Ecodan - room temp auto adaptation and multiple zones

[BEJB]

I have a 14kW Mitsubishi Ecodan, which heats 2 zones (zone 1 = house with rads and zone 2 = kitchen with UFH) and DHW.

I spent a good time playing with weather compensation only to find that room temperature with auto adaptation heats better with a higher COP - happy bunny!

However, there does seem to be a slight issue. Auto adaptation seems to set itself to the lowest flow temperature to match heat input to heat output. So zone 1 heats well and is very efficient. But the system doesn't run zone 1 and zone 2 at the same time - zone 1 takes precedent if it calls for heat. So zone 1 seems to be on all the time (nice and snug!) and zone 2 seems to be off most/all of the time (a bit chilly). 

Does anyone have any suggestions as to how I might be able to get some heat to zone 2, while still being able to benefit from auto adaptation?

Thanks in advance for any help or advice you can give.

[JohnMo]

1 hour ago, BEJB said:

Auto adaptation

You are aware that auto adaptation isn't for use with UFH? Only works with radiator systems. Think the issue with UFH is the inertia is to large and throws the auto learning out.

 

UFH is very slow, so would really benefit being the lead.

[PhilT]

When i spoke to a Mitsubishi tech about auto with ufh, he said it wasn't so much that it doesn't work, but rather it's an unknown quantity because they have no user data experience, and the software could take much longer to "learn" how your room temperature reacts to changes in heat input, you would need to leave it in a steady state 24/7, eg target room temp at 20degC all the time, until it settles. Do you have separate Ecodan remote controllers for each zone?

Edited December 8 by PhilT

[BEJB]

2 hours ago, PhilT said:

When i spoke to a Mitsubishi tech about auto with ufh, he said it wasn't so much that it doesn't work, but rather it's an unknown quantity because they have no user data experience, and the software could take much longer to "learn" how your room temperature reacts to changes in heat input, you would need to leave it in a steady state 24/7, eg target room temp at 20degC all the time, until it settles. Do you have separate Ecodan remote controllers for each zone?

That's interesting. Yes, I do have separate Ecodan remote controllers for each zone. 

 

Although I have 'set back differentials' for both zones (reduced thermostat overnight), I have less for the UFH and the UFH starts earlier, so it gets a boost first thing in the morning. I could have a go at further reducing or removing the setback differential for zone 2 and raising it even earlier (if there is still a setback differential). 

 

I'd still have the thing where zone 1 wants to just run continuously during the day, rather than heating the house so zone 2 gets a chance. But maybe getting heat overnight would be ok.

 

I do wonder if the auto adaptation can 'learn' the heating of the two different zones - or if it pretends its just one zone and produces a sort of 'average' which is not right for either.

 

I also think there is a design flaw, in that the two zones have very different capacities. Zone 1 has lots of rads and the heat pump has obviously been sized for that. I think the heat pump is therefore oversized for the comparatively small volume of the kitchen UFH. So it can sometimes have comparatively inefficient sawtoothing. This seems less of a problem with auto adaptation than it does with weather compensation, so maybe the auto adaptation does learn something.

 

Thanks for your replies and ideas.

[PhilT]

14 minutes ago, BEJB said:

I do wonder if the auto adaptation can 'learn' the heating of the two different zones - or if it pretends its just one zone and produces a sort of 'average' which is not right for either.

In theory it can but with UFH in a kitchen zone, that's a huge (perhaps impossible) challenge of "learning" in a constantly fluctuating temperature environment, with all manner of appliances going on and off, warm bodies going in and out, sun coming through windows periodically, etc, and how isolated is the kitchen from the rest of the house - possibly different temperature air is wafting in and out? Have a go with the kitchen zone set to WC mode and see what happens.

[BEJB]

I can't set different heating modes for the two zones. I set it for zone 1 and the same applies to zone 2. Room seems to be the best compromise.

I don't know if this is just the way it is setup, or if I could change this to allow different heating modes for different zones.

[PhilT]

15 minutes ago, BEJB said:

I can't set different heating modes for the two zones. I set it for zone 1 and the same applies to zone 2. Room seems to be the best compromise.

I don't know if this is just the way it is setup, or if I could change this to allow different heating modes for different zones.

I can see this screen in the Melcloud app which suggests that you can set the mode by zone, but  I only have one zone so I could be mistaken

[sharpener]

Sounds like this might be a rare case for 3rd party controls, how about

• Optimise for Zone 1 as above which will be correct for rads but too hot for the kitchen UFH
• disconnect/disable Zone 2 controls on Ecodan
• turn down flow rate through kitchen UFH loop(s) until it (almost) requires the same flow temp
• fit 3rd party thermostat in kitchen to control the actuator(s) and take account of cooking gain etc

@JohnMo will be able to tell us if this could work.

