On 29 Nov 2006 11:55:25 -0800, in uk.d-i-y "Velvet"
wrote:
Velvet wrote (and wrote and wrote, then snipped it all).
I've googled, read the faq's, but I still have some questions.
Aha!
I've experimented, having found a control box on top of the pump marked
up with I, II, and III. No prizes for guessing which one it was set
on...
It's now set to the other end of the scale. Rads are now warming up
more in the manner I would expect (ie, I can finally be sure the one in
the hall really IS the furthest from the boiler). All LSVs and TRVs
So you do have one that is slower than the others, therefore the system
is not balanced. Next step is to leave that ones LSV wide open and
close off the others, using a recording sheet from the FAQ to keep track
of what's happening, until that slowest/furthest one is heating as quick
and as hot as the hottest of the others.
fully open, boiler's set to max, and I'm waiting for it to get up to
temp before I shut off all the trv's and work out how far I can close
the bathroom (non trv) rad before the boiler complains.
You should still include that bathroom rad in the balancing, before you
start to adjust its control valve.
Some combis allow you to have TRVs on all radiators because they have an
internal (automatic) bypass. Are you sure yours doesn't?
That'll give
me a baseline for that radiator, and I should (hopefully!) then be able
to throttle back all the others (apart from the index, which is the
No. As already said ALL radiators should be balance first. This makes
sure they all get a fair share of the water flow. Throttling one back
afterwards is ok, as that will then just make slightly more available
EQUALLY to all the others.
Also the wider open the bathroom rad finishes up, the less kettling you
will have, though I suspect when properly balanced that problem will
disappear anyway. There is no point in turning it down to 'just not
quite kettling'. Only turn it down if the bathroom gets too hot (but
obviously no to the point of kettling).
hall) to what's needed for them to be a little more balanced.
There's really very marked difference in the flow reaching the hall rad
(water has to go up to the bathroom from the boiler, across to the
front of the house via all the upstairs rads, and then down the wall,
to the hall rad by the front door).
That's normal, and is the reason for balancing. The other rads are
effectively short-circuiting the hall one, so you have to increase the
resistance in them so they take less flow and make more available for
the hall. Once a rad has enough flow to fully heat it, giving it more
flow wont get it any hotter, but will steal flow from the furthest rads
which then wont get so hot.
I'm thinking I may find the pump
speed needs to be set for the middle, not sure if the up - across -
Use the slowest speed that all gets the rads fully hot. Rads are
normally spec'd to give full output with 11C drop across them, so there
is no point in running the pump faster than what's needed to get in the
region of 11C.
down - up - back - down to boiler again means it's still only once the
head or if it's twice...
Eh??
Phil
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