Confused at Marford.
The plumbers flew in and fitted the new boiler, associated heating
manifold connections, diverter valve and coupled up the DHW header.
For some reason they appear to have fitted a pressure operated relief
valve directly across the tank coil!
When I queried the purpose there was some mumbling about it being shown
on the boilermate connection diagram. When I persisted they said it gave
a route for the water when the valve closed.
This is a W plan system using a Honeywell V4044C diverter valve. I
suppose there may be a short period as the valve transits from hot water
to heating when there is no flow. Even so, this diverter appears to be
in the wrong position.
Sounds like a by-pass valve. There may be some point in having one
between the pump outlet (before the diverter valve) and the boiler
return. But if it's after the diverter and directly across the coil it
will never do anything because the coil will always present a lower
resistance path than the by-pass valve.
Any chance of one or two photos?
I supplied the valve definitely V4044C although they had fitted
something else. When I asked why they said it was because they needed
something to finish the connections having not *found* the valve I gave
Either way the device is in the wrong place. If there is printing on the
red knob, my eyes aren't good enough to read it.
On Thu, 22 Mar 2018 09:19:17 +0000, Tim Lamb wrote:
From what I can recall of the image (it seems to have disappeared now),
that valve didn't seem to serve any useful purpose such as to aid in
drain down/refill operations. It's possible it might have intended to be
in series with the flow to the H/E coil to save it hogging the flow when
both HW and CH were being called for.
I've got a similar, if less complicated, plumbing arrangement in my own
airing cupboard, also including a couple of extra valves which I couldn't
initially explain their intended purpose. My setup, although similar,
does vary in an important way, both valves do have logical reasons for
The first one, missing (or simply misplaced) in your case, being a valve
in line to the 22mm feed to the H/E coil from the mid position valve DHW
port. It's value, imo, seems rather questionable so I've got it backed
off half a turn from fully open (wide open but parked so if it gets stuck
through lack of use, I've got two directions I can 'exercise' it to free
it off). The outlet of the H/E coil has its own 22mm pipe connection to
the return manifold into which is teed a 15mm pipe from the other valve
which is plumbed to the outlet of the pump, immediately after the pump's
isolating valve in the 28mm boiler flow line.
This is a bit like that red valve of yours except it bypasses the flow
to the return pipe before it reaches the 3 way mid position valve (IOW,
it has nothing to do with bypassing the H/E coil other than utilising the
H/E return pipe to bypass some of the main pump flow). Since we've always
had one radiator (now a heated towel rail) to act as a bypass to guard
against the unlikely event that the other 12 rads with TRVs all shut
down, such a bypass control valve seems to be redundant, so much so that
I keep that valve completely shut off.
After considering the existence of these valves, I came to the
conclusion that the first valve's purpose was to balance the flow between
HW and CH demand 'according to taste' (my 'taste' being that, "You're
damned if you do and damned if you don't" so I "didn't"(throttle the
flow, that is!)) and that the "bypass valve" is actually a drain down/
refill aid just like that little lever on the motorised valve's motorhead
It's only when draining or refilling the system that you need to
manually move that little lever so it drops into the mid position detent
and you turn the "Pump Bypass Valve" from fully closed (normal
operational state) to wide open. Whilst the lever on the motorhead unit
will automatically unlatch when you've refilled the system and restarted
it, you have to remember to manually close the pump bypass valve if you
don't want to compromise the system's performance (it does no harm if you
forget other than reduce pumping efficiency).
Hopefully, this description of those "Two Mystery Valves" amongst the DHW
tank, 3 way mid position valve and the pump plumbing in my own airing
cupboard, should give you a clue as to what your plumbers *thought* they
were doing and give you a better idea about how to remedy the situation.
During *diversion* is there a temporary fully closed moment? I wonder if
they thought it necessary to avoid boiler pump pressure surges. Still in
the wrong place!
I can't see it doing any harm but it is annoying to have ones wallet
Speaking of coils... Today I gathered various bit of garden hose and set
about getting the air out of the floor heating pipes.
Absolutely amazed how many buckets of water went down the toilet before
the first circuit ran clear of air. (about 7, say 10 gallons)
First job tomorrow is to insert a bit of clear pipe so I can see the
bubbles without needing to drain to a bucket.
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