Which ends of a radiator do TRV and lockshield go?

by **Andy760** » Wed Dec 03, 2008 2:27 am

Hi. I have always worked with heating systems on the basis that a TRV or standard valve is fitted to the flow side of the rad and lockshield on the return. Is this correct? I have a microbore system in a new flat - all TRVs bar one are on the return side of rads/towel rails. Surely this will make balancing a nightmare if not impossible? It's getting towards the time of year when this system is going to have to be switched on and as I have to get this sorted by the builder, advice / confirmation would be very helpful! The rads/towel rails do heat up. Thanks in anticipation!

Andy

by **Tekenbarba** » Wed Dec 03, 2008 4:19 pm

Forgive me please Andy because I would like to 'piggy back' my question onto yours as it is very nearly the same.

Recently had a new boiler fitted and have found out that the flow is the wrong way round - in at the lockshield valve and out at the thermostatic valve. The installer has just told me that with a combi boiler the flow direction is immaterial. Is this the case as it sounds counter intuitive to me?

Hope you do not mind Andy. It seemed that our questions were so similar that it would be silly to open a new topic.

by **plumbbob** » Wed Dec 03, 2008 11:09 pm

Unlike old TRV's and lockshield valves most modern valves will now work in either direction, and it is no longer standard to fit as you mention. Generally most installers fit the TRV on whichever end is open to the room. My colleague on the other hand likes to be different and always puts them on the right for neatness.

https://www.diydoctor.org.uk/forums/view ... hp?t=14745

by **Tekenbarba** » Thu Dec 04, 2008 8:46 am

Thanks plumbob.

by **roadie** » Sun Dec 14, 2008 8:38 pm

so how do you balance a system that has the TRV on the return?

do you still restrict the flow on the lockshield to maintain a temp balance?

by **plumbbob** » Mon Dec 15, 2008 9:13 am

Yes indeed just forget the flow direction and use the lockshield to restrict flow as necessary.

The only point to remember is if radiators with lockshields in the flow require bleeding, the heating may need to be turned off first. If the system is a vented low pressure type with header tanks, opening the bleed valves may result in air being drawn in rather than expelled.

by **roadie** » Sun Dec 21, 2008 9:37 pm

ta for the reply. Been busy sorting the rest of the new kitchen :)

Its a pressured system but still switch the system off when bleeding. Need to drain to refill with inhibitor so will re balance when finishing off.

by **TheDoctor4** » Fri Oct 30, 2015 12:25 pm

Hi All

We now have a handy DIY how to guide covering thermostatic radiator valves and TRV's that covers this particular subject and also others such as fitting and changing TRV's. Check out our TRV and thermostatic radiator valves project here if you are interested