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Mitsubishi Ecodan ASHP general set-up and efficiency

 
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Air Source Heat Pumps (ASHPs)
Last Post by ngillam 1 year ago
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 ngillam
(@ngillam)
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Joined: 2 years ago
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Topic starter 12/01/2025 4:08 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
(@gary)
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12/01/2025 4:14 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 4:18 pm  

@gary Will give it a try, thanks Gary.



   
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 ngillam
(@ngillam)
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Topic starter 12/01/2025 5:46 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.......

16

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

Thanks,

Neil.



   
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 Gary
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12/01/2025 6:29 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 6:58 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.

1730


   
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 Gary
(@gary)
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12/01/2025 7:03 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
(@ngillam)
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Topic starter 12/01/2025 7:52 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.

BR

Neil.



   
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 HarriUp
(@harriup)
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Posts: 108
13/01/2025 1:05 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
210l Mitsubishi solar tank
Solar thermal
3.94kW of PV


   
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 ngillam
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Topic starter 13/01/2025 8:19 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
(@gary)
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13/01/2025 9:19 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.

image

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.

 

image

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 9:40 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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