Hyco Powerflow 50 help

Discussion in 'Plumbers' Talk' started by Gonz46, Feb 13, 2018.

  1. Gonz46

    Gonz46 New Member

    Hi all, first post here and as an electrician, please be gentle with me in your plumbing forum...

    My wife and I also own a hair salon. The hot water comes from the above named unvented cylinder. The issue is, the hot water keeps going cold. After 5 minutes or so it comes back warm and then red hot, there is no known pattern to it, so randomly goes, once one day, none the next, twice the next etc...

    I’m unsure if it would have helped but I put double check valves in on the hot (it’s T’d just below the hot pipe to go to back wash basins and kitchen tap) because I didn’t know of the taps etc... could be back feeding up the hot? Anyway, that did nothing, I have changed all taps in the Salon for the same reason. Yet it still happens. All valves were recently changed as a precaution too, pressures in the expansion vessel at at 3bar. I have drained the hot down and refilled as per the manufacturing instructions and still this is happening.

    I have just ordered a new thermostat and element, however, as the water comes back after 5 minutes, I don’t know if it can be this.

    One theory I have I want to run by you is, the house next door (owned by the same people we lease the Salon from) is on the same water supply. Now if they fornwxample, run a bath, or do any washing etc... I’m sure our water pressure drops. If our water pressure drops, will this have the effect I describe above on our hot water?

    I know it’s a long post but I’m at the end of my tether, no plumber so far has had the answer either.

    Thanks in advance
  2. KIAB

    KIAB Well-Known Member

    A unvented multipoint, has a 3.0 kW element as standard, it is available with a optional thermostatic mixing valve, have you got that.
  3. Gonz46

    Gonz46 New Member

    No, I don’t have a thermostatic mixing valve. Turns out it comes back warm after 15 minutes or so, so I’m going to change the element and the thermostat and see if that fixes it?
  4. kiaora

    kiaora Well-Known Member

    It sounds like un equal hot and cold pressure, and a failed non return valve, on the mixer hot supply,

    If it’s possible, are you able to pipe the cold supply to run from the balanced pressure outlet feeding the cylinder?

    Any mixer taps you have must have check valves on hot and cold, debri in the valve will cause this problem

    KIAB likes this.
  5. Gonz46

    Gonz46 New Member

    The cold does not come from the balanced cold on the heater, but then it was okay for three years, until a couple of months ago...

    I’ve replaced the check valves on the cold and installed new ones on the hot as there weren’t any. Going to replace the stat and element too, is that something I can do though, because it’s unvented I’m not sure I can take the element out, or does a qualified plumber need to do it for unvented cylinders?
  6. KIAB

    KIAB Well-Known Member

    You need a G3 ticket to work on unvented cylinders.
  7. Gonz46

    Gonz46 New Member

    Okay, will have to get a plumber back to sort, thanks
  8. Gonz46

    Gonz46 New Member

    In addition, this now seems to only happen in the afternoon, never in the morning.

    The thermostat, cut out, and element have been replaced, on Hyco's say so, and, low and behold, this afternoon, it happened again.

    Kiaora, what affect will not having a balanced cold have? It runs fine all morning, then seems to go cold after running a while in the afternoon

  9. kiaora

    kiaora Well-Known Member

    The water pressure can vary a lot, in some areas, the pressure is low in the morning and gradually increases during the day,
    High usage in the area, lots of houses, and undersized water mains, sometimes over looked by developers!


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