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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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ngillam

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Topic starter 12/01/2025 3:08 pm

@gary Yes the heatmiser is set for 24 hrs running. The reason being we never really know when HW might be needed at the taps, especially the weekends. But during the week for hand washing etc.

What op time would you recommend?

And the FTC schedule is set for a couple of hours in the morning for showers etc and and the same in the evening for the same reason. The premise being the DHW heat will switch off the UFH whilst it heats the tank.

Thanks,

Neil

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Gary

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12/01/2025 3:14 pm

So is a pump running constantly that is linked to the Heatmiser?

if so, set it to be off when the hot water is heating see if that makes a difference

If you have the schedule set for 2 hours it will only ever run for 90 mins as the max op time is shorter than your schedule.

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ngillam

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Topic starter 12/01/2025 3:18 pm

@gary Will give it a try, thanks Gary.

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ngillam

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Topic starter 12/01/2025 4:46 pm

@gary The HW schedule has kicked in for evening showers, despite the timer for pump set to 24hrs the pump has auto switched off for the hot water heat. It's taking it's time heating though.......

The UFH timing and pump are still running.....thoughts?

Thanks,

Neil.

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Gary

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12/01/2025 5:29 pm

The only suggestion I have is there is an eco and std setting for HW heating, if it’s on eco change it to std it will make the HP worker harder for the HW cycle

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ngillam

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Topic starter 12/01/2025 5:58 pm

@gary It's already on Std , it was one of the things I checked earlier, I've been watching it for the last coupe of hours, it's just paused the DHW heat at 40 degs and switched to heating despite the DHW set to run for another hour according to schedule!! Really confused now! I can't get it above 40ish, even when I force it using the FTC function.

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Gary

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12/01/2025 6:03 pm

As I said in a previous post your max duration is set to 90 mins you need to change it to at least as long as your schedule if you want it to heat for that length of time

I think you need to get your installer back something isn’t right.

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ngillam

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Topic starter 12/01/2025 6:52 pm

@gary Agreed, installer needs to look. I did up the operation time to match schedule but it's still struggling to reach temp and it still switched to heating.

Thanks for your help, enjoy what's left of your Sunday. I do owe you pints if ever you venture to my neck of the woods.

Neil.

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HarriUp

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13/01/2025 12:05 am

Have you checked the pump speed in the settings menu for the HW cycle? And maybe check the flow rate while the HW cycle is running. The defrost cycle looks to be taking a long time to get going.

Mitsubishi EcoDan 8.5 kW ASHP - radiators on a single loop
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ngillam

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Topic starter 13/01/2025 7:19 am

@harriup Morning, yes, my pump speed is 3, flow rate of 9 off the top of my head. does that seem OK? My issue is the fact we've struggled to reach 47degs whilst defrost cycle kicks in. This means us both having to wait between showers for reheat, never been an issue before, appears to be the defrost disrupting heat and drawing down HW tank temp.

Thanks,

Neil.

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Gary

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13/01/2025 8:19 am

@ngillam Depending on your controller the pump speed for the HW can be controlled in 2 ways newer versions have pump speed in the service menu for both hot water and heating you can set a different speed for each pump. I can't find an image of that menu but if you have an older controller then the pump speed menu just looks like this. This only controls the speed of the primary circulation pump.

If you have this version then you have to manually change the pump speed for the hot water tank on the pump by flicking the switch, should look something like this. The switch should be set to 3.

Apologies if you already checked all this but with both HW and circulation pumps set to 3, I just wanted to check you understood it correctly.

If this isn't set to the highest speed this could be the issue, if not, I do think from what you have described then you have a hot water recirculation circuit that is cooling the hot water and at these outside temps the HP just isn't capable of heating the hot water.

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ngillam

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Topic starter 13/01/2025 8:40 am

@gary Morning, yes, both of these are set to 3 on physical pump but also on the FTC. I think I've upped the speed to 4 on the FTC just to see if it made a difference.

I think you're correct on the outside temp causing the issue, it's been -7 the last week and it seems to be the defrost kicking in that drags down the DHW tank temp. Even at the best of times the HW tank only stays in the 40's for a few hours.

Thanks,

Neil

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