 

[JohnMo]

Above sounds about right. Depending on thickness of screed you would need to fiddle with thermostat hysterisis. So get one that can go as low as 0.1 degs hysterisis.  Then if your overshooting, undershooting, you can correct with hysterisis.  Trying to run two systems with very differing inertia isn't easy. You either accept one is always wrong or put a controller to limit it.

[BEJB]

2 hours ago, PhilT said:

I can see this screen in the Melcloud app which suggests that you can set the mode by zone, but  I only have one zone so I could be mistaken

I have the two zones but only one option 

[BEJB]

When I first got the house , the kitchen/utility had third party controls. Dividing the UFH into 2 definitely meant the loops were too small for the ashp to heat!

Anyway, I swapped that out for an ecodan thermostat,which controlled both ufh loops and so worked a bit better. It also showed the temperatures on the Melcloud reports.

I do wonder if there is a setting or a dip switch that allows me to control the heating modes for both zones ....

Edited December 8 by BEJB

[PhilT]

38 minutes ago, BEJB said:

When I first got the house , the kitchen/utility had third party controls. Dividing the UFH into 2 definitely meant the loops were too small for the ashp to heat!

Anyway, I swapped that out for an ecodan thermostat,which controlled both ufh loops and so worked a bit better. It also showed the temperatures on the Melcloud reports.

I do wonder if there is a setting or a dip switch that allows me to control the heating modes for both zones ....

Give Ecodan home owner tech support a call. They have always been very helpful for me

[BEJB]

3 hours ago, PhilT said:

In theory it can but with UFH in a kitchen zone, that's a huge (perhaps impossible) challenge of "learning" in a constantly fluctuating temperature environment, with all manner of appliances going on and off, warm bodies going in and out, sun coming through windows periodically, etc, and how isolated is the kitchen from the rest of the house - possibly different temperature air is wafting in and out? Have a go with the kitchen zone set to WC mode and see what happens.

I think this is very true. I find it difficult to see how the auto adaptation can learn for the kitchen. It does have oven & hob, plus heat from things like the dishwasher etc. Also, it has several windows that face south-east, so gets quite a lot of solar gain. It can be quite cold outside, but if it's sunny it can be quite warm in the kitchen. 

While I think auto adaptation is good for zone 1, if I could set zone 2 to WC, that would definitely be worth a go.

[Gary68]

Are you saying that you can only heat zone 1 or zone 2 at once, or is just that you haven't got the thermostats calling for heat at the same time?

If its the former then something have been wired up incorrectly.

 

I have UFH downstairs and rads upstairs they are on separate stats and both can call for heat independently or together they just have different pumps for each circuit.

 

 

[BEJB]

1 hour ago, Gary68 said:

Are you saying that you can only heat zone 1 or zone 2 at once, or is just that you haven't got the thermostats calling for heat at the same time?

If its the former then something have been wired up incorrectly.

 

I have UFH downstairs and rads upstairs they are on separate stats and both can call for heat independently or together they just have different pumps for each circuit.

 

 

Mmmm- that is interesting. The heating system can heat zone1, zone 2 or DHW but only one of them at a time. I know DHW claims priority, but if I could have zone 1 and zone 2 independently or together, that would probably help. Thanks for the tip - that's something to look at.

 

Interestingly, if I have either zone 1 or zone 2 calling for heat, the Melcloud app shows both of them operating. I always assumed that was an artefact of the software, but maybe it is another thing pointing to some sort of configuration error.

[Gary68]

19 hours ago, BEJB said:

Interestingly, if I have either zone 1 or zone 2 calling for heat, the Melcloud app shows both of them operating. I always assumed that was an artefact of the software, but maybe it is another thing pointing to some sort of configuration error.

 

Mine does that too, I think its just the app.

 

Do you have a mitsubishi preplumbed cylinder, if it was for 2 zones there should be 4 pumps in total, 1 for the primary circuit, 1 for each zone and 1 for dhw.

 

If you turn both stats on to call for heat you should have 2 pumps lit up with lights if they are the std grundfos pumps that are usually on the cylinder

[BEJB]

On 10/12/2024 at 08:42, Gary68 said:

 

Mine does that too, I think its just the app.

 

Do you have a mitsubishi preplumbed cylinder, if it was for 2 zones there should be 4 pumps in total, 1 for the primary circuit, 1 for each zone and 1 for dhw.

 

If you turn both stats on to call for heat you should have 2 pumps lit up with lights if they are the std grundfos pumps that are usually on the cylinder

Mmm - again, you have got straight to the point.

 

I have a Mitsubishi preplumbed cylinder, with four pumps.

 

It has a low loss headerm with zone1 pipes coming off the top of the LLH and zone 2 coming off towards the bottom.

