs help.
Running boiler with all rads shut not recommended.

HTH

 

[ianniann]

Usually the inlet will be hot and the outlet cold when there is very little flow through the radiator. With good flow, both pipes should become hot. It isn't critical, but for balancing you would normally reduce the flow on the inlet. Sounds like your plumber is a numpty if he doesn't even know how to balance the radiators, whioch based on your description he doesn't.

I'm guessing you don't have TRVs, that is thermostatic valves with big heads on. The regular valves are not for controlling room temperature. You will not be able to reduce the flow through a radiator sufficiently to limit the room temperature. If you try you'll just make the pipes noisy and eventually shut down the radiator completely. Even a pretty low flow will make a radiator hot.

The valves are just for reducing the flow a little on the radiators closest to the boiler to increase the pressure at the ones furthest away. This allows all the radiators to get hot. Even 20% is pretty wide open for a valve. Try it with them just half a turn from closed and see if that helps. That will limit the flow a lot in those radiators and might make them noisy if your pump is strong enough, so you might want to open them up a bit more when you're finished. The first aim of balancing is to get all radiators to warm up, and the second to have them warm up at more or less the same speed. Ideas of temperature drop across the radiators are probably a bit too much to worry about for now.

If you have a single radiator that doesn't get hot even when you close down the others, and especially if it isn't the last one down the line, then you usually have some sort of blockage. It could be a knacked valve or sludge, occasionally an air lock. Occasionally a radiator is just stuck on a piece of pipework that doesn't get good pressure, amazing how many houses have them. Ground floor on an extension, solid concrete floors with the radiator feeds dropped from upstairs, is very likely the end of the line in your system. Sounds like you do have limited flow so you might want to go with it for now.

 

[MoonMan2]

I looked up TRV controlled radiators on internet. Apparently they tend to make radiators more cool than non-TRV ones.

See ref: http://www.miketheboilerman.com/thermostaticvalves.htm

Is it maybe because it's the summer, my TRV was sensing the higher room temperature thus preventing flow like it's supposed to do?

 

[Goldspoon]

To test this theory take the TRV top off (just unscrews, no water can escape).

 

[ianniann]

I think you misunderstood the article. TRVs cool down radiators when the room is warm enough, simply by turning them off (almost off, but don't worry about the difference). When the room is cooler than the position set on on the TRV then the radiator will operate completely normally. Don't panic about TRVs reducing the effectiveness of your heating.

They're a thermostat, it's right there in the name. Cold room, radiator full on. Hot room, radiator full off. For a few degrees near the correct temperature, radiator gradually turning off. Your own little central heating control on every radiator.

 

[MoonMan2]

From this guys, I am guessing that the TRV radiator is indeed faulty. So in reading my OP again, I think I am going to go with getting a new TRV valve on it. If it turns out it's not a faulty TRV value, then I'll get him to put spare one on bedroom radiator.

Maybe I should get out a different company cause you all think this guy isn't very bright??

 

[holty]

one thing being missed except from ianniann.is that some times to many rads off a very little circuit e.g 15mm pipe will eventually cause problems.