Mitsubishi Ecodan Air Source Heat Pump - Low Efficiency

[ReedRichards]

If the house (2019) was a new build then it's possible that it did not qualify for RHI in which case the OP may not have used an MCS-accredited installer. 

[TimToos]

Hi RR,

The house did and does qualify for RHI.  YES are MCS accredited.

 

All,

I have changed these setting:

Set all the downstairs room t'stats to 1C temperature higher than what I require.

Changed the upstairs temperature to a temperature I require.

Changed the ASHP to run with a fixed temperature.  Zone 1 (upstairs) is set at 18C and zone 2 (downstairs) is set at 20C.

Changed the HW tank setpoint to 49C.  Left the 10C drop as it was.

Thoughts?

[JohnMo]

Keep an eye on room temps.  So if the thermostats start controlling the temp the temp in that room is too high.

 

If all or most room are controlled by the thermostats the flow temp is to high so reduce a degree or two at a time .

 

If only one or two room are not getting to temp or are too hot, you need to increase flow at UFH loop flow meter at the UFH manifold or at the rad to make room warmer, reduce flow to make cooler.

[TimToos]

What I dont understand is how the system knows the upstairs temperature.  Theres a ASHP temperature sensor in the room where the cylinder is located (utility room).  I have it to control to this sensor and set this at 21C.

Zone 1 upstairs, only calls for heating from a t'stat as theres no probe for upstairs.  So how will the system know when this zone is at setpoint?  I ask this as both zones have a setpoint each, so downstairs (zone 2) will aim for 21C and upstairs (zone 1) 18C.

 

[JohnMo]

This is why you have to balance the system, it doesn't know the temp 

[Kevm]

11 minutes ago, TimToos said:

What I dont understand is how the system knows the upstairs temperature.  Theres a ASHP temperature sensor in the room where the cylinder is located (utility room).  I have it to control to this sensor and set this at 21C.

Zone 1 upstairs, only calls for heating from a t'stat as theres no probe for upstairs.  So how will the system know when this zone is at setpoint?  I ask this as both zones have a setpoint each, so downstairs (zone 2) will aim for 21C and upstairs (zone 1) 18C.

 

 

If you use external thermostats then the system doesn't know the room temp; all the stats do then is switch the ASHP off and on (or maybe open and close a valve if you have zones).

 

Have a look at page 16-17 below; it explains the different ways of controlling an Ecodan and may explain what's going on.

 

https://library.mitsubishielectric.co.uk/pdf/book/Ecodan_FTC6_PAC-IF071-3B-E_Installation_Manual_BH79D843H02#page-16-17

 

Why is the ASHP sensor in the utility room?  Shouldn't it be in your main living area?

 

It sounds like your ASHP may be barely ticking over - 8500 kWh isn't a lot in a year for a 11.2 kWh Ecodan. The COP is likely to be lower in this scenario, especially if it's switching on and off a lot.  You might find the COP goes up if you're working it harder.  Of course, COP isn't everything and that might cost you more.  I would love to use only 3600 kWh to heat my house.

 

 

 

 

[markocosic]

Sounds like an cluster fudge of a design.

 

Do you have a schematic? If it has a "header" in it, or a buffer vessel with four pipes, then you COP will definitely be awful. Design fault.

 

Do you have a thermostat? Then your COP will probably be awful. Design fault.

 

Share the installation drawings and the control methodology with us?

 

If you don't have this from the installer then you'll need to find a competent one to correct the.mess that the previous one has left you with.

 

 

Note that Mitsubishi are sharks, along with most of their distributors, and will advise you to install and operate the heat pump in a way that is totally different to the way that it is efficiency is tested.

 

The efficiency is tested on a directly connected (no header or buffer vessel), fully open (no thermostats or zoning) system that runs entirely on weather compensation. This is efficient but it needs half a brain to make sure that there is enough flow through the system at all times for the heat pump to work.

 

The manuals / distributors tell you to fit headers/buffer vessels and zoning etc. It will always work (so no callbacks) even if the installer is thick as mince. (or if the homeowner is thick as mince and refuses to operate the heat pump properly) Unfortunately the efficiency will be godawful as a consequence.

[TimToos]

15 minutes ago, Kevm said:

 

If you use external thermostats then the system doesn't know the room temp; all the stats do then is switch the ASHP off and on (or maybe open and close a valve if you have zones).

 

Have a look at page 16-17 below; it explains the different ways of controlling an Ecodan and may explain what's going on.

 

https://library.mitsubishielectric.co.uk/pdf/book/Ecodan_FTC6_PAC-IF071-3B-E_Installation_Manual_BH79D843H02#page-16-17

 

Why is the ASHP sensor in the utility room?  Shouldn't it be in your main living area?

 

It sounds like your ASHP may be barely ticking over - 8500 kWh isn't a lot in a year for a 11.2 kWh Ecodan. The COP is likely to be lower in this scenario, especially if it's switching on and off a lot.  You might find the COP goes up if you're working it harder.  Of course, COP isn't everything and that might cost you more.  I would love to use only 3600 kWh to heat my house.

