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Myson Power Extra MPE 322

Discussion in 'Plumbing and Central Heating' started by jdesmet, 4 Feb 2011.

  1. jdesmet

    jdesmet

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    Myson Power Extra MPE 322

    I wonder if anyone can help me?

    About 18 months ago we had a new Myson Power Extra MPE 322 three port valve fitted, and I don’t think it has ever worked properly, let me explain... It was fitted during the summer so I didn’t notice the following problem with the hot water until the following winter when we needed the heating on as well, & since then we have just lived with it, but it's now becoming a real pain...

    Here is what’s happening: - On the boiler (Potterton Suprima 30) there is a very basic programmer that just has CH on – off – timed & HW on- off- timed.

    • When the heating is turned off at the programmer & the water is on, the HW light comes on the Myson & heats the water without any problem.

    • When the Hot Water is turned off at the programmer & the heating is on, the CH light comes on the Myson & heats the radiators without any problem.

    • When the Hot Water is turned on at the programmer & the heating is then turned on as well, both the CH & HW lights on the Myson come on & we have heat & Hot water... BUT

    • When the heating is turned on at the programmer & then we put the Hot water on as well, only the CH light on the Myson comes on & NOT the HW light & the water is not heated?

    I don’t know if this is a wiring problem with the Myson, a fault with it, or even a problem with some other part of the system altogether... any ideas would be appreciated before I spend a fortune trying to sort it out?
     
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  3. oilhead

    oilhead

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    Do you have a connection from the programmer hot water off terminal to the grey wire from the valve? If this feed is picked up from the heating switched live, then it will do exactly what yours is doing.
     
  4. jdesmet

    jdesmet

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    Hi,

    Thanks for your reply... I've taken the cover off where all the wires are in the airing cupboard & to be honest I haven't got a clue what I'm looking at (loads of wires all going into a block from various locations).

    If you think it sounds like it's been wired wrongly, I'll see if I can get the plumber back out.

    Many thanks...
     
  5. jdesmet

    jdesmet

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    Hi,

    I 'think' i've added the image... I don't know what this was a replacement for unfortunately?

    Thanks
     
  6. jdesmet

    jdesmet

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  7. oilhead

    oilhead

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    You need a professional to sort out. Still feel that problem is that you are feeding the auxiliary switch in the heating mode from the switched feed to the valve. This holds the valve open until all power is taken off.
     
  8. jdesmet

    jdesmet

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    Ok many thanks... at least I have a clue :)

    John
     
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