Spoke Too Soon!! New Pump hasn't solved CH Problem

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 reset it.
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?
--
Richard Faulkner

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Richard Faulkner wrote:

Could be the air pressure switch.
Andrew
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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 it.
--
Richard Faulkner

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The order in which things happen is not a problem.
Exactly what boiler you are on about would help in peoples ability to give you some direction is more important
--
geoff

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From your descriptions the order of things sounds like this..............
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.
--
Tony Williams.

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wrote:

It is a combi.
--
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Richard Faulkner wrote:

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 tho.
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.
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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 FAQ).
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.     Bad PCB.     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
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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!!
--
Richard Faulkner

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Richard Faulkner wrote:

Might be a cracked PCB. Unless you are a soldering expert, replace it.

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This sounds very much like a dry solder joint on the PCB.
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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?
--
Richard Faulkner

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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 Tuesday
--
geoff

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... ...

No, you'll have to refresh me. What boiler?
--
geoff

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writes

See my reply to Ed.
--
Richard Faulkner

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writes

Geoff,
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>)
Kind Regds
--
Richard Faulkner

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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 - snipped-for-privacy@cetltd.com
p.s. There's another post which I sent before I saw this one

--
geoff

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