 

Hi Kevm,

The temperature thermistor sensors is there as thats where YES put it.  I was never asked.  We have 5 sensors, return flow, feed flow, tank temperature, outside temperature and room temperature.

 

Does anyone recommend someone who can come and commission the system at all?  Maybe put things right.  We dont know anyone and I dont want to use YES anymore.

 

Thanks

15 minutes ago, Kevm said:

 

 

 

[TimToos]

16 minutes ago, markocosic said:

Sounds like an cluster fudge of a design.

 

Do you have a schematic? If it has a "header" in it, or a buffer vessel with four pipes, then you COP will definitely be awful. Design fault.

 

Do you have a thermostat? Then your COP will probably be awful. Design fault.

 

Share the installation drawings and the control methodology with us?

 

If you don't have this from the installer then you'll need to find a competent one to correct the.mess that the previous one has left you with.

 

 

Note that Mitsubishi are sharks, along with most of their distributors, and will advise you to install and operate the heat pump in a way that is totally different to the way that it is efficiency is tested.

 

The efficiency is tested on a directly connected (no header or buffer vessel), fully open (no thermostats or zoning) system that runs entirely on weather compensation. This is efficient but it needs half a brain to make sure that there is enough flow through the system at all times for the heat pump to work.

 

The manuals / distributors tell you to fit headers/buffer vessels and zoning etc. It will always work (so no callbacks) even if the installer is thick as mince. (or if the homeowner is thick as mince and refuses to operate the heat pump properly) Unfortunately the efficiency will be godawful as a consequence.

 

Doesnt it indeed?  I dont know who to get in touch with who could advise.

[TimToos]

24 minutes ago, Kevm said:

 

If you use external thermostats then the system doesn't know the room temp; all the stats do then is switch the ASHP off and on (or maybe open and close a valve if you have zones).

 

Have a look at page 16-17 below; it explains the different ways of controlling an Ecodan and may explain what's going on.

 

https://library.mitsubishielectric.co.uk/pdf/book/Ecodan_FTC6_PAC-IF071-3B-E_Installation_Manual_BH79D843H02#page-16-17

 

Why is the ASHP sensor in the utility room?  Shouldn't it be in your main living area?

 

It sounds like your ASHP may be barely ticking over - 8500 kWh isn't a lot in a year for a 11.2 kWh Ecodan. The COP is likely to be lower in this scenario, especially if it's switching on and off a lot.  You might find the COP goes up if you're working it harder.  Of course, COP isn't everything and that might cost you more.  I would love to use only 3600 kWh to heat my house.

 

 

 

 

Hi,

The ASHP has 5 thermistor sensors.  Flow to and from temps, DHW tank, room temperature (utility room) and outside temperature.  I was never told about these sensors so thats where its located, in the utility.

 

Does anyone recommend someone who knows these systems and can fully set-up?

[TimToos]

Ive just had a look at some accessories and theres a wireless controller and receiver unit for this ASHP.  Is this a worthwhile investment, installing this another room and controlling with this?

[MikeSharp01]

11 hours ago, TimToos said:

Now I am thinking that once the kids grow up will the 250L be too small?

Maybe for a few years you need to get organised but then - when the kids have gone to Uni and beyond things will settle down. I worry that we size for the maximum using one scheme (ASHP) when doing it for the average and then having a strategy for maximum (immersion ++) would be better.

[ReedRichards]

12 hours ago, TimToos said:

 

Does anyone recommend someone who knows these systems and can fully set-up?

 

Within reach of Halifax?

[PhilT]

On 05/09/2022 at 19:35, TimToos said:

 

Hi ProDave,

 

This is very interesting and also worrying!

which exact model do you have?

[TimToos]

11 hours ago, ReedRichards said:

 

Within reach of Halifax?

Yes, West Morton area BD20

[TimToos]

1 hour ago, PhilT said:

which exact model do you have?

Mitsubishi Ecodan ASHP - manufactured 03/19.

ASHP: PUHZ-W112VAA

Cylinder: EHPT25X-VKHCW

Edited September 7, 2022 by TimToos

[TimToos]

Does anyone use the wireless controllers and receiver units?  If I had 2 controllers, could I place one upstairs and downstairs and allow the ASHP system to run to these instead of the wall thermostats?  Can the ecodan run both heating zones at the same time?

 

Also, what about the MAC-567IF-E Wi-Fi Card?  Does anyone use this for connecting to the MELCloud service and if so is it any good?  What about the installation on the units onto the board?  I cant find the manual on the actual fitment of this wi-fi unit, just the setting up of it.

 

Thanks 

Edited September 8, 2022 by TimToos

[ReedRichards]

On 06/09/2022 at 17:16, TimToos said:

Hi RR,

The house did and does qualify for RHI.  YES are MCS accredited.

 

In which case you should have got a big pack of documents after installation.  Your MCS Installation Certificate should state what SCOP you are expected to achieve and what your calculated space and water heating demands are (as per your EPC).

