Danfoss Flow Selectable Valves - rad hot top, cold bottom

[ifatfirst]

First post, advice appreciated.

Problem: Stelrad K2 Compact 600 x 1600 radiator, hot at top, no heat bottom or left hand side.

(2 new rads in new extension added to system. One hot all over - top mounted TRV on feed, one never hot all over - top mounted TRV on return. Top mounted TRV essential - elderly user. B Gas say installation incorrect - coming to change pipework, want to be ready!)

Radiator: small pipe (10mm?), feed bottom right hand lock shield valve, return top left TRV - Danfoss RA-FS flow selectable valve (grey direction selector arrows), RAS-C2 sensor (also tried RAS-D2), last radiator in system. Installer: Corgi registered, ex B Gas.

System: Worcester 280 RSF gas combi, sealed system, 11 radiators, bungalow, pipes down from loft - all other TRV on feed (2 top mounted Stelrad) with no problems.

Tried (thanks to info read on this site) : a) bleeding - no air, b)all radiators off except this last one to force through - no change, c) check valve pin - free moving, d) leave TRV off - no change, e) tried both arrow selections on flow selectable valve (checked Danfoss site - v helpful) - no difference. Grateful for guidance.

 

[corgiman]

probably needs balancing

see the FAQ's

 

[superdupergasman]

you may have a resrtiction in the new pipework, maybe a kink in a pipe or debris being picked up from when feeding the pipes to rads.

 

[ChrisR]

top mounted TRV on return

Not surprised it doesn't warm up!

The return connection has to be at the bottom or the rad won't fill with hot water. You can have the FLow at the top.

 

[ifatfirst]

Thank you kind people for quick replies. Looks as if pipework will need to be altered, think flow is OK as gets v hot at top. How should pipes enter and exit in order to enable top mounted TRV?

Is flow IN at top plus TRV
Flow OUT at bottom plus lockshield valve OK? Plus balancing.

 

[ChrisR]

Top entry, bottom exit.
ie flow pipe comes up the side of the rad, goes into right angled trv which has head horizontal. Standard for older folk. ( you could put the head vertical I suppose but the thermostat works better horizontally mounted.)

Normally you'd want the exit the opposite end, but it does work if the exit's the same end, at the bottom.

 

[D_Hailsham]

How should pipes enter and exit in order to enable top mounted TRV?

Flow in at the top. Return out at the bottom on the opposite side is the best way. It will actually give about 5% more heat than the normal flow and return both on bottom connections.

 

[ifatfirst]

Thanks everyone. Bacon sandwiches all round. Won't look so thick when gas man comes. Will post when work has been completed

 

[ifatfirst]

All sorted out. Lovely hot radiator. Thanks for help.