Hi appreciate some advice- SYSTEM WORKING FINE TILL I recently removed
a radiator for decorating after replacing,had no hot water but ch ok I
have a conventional wet system, 3 port valve
pump/ cylinder stat/ drained system also replaced port valve and
bled rads. Iam guessing its a air block but cant figure how to shift
when timer calls for ch ok but no response for hw. pipes are hot at
ports but cold going into cylinder, any opinions would be greatly
On 1 Jan 2004 14:19:54 -0800, email@example.com (B C) wrote:
Are you sure that you have wired the 3 port valve correctly, and have
you got the correct replacement? There are diverter and mid position
"when timer calls for ch ok but no response for hw. pipes are hot at
ports but cold going into cylinder"
is a bit cryptic. What do you mean? Which ports? Can you expand
this a little bit, please.
You could try taking the motor head off of the 3 port valve and
operating the cam manually - e.g. with the CH on. See if the
cylinder coil starts to receive heat.
If there is a high point on the cylinder coil connections (i.e. pipes
come from below) there should be a means to vent it at or near the
upper connection. If somebody was lazy when plumbing then this could
explain your problem. It's easily fixed with a small manual air
vent. e.g. www.bes.ltd.uk part no. 6793.
You would arrange one of these on the top of a short branched piece of
15mm tube teed onto the upper cylinder connection.
To email, substitute .nospam with .gl
Silly question: I suppose the new cylinder stat *is* set correctly and not
turned right down? Ok then, well is it *wired* correctly - bearing in mind
that it's got (or should have!) changeover contacts. [If these are wired the
wrong way round, the 3-port valve will only feed boiler water through the
indirect coil when the cylinder is *hot* - so it never gets hot!]
What length is the pipework between the 3-port valve and the hot cylinder?
Is there a gate valve somewhere in it to balance CH vs HW when they are both
on? Is it turned off? [Might you have turned it off when you drained the
system, and then forgot to turn it on again?]
thanks for taking the time to answer,re/cylinder stat/ Iam sure it is
and temp set correctly, pipe work is a short run to cylinder with a
bleed spured of it which I have bled. the pipe from 3 port/v into
cylinder remains cold and I also have a radiator which is hot at base
cool at top which cant be bled due to there being no bleed valve apart
from this and my wifes mood central heating works on demand.
Does your 3-port valve have a central position where it feeds CH and HW at
the same time - or is it a diverter valve which only produces one at a time?
Have you tried removing the actuator from the valve, and turning it manually
to see whether the pipe to the cylinder then gets hot?
If no water is flowing to the indirect coil in your HW cylinder this has to
be due to one of two basic causes - either the HW port on the 3-port valve
isn't opening or it *is* opening but there is an airlock or blockage in that
part of the circuit.
If you have well and truly bled that part of the system, and have made sure
that there are no gate valves turned off, the second cause seems unlikely -
so it's best to concentrate on the first. If you can get HW by moving the
valve manually when the CH is on, that would confirm that the problem is in
the valve control system. If the valve never goes to the HW position, this
could be due to:
* seized valve (unlikely if it's new)
* faulty actuator (Also unlikely - and its spring return would likely take
it to the HW position anyway)
* No HW demand from the programmer
* No unsatisfied HW demand from the cylinder stat
* Incorrect connections to 3-port valve
As you have apparently just changed both the 3-port valve and the cylinder
stat, I would put my money on the wiring of these. Do all wires come
together in a 10-way junction box? Assuming it's a mid-position valve, have
you verified the connections by looking at the Y-plan details in
Regarding your radiator with "no bleed valve". Sounds unlikely! Some
radiators hide their bleed valves fairly well by putting them near the top
of the back face rather than at one end. Feel along the back over the top
edge - or have a look with a mirror.
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