Mitsubishi Ecodan Air Source Heat Pump - Low Efficiency

[PhilT]

18 hours ago, TimToos said:

Mitsubishi Ecodan ASHP - manufactured 03/19.

ASHP: PUHZ-W112VAA

Cylinder: EHPT25X-VKHCW

Your 11.2kW PUHZ version uses R410 coolant and a twin rotary compressor. The latest 11.2kW PUZ version uses R32 coolant and a scroll compressor. The good news is that the quoted overall performance ratings are similar between these two models so, as others have suggested, your PUHZ setup just needs more effort to find the efficiency sweet spot. If you haven't already, I would strongly recommend an inspection/service to ensure no faults.

[ReedRichards]

4 hours ago, JohnMo said:

Are you just reading my first reply and rewriting it?

 

No, I was reiterating it but adding a dash of scepticism. 

 

For as long as I could program a room temperature (about 25 years now) I have made it cooler in the morning when I'm active, edged the temperature up during the day so it is warmest in the evening when I tend to be more sedentary, then set back the temperature overnight.  To my mind this is the most desirable pattern of use for any form of heating but those Heat Geeks don't even countenance it.  When the starting assumptions are wrong, and they're wrong for me, then this makes me sceptical about the conclusions.       

[JohnMo]

But your only moving the heat a degree or so either direction.  No different to an overnight setback, then adding the temp back in a couple of stages, which allows the heat pump to gently heat the house up.  Which is pretty much what heat geek and others and your general common sense says is the right thing to do for the best CoP. Basically slow and gently does it.

 

The OP hasn't or isn't doing that, he has most of the house heating off, which doesn't let the heat pump flow at the correct rate, and the rooms he is trying to heat, cannot heat up well because the heat is moving to anywhere colder in or outside the house.  Those two things on there own will give a rubbish CoP.

[ReedRichards]

That may well be true.   The OP is trying to keep their house warm with no heating on the second floor and finding that the heating on the first floor is insufficient; cause and effect?  If so, then the heat pump will be on all the time, struggling to get the house up to temperature using fewer radiators than was envisaged, having to raise the output water temperature to try to do this at the cost of degraded efficiency.  If it was winter now they could observe the heat pump to see if this seems to be true.

 

On the other hand, the although the COP figures are reported to be very poor, the actual electricity being consumed seems to be broadly what was predicted.  So the most fundamental problem is that the house, or some of it, is not warm enough.

 

What should the OP do?  I would begin by setting the flow temperature to a fixed 45 C (as per the MCS spec) turn on all the radiators and check that the house is as warm as they want it to be.  It's relatively mild out so the heat pump, set to 45 C, should cycle.  Then reduce the set temperature until the heat pump is on the majority of the time but the house is still warm enough.  Check that the new set temperature is broadly in line with what the weather compensation, if engaged, would set.  If it is, that may well be that, engage weather compensation and everything should be fine.  If not then the weather compensation settings would need to be reviewed and altered.

 

Do you agree, @JohnMo  ?                    

[JohnMo]

I am in complete agreement, it's a logical easy enough plan to follow.

 

Only thing I would add is to take all the timers off the central heating, set the thermostats to around 24 and trvs fully open.  Start the testing at a weekend when you home for a couple of days.

[SteamyTea]

On 08/09/2022 at 12:25, JohnMo said:

Are you just reading my first reply and rewriting it?

What I did during my Master's.

I did not understand why we had to "rewrite, using your own words" in English O Level until then.

[dave 57]

I'm trying to get to grips with the controls on our new Ecodan 8.5Kw  heat pump. This thread has been very helpful - thanks all.

Our system has been fitted with a Nest remote thermostat. 

To use the fixed temp mode or the weather compensation mode on the FTC unit, I need to trigger the nest thermostat to call for heat.

When I select room thermostat mode on the FTC unit it shows a  different room and call temperature setting than on the Nest.

Is there a way to get the room temp and call temp from the Nest to the FTC unit?

I guess the auto adaptive heating option on the heating pump will not work properly , and the call temp on the FTC needs to be set to at least the maximum I'll call on the Nest.

Thanks for any insights. dave

 

 

 

 

[JohnMo]

I think the thermostat calling for heat while weather comp is operative goes against the basic principles of weather compensation. The weather compensation basically runs 24/7, so isn't looking for a thermostat.  The controller follows the heating curves as outside temp varies, and if you have a setback it just lowered the flow temp a few degrees.

[dave 57]

Yes, I agree, it looks like the Nest is an overriding  on/off switch, with no linking of the temperatures.

I plan to run it on weather compensation, so feel as though I can now do that!

My next query is how do you program Setback is it in the scheduling menu, I've yet to try doing this?

Is there any guides as how if to use Heat Pump setting/Quiet Mode, would you time this to be the same as our setback?

dave

Edited September 10, 2022 by dave 57

[PhilT]

2 hours ago, JohnMo said:

I think the thermostat calling for heat while weather comp is operative goes against the basic principles of weather compensation. The weather compensation basically runs 24/7, so isn't looking for a thermostat.  The controller follows the heating curves as outside temp varies, and if you have a setback it just lowered the flow temp a few degrees.

