In an earlier contribution to this discussion,
new to diy wrote:

Ok, I've just bought an IR thermometer with laser guide (IR89 -
awesome) and have began balance my rads in earnest.

I have a choice of 2 rads which could be considered closest to the
bolier. One rad has a 4 degrees C drop across it (20-16) but the
other, get this, has an increase across it (21-27)? Have the builders
put the wheelhead/lockshield valves on the wrong way round? Would the
central heating system still work ok if this were the case?

Any advice greatly received as always.

A radiator can't *heat* the water - unless it's got an electric heater
inside it! So what you *think* are flow and return are actually the other
way round.

In what units are you measuring the temperature? I don't know of *any*
measurement units in which a number in the 20's would be a sensible reading
for a radiator! Or maybe you're pointing your IT thermometer at the *wall*?
--
Cheers,
Set Square
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