Mixergy Tank Failure

bontwoody · 2025-09-13T05:40:14Z

Hi. I had my Mixergy tank fitted nearly three years ago and on the whole I've been very happy with it. A week or two ago we noticed a small leak on the floor beneath the piping. Initially I thought it was a leakage compression joint which I nipped up. This week I was woken by the sound of water and saw that the tank was discharging water via the tundish when heating. The most likely reason seemed to be a low charge in the expansion vessel, so I removed this and checked it. It was at 50psi. I've contacted mixergy and they suggested I reduce this to 2.5 bar and monitor the situation. It was at this point I noticed that the side of the tank seemed bulged out. When I had the tank installed the plumber pointed out to me a slight bulge in the outer case which I put down to over zealous insulating foam insertion at the time. I recontacted Mixergy and they told me to stop using the tank and they would replace it under warranty. That was Wednesday and I have heard nothing since. What I would like to know is what might have caused the problem and if it lies with the tank or the installation by the G3 plumber or the failure of a part, presumably either a valve or the expansion vessel which seems fine. Images attached. Any comments welcome. Thanks

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bontwoody

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Topic starter 01/11/2025 3:45 pm

So after playing about with DHW settings for a while I think the optimum use of the coil is for about 30 mins. After that time the COP drops to a point where I wonder if the cost saving is worth the wear on the heat pump 🙂

The COP over this time is about 1.9 which nearly doubles the efficiency compared to the immersion. (So costs about 3.5p per unit compared to 7p overnight). I think that the 30 min slot provides about half of my daily DHW needs.

Im sure the situation could be improved if I got the destratification pump working when running but thats a job for another day. 🙂

House-2 bed partial stone bungalow, 5kW Samsung Gen 6 ASHP (Self install)
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