@derek-m Not very. I've read a fair amount and understand roughly how things work (i think!).

I suppose what I'm trying to do is verify which parts of the report are correct and if there is anything else not mentioned on the report that I need to know before I go back to the installers and ask them to rectify things.

Its a detatched property.

@tobydeh

Before delving into the delights of the ASHP and its controller, it may be beneficial if I go through how your system appears to have been designed to operate, so that the weaknesses can be identified. It should then be possible to decide upon the best course of action.

Before I start can I clarify a few points?

You are the first owner, so should have received a handover pack from the builder? Did you receive any face to face instruction from the installer on how to operate the heating system in the most efficient and effective manner? If so what did this entail? What manuals were provided?

As far as I am aware, the handover pack should have contained heat loss calculations, room by room, but @Transparent will be able to quote chapter and verse of what is stipulated in the the building regulations.

How many electrically operated valves are present and where are they located? Are they two port or three port?

Which is the coldest room, most difficult to keep warm?

Do you have any TRV's on any of the radiators?

Your home has approximately 380m2 of floor space, including upstairs and down, so is of quite decent size. It is also more rectangular rather than square, which is not the most beneficial from an energy efficiency point of view.

Based upon the data provide, your heating system supplied an average of 7.4kWh of thermal energy to keep your home warm and heat the DHW in December, but of course it will have used more when the weather was colder, and less when the weather was milder. Where is your approximate location? What internal temperatures do you normally have?

Dealing with the radiator system first, since it is the simplest and most easily understood.

Upstairs you have 6 radiators, all controlled from a single thermostat which should switch on the primary water pump and heat pump when calling for heat. The radiators should have been bled and balanced to distribute the thermal energy evenly.

Downstairs has 2 UFH zones which will probably operate in the following manner.

Let me identify the individual component parts and then how they operate together.

Each system consists of a mixing valve, a water pump, a flow header in which is installed a flow regulator for each UFH loop, the UFH loops themselves, and a solenoid valve on the return from each UFH loop located in the return header. There is also a UFH controller for each system and the various thermostats.

The warm water coming from the heat pump passes into one of the two inlet ports on the mixing valve, and flows through to the outlet port. The outlet from the mixing valve feeds the inlet of the water pump, which pumps the water into the flow header. The water in the flow header can flow through the flow regulators into the appropriate UFH loop, but only if the relevant solenoid valve is open. The water from the return header flows to both the second inlet port on the mixing valve and also to the return pipework back to the heat pump.

Each system should operate in the following manner.

If any of the thermostats connected to the particular system calls for heat, a signal should be fed into the relevant UFH controller. The controller should start the water pump and open the appropriate solenoid valve or valves. Water should therefore flow through the relevant UFH loop or loops and transfer thermal energy into the room in question. If the water coming from the heat pump is warmer than the setting on the mixing valve, the mixing valve will start to open and mix in some of this cooler return water with that coming from the heat pump, and in so doing will limit the maximum temperature of the water going through the UFH loops. This is the primary reason for the additional water pump and mixing valve.

In the Mitsubishi Engineers report I would question his understanding of UFH systems, since removing the mixing (blending) valves would not be advisable if the maximum permitted temperature of the UFH loops could be exceeded. Also the reason for the UFH water pumps is to make the mixing valve function correctly, so therefore it may be possible to also have the UFH water pumps removed.

I think that is probably enough for you to digest at the moment, but we will continue later.

@tobydeh based on the info provided I cant see any reason to suppose that its anything other than largely correct and also every reason to suppose that the system is well oversized.  There are two reasons to conclude this:

• a house built to 2020 building regulations shouldn't require 77W/sq m.  Also the amount of heat delivered is more consistent with 6-8kW than 14kW
• the graphs show pretty good COP (ratio of energy consumed to energy delivered) for space heating during Dec and Jan, but very poor COP in the shoulder season, this is consistent with oversizing causing and excessive cycling in the shoulder season

Additionally the COP for DHW appears to be close to or even less than 1 which is pants, you would probably be better off disabling the HP for DHW and using the immersion!

I think your Achilles heel might be the rads.  if you asked for these then the blending valves are probably unavoidable as is operating at a higher flow temp than necessary for the UFH.  Many on this and other forums report little or no need for upstairs heating in a modern house with UFH so I question how much the system needs to take them into account.  Nevertheless as they were customer specified the installer may use this as a get out for several issues that Mitsubishi have pointed out.  

