Potterton Profile 100e Pump continuously on, odd firing

Discussion in 'Plumbing and Central Heating' started by landbeach, 16 Oct 2008.

  1. landbeach

    landbeach

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    Evening All!

    I wonder if I can get some help as to what's not right with my CH/Hot Water.

    Circulation Pump is running 24/7 and boiler fires at odd times even through the night when programmer not 'on'. Previously I thought this was just the frost thermostst kicking in - (boiler in integral garage) but have noticed this happening earlier in the summer.

    The boiler failed to light a couple of months ago and the fan was replaced by emergency insurance contractor yesterday (We've been heating H/W with immersion over the last few months). After contractor left yesterday I switched off immersion and as the pump was still running with C/H off I switched off timer H/W and C/H to see if it was a pump over-run issue. Anyway, forgot to switch either immersion or H/W back on last night but this morning still had plenty of H/W. This evening, kids bath - still loads of piping hot water, pump still going and inlet/outlet pumps boiling hot! So, pump has been running and boiler firing during the day! I'm wondering if this is either a pump overrun issue or whether there's a problem with the flow through the bypass valve. Have read loads of posts here but am none the wiser!

    System is Potterton Profile 1000e, vented, motorised valves for C/H & H/W circuits, bypass with manual valve.

    Thanks in advance - Landbeach
     
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  3. namsag

    namsag

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    Microswitch sticking in one of the motorised valve and HW valve passing or HW valve wedged/jammed open
     
  4. landbeach

    landbeach

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    Thanks Namsag.

    have just checked valves - both appear to be opening & closing with H/W & C/W activation.

    If its a microswitch on one of the valves that is keeping pump switched on - can this be replaced or fixed separately, or is a new valve assembly needed. Would this also be initiating the boiler to stay on?
     
  5. landbeach

    landbeach

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    update: both valves activate the microswitches correctly and these click in and out nicely and theres' no clear sign of which may be at fault. I'm thinking I'll have to obtain a new motor and try swapping one at a time to see which is at fault.
    Unless there are any other useful tips forthcoming!!
     
  6. Agile

    Agile

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    I would never assume a microswitch was operating just becase it was clicking!

    To professionally test them you have to measure the contact resistance on each position!

    Tony
     
  7. namsag

    namsag

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    NOthing up with motor , each valve will have an orang and a grey wire . disconnect one grey at a time and see if this stops the boiler coming on if it does that tells you which switch is faulty.
    Be careful as the wire may still be live after disconnecting so make sure its not touching anything
     
  8. landbeach

    landbeach

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    quote]

    I would never assume a microswitch was operating just becase it was clicking!

    To professionally test them you have to measure the contact resistance on each position!

    Tony[/quote]

    Hi Tony, no I realise that - what I meant was that as they were both being actuated correctly and positively clicking into position I couldn't obviously tell whether one or the other was at fault - and had concluded it was most likely a electrical/contact problem which I didn't think I would be able to identify!

    Until Namsag came along again! Thanks, I'll try disconnecting the grey wires tomorrow evening. If that identifies the fault it's a replacement 'powerhead' I'll be after rather than 'motor' :oops: .
     
  9. landbeach

    landbeach

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    Well Couldn't wait til tomorrow to try!

    But disconnected each valve grey wire in turn and then both together and still the pump runs! Looks like my options are running out!
     
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  11. namsag

    namsag

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    Never thought should have told you to do with the system cold .

    The pump will have carried on running because there was heat alredy in the system . And pump over run will have been in operation.
    So get the system cold by either turning fused spur off or boiler stat to off.

    So what you have to do next is have power on and programmer not asking for anything turn boiler stat up and if a microswitch is sticking the boiler will fire up.
    Redue the disconnecting of the grey wires and see which one stops boiler firing.
     
  12. Clive100

    Clive100

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    When you switch off the programmer ch/hw there should be No switched live to the boiler. The pump will only run for a short time after boiler firing to enable wall hung high output boiler to cool itself (Just like electric fan on car). This is why pumps are wired from boiler and controlled usually by a purpose boiler mounted pump stat. Your boiler is getting a switched live from somewhere. (I have often found that installations are quite often incorrectly wired from the day they were installed and boiler manufacturer's wiring instructions ignored.) The boiler should only fire if either room/hw stats call for heat - they control boiler/pump switching (but only if individual programmer functions on). I recommend you request a return of the engineer to finish the job he was sent to do. He should have tested the boiler operation and secondary controls thoroughly before leaving. You have comeback without cost. Your installation wiring/components requires a thorough inspection/testing by an experienced RGI.
     
  13. landbeach

    landbeach

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    Have just repeated test with system cooled overnight - with both grey wires disconnected and mains power restored the pump ran instantly and the boiler fired a couple of seconds later (programmer set to off)!

    Any last suggestions before I resort to getting an engineer out?

    Many thanks for all the responses so far!
     
  14. tonybhoy

    tonybhoy

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    You need to look at both stats and the programmer also could well be the guy who changed the fan doubt it but you never know.

    Remove the programmer face plate to see if the boiler stops working. If it doesn't stop working with the face place removed I'd be looking at the room stat.

    Had this before and it was the room stat that was faulty however I changed both motorised valves at the same time.
     
  15. namsag

    namsag

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    Definitley wired up wrong then, (must have been like this all the time then if it hasn`t then your missing something) ) boiler should not be firing with the switched live removed which by disconnecting the greys (or orange wires) is what has been done.

    You have definetly eliminated the frost stat has got no power leaving it
     
  16. landbeach

    landbeach

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    Well, I think I'll have to give up on this! Just disconnected the frost thermostat, both motorised valve switches, took the programmer off the back plate all at the same time, put the power back on - and yes, you've guessed it, pump on, boiler fired up!

    So seems like its almost certainly wired up with the pump permanently on - and the boiler fires once the water in the boiler feed/return falls below a certain temp.

    Time to get someone out! (But thanks for all the help/ideas!)
     
  17. tonybhoy

    tonybhoy

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    I'd bet my mortgage (har har) on the culprit being your roomstat.
     
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