Some radiators fail to heat

[gboyd]

Very useful info, thanks.

Just to ask a stupid question but would you expect water to flow out of the LS valve? In my head I imagined that side of the rad was the water flowing down the LS pipe rather than pouring up.

The balancing wasn't professional to that degree so I'll retract that statement. But he tried balancing from the nearest outwards then when the inlet pipe failed to heat in the furthest away radiator (also the problem radiator) he balanced backwards. One thing I do know is it doesn't matter what position the other 6 working radiators have the LS valve set, when you turn the TRV even an centimeter from the off position you hear a rush of water and it heats very quickly.

The other 3 just seem so far away from working the same although I can confirm that the pressure on these faulty rads is pretty strong on both valves when loosening off the nuts.

 

[D_Hailsham]

Just to ask a stupid question but would you expect water to flow out of the LS valve? In my head I imagined that side of the rad was the water flowing down the LS pipe rather than pouring up.

Don't forget that the water is being pumped all the way round the circuit. So the water flowing down the main return pipe from a rad further away from the one being tested will, instead of just flowing past the junction with the pipe from the rad, come up the pipe and out of the open LS valve, as it will be the path of least resistance.

 

[gboyd]

So if the water flows steadily from the return pipe with LS fitted then I can assume there is no blockage in the return pipe?

Do I need to test this for all 3 rads that are not heating up beyond luke warm?

What on earth could be stopping the hot water flowing from the hot inlet pipe into the radiator then?

Also, just another bit of info incase it helps but the CH inlet and outlet pipes coming from my boiler are absolutely red hot to touch so the return pipe must be getting the water back from the working rads .....

Complicated for someone that has never so much as fitted a bookshelf when it comes to DIY

Thanks again for your time D_Hailsham

 

[D_Hailsham]

So if the water flows steadily from the return pipe with LS fitted then I can assume there is no blockage in the return pipe?

This proves that the main return pipe up to the rad and the short link from them main return are not blocked.

Do I need to test this for all 3 rads that are not heating up beyond luke warm?

Yes

What on earth could be stopping the hot water flowing from the hot inlet pipe into the radiator then?

But you have proved that water is flowing into the rad and out again. What it is not doing is flowing down the return pipe.

Also, just another bit of info in case it helps but the CH inlet and outlet pipes coming from my boiler are absolutely red hot to touch

You should have mentioned this earlier!
What make model boiler do you have?
What make model pump do you have?

 

[gboyd]

No idea what pump I have mate but the boiler is a SIME Format 100C.

Sorry for not mentioning this earlier, what difference might this make?

 

[gboyd]

Still no luck but just to update my list of clues.

I turned every single rad off last night both at the tvr (which does close fully) and the LS valve.

I then turned the boiler on and went to the furthest away rad that is not working (in my livingroom) and opened the LS valve fully.

Then I slowly turned the tvr and as I hit approx 1 (on a 0 to 5 scale) I started to hear a hissing sound like the water was flowing. With this said it was not of a volume which can be heard on the other 6 working rads.

I thought great and continued to open the tvr but as I moved it just a tiny bit further the sound stopped and did not come back all the way to 5. I then turned it backwards towards 0 and when it hit the 1 position the sound started again.

I repeated this for the other 2 non working rads and the same result although not at the same reading on the tvr.

Plot thickens and not sure if this means anything but I thought I'd update with my findings.

 

[gboyd]

I have turned off all rads except one of the problem rads.

Noticed now that my boiler is making some bizzare noises!

Best way i can describe it is like when you boil a kettle with little or no water.

Is this a good thing and potential air blocks are being cleared or is this a bad thing that I should stop immediately?

 

[gboyd]

Also, forget to say that with only the problem radiators turned on the CH outlet pipe coming from my boilder does not get hot. Only when a working rad is turned on does it heat up.

When I flushed the radiator in the livingroom there was a big build up of white type powder which I had to clear. Sort of like if you put too much washing power into a washing machine and your clothes come out covered in a white type powder/paste.

I wonder if perhaps the wrong type of cleaning product was put into the the rads?

I would hazard a guess that this is built up elsewhere in the return pipe and causing the blockage.

Is there anything I can do to try and clear this now without having to lift floorboards and cut pipes?

Or again I may be totally wrong with all of the above

 

[D_Hailsham]

Do I need to test this for all 3 rads that are not heating up beyond luke warm?

Yes

Have you done this? If so, what were the results? If not, why not?

 

[D_Hailsham]

Noticed now that my boiler is making some bizzare noises!

Best way i can describe it is like when you boil a kettle with little or no water.

When I flushed the radiator in the living room there was a big build up of white type powder which I had to clear.

Do you live in a hard water area?

The noise is called kettling and the white powder is probably limescale. In a hard water area the heat exchanger gets furred up, like the inside of a kettle, so the water is not able to move through at the correct speed. This causes localized overheating and the noises you hear.

Limescale can block the pipes.

 

[gboyd]

Do I need to test this for all 3 rads that are not heating up beyond luke warm?

Yes

Have you done this? If so, what were the results? If not, why not?

Going to do it today mate.

Can I check, should I have all working rads open and the heating turned on?

 

[gboyd]

Noticed now that my boiler is making some bizzare noises!

Best way i can describe it is like when you boil a kettle with little or no water.

When I flushed the radiator in the living room there was a big build up of white type powder which I had to clear.

Do you live in a hard water area?

The noise is called kettling and the white powder is probably limescale. In a hard water area the heat exchanger gets furred up, like the inside of a kettle, so the water is not able to move through at the correct speed. This causes localized overheating and the noises you hear.

Limescale can block the pipes.

I think this might be the issue then from everything I've described so far.

Is there any product I can buy that will break down this potential limescale blockage?

 

[D_Hailsham]

Can I check, should I have all working rads open and the heating turned on?

Better to have other rads off, so you are just sending water round the main pipe. The boiler need to be on (turn the boiler stat right down) so the pump is working and sending water round the circuit.

Just to make sure you do it right, here is what to do

You need a container for the water from the rad and from the LS valve.

1. Close the TRV completely

2. Close the LS valve completely

3. Disconnect the LS valve from rad, leaving connected to the pipe and drain the rad (open bleed screw to let air into rad)

4. Open the LS valve slowly until you get a flow of water from the radiator connector.

5. Close the LS valve and reconnect to the rad.

If no water comes out of the LS valve, or it is very slow, there is a blockage upstream of that rad.

It might be worth doing this on a "good" rad; then you will know what sort of flow to expect.

 

[richmof]

I have exactly the same problem, with exactly the same number of rads, running off the same system, in a hard water area and have driven myself nuts trying to fix it. Let me know if you find a solution. Good luck

 

[gboyd]

Right mate, done exactly what you said.

When I released the ls valve at first the water came rushing out big time spraying all over the place, despite using a funnel into a pan.

Anyways, it was strong for about 15 seconds but started to weaken until I got the valve fully open and absolutely no water coming out!