If this were mine I would be submitting the Mitsubishi report, along with some concrete information on your meter readings, to the installer/NHBC and asking them to respond with their proposals.  You have every right to expect an average COP of 3.  However expect push back, attempts to blind you with 'science', etc.

Remember the basic rule - the way to run ASHPs efficiently is to have them operating 24x7 delivering water at the lowest flow temp possible consistent with the house being warm with thermostats and thermostatic radiator valves never or rarely needing to shut down (off) and no mixing anywhere in the system.  Any on/off switching is detrimental, lots of on/off switching and micro zoning doubly so.  An ASHP can only do this if it is reasonably well matched to the demand, which yours is not.  DHW is run separately (never the two at the same time) at a higher flow temp, typically 55-60, with a tank that has a large coil.

Good luck, feel free to post here responses you receive.

Posted by: @derek-m

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As far as I am aware, the handover pack should have contained heat loss calculations, room by room, but @Transparent will be able to quote chapter and verse of what is stipulated in the the building regulations.

Thanks @derek-m There are two points here which I need to address separately.

A: Before a heat-pump is installed there must be an energy survey performed within the PAS2035 rules.
You can get this done independently, but most installers like doing their own because it adds to the profit.

That survey will assess the fabric of the house and arrive at a heat-loss calculation for each room, and also the total for the entire house.

• The total heat-loss figure allows the installer to specify a heat-pump with the output you require.
• The figure for each room is used to calculate the size of radiator or UFH radiation-plate area.

If no energy survey has been done then the installer can't have applied the MCS design rules.
So that would be a breach of the MCS accreditation.

B: Building Regulations are different, but also apply.

The mains electrical work must be undertaken by a qualified electrician. That's how you get sent a Part-P certificate by the electrician's professional accreditation body, such as NICEIC.

Part-L of the Building Regs lays down the standards for conservation of energy/heat.

The installer is regarded as a 'Competent Person' and notifies your Local Planning Authority that his/her work has been completed within the Regulations.
The LPA then issue you with a letter that certifies compliance with Part-L.
Currently there are no checks made regarding Part-L, and I have never yet come across a heat-pump installation which complies. 😥 

There are four main issues which installers regularly fail to do:

1. Properly insulate the pipes, including all valves, and particularly the connections to the external unit.
2. Commission the installation so that it operates efficiently. It is not sufficient merely to turn it on and check that the radiators get warm!
3. Hand over documentation to the homeowner which is specific to your house. This will include a schematic diagram of the layout, and identification of the position and function of each control/sensor. I would expect a copy of the original energy survey to form part of this documentation. A pile of manufacturers' manuals will not do!
4. Instruct the homeowner how to operate and maintain the system so that it uses the least amount of electricity (its energy input).

Here are the relevant sections of the Building Regs Part-L document (and I'm copying here from two different iterations of Part-L):

If, as I suspect, your installation has not been completed to the standards required by Part-L, then I would urge you to contact the Borough/District Councillors for your ward.

You may be the first person ever to do so, and they may initially be wary of trying to understand the technical issues.
However, it isn't necessary for an Elected Member to have that level of comprehension. A Council has professional staff/officers to perform those tasks.

The point they will want to ask those Officers is "Why is this Council issuing Letters of Compliance for Part-L of the Building Regulations without any evidence that its provisions have been properly followed?"

There is a systemic failure which needs addressing.
Councillors are more powerful than they might wish to believe.
They will probably want to discuss the matter with local MPs and ask why Parliament is releasing later versions of the Building Regulations which are no more enforceable than the previous set.

The Leader of the Council (or Mayor) may also take the matter to the Local Government Association.

You will quickly be gathering around you a group of people who are on your side, and will be demanding that the system is changed for the better as a matter of urgency.

Isn't democracy wonderful? 🙂 

@transparent

Thanks @Transparent. It all sounds good in theory, but as you have stated leaves a great deal to be desired in practice.

In a new build the installer may have disappeared rapidly into the sunset before the new owners take possession.

Also where it states 'commissioning by testing and adjustment as necessary to ensure that they use no more fuel and power than is reasonable in the circumstances' is very much open to interpretation and conjecture. Who decides what 'is reasonable in the circumstances'?

