Do TRVs have to be on flow or return side?

[diyplumber1980]

Hi, i'm adding TRVS to my central heating system, but due to the nature of the property, its difficult to tell if the flow and return pipes are the same all around the system, as in i'm nogt sure if some are conected to the lef of the rad and some to the right. Its seems like they are. Now I want to add TRVs to every rad, but does it matter if the TRV is on the flow or the return side?

Also, maybe dumb question, but due to the nature of the layout of pipes, i may end up putting some TRVs on the return and some on the flow side. Will this make a difference to the system and stop it working?

 

[Whitespirit66]

Get bi-directional TRVs and it won't matter. TRVs like the Danfoss RAS C2 series have a selector ring on them that you turn depending wether it's mounted on the flow or return.

And don't put TRVs on the rad(s) in the room where the room stat is.

 

[diyplumber1980]

thanks for the reply. I've just had a look at the ones ive brought, it doesnt say bi-directional. It also says only "The TRV is only suitable for use as a reverse flow valve when the system differential pressure, across the valve, does not exceed 0.25 bar"

Can someone explain what this means for dummes like me?!

this is the one i have

http://www.mrcentralheating.co.uk/r...s/evolve-range-of-trvs/evolve-15mm-angled-trv

 

[gas112]

trvs are always better on the flow as this allows the system to be set up correctly ie flow completley open and return restricted down on lockshield to give correct temp drop across rad.
Also bi directional valves do not always do what it says on box