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11.2kW Mitsubishi Ecodan replacing LPG boiler

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(@markc)
Reputable Member Member
93 kWhs
Joined: 3 years ago
Posts: 97
 

My setup is very similar to yours @Peterr although I am in a 1950s house with insulation added post construction and don't have any SPV. I'm running with a weather curve 24/7 and looking at the period 1-18/11/21 I used 271kWh on heating. average COP of around 4.

What system are you running now (curve or flow temp) and have you seen any drop in electricity usage?

 


   
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(@derek-m)
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13737 kWhs
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Posts: 4168
 
Posted by: @peterr

@derek-m 

Hi Derek,

It is the downstairs rooms that are sometimes a bit colder than desired.  If we turn up the flow temperature to get the downstairs rooms right, then the upstairs becomes too warm.

As far as I can tell there must be some sort of control between the UFH and the FTC.  The heat pump responds to demands for heat from the UFH pretty quickly. I think this is the control that goes in to IN1 on the FTC, although it's little tricky to trace because the wiring is a complete mess!  I have been trying to get this information out of our installer for a while now, but they are not being very cooperative.

We don't have a buffer tank, the cylinder is a Telford Tempest.

There isn't a pump specifically for the radiator circuit.  There is one pump that circulates the flow from the ASHP to either the DHW or the heating circuit, depending upon the setting of the 2x 2-port valves controlled by the FTC.

Hi Peter,

Just to clarify, how many water pumps are there external to the ASHP, one or two?

If my understanding of how your system is laid out is correct, then the easiest method, in the short term, to achieve the desired temperatures both upstairs and downstairs, would be to set the weather compensation curve slightly higher, and regulate the upstairs temperatures using the TRV's. Whilst not the optimum solution, it should give reasonably accurate control in quite an efficient manner.

A longer term solution would probably be to install a further 2-way valve, so that both zones can operate independently.


   
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(@peterr)
Estimable Member Member
551 kWhs
Joined: 3 years ago
Posts: 67
Topic starter  

@markc 

We are now running with weather compensation 24/7.  Our installer originally left us running on fixed flow temp at 50C.  I don't really have any figures to compare consumption from before the switch to after.


   
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(@peterr)
Estimable Member Member
551 kWhs
Joined: 3 years ago
Posts: 67
Topic starter  

@derek-m 

Just the one pump external to the ASHP (excluding the UFH pump).

Your longer term solution is certainly the one that I would prefer, but just need to work out who is going to do the work.

I am still trying to discuss the state of our system with our installer, although they are being very unresponsive.  When we originally spoke to their "Renewables Consultant" we told him that we wanted to be able to control the UFH and rads separately and he assured us that we would be able to - it seems either he was lying, or the message didn't get back to the install team!


   
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(@peterr)
Estimable Member Member
551 kWhs
Joined: 3 years ago
Posts: 67
Topic starter  

Had a local installer come out to look at our system yesterday (judging from the Google reviews they're pretty good).  Overall he was not very complementary!

Main issue is that the current flow rate being achieved is around 20l/min, it should be a minimum of 28l/min for the ASHP that we have.  He described the system as a bare, basic install that is inadequate for the size of unit and house.  UFH has no way of creating a demand to the system.  No strainer installed. External insulation not installed to any standard, and uses insulation intended for indoor use.  No low-loss header.  Confirmed my thoughts that there is no way of independently controlling the UFH and rads.

It is all fairly easily correctable - adding a low loss header and an extra pump should resolve the flow issue, and a little bit of re-plumbing and re-configuring should get us back to what we had with two independent heating zones.  All I need to do now is work out how to get the original installer to pay for it.  I do not want them doing the work, but unfortunately I have to give them the opportunity to correct their errors.

What really irritates me is that an installer can put in a system like this, and yet still claim that they are MCS certified.  The guy who came yesterday was so apologetic when he was giving me the bad news, but he said that it was sadly all too common.


   
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(@batalto)
Famed Member Member
3655 kWhs
Joined: 3 years ago
Posts: 1091
 

@peterr you should have an insurance agreement as part of the install to cover "workmanship" and "quality"

https://mcscertified.com/ibg/

In addition to your legal obligation to give customers a free guarantee against manufacturing faults in goods supplied, you must guarantee the installation work for a minimum of two years

12kW Midea ASHP - 8.4kw solar - 29kWh batteries
262m2 house in Hampshire
Current weather compensation: 47@-2 and 31@17
My current performance can be found - HERE
Heat pump calculator spreadsheet - HERE


   
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(@peterr)
Estimable Member Member
551 kWhs
Joined: 3 years ago
Posts: 67
Topic starter  

@batalto Thanks, I shall remind the original installer of this when I try and contact them.

 


   
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(@markc)
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93 kWhs
Joined: 3 years ago
Posts: 97
 

@peterr

I think it's very often true to say that if you were to get 3 plumbers to design a plumbing system, you'd get 3 designs, all of which would be sub optimal according to the other 2 plumbers. Whilst all 3 designs would be functional.

Asking your installer to pay for changes suggested by a third party might be a stretch, but I guess it depends on whether they agree with the third party. I'd ask politely but wouldn't get upset if they declined.


   
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(@peterr)
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551 kWhs
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Topic starter  
Posted by: @markc

@peterr

I think it's very often true to say that if you were to get 3 plumbers to design a plumbing system, you'd get 3 designs, all of which would be sub optimal according to the other 2 plumbers. Whilst all 3 designs would be functional.

Asking your installer to pay for changes suggested by a third party might be a stretch, but I guess it depends on whether they agree with the third party. I'd ask politely but wouldn't get upset if they declined.

I understand what you're saying, but it's not just that the guy who came yesterday thinks it is sub-optimal, it is actually wrong.  Continuing to run the ASHP with a lower flow rate than required has the potential to cause expensive faults in years to come.

I shall, of course, be polite in my comms with the original installer when pointing out the serious problems with the install, and remind them of their obligations to correct them under their own guarantee.  I shall also give them a date by which they have to respond, otherwise I will deem them to have given permission for me to use a 3rd party to correct their problems with them paying the bill.  I am fairly certain that they will continue to ignore me!


   
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Morgan
(@morgan)
Noble Member Member
4052 kWhs
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Posts: 540
 

@peterr 

Ensure you have the various elements in writing, particularly the inspection you’ve just had, and present to the MCS, insurers or even if necessary the small claims court.  Good luck.

Retrofitted 11.2kw Mitsubishi Ecodan to new radiators commissioned November 2021.


   
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