NO HW NO CH, Honeywell diverter valve

Hello,
Can anyone give ideas on what the problem might be with neither HW nor CH working on a gas ch system?
The setup is like this.
Conventional boiler > Pipes > (1) Pump In > (2) Pump Out > Honeywell motorised mid-positioned diverter V4073A valve > Splits water to (A) HWC feed (B) Radiator feed > and so on water returns to boiler
Now I got the boiler going by setting thermostat temperature high.
Went to pump and touched it - fantastically hot but not spinning
Water feed into pump (1 above) very cool
Water flow out of pump (2 above) very cool
Water flows to HWC and Rads (A and B above) very cool
So why is the pump hot?
I switched the pump (CELCIA?) to highest speed and it span for say 5 seconds max then stopped.
My GUESS is this - can't explain all I have observed - especially the cool flow into the pump (1 above) . The pump was spinning for quite a long while, but not pumping, hence the pump over-heated. Now I GUESS there is some thermal trip in the pump which has shut it down.
What I have done is set the diverter valve to permanently open by pushing the lever behind the little notch.
I have noticed the flow from the pump (2 above) has become quite hot in 30 minutes but the pump is not spinning (no noice - no vibration). The A and B flows are now very slightly warmer than they were at the start of the investigation. I am thinking that by opening the diverter valve the warm water is flowing or conducting / convecting heat along the pipes (very slowly) and maybe over the next few hours this will take enough heat away from the pump for it to "kick in".
If all the above is true then I guess the pump will over heat again because no water is being pumped and I will be back to the start
Any other ideas on cause that matches the symptoms I have seen? Anything I can easily test to help isolate the problem?
I have been told it is relatively easy to replace the pump body as it can be disconnect via four allen bolts - but if the problem is the diverter valve than that won't help.
Any ideas, suggestions etc. will be most gratefully received.
Clive
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Sounds like a duff pump to me. If the pump is consuming electricity but not revolving it will get hot - from electrical energy dissipated in it.
If the pump is not pumping, little or no water will circulate. The pipes may get slightly warm due to conduction and natural convection.
If the water heated by the boiler cannot go anywhere, the boiler will either stop firing when its stat opens (if you're lucky) or will more likely overheat so that its safety cutout trips. Does the boiler still fire?
If I am right, replacing the pump and, if necessary, re-setting the overheat trip on the boiler should fix your problem.
Roger
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Roger,
I am coming to your way of thinking that is it the pump. When I listen carefully to the pump it make a faint grinding noise - when the CH timer is "ON". When the timer is "OFF" - no grinding noise from the pump. When I say "grinding" the noise is very faint, not even as loud as the familar "whoosh" and "whir" of an operational pump. This pump is only 2 years old !!!
Now, I have been told you can take the pump bit off and leave the plumbing bit in - by undoing the four Allen bolts attaching the electric pump housing to the "rest".
How do I know it is the "electrical pump" that is the problem rather than the "vanes" that are in line in the water flow?
The model is a Potterton Myson Celsia (I didn't note the exact model)
I have searched and searched on the net for spares for this model and can't find them anywhere.
If I buy the new pump , will it come with the "vanes" that sit in the water flow. It is possible on this installation to isolate the whole pump and replace it as the installer put an isolation valve both above and below the pump. However, I want to avoid removing the whole lot if at all possible
Thanks,
Clive

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seized - because the electrical bit is still consuming power, and may be ok - except that overheating won't have done it any good.
Far safer to replace the lot. If, as you say, there is an isolation valve either side, it should be easy enough to replace it without draining the system.
Roger
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Clive Long,UK wrote:

Its very common at this time of year for pumps to be found locked by crud due to not being used over the summer. Have you tried freeing the pump by turning the shaft with a screwdriver? There is usualy a cover in the middle of the round end that you take off with a coin to get to the screwdriver slot.
If the pump is u/s its standard practice to change the whole pump. That why the isolating valves are there. The shed all have pumps, get one with the same or higher head rating. Virtually all replacement pumps should fit but trying to get bits of a new pump to fit into old pump body would be fun to watch :-)
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Hi,
I did wonder if the pump is "stuck" rather than "stuffed" . At the end of the pump head is a black plastic hexagonal nut. This just sits on top of a smaller hexaganol brass nut. No "slotted" screw head to enable me to try to "hand crank" the pump. I am going to take the hexagonal nut off and see what is underneath. It might leak - who knows? There is NO technical info for this pump anywhere on the Net. The model number on the body is IP41.
By the way I found out the company that makes these pumps underwent a Management Buy-out. They are now called CIRCULATING PUMPS and are still located in their Kings Lynn Norfolk premises
The supplier of this pump in North London is Fountain Thomson Moore - so I might be there at 8am tomorrow. Why couldn't the plumber have fitted a Grundfos? Everyone stocks those.
Clive

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Final story
I was the pump wot did it
The original "pump inlet" was completely bunged up with what is politely called detritus
Taking the old pump head off and fitting the new one - say 60 minutes - I had never done one before. Made much, much easier (in fact could not have done the job other wise) was the presence of the two isolating valves around the pump body.
No leaks from the pump - hot water cylinder heated up in a couple of hours - rads slowly getting warmer.
A real plumber suggested I flush with Sentinel 400 and then finish off with Sentinel 100 - I will do that in a couple of weeks. However, if there are lots of bits of rust floating around in the system - I don't give the new pump much longer than the 3 years the other one lasted
All the materials - 63 inc. VAT. My time overall - 4 hours plus thinking time.
Thanks to PMT, Russell Lane, London N20 for all the help and advice. I recommend them.
Clive
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