You will recall my ongoing intermittent C/H boiler problem, and that I
proclaimed success after telling my plumber to replace the pump.
Well it hasn't worked, so I was wrong !!
However, the problem is so intermittent, that it has never arisen when a
plumber has been here, so I am going to have to continue to try and
diagnose it myself.
I have bought a multimeter, opened the box where the wire from the pump
goes, and attached it to the pump wires which I am presuming are
connected to the PCB - it certainly looks like a PCB. The meter reads
anything between 240-250V when things are working, and it seemed to be
working fine so I risked a shower. This went fine until I turned the
water off and back on again when it ran cold.
I had a look at the multimeter and it read zero volts. Also the overheat
sensor had activated its cut-out which requires pressing a button to
I fired up the heating and it worked fine, and finished off my shower.
It's working fine as I write.
I am 99% certain that something in the control box, (PCB??), is cutting
the power to the pump, then the non running water overheats, and the
sensor does its job and cuts the burner.
I am wondering if there is anything in the safety system of a boiler
which would stop the pump before cutting off the gas. I cant think of a
reason why his would happen as it actually causes the overheat.
Could this be anything other than a problem with the PCB?
Would this stop the pump without shutting off the gas burner?
I know I am harping on about it, but stopping the pump and not the
burner, causes an overheat, which seems crazy.
I suppose I should call Heatcall and see what order things happen with
From your descriptions the order of things sounds
There is a boiler, with an automatic temperature control,
plus a safety overtemperature cutout.
There is a shower pump wired up so that it has power
when the boiler is operating normally, but that power
is cut when there is a boiler fault, eg, the overtemp
cutout has operated.
Everything works ok when you turn on the shower, (at a
reasonably high flow rate) but, as you turn down the
shower, the boiler's temperature controller does not
respond, instead the overtemperature cutout operates.
Result= Cold water and no power to the shower pump.
It sounds like a temperature control problem... either
the boiler's controller is not operating properly, or
the control temperature and cutout temperature are set
too close together.
Try turning down the boiler's control temperature.
Richard, I haven';t been follwing this thread much...I am a little
confused. On my boiler for example, if the pump stops, so does the
boiler. They are, in fact, wired together.
That is, if anything wants 'heat' the combinations of time switches and
thermostats move motorised valves to open a flow path for the hot boiler
water. The motorised valves have little switches on them, and once they
are in the open position, they switch the boiler and pump on together.
The boiler fires up, and stays up until the return water temp is good,
and then the boiler cuts out as it should, but the pump stays running
beyond the boiler cut out, moving the hot water around till it cools
down, and the boiler fires up again...But this is an indirectly heated
hot water system...
Now I assume you have a combi boiler, in which case it probably has
direct heated hot water? In which case I am at a loss to know why the
pump is running at all when you call for hot water? What I assume
happens in a combi, is that there is a flow switch that activates when
hot water alone is needed, the boiler fires up, and when the flow stops
(you turn off the tap) the bloody thing shuts down. I am no combi expert
If that IS how they work, then it would seem that your flow switch is
sticking. So the boiler does NOT shut down when water flow is stopped.
Then if the CH is on as well, it doesn't matter, because the extra heat
diverts to the CH circuit, but if CH is off, the boiler is overheating
the water and the safety cutout shuts it down.
As I say, I am no combi expert, and hope that others will confirm/refute
what I have said.
Ther is confusion in my mind as to what sort of system you have, and
what the pump is actually for.
On Tue, 30 Dec 2003 11:44:19 +0000, The Natural Philosopher wrote:
OK I also was not not in on the ground floor on this one.
In almost all combi boilers (except Ferrolis and maybe some others) the
pump is needed to circulate the primary water from the gas/water main HE
to the smaller water/water secondary heat exhcanger (this is in the main
I would strongly hazard a guess that the over heat sensor is tripping when
you turn the water off.
There could be a number of reasons why this would happen including:
Out of spec sensors.
Stuck water flow sensor.
Anyway the make and model should start us off on the right track.
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at www.diyfaq.org.uk
Jaguar 23Kw Wall Hung Combi Boiler - made for Plumb Centre by Hepworth
Heating. I presume it is some form of Gloworm, but I cannot find an
exact match. Fitted in February 2001. Not many people seem to have heard
of it, or had experience of it.
One thing I have noticed tonight is that when the volts to the pump read
0V, if I waggle the ends of the multimeter which are poked into the pump
power connectors at the PCB end, there is a click, the volts go back to
240V, and all works well. I am now guessing that there is a faulty
electrical connection which might be as simple as disconnecting and
reconnecting the wires. I'll give that a go in the morning.
The problem occurs with both hot water and heating, and it always
coincides with the pump going off, and the burner continuing until the
thermostat cuts the gas off.
Any more thoughts welcome!!
That's what I'm thinking. Certainly something to do with either the
wires that connect to the PCB, or the PCB itself.
I'm not sure whether to just buy a new one of the shelf, or to send it
off to CET for refurbishment. I wonder how long it is likely to take?
Well, I still don't know what pcb you're on about.
If you tell me, I might be able to tell you if I have any in stock, in
which case if you ordered it on Monday when we reopen, you'd have one on
After my multimeter test, it is fairly clear that there is an
intermittent problem with the power supply from the PCB to the pump.
This looks like it could either be a loose wire in the plastic connector
which slots onto the PCB, or a problem on the board itself.
Unfortunately, having established the above, I made some kind of
connection with the multimeter prongs which blew one of the fuses on the
board. These dont seem to be easily replaceable?
The boiler is a Jaguar 23Kw Wall hung combi, manufactured for Plumb
Centre by Hepworth heating. It was fitted around February 2000.
I'm not sure how common these boilers are, so I am wondering how likely
it is that you have a reconditioned PCB in stock, or would you have to
recondition mine if I sent it to you. If the latter, how long is it
likely to take? (and how much would it cost <g>)
I don't know the Jaguar but a quick google shows it to be a Glowworm,
although I can't immediately see which one.
Take this to email - firstname.lastname@example.org
p.s. There's another post which I sent before I saw this one
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