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

(@bontwoody)

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Joined: 4 years ago

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Topic starter 20/10/2025 12:32 pm

@jamespa The flow temps scale is on the image James, but now I look at the values rather than the difference between them they are very low 24C flow with a Delta T of about 4C.

I cant help but think i must have a setting wrong somewhere.

Without jury rigging something I wone be able to run the destratification pump as it loops through my PV diverter.

House-2 bed partial stone bungalow, 5kW Samsung Gen 6 ASHP (Self install)
6.9 kWp of PV
5kWh DC coupled battery
Blog: https://thegreeningofrosecottage.weebly.com/
Heatpump Stats: http://heatpumpmonitor.org/system/view?id=60

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Old_Scientist

(@old_scientist)

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20/10/2025 1:09 pm

Posted by: @bontwoody

↑

@jamespa The flow temps scale is on the image James, but now I look at the values rather than the difference between them they are very low 24C flow with a Delta T of about 4C.

I cant help but think i must have a setting wrong somewhere.

I can't see anything obviously wrong in your settings that would cause the behaviour you are seeing.

Can you check FSV 105*

Can you increase #3021 to 55C?

What temp have you set on the controller as the set point (desired temp) for the DHW? Also, what mode does the controller show (Economic, Standard, Power, Forced?). Just stick with Standard whilst you are trying to get things working.

How is your immersion wired? Is it wired directly into the mains or is it wired into the Samsung controller?

#3031 controls this (Samsung refer to it as Booster heater). If it's wired directly into the mains on a manual on/off switch, then you can set to NOT USE as the Samsung controller cannot see it anyway.

If you want to use the booster heater (immersion) to top up the DHW tank temp after a heat pump run with the indirect coil, then #3032 needs to be less than #3025 (both currently 95mins)