Flow temperature up and down like a yo-yo

greekgoddj · 2023-11-25T12:38:37Z

Hello all, I have started having an issue with my Mitsubishi Ecodan ASHP, whereby every few minutes it gives up trying to run even though the thermostats are asking for heat the entire time. You can see this in the attached 3 hours worth of flow temperature data from unit. You can see the temperature climb and then after a few minutes it gives up, lowers, and tries again. Periodic enough.. there is a pattern there. Mitsubishi noted that the flow rate is lower (16l/min) than it needs to be (20-32l/min) (pump is running at max, external unit only behind the adjacent wall, so waiting for a new pump - they already sent the wrong item out once). However, I would expect a lower flow rate to affect efficiency of the unit, not necessarily result in the heat pump giving up every few minutes. Does anybody have any thoughts? Thanks

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Air Source Heat Pumps (ASHPs)

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Derek M

(@derek-m)

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Joined: 5 years ago

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27/11/2023 2:00 pm

Posted by: @greekgoddj

↑

@glpinxit yup, that is more of less like what mine looked like last year.. so clearly something has gone wrong at the moment. I am very much looking to get it back into health! 🙂

Have you resolved your problem? Feedback is always welcome.

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greekgoddj

(@greekgoddj)

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Joined: 4 years ago

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Topic starter 30/11/2023 9:27 am

@derek-m No update yet... Still (2 weeks now) waiting for Mitsubishi to send the replacement circulation pump first. Will for sure update this thread when I have an update.

Mitsubishi Ecodan 11.2kW ASHP

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zubadanwoes

(@zubadanwoes)

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Joined: 2 years ago

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05/12/2023 7:34 pm

@greekgoddj Hello , I am not a plumber just a DIY'er, so any advice is without warranty. Have you checked your exspansion vessel for pre-charge pressure, it should be around 0.3 bar Higher than your cold fill pressure, and if it is holding water on the air side? My ASHP was aggressivley cycling on for 5 minutes, off for two, all the time it was on. I went around the house's with the pump's and system balance but after a year I checked my vessel and the diaphragam had burst , so I got blue coolant come out of the schradder valve. First hook your valve up to a bike/foot pump with a pressure gauge to see what the pre charge is, then you can remove the pump and just touch the middle of the valve for half a second to see if you get water out of the air side.

Hope you get sorted.

👍

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zubadanwoes

(@zubadanwoes)

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07/12/2023 1:18 pm

I forgot to mention, when you are checking your air charge pressure, your water side needs to be decharged ie no pressure, usually bleeding a radiator for ten seconds will do that job, you just need a bucket or pan handy.

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