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Newbie: utterly confused with my Mitsubishi Zubadan air source heat pump running on 55C set flow temperature

 
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Air Source Heat Pumps (ASHPs)
Last Post by JamesPa 16 hours ago
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 Sandman1600
(@sandman1600)
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Topic starter 18/03/2025 5:55 pm  

@davidnolan22 Thanks. It looks like this is some kind of Mitsubishi "collab" so I think arguing that this is wrong be tough. 

We'd never have known any better if we'd have specced this ourselves so I think it's something we might need to just live with.

So should this help to minimise short cycling too? I'm just trying to anticipate the installers response.

The flow rate still needs addressing by them.

 

 


   
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 Sandman1600
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Topic starter 18/03/2025 5:57 pm  

@jamespa Thanks for the information. I will ask for the justification but I'm guessing it's a kind of "easy" package along with the heat pump. Saves them having to spec too much for each individual install.


   
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 davidnolan22
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18/03/2025 6:03 pm  

@sandman1600 

yeah, they'll just turn the pump speed up. might not help you as much as you think. you need someone to measure what's happening across both manifolds to see what's happening ton the secondary side. and you might get it working OK.  But, you'll keep running up against the fact is probably oversized by some way and them swapping units will cost 4-5k.  so I imagine this may be a sticking point. I've never heard of 14kw pump in a 130m2 house before. but I'm no expert. 


   
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 JamesPa
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18/03/2025 6:09 pm  

Posted by: @sandman1600
↑

So should this help to minimise short cycling too? I'm just trying to anticipate the installers response

Not necessarily, wrongly set up it will make cycling worse (sorry, comment refers to buffer not turning up pump speed)

The solution is to replumb as a 2 port volumiser and delete the secondary pumps.  I doubt they will do that but it's worth a try. 

Heating industry has form when it comes to setting up heating sub-optimally.  Almost all condensing boilers installed since they became mandatory in 2005 are installed so they don't condense, negating the benefits of condensing boilers and costing us all 10% on our gas bills.  Why?-to reduce call outs.

I reckon that if the buffer and size were fixed, you have a very good chance of achieving the performance quoted in the proposal.  Unless they do that you won't.  The buffer is probably the more important, it's labour only no parts to change this so no material cost to the installers.  With a handful of shut off valves it's even possible to do it reversibly so it can be reverted in a few minutes.

 

Posted by: @sandman1600
↑

I will ask for the justification but I'm guessing it's a kind of "easy" package along with the heat pump. Saves them having to spec too much for each individual install.

Yes, it means they can ignore what's already there.  Although really this doesn't provide much advantage in most real cases.

This post was modified 16 hours ago 4 times by JamesPa

4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.


   
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