It is likely that most planned installations will be carried out during milder weather conditions, which of course makes correct testing, commissioning and optimisation rather difficult to achieve. Should it therefore be a necessity for this work to be carried out and completed during the heating season?

I hope you don't mind if I don't hold my breath.

@tobydeh,

- is it just the downstairs that is 180m2?  From the plan it looks like the total is 360m2 or so.  If so, your consumption and the ASHP size isn't excessive. If not I take that back!

-  You use a lot of energy for HW.  That will lower your SCOP.  It will also make the COP in the months you use less heating lower because a bigger proportion will be HW, which usually has a lower COP than heating.  What temperature is your HW set at?

- You winter use is high but not excessively so for a big house.  And your overall heating consumption at 5000kWh is quite respectable.  

What made you think your bills were particularly high?  

Posted by: @derek-m

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@transparent

Thanks @Transparent. It all sounds good in theory, but as you have stated leaves a great deal to be desired in practice.

In a new build the installer may have disappeared rapidly into the sunset before the new owners take possession.

Also where it states 'commissioning by testing and adjustment as necessary to ensure that they use no more fuel and power than is reasonable in the circumstances' is very much open to interpretation and conjecture. Who decides what 'is reasonable in the circumstances'?

It is likely that most planned installations will be carried out during milder weather conditions, which of course makes correct testing, commissioning and optimisation rather difficult to achieve. Should it therefore be a necessity for this work to be carried out and completed during the heating season?

I hope you don't mind if I don't hold my breath.

Your pessimism may well be justified, but you seem to want to do something.  So your recourse potentially is to

• The builder
• The Installer
• NHBC if the install was part of the original build
• the previous owner of the house (unlikely)

and you can potentially make it more difficult not to comply by recourse to

• MCS if the installer was an MCS member, but if its a new build there is no guarantee that would be the case
• Another professional body of which the installer is a member
• The building inspector who signed it off (who may not be from your local authority, a developer has a choice of building inspectors these days and many LAs have outsourced building control to separate organisations)

Otherwise (or if the above fails) your options are

• suffer the extra cost
• pay someone to fix it up (if you can find anyone)

I am unclear whether the install was, or was not, part of the original build.  If it was, then there will likely be no energy survey, but the calculations should still have been done!

On this forum others will willingly provide advice, but ultimately only you can decide what to do!

Posted by: @derek-m

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In the Mitsubishi Engineers report I would question his understanding of UFH systems, since removing the mixing (blending) valves would not be advisable if the maximum permitted temperature of the UFH loops could be exceeded. Also the reason for the UFH water pumps is to make the mixing valve function correctly, so therefore it may be possible to also have the UFH water pumps removed.

Contrary to what I said earlier I do agree that mixing valves are likely necessary because of the radiators.  If there werent radiators then they would not be necessary and shouldnt be fitted, but because you effectively need two different flow temps at the same time there is no altertnative.

Also if your house area is really 360sq m not 180 then the apparent demand is about 39W/sq m which is more reasonable.

However I stand by my comments (based on the bar charts, the accuracy of which I cannot comment on) that:

• The COP in the shoulder season is poor, suggesting a problem or oversizing or both
• The COP for DHW is shockingly poor, suggesting misconfiguration

Posted by: @jamespa

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Posted by: @derek-m

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In the Mitsubishi Engineers report I would question his understanding of UFH systems, since removing the mixing (blending) valves would not be advisable if the maximum permitted temperature of the UFH loops could be exceeded. Also the reason for the UFH water pumps is to make the mixing valve function correctly, so therefore it may be possible to also have the UFH water pumps removed.

Contrary to what I said earlier I do agree that mixing valves are likely necessary because of the radiators.  If there werent radiators then they would not be necessary and shouldnt be fitted, but because you effectively need two different flow temps at the same time there is no altertnative.

 

Also if your house area is really 360sq m not 180 then the apparent demand is about 39W/sq m which is more reasonable.

 

However I stand by my comments (based on the bar charts, the accuracy of which I cannot comment on) that:

• The COP in the shoulder season is poor, suggesting a problem or oversizing or both
• The COP for DHW is shockingly poor, suggesting misconfiguration

 

Am I misreading these graphs?  It looks to me as if the overall COP is around 3 across the year, including the shoulder months.  With HW being 40-50% then, the heating COP is going to be very respectable. 

