---- radiators going cold

[jkdh1527]

thank u D!! I was unaware of the room thermostat but they are coming next week to fit one, free of change.

They engineers decided on the size and quants. I just said i needed a system and for them to price it up for me.


They come and quoted by measuring up etc, so i put my faith in someone who was supposed to know what they were on about to do what they thought was best.

I explained that i needed the most heat in the living room as its open plan, but i got the complete opposite

 

[jkdh1527]

oh and the trvs were on when they balanced them

 

[jackecole]

trvs should be turned to max when balancing i believe. i am not sure what taking them off would achieve? not that i have balanced a whole system before in 1 hit.

 

[jkdh1527]

they do seem to have tried alot of things and they themselves said they have never come across this situation in all the years of business, but iuts obvious that something is not right somewhere along the line

 

[GPlumb]

OK OK OK.

This is what i would try.

First make sure all the lockshield valves are open (thats the other radiator valve)

Then set all the trvs to full.

Turn heating on and set the boiler temp control to say half.

See what happens after say 30mins.

You do need a roomstat, they cost £10 and it should have been fitted at the time of installation.

You could possibly break the boiler without one. If all the trvs are shut and there is no automatic bypass.

Are the pipes to the cold radiator warm?

 

[Clive100]

Flow/return pipework undersized- inedequate flow rate or boiler bypass problem? I get the feeling that its a boiler based problem since it should respond/sense the cooler water returning and fire up to reheat especially since it's on max stat setting. The trv's are highly unlikely to be all defective - check you have read their user instructions and are operating them correctly - some are designed child/fiddle proof.

 

[jkdh1527]

Graham

yes the pipes are warm and as soon as you take the trv completely off and press down the pin, the heat starts gushing through again.


I will try everything you have mentioned.

Glad everyone mentioned the room stat as they only mentioned it to me today and saids they would fit 1 next week and try that

 

[jkdh1527]

clive

Trvs are all fine,,, i have had the engineers out numerous times and even them theirselves dont know what is going on and have never come across it before. My boiler is ferrolli and i only have 5 rads coming off it. they are all only single ones, 4 big and 1 small

 

[jackecole]

boiler flow and return should be 22mm for about 600mm or so (depending on boiler manufacturer) - also maybe the system just isn't balanced correctly.

a room stat is a MUST though, and as mentioned a few posts ago, if all trvs close down the pump can knacker (fire against a dead head) and the boiler heat exchanger may overheat (you will hear oud and strange noises "kettling" type if this happens.

can someone please educate me as to why systems should be balanced with TRVs off? it was mentioned earlier and is interesting to know...

 

[D_Hailsham]

trvs should be turned to max when balancing i believe. i am not sure what taking them off would achieve? not that i have balanced a whole system before in 1 hit.

The problem with leaving TRVs on is that they can have an effect on the flow through the radiator. Setting the TRV to max does not mean that the valve is permanently open, just that the required room temperature is about 30°C or even greater. The only way of ensuring that the TRV stays open while balancing is to take the top off.

Balancing procedure:

You will need either two clip on pipe thermometers (£12 each) or an infrared thermometer (about £25 from Maplin). I have used both and prefer the infrared as it has a faster response, is more accurate and can be used for other things, e.g checking the temperature distribution over the surface of a rad.

1. Turn boiler off and allow to cool
2. Make sure HW is turned off
3. Open all LS valves fully; remove all TRV heads and open all manual rad valves fully.
4. Turn the boiler temp to 75°C and bring system up to temperature.
5. Check, by feel, the order in which the rads warm up and make a list.
6. Adjust the bypass (if fitted) as per mfr instructions
7. Measure the temperature differences between the flow and return pipes at the boiler. What it should be will depend on the boiler -refer to the installation manual. If the temperature is not right, you need to adjust you pump speed (higher speed gives smaller difference and vice versa). Set the speed to give a difference as close to the mfrs recommendation as possible.
8. Turn the boiler off.
9. Close all lockshield valves. Leave TRV heads off.
10. Restart boiler
11. Go to first rad in list made in step 5
12. Attach the pipe thermometers (if used) to the rad and open the LS valve a quarter turn.
13. Wait until temperature has stabilised on the two thermometers (or use the IR thermometer to measure flow and return temp in the pipes adjacent to the valves). If the difference is smaller than that at the boiler, close the LS valve a fraction, or vice versa. Wait until the temp has stabilised and check again.
14. When you are happy with the first rad, move on to the next on the list.
15. Repeat steps 12, 13 and 14 for each rad on the list.
16. When you have reached the last rad, check the boiler temp difference and adjust pump speed if necessary.
17. Go back to the first rad and test it is still giving the correct difference
18. And so on, going round and checking the temperature difference until they are all as near the required drop as you can make them. Don't expect perfection
19. Replace TRV heads and set to required temperature

A very small change in the amount a LS valve is open can have a considerable effect on the temperature difference. Because of the way LS valve are constructed, it is virtually fully open when it is one and a half turns open. So most adjustment will be within one turn from closed.

If you find that the wall thermostat is turning the boiler off before the TRVs in the other rooms work, you should close the wheel valve slightly, so the rad gives out less heat and the room/hall warms up slower. It's a matter of trial and error.

 

[GPlumb]

Is the trv of the offending radiator obstructed in anyway?

Their needs to be airflow around the head for it to work right, are curtains, furniture etc getting in the way of that?

 

[gigz]

How big is the room and what size rad is it ? also what size pipes are fitted to the radiator ?

 

[jkdh1527]

D Hailsham


Thank u very much for your advice.

 

[jkdh1527]

Graham

The trv has nothing obstructing it at all,its totally clear, the closest item to it is our sofa which is about a foot away

 

[jkdh1527]

gigz

the room is not too big as they are only small houses, but its open plan, where the stairs are in the living room.

Rad is a big one but only single, not a double