microbore heating system question

In article , snipped-for-privacy@bluemore.com writes

One is hot, the other is not (as much), use a calibrated finger.

It allegedly doesn't matter which is which as modern TRVs will operate correctly with flow in either direction but after having bother in the past I prefer to have the flow pushing so as to open the washer, that is with flow out of the pipe at right angles to the TRV body. That means having the TRV on the inlet side if you like your TRV vertical or outlet side if you prefer your TRV horizontal.

On Thu, 18 Jan 2007 14:40:31 -0000 someone who may be wrote this:-

Turn the heating on. Feel which one warms up first.

flow and return. I have often pondered this as I want to replace a pipe. I had thought (but not tried) - starting with a cold system - turn off each radiator's flow and lockshield - leaving just one open. Fire up the boiler and feel which pipes heat up (flow first followed by return). There shouldn't be any flow to the isolated radiators so their pipes should remain cold. Repeat progressively to identify the others.

Is this what you meant?

On Thu, 18 Jan 2007 17:22:59 GMT someone who may be "John" wrote this:-

And label each one in some way, so as not to forget which is which.

Of course, depending on what work is to be done and the current system, there may be no point in identifying the flow and return to an individual radiator.