I'd agree about the HW and suggest the target temp is high, the immersion is being used excessively or something else is wrong.  

It looks to me that despite the best efforts of the installer, this system is running quite efficiently. That's not to say the OP shouldn't try and improve it. 

And to answer a previous question, 4.5 starts an hour is a bit more than ideal but not excessive.  I don't know for sure but I think a start will include temp setbacks, when the HW kicks in (which can be a lot depending on how it's set up) and defrosts (2-3 times per hour when it's cold outside). 

Posted by: @kev-m

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Posted by: @jamespa

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Posted by: @derek-m

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In the Mitsubishi Engineers report I would question his understanding of UFH systems, since removing the mixing (blending) valves would not be advisable if the maximum permitted temperature of the UFH loops could be exceeded. Also the reason for the UFH water pumps is to make the mixing valve function correctly, so therefore it may be possible to also have the UFH water pumps removed.

Contrary to what I said earlier I do agree that mixing valves are likely necessary because of the radiators.  If there werent radiators then they would not be necessary and shouldnt be fitted, but because you effectively need two different flow temps at the same time there is no altertnative.  The Mitsubishi engineer might not have known this if he didnt go upstairs, as indeed we didnt until the floor plan was posted.

 

Also if your house area is really 360sq m not 180 then the apparent demand is about 39W/sq m which is more reasonable.

 

However I stand by my comments (based on the bar charts, the accuracy of which I cannot comment on) that:

• The COP in the shoulder season is poor, suggesting a problem or oversizing or both
• The COP for DHW is shockingly poor, suggesting misconfiguration

 

Am I misreading these graphs?  It looks to me as if the overall COP is around 3 across the year, including the shoulder months.  With HW being 40-50% then, the heating COP is going to be very respectable. 

I'd agree about the HW and suggest the target temp is high, the immersion is being used excessively or something else is wrong.  

It looks to me that despite the best efforts of the installer, this system is running quite efficiently. That's not to say the OP shouldn't try and improve it. 

And to answer a previous question, 4.5 starts an hour is a bit more than ideal but not excessive.  I don't know for sure but I think a start will include temp setbacks, when the HW kicks in (which can be a lot depending on how it's set up) and defrosts (2-3 times per hour when it's cold outside). 

 

On rereading the charts with a sensible size screen (originally I was reading on a mobile - I did say it was a 'quick look') then I would say that you aren't reading them incorrectly, I am.  Apologies for the confusion.  So I think we are agreed now that the space heating COP appears to be OK but the DHW cop poor.

And overall (if the graphs are to be trusted) I would now tend to agree with your conclusion 'It looks to me that despite the best efforts of the installer, this system is running quite efficiently. That's not to say the OP shouldn't try and improve it.'

@tobydeh can you please post the actual electricity consumption that presumably your comments about excessive heating costs were based on.  Also confirm the floor area.  If its 360sqm not 180sq m and based on the graphs, the accuracy of which we don't know, then, on deeper investigation, it doesn't seem to be performing so badly with the exception of DHW.  Do you use a lot of DHW and/or is it set to a really high temp?

@tobydeh

Are you ready to continue the assessment of your system and how it may be improved?

@JamesPa We're using roughly 14,000kwh per year. If the Mitsubishi app is correct in its 'consumed' energy figure of 7,892kwh then we are using an additional 6,108kwh hours elsewhere which seems utterly impossible! Also, our usage is much higher through the colder months which means that whatever is using the additional kwh is only used during winter e.g. electric towel rails (which we barely ever turn on).

@derek-m We did receive a handover pack but we did not receive any 'real' education on how to use the heating system - we were shown how to use the room stats and that's about it.

None of the rooms are hard to keep warm, the house is always on the warm side and is very well insulated. We are located in the Midlands and the stats are always well above 20deg until winter kicks in (room stat next to me currently shows 24).

All of the rads have TRVs.

Please continue with your assessment 🙂

@kev-m It's just the downstairs that is 180sqm (it might be closer to 200sqm), the total is around 380sqm.

We are using roughly 14,000kwh per year, nearly double the MEL cloud 'consumption' number of 7892kwh, I cannot believe that it is something unrelated to the ASHP system causing that usage.