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Ecodan - Legionella Operation Time and Target Temperature

Richard24738 · 2024-06-14T15:37:43Z

Hi. What's a realistic operation time for a legionaire cycle? New system: Ecodan 11.2kw and Telford Tempest HP 250L tank. Mine is set for two hours with a 60 degree target. 1st half hour the heat pump flow temp gradually ramps up and Tank temp goes from 20 > 49 2nd half hour the flow temp starts to drop and tank temp goes up by 1 to 50 3rd half hour the flow temp continues to drop and the tank temp goes from 50 > 56 (Immersion on) 4th half hour the flow temp continues to drop and the tank temp goes from 56 to eventually just reaches 59 on the 2 hour mark. I guess if I extend the run to over 3 hours it might get to 60 but that seems an awfully long time to be without any heating next winter. Any thoughts?

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Transparent

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30/10/2024 8:02 pm

Posted by: @toodles

↑

But it may be necessary to ‘clear up’ behind the installer!

The need to clear up behind the installer is dictated by two further factors.

1: If he's not fitted a bend-free route leading away from the tundish with a pipe of adequate diameter, then the test of the release valve will have sprayed hot water all around the room.
The air-intake ports on the sides of the tundish are equally capable of giving the floor a 'hot wash'.

2: With due regard to the subject of this discussion topic, if the anti-legionella cycle hasn't been properly commissioned, then the bacteria will also have been sprayed into the air...
... in which case the state of his soil pipe is the least of his worries.

This post was modified 9 months ago by Transparent

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TRBob

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31/10/2024 2:32 pm

@transparent

Below the Tundish the pipe goes to the exterior, the 2nd pic shows what is above.

They were a bit miserly with insulation, I have added quite a bit myself.

I'm going to add some over the hole where the temperature probe is as I can feel warmth when I put my finger in, there is another as well near the top of the tank. Thank you for the heads up.

I emailed Mitsubishi on Sunday about the Legionella cycle, haven't heard back yet though, will try calling them when I get chance. Another thought is to set the cycle temp to 59 instead of 61 and hopefully it will end the program when it reaches 59.5.

This post was modified 9 months ago by TRBob

Mitsubishi Ecodan 8.5kWh
4.4kW Solar PV
5.2 kWh Battery Storage
1983 build, 300mm loft insulation, cavity wall insulation (beads)

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Transparent

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31/10/2024 3:26 pm

That tundish looks ok.

They were more than just "a bit miserly" with the pipe insulation.
They've breached the regulations.

The rule is that all pipes should be insulated within a metre of a hot water tank.
It doesn't matter whether the pipe is meant to carrying cold-input, or if it's empty, such as the pressure release system.
The pipe still needs insulating because the copper 'sucks' energy out of the tank.

Save energy... recycle electrons!

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TRBob

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31/10/2024 3:45 pm

@transparent Oh right, I'll get all of that insulated as well. They actually left quite a lot in the rubbish pile, which I kept. Out of interest, all of the pipe that goes from the tundish to the ground is copper which seems a bit wasteful, should it not be plastic instead? Thankfully no one has stolen it from the side of the house.

Mitsubishi Ecodan 8.5kWh
4.4kW Solar PV
5.2 kWh Battery Storage
1983 build, 300mm loft insulation, cavity wall insulation (beads)

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Transparent

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31/10/2024 3:53 pm

The pressure release pipe to the outside is usually in copper.

The crucial thing to note is that it shouldn't go through several right-angle bends.
Either it needs to be bends formed in the pipe itself, or else uses swept-elbow fittings.