Flow and Return of each radiator...

[tvradict]

I'm currently replacing the maze of spaghetti pipework that fed my radiators. I've already stripped out the old st, but stupidly, forgot to note the 'in' and 'out' of each of the rads.

My rads all have thermostatic valves and I'm almost certain I read somewhere that the thermostatic valves should be on the 'out' pipe.

How do I work this out, is it as simple as the thermo valves are on the return side or is it more complex than that?

TIA
Stuart

[danger mouse]

Not so easy with more the than one to work out but when I did this the other day I just turned on the heathing and felt for which pipe went hot first.

I know it is recomended the TRV should come after the radiator, but as all radiators should be piped in parrallel, and the TRV in series with the respective radiator, why does in matter which way round they are?

[Dogwatch]

TRV's should come on the inlet side, however the better makes don't care which end they are. Cheaper makes may 'chatter' if the flow is in the wrong direction.

[danger mouse]

Got it.

That could be a way to work out the flow direction though, kinda.

My TRV's must be ok then or I've just got lucky.

Edited by danger mouse on Thursday 29th July 10:58

[tvradict]

Thanks for the replies.

Unfortunately since I posted my question I had to take the a rad off the wall to get access to the valves and pipework, twas a bit tight you see, and discovered the TRV on this rad is an innie, whereas the TRV on the rad I changed yesterday (had a spare, and the one that was there was st) was an outtie.

I can see this job is gonna be a bh.

cheers

[danger mouse]

Keep smiling and good luck!

[tvradict]

Cheers

But I need a Miracle more than luck

[Trevelyan]

Have a look on the body of the valve. I think that most of the ones I've fitted have got a directional arrow as past of the casting which indicates the direction in which the water should flow. As stated above most of the newer ones are quite happy with flow in either direction anyway.

[Ferg]

Be warned, though, that EVEN IF the TRVs are bi-directional, they CAN still cause problems if the flow is reversed from how a conventional valve works. They can only accept a certain flow through them 'backwards' and this is unlikely to be acceptable without a differential bypass valve on the system.

[danger mouse]

Is that usually catered for by making sure there is always one radiator that cannot be shut off thereby allowing a perminently open circuit for water to escape down?

[Ferg]

danger mouse said:

Is that usually catered for by making sure there is always one radiator that cannot be shut off thereby allowing a perminently open circuit for water to escape down?

No. All of the bi-directional valve I know off aren't capable of flowing enough 'backwards' through just one radiator to avoid problems depending, of course, on the sort of flow being provided by the pump.
This is exacerbated by the fact that since the unregulated radiator MUST be in the space with the Room Thermostat, it MUST be restricted quite heavily to enable all other radiators to get hot before the boiler turns off. A differential bypass is really the only way, which is fine if there's an 'S'-Plan type system fitted since it will most likely have one anyway, but 'Y'-Plans and Combination Boilers are another issue.

Edited by Ferg on Thursday 29th July 14:33

[danger mouse]

Good to know, I will have a look in to my system and see if it needs a valve then. I could explain a couple of things. Cheers!

Edited by danger mouse on Thursday 29th July 14:40