In an earlier contribution to this discussion,
Fred wrote:


I think the FAQ advises 1/4 turn adjustments. I thought that valves
like lock shields are non-linear. Does this mean that the first few
turns will make no difference and then near the end, the slightest
turn will make a difference? Should I use turns smaller than 1/4 to
fine tune?

It's certainly non-linear, and most of the action occurs when it's getting
on for closed, so you can certainly turn it down quite a lot - maybe
half-way - to start with. The rest is really 'suck it and see'!


I'm having most problems with the towel radiator in the bathroom. It's
scalding hot to touch but not showing much of a temperature drop.
Should the drop across a towel radiator be the same as the
"conventional" radiators?

Towel radiators are a waste of time as space heaters anyway, but you'll get
a *bit* more out of one by running it at a higher average temperature - i.e.
with a smaller drop. But don't go below (say) 5 or 6 degrees, or you'll be
at risk of starving the other radiators.

How accurate should I be in matching temperature drops. Should I try
to get each rad. to have a drop of say 10C, or does it matter if one
has 8C, another 12C, another 9C, etc?

It's not an exact science - and you'll never get then all exactly equal.
Variations of a couple of degrees don't really matter. What you are trying
to avoid is having some with a 2 degree drop and others with 20 degrees or
more - which is probably what you'll have at the beginning.


Daft question: does the boiler need to be firing? Or as long as the
pump is circulating hot water is that enough?

Ideally the boiler *should* be firing but that is virtually impossible to
achieve. Unless the system is dissipating the full output of the boiler, it
will inevitably cut in and out on its own thermostat. But that at least
means that the water being circulated is at a more or less constant
temperature - within the hysteresis of the boiler's stat. Don't forget that
you're measuring the *difference* across each rad, so if the flow
temperature varies slightly, it's not a disaster. It *is*, of course, vital
to keep the pump running - by turning up the room stat and, if necessary,
opening a few windows to stop the house getting too hot - although that
shouldn't be necessary this time of year!
--
Cheers,
Roger
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