trv valves not working

[messina1]

Last summer I had bit of time on my hands so I decided to spend a bit of effort cleaning up my heating system.I used a sludge remover and after flushing the system out I decided to take each rad off and cleaned them with with a hose in the garden.After this I went to my local SCREWFIX and bought some trvs which were made by heatline which were the cheapest they do.
After this I refiled the system and everthing was fine,no leaks or rads not heating up,the only problem was that none of the 7 trvs that are fitted work properly.As soon as you turn them down they switch off the rad and do not come back on unless I open them up again.
I made sure I put them on the right side of the rads so this is not the problem.I also have noticed that 2 rads downstairs start off hot and then cool down even when I switch off the rads upstairs it does not make any difference and the pump is on setting 3 max with the boiler a Potterton PRIMA on 5 just below max.
Looking on the web seems using trvs you should have a bypass system fitted and I know mine does not.Could this be the reason?
Any help much appreciated!!!

 

[D_Hailsham]

I decided to take each rad off and cleaned them with with a hose in the garden.

Did you fiddle with the lockshield valve (opposite end to TRV)?

After this I went to my local SCREWFIX and bought some trvs which were made by heatline which were the cheapest they do.

Why buy the cheapest when you want them to last at least until you move out of the house?

the only problem was that none of the 7 trvs that are fitted work properly.

That's what happens with cheap TRVs.

As soon as you turn them down they switch off the rad and do not come back on unless I open them up again.
I made sure I put them on the right side of the rads so this is not the problem.

The TRV's may be sticking. Remove the head and you will see a pin sticking up from the body. You should be able to press this down easily - use a piece of wood - and when you let go it should spring up. If this is OK, the heads are faulty.

Most TRVs can go on either end - a double headed arrow on the body.

I also have noticed that 2 rads downstairs start off hot and then cool down even when I switch off the rads upstairs it does not make any difference

The system may need rebalancing; this is normally necessary when TRVs are fitted.

Looking on the web seems using trvs you should have a bypass system fitted and I know mine does not.

If you have a Mid-position valve, pic below, a bypass is not essential.

View media item 5946

 

[namsag]

Dhalisham if he has trvs on every rad then even with a 3 port valve he needs bypass.
To OP NOT having bypass will not cause your problem .(but if you have trvs on all rads on a fully pumped system you should take one off)
Valves not opening again unless you turn the is down to cheap valves and really slow response time.
As for 2 rads not heating could be down to balancing/airlock or pump on its way out

 

[D_Hailsham]

Dhalisham if he has trvs on every rad then even with a 3 port valve he needs bypass.

This has been debated many times on this site and no one has given a definitive answer.

It depends on why a bypass is required. If it is to provide a path for the water to flow when the pump is in overrun, then it is not really necessary as one port of a 3-port valve is always open. If, on the other hand, a minimum flow is required though the boiler and this would not be met as TRVs close, due to the increased head, then a bypass is required.

The other reason for installing a bypass is to maintain a constant differential pressure as the load changes. This is done by putting an automatic bypass across the pump.

 

[messina1]

Gents thanks for the replys,I realise I should have gone for the more expensive better known models but I was on a budget at the time and thought these would be fine.I have checked the trvs and all the pins spring up,as you said.
The trvs do not have a double headed arrow on the body but one on each side pointing into the rad.I do have a mid-position valve fitted,and the trvs are not on all the rads,the bathroom and on-suite do not have them fitted.It is possible I have moved the position of the lock shield valve but I have tried to balance the system to the best of my ability.I must also say that I changed the pump about a year ago as the old one seized so could that be going already?As I said the system was cleaned and topped up with inhibitor after this was done. As for the 2 radiators,when the boiler is switched on they are fine for about 2 to 3 hours then they start to cool,I thought this was a flow problem so I turned the upstairs ones off but no change.

 

[namsag]

dhalisham it does not matter if one port is ALWAYS open for pump over run (on a system with all trvs) as it is more than likely the heating port that is open and if every trv had already closed there would be nowhere for the water to flow.So a bypass would be require on such a system anyway.

To OP IF the rads heat up perfectly ok to start with then when hot they dont come back on after cooling down this would suggest trv problem.
As a rule of thumb close the lockshield valves completly upstairs then crack them open a quarter to half a turn. down stairs open them fully

 

[D_Hailsham]

dhalisham it does not matter if one port is ALWAYS open for pump over run (on a system with all trvs) as it is more than likely the heating port that is open and if every trv had already closed there would be nowhere for the water to flow.So a bypass would be require on such a system anyway.

I can see your argument: though why should it be more likely that the heating port is open? That will depend on the user's hot water requirement - which is unknown. I suppose you must work on a worst case basis and assume only the CH port stays open.

I do have a mid-position valve fitted,and the trvs are not on all the rads, the bathroom and on-suite do not have them fitted.

Where is your room thermostat? Is there a radiator with a TRV in the same area? If so, this should really be changed to a wheel valve. If you don't want to do that, remove the valve head so the TRV will not work.

If you have a room thermostat and a TRV in the same room you will get a conflict. If the room stat is set lower than the TRV, the room stat will operate first, so the TRV is redundant. If the TRV is set lower than the room stat, the TRV will close the rad and the room stat will never reach temperature. The boiler will continue to run until the boiler's own thermostat shuts it down.

 

[messina1]

Thanks!The room thermostat does have a trv on the rad but this rad is always on as it is in the kitchen diner and has to basically heat the kitchen too.Having said that I have never had a problem with the thermostat not responding to the temperature and in all instances this has always been controllable.Going back,its the trvs in the other rooms that don't do their job that is the biggest headache.Any suggestions appreciated!

 

[namsag]

Dhalisham .Why heating more than likely the open port .
Simple hot water cylinder is usully satisfied(even if set to be on for hours) within half hour heating is usually on for hours at a time and more than likely still being demanded by roomstat when clock goes off.

OP take the trv heads off the ones that are playing up if you cant afford to change them but bulldogs from plumbcentre re a good valve at 9 quid

 

[D_Hailsham]

Thanks!The room thermostat does have a trv on the rad but this rad is always on as it is in the kitchen diner and has to basically heat the kitchen too.

Having said that I have never had a problem with the thermostat not responding to the temperature and in all instances this has always been controllable.

So the TRV on that radiator never works, but the room stat shuts the boiler down when it reaches the set temperature? Then either the TRV is set higher than the room stat or the TRV is faulty.

Namsag: I can see the logic of your reasoning.

 

[messina1]

Thanks for the advice,pumbcenter prices gone up with everything else,now tvs £12.85 vat included!

 

[D_Hailsham]

Why is there nothing about Bulldog TRVs on Pegler's website? The only TRVs they show are Terriers. Plenty of Bulldogs are available from on-line shops and in Ebay. Are they now a discontinued item?