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Mitsubishi Ecodan ASHP general set-up and efficiency

ngillam · 2024-08-27T16:02:15Z

Hello all, new to the forum and keen to get the most out of our system. Long story short we live in a 185 sq metre new build barn with what I believe is an ECODAN 5kw ASHP coupled to underfloor heating. The building is very open plan consisting of two large bedrooms with two large bathrooms two large open lounges an open kitchen, boot room and attached art studio/workshop. We're located atop a hill in North Oxfordshire with south facing glazing to the rear so the sun does play it's part in cooking us in the summer. The installers provided an original set-up at the beginning of the year but without dwelling too much the property had a flood which resulted in the dehumidifiers and the heating ramp up to clear the effects of the flooding which is thankfully done with no lasting effects. It's been a number of months but I'm keen to get the set-up back to design intent, I'm a quick learner and would like to know all and eek the best out of what we have, we suffered a number of power-cuts recently and my partner jabbed away at god knows what to get things back on, she can't resist pushing buttons, it's an odd thing! but I wasn't around to prevent it. The attached images show the set-up, I've noticed since the powercuts the timers (of which we have two) need to be on for the showers to have hot water supplied to them. If off the water is cold despite hot water in tank...don't remember that being the case prior to power outage?? I have 2 x timers, one next to water tank (210 litre) and one above UFH manifolds so assuming each control each, water and heating? Each room has it's own similar thermostat and with it getting colder I'm keen to get the set-up running as efficiently as possible. There's two of us, occasional guests/kids visiting at weekends. Tank set to 48 degs with a drop of 7 before reheat. I think the timing thing has thrown me a little, which is master? The FTC or the individual timers I've indicated in photos? Can any kind soul see anything obvious or give a base setting I should be looking at to work from? Thanks, Neil.

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Air Source Heat Pumps (ASHPs)

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Gary

(@gary)

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10/01/2025 11:01 am

@ngillam No way to control defrost cycle, but that isn't your issue it only increased 5C in 30 mins before the defrost started that isn't normal, its as if you were emptying the tank as it was trying to heat it back up.

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ngillam

(@ngillam)

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Topic starter 10/01/2025 11:48 am

@gary That's a good observation on emptying the tank!! I wasn't at home but will check with the other half if she was up earlier than planned. Once again, you're a fountain of knowledge.

Does my flow and return seem nominal to you?

Thanks,

Neil

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Gary

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10/01/2025 11:59 am

Flow and return are fine, what isn't is the rate at which it is changing.

If I look at my HW run last night to get from 37C to 42C flow mine took 5 mins yours took 30 mins, hence my comment on was the HW being used at that time, if you have never had an issue before with HW heating up in that time period there is some other factor here. See what happens tomorrow morning I guess

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HarriUp

(@harriup)

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10/01/2025 12:40 pm

Is this a pump issue? What jumps out at me on the chart at the the time of the defrost cycle is that the return drops dramatically first, and pulls the flow temp down slightly with it. Two minutes later the flow drops right down and only then looks like a normal defrost cycle, but rather than the flow temperature bouncing straight back up at the bottom of the cycle it takes few minutes and in addition the tank cools slightly as the return temp goes up several degrees before the flow temp goes back up. None of that looks normal, but I can't think of an obvious cause. The latter bit looks like the HW pump might be running while the defrost is taking heat out.

I would expect a HW cycle to stop when a defrost is needed (I don't HW at night though) and then just restart. There is meant to be enough volume in the primary circuit to enable defrosts.

Mitsubishi EcoDan 8.5 kW ASHP - radiators on a single loop
210l Mitsubishi solar tank
Solar thermal
3.94kW of PV

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ngillam

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Topic starter 12/01/2025 2:31 pm

@harriup @gary I really do need some help with this one. It seems my HW never gets up to 47 target now due to defrost cycle running every hour. It gets to 41 or 42 before defrost cycle (the controller shows inverted colour heat pump symbol) which seems to draw down the tank temp to 38ish before defrost cycle ends.

Gary, your comment on slow warm up, yours seems a lot quicker than mine, I have a 5kw but even allowing for your step up in power it still seems very slow. Thinking about it a historical comment of yours mentions enough heat throughout the day. My tank once up to temp seems to dwindle back down quite quickly, it's a pre-plumbed cylinder 210L, I have timers set to 24hrs on pumps and can only think all this is related.

Can I ask what other ECODAN owners have there settings on for defrost and settings for HW duration etc.

My partner went out last night so I had to put the HW on constant to ensure she had hot water for shower, checked in the early hours when she came in and immersion heater had stepped in, disappointing!

Suggestions welcome, it's only 2 degs outside but defrost seems to be really hampering our comfort at present.

Thanks,

Neil.

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ngillam

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Topic starter 12/01/2025 2:33 pm

@gary Weird one, checked with partner, she wasn't using the hot water during this period!

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Gary

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12/01/2025 3:06 pm

check what the HW pump is set to on the cylinder it should have 3 positions it should be on 3 which is the highest setting

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ngillam

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Topic starter 12/01/2025 3:21 pm

@gary Yep, it's on 3. Here are the last two hours of info:

Every hour it does this, this is the first winter we've gone through since heat pump installation so first time it's seen these temps.

Thanks,

Neil.

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Gary

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12/01/2025 3:23 pm

Posted by: @ngillam

↑

have timers set to 24hrs on pumps

What does this mean do you have hot water being pumped round a circuit?

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Gary

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12/01/2025 3:26 pm

@ngillam that all looks normal it’s just defrosting

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ngillam

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Topic starter 12/01/2025 3:44 pm

@gary

I have two of these in the control room, one looks to be UFH manifold side and the other DHW. I have it set 24hr because if it isn't then outside of times it won't send hot water to taps/showers or bath.

My DHW settings:

Max temp - 47

Drop temp - 7

Max op time - 90mins

Mode Restrict - 55mins

Similar to yours?

Thanks,

Neil.

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Gary

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12/01/2025 3:49 pm

So it will only run for 90 mins before shutting off and that currently isn’t long enough to reach your set temp

In the HW schedule on the FTC when is that set for? .

Is a pump running constantly if you have that Heatmiser thermostat set to on 24hrs a day?

If so I’m wondering if you are circulating HW round a pipe which would explain why your hot water is losing temp quickly and won’t be helping with the hot water heating up

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