Radiator TRV's

Verb

Hi

I have 4 radiators upstairs 3 with TRVs and 1 in the bathroom without.

All 4 are set to between 2.5 and 3. Bathroom constantly puts out some heat as you would expect due to not having a TRV on 

The 3 with the TRV's when the heating comes on they heat up dead hot and then for the rest of the evening the radiators are off, they may occasionally come on and if I move the TRV only slightly you can hear the radiator kick in to heat up, but goes dead hot and then off again.

Full system has been blead and balanced.

My questions are

What is going on here?

Is this right?

Can I just change the TRV head (which is currently a Bulldog with a 28 - 30mm treaded screw head)?

Can I go swap from a TRV to a manual head?

NSG666

The TRVs limit the temperature of the room not the temperature of the central heating water entering them. What is the actual problem / symptoms that you are trying to overcome?

neilmcl

Everything sounds like it's working fine.

Belenus

As above, all that sounds normal to me.

The TRVs are doing what they are supposed to do.

Bendy_House

Verb, you think they are working a bit too 'on-offish'? It does sound like that, right enough - TRVs should shut of slowly just like a manual valve. Ie, they don't go 'click' and go off, but do shut down slowly and evenly, so you'd expect them to remain, say, luke-warm in order to keep the room at a steady temp.

I don't know if some TRVs are better than this than others, but I have to say that my experience of them is like yours - the rads are either hot or cold, and not in-between :-(

BooJewels

I was actually going to start a similar post myself, as I'm experiencing something similar - but in my case, I've just had a new boiler and thermostat and the TRVs seem to be behaving differently now from previously.   The TRVs have not changed, apart from the engineer changing the settings on a couple, which I think I've now got back to how they were.

With the old boiler, they'd often sit at a modest heat for a good while (often come on from cold quite hot, then settle down for a while), just keeping the room at a steady temperature - but now they seem to come on raging hot for 20 mins, then either that individual rad - or the boiler - goes off, the whole thing pretty much goes cold, then the heating fires up again to repeat the process.  It seems a bit 'all or nothing' to me - I feel that it needs to be a bit more subtle. 

So my thinking is that something in my system - and possibly yours too - isn't quite balanced properly.  I don't know if it's the thermostat, that I need to change the values on the TRVs to better suit the new arrangement, or the temp of the water in the boiler that isn't quite optimal.

Verb

Thanks "BooJewels & Bendy_House"

Yes my main issue is the constant 1 extreme to the other. Controlling the heating at the boiler is not an option as I have a large downstairs space and the boiler is set up to accommodate that.

I think I would rather a constant temp on the radiator be better than red hot or off.

I've since read that my TRVs where 10 years out of production, 6 years ago so it may be time to replace the 3 radiators and TRVs.

Is there any option to replacing the TRV head for a manual head??

coffeehound

It sounds like you might both prefer a lower flow temperature from the boiler.  This should be set-able on the boiler itself either as a simple dial (the one with the pseudo radiator symbol next to it if there are two dials) or digitally

plumb1_2

Yes you can change to manual valves, Pegler would be my choice. But under regs/ good practice trv should be fitted.
plus always best to fit Trvs horizontal as it getting be better scorch of room temperature and not so much affected by heat off the rad.
Danfoss make a trv with remote wire sensor that can be fixed to skirting or away from curtains etc which give better room temp.

BooJewels

Thanks @coffeehound - that was what I was thinking to try, as I think it's higher than my previous boiler.   I know how to change that, the engineer did show me - it's a digital panel. 

It makes sense - as if the water is cooler hitting the radiator, it can't get quite as hot to start with and should therefore stay on longer at a more modest temp.  I'll try 5C first and see if it makes a difference.

plumb1_2

BooJewels said:

. 

It makes sense - as if the water is cooler hitting the radiator, it can't get quite as hot to start with and should therefore stay on longer at a more modest temp.  I'll try 5C first and see if it makes a difference.

5 c    Is a no 
best to make your own post Boojewels