On my Ecodan the room stat rules even in WC mode. This is ok because sunny days warm the house more for a given outside temp, and WC mode is not smart enough to reduce the flow temp as the room reaches the desired temp and keep the HP efficiently ticking over bang on that room temp setting, which is a pity.

[JohnMo]

So it weather compensation with load compensation.

 

6 minutes ago, PhilT said:

 WC mode is not smart enough to reduce the flow temp as the room reaches the desired temp and keep the HP efficiently ticking over bang on that room temp setting, which is a pity.

That's why you need to ensure the system is balanced and the curve is right.  If your room is overshooting, either flow temperature is too high, or the flow rate in that room is high.  You need to set the flow temp to most of the rooms at the correct temp, then tweek the flows up/down to get the rest of the rooms correct.  Once you have that correct you have to twerk the curve.  The thermostat should really be set above the target room temp, so if you get solar gain say, the flow temp is reduced to compensate.

[dave 57]

 

1 hour ago, PhilT said:

On my Ecodan the room stat rules even in WC mode. This is ok because sunny days warm the house more for a given outside temp, and WC mode is not smart enough to reduce the flow temp as the room reaches the desired temp and keep the HP efficiently ticking over bang on that room temp setting, which is a pity.

I'd not thought of this scenario, we get a lot of solar gain from our conseratory

[PhilT]

31 minutes ago, JohnMo said:

So it weather compensation with load compensation.

 

That's why you need to ensure the system is balanced and the curve is right.  If your room is overshooting, either flow temperature is too high, or the flow rate in that room is high.  You need to set the flow temp to most of the rooms at the correct temp, then tweek the flows up/down to get the rest of the rooms correct.  Once you have that correct you have to twerk the curve.  The thermostat should really be set above the target room temp, so if you get solar gain say, the flow temp is reduced to compensate.

Solar gain outside yes. The solar gain inside, which can be significant with a lot of glass/south facing etc. does not affect the WC curve - at least not on mine - it's a straight relationship between outside temp and flow temp. My system is well balanced but my preferred setup would be at 6am for the flow temp to be higher to get the room temp back up to my set level asap. As it approaches that set room temp I would like the HP to be smart and back off the flow temp to maintain room temp at my set level. Presently I have to do this manually by knocking a few degC off the flow temp once room temp has been reached. I don't want to lower the WC curve it would take too long in the morning to get the rooms up to temp. Like someone said, it would be good to have the WC curve on some kind of timer, like the temp timer, or, best of all, make the controller smart enough to reduce the flow temp as the room temp reaches the set level.

[ReedRichards]

I have a third party controller with my heat pump, similar to the Nest, and it does not stop me using Weather Compensation.  When the third party thermostat calls for heat, the heat pump comes on and uses a maximum output water flow temperature that is set according to the weather compensation curve.  This doubtless means I need a Weather Compensation curve a tad higher than if I was trying to do it thermostat-free but I doubt that it will make a huge difference. 

 

9 minutes ago, PhilT said:

... best of all, make the controller smart enough to reduce the flow temp as the room temp reaches the set level.

This is called "Load Compensation".  That, regretfully, I cannot with my third party controller because the heat pump does not know the desired room temperature.  There isn't the equivalent for heat pumps to the Opentherm control system for gas boilers that would allow you to do Load Compensation with a third party controller.  But I think if you use Ecodan's own controller you can have both Weather and Load Compensation.  

[PhilT]

50 minutes ago, ReedRichards said:

I think if you use Ecodan's own controller you can have both Weather and Load Compensation.  

That would be great if true does anyone know how to set load compensation on the Ecodan controller?

[ReedRichards]

Quoting a reply about this on another forum:

 

Quote

Mitsubishi Ecodan heat pumps can do this with the FTC5/6 controllers.  It's called auto adaptation.  It will work either (1) with the wired controller if it's in a suitable place to detect the room temperature (2) with a separate wired in thermistor to detect room temperature or (3) with Mitsubishis's own wireless controller.  It won't work with 3rd party thermostats which, no matter how 'smart' they are, are effectively just on/off switches to the ASHP.

 

[PhilT]

14 hours ago, ReedRichards said:

Mitsubishi Ecodan heat pumps can do this with the FTC5/6 controllers.  It's called auto adaptation

Thanks! I hadn't been able to find a detailed explanation of this mode in any of the manuals. I also listened more carefully to one of Mitsubishi's own videos on YouTube ("Ecodan Heating Modes") which, at 2:20 briefly mentions the magic words "...auto adaptive..." and "...uses weather compensation in the background..." bingo! So the Ecodan does in fact have exactly the "smart" function I was looking for, as long as you are using its own compatible controller.

[Kevm]

On 11/09/2022 at 11:57, PhilT said:

Thanks! I hadn't been able to find a detailed explanation of this mode in any of the manuals. I also listened more carefully to one of Mitsubishi's own videos on YouTube ("Ecodan Heating Modes") which, at 2:20 briefly mentions the magic words "...auto adaptive..." and "...uses weather compensation in the background..." bingo! So the Ecodan does in fact have exactly the "smart" function I was looking for, as long as you are using its own compatible controller.

 

Try this

 

http://www.sunergy.ps/data/itemfiles/0a597ef3b3346a2451fbbda7f02ea637.pdf