"Mike Barnard" wrote in message
...
Hi.

Silly question time. Enjoy your laughs!

I am adding a 22 mm pipe run along the back wall which will feed 2
rads and a towel rail. Should I join the feed and return pipes at the
end of the run (making it into the proverbial loop) or make going
through a rad the only way back for the water?

If I join the ends, I assume the path of least resistance will mean
the water won't be keen to run through the rads at all, just keep
going round the loop. But if there is no loop what happens if all the
TRV's are closed and there is no return route? Is this accounted for
in boiler design so it just stops?

I think that not joining is the correct answer, but I want to be sure
before I finalise the pipework, so answers on a postcard please.

Thanks.



An Automatic Bypass Valve (ABV) fitted after the pump but before the zone
valves is a good solution - it is adjustable, with all trv's open you
increase the pressure setting on the valve until all radiators heat
normally - then as the trv's close, it gradually automatically opens to
balance the flow and cuts-down the noise of water that would otherwise rush
through the trv's.
It is only a mechanical spring loaded valve - but can be fairly expensive
(£15-20)
Alternatively/additionally it is possible to get a pump that senses the
increases in pressure and automatically compensates by reducing the pump
speed (Grundfos Alpha).

Dave