[TimToos]

1 hour ago, ReedRichards said:

In which case you should have got a big pack of documents after installation.  Your MCS Installation Certificate should state what SCOP you are expected to achieve and what your calculated space and water heating demands are (as per your EPC).

You are right, just found the doc!! 

 

These are what it informs:

 

• Flow temp: 45C
• SCOP: 3.80
• Est annual generation: 20305
• Space heating: 16806
• Water heating: 3499 

 

Am I right to assume that if our SCOP is 3.8, and annual generation is 20305 then the ASHP power to be consumed is 5343?

 

In our case, in 2021, the ASHP actually consumed was 5427 but the house was running on the room stats (set lower than as I thought this would save money) and so the system was most likely switching on and off like a yo-yo.  Is this most likely my issue?

 

If I run the system on 2 wireless controllers, one for zone 1 and one for zone 2 would this make the system function more efficiently?

Edited September 8, 2022 by TimToos

[ReedRichards]

25 minutes ago, TimToos said:

Am I right to assume that if our SCOP is 3.8, and annual generation is 20305 then the ASHP power to be consumed is 5343?

 

Yes, although these are calculated figures for a year with average (winter ) temperatures.  I would have thought that 20305 kWh is a big heat requirement for a modern well-insulated house but the self-builders here are better placed to comment than a retro-fitter like myself.

 

34 minutes ago, TimToos said:

If I run the system on 2 wireless controllers, one for zone 1 and one for zone 2 would this make the system function more efficiently?

 

 If I were you I would first figure out how your zones are controlled now and how your upstairs zone manages to call for heat when required.  Do you actually have the motorised valves necessary to control both zones independently?     

[TimToos]

18 minutes ago, ReedRichards said:

 

Yes, although these are calculated figures for a year with average (winter ) temperatures.  I would have thought that 20305 kWh is a big heat requirement for a modern well-insulated house but the self-builders here are better placed to comment than a retro-fitter like myself.

 

 

 If I were you I would first figure out how your zones are controlled now and how your upstairs zone manages to call for heat when required.  Do you actually have the motorised valves necessary to control both zones independently?     

I need to check how the zones operate.  Im sure its a motorised valve but not sure if zone 1 and zone 2 can be heated at the same time.

 

Im not sure about the heat requirement or what I should expect.  The house isnt particularly large but suppose its slightly bigger than a normal 'Wimpy' type affair.  I cant remember the foot print buts its 5 bedrooms with ground, floor 1 and floor 2.  We had the calcs done for the required heating etc and the ASHP was based on these figures.  The cavitys have 75mm insulation and air gap and the roof and ground have 6" plus the tops rooms are boarded out with insulated board.

 

Hopefully we can get the costs down.

[ReedRichards]

1 hour ago, TimToos said:

Am I right to assume that if our SCOP is 3.8, and annual generation is 20305 then the ASHP power to be consumed is 5343?

 

In our case, in 2021, the ASHP actually consumed was 5427 but the house was running on the room stats (set lower than as I thought this would save money) and so the system was most likely switching on and off like a yo-yo.  Is this most likely my issue?

 

 

Thinking about this some more, your actual electricity consumption is close to what it seems you were given to expect.  Your most fundamental problem is that most of the time you kept some or all of your house colder than was (probably) assumed in the heat loss calculations but did not reap any benefit.

 

Short cycling has a terrible reputation with gas and oi boilers and this bad reputation has been carried over to heat pumps.   How bad it really is for a heat pump will depend on how your particular model works and how short the actual cycles are.  My heat pump is limited to a maximum of four cycles per hour and seems to do fine with that.     

[TimToos]

11 minutes ago, ReedRichards said:

 

Thinking about this some more, your actual electricity consumption is close to what it seems you were given to expect.  Your most fundamental problem is that most of the time you kept some or all of your house colder than was (probably) assumed in the heat loss calculations but did not reap any benefit.

 

Short cycling has a terrible reputation with gas and oi boilers and this bad reputation has been carried over to heat pumps.   How bad it really is for a heat pump will depend on how your particular model works and how short the actual cycles are.  My heat pump is limited to a maximum of four cycles per hour and seems to do fine with that.     

Correct, I thought we would save money by not heating all rooms up.  We dont use all rooms.  Instead I let rooms cooldown during the night then come back up to temperature in the early hours, from 3:30m.  Whilst other rooms we didnt use had their stats basically on frost protection only.

[ReedRichards]

There is a school of thought that says leaving some rooms unheated does not necessarily save money with a heat pump.  The argument goes like this:

 

If the unheated rooms are not well-insulated from the heated rooms (which would normally be true) then the heated rooms will lose more heat than otherwise so will require a higher water temperature (this assumes you are using Weather Compensation) to maintain their desired temperature.  The heat pump will therefore perform less efficiently and the reduction in efficiency outweighs the reduction in heating load.

 

Personally I think this could well be true in some circumstances, not necessarily in all circumstances.  But it's certainly worth being aware of this possibility.        

 

[JohnMo]

Are you just reading my first reply and rewriting it?