 

However, for some reason best known to the installer, if the pumps for both zones are pumping, the pipework for zone 2 doesn't get hot - all the heat goes to zone 1. 

 

So with Room setting, if zone 1 pumps all the time, zone 2 gets no heat. Sad face. 

[JohnMo]

A low loss header, is just a hydraulic separation device. The flow goes in and out at the top, the return in and out at the bottom.

 

If you are taking zone 2 off the bottom it's just getting the return water from zone 2.

 

Think you need to post some photos 

23 minutes ago, BEJB said:

zone 1 pipes coming off the top of the LLH and zone 2 coming off towards the bottom.

Suspect the LLH is plumbed incorrectly.

[Gary68]

Agree with John sounds like its plumbed incorrectly and its not getting hot as its just pumping the return water from zone 1 that is already cool.  If you ramp up the flow temp to 45C and the ufh start to get warm then that would confirm it.

[sharpener]

18 hours ago, BEJB said:

It has a low loss headerm with zone1 pipes coming off the top of the LLH and zone 2 coming off towards the bottom.

 

However, for some reason best known to the installer, if the pumps for both zones are pumping, the pipework for zone 2 doesn't get hot - all the heat goes to zone 1. 

 

Maybe it was done this way deliberately so the flow to zone 2 came preferentially from the return from zone 1, so temp for zone 2 was lower as befits UFH.

 

Problem is to adjust the 3 pumps so that it actually works like this. Try turning zone 1 pump down and/or primary pump up so zone 2 can suck a hotter mix from the LLH.

Edited December 16 by sharpener

[BEJB]

OK, so I might has been exaggerating when I said 'bottom'. Zone 2 is lower down the LLH than zone 1. I've tried to attach a picture.

 

What it does mean is that the hot water just seems to be scooted off into Z1 if the Z1 pump is running, leaving nothing left for Z2. I don't know what the Z2 pump pumps through the UFH - all I can think is that it is the return water from the bottom of the LLH. When I think about it, it makes my head explode!

 

I tend to think the whole thing suffers from poor design, caused by a heating engineer more used to gas boilers. Zone 1 is OK - the radiators have a greater capacity than the 14kW heat pump. But if the zone 2 UFH runs buy itself, I don't think the emitter capacity is up to dealing with the heat pump - the return temperature is only a degree or two below the flow. So the system starts sawtoothing. At least it is only a couple of 'tooths' per hour and the floor does heat. But for that to work, I have to have zone 1 off.

 

Generally, I can get by and ignore it. But when the cold weather strikes and the outside temperature doesn't rise above zero for a week or so, it doe highlight these weaknesses. 

 

I think I need to follow the advice given when it turns cold - just switch to flow temperature and whack it up to 45 - and accept the bills going through the roof!

[Kelvin]

1 hour ago, Gary68 said:

Agree with John sounds like its plumbed incorrectly and its not getting hot as its just pumping the return water from zone 1 that is already cool.  If you ramp up the flow temp to 45C and the ufh start to get warm then that would confirm it.

I’d have thought these pre-plumbed cylinders are hard to get wrong. 
 

Two zone systems are typical though albeit it’s more normal for it to be a large ground floor UFH zone and a smaller upstairs rad zone. This system is the other way around with a very large heat pump. It probably would have been better to have also used rads in the smaller zone snd run the whole system as one zone backed up with electric UFH. It might be better to just fit an electric wall mounted emitter and switch off the UFH in the kitchen assuming there’s wall space. 

Edited December 16 by Kelvin

[ringi]

Something I thought I would never say for a heatpump UFH....

 

What about putting a mixing pump on the UFH manifolds control by a fixed return UFH temperature, and overheat room thermostat that turns off the UFH pump.   Then run the home as a single zone with the heatpump controlling the flow temperature based on the requirements of radators.

 

The cylinder would need a little replumbing, so the UFH manifold is connected as if it is an additional radiators.  Careful balancing.  Should be able to use the redundant zone pump for the UFH manifold by combining with 4 way mixer value.

[BEJB]

Being a scientist, I know you should change one thing at a time, then evaluate the impact of that. However, I'm retired, so I've had a go at:-

1. reducing the speed of the zone 1 pump
2. setting the zone 2 pump to the UFH setting (I think the Ecodan engineer probably changed that to higher constant speed)
3. reducing the 'set back' of the UFH thermostat, so the floor temperature doesn't drop so much overnight. 
4. altering the wiring for the zone 2 (UFH) pump to connect it to OUT2 rather than OUT3. OUT 3 provides pump power if Zone 2 calls for heat. OUT 2 provides power if either Zone 1 or Zone 2 calls for heat. So if Zone 1 calls for heat, it heats both the radiators and the UFH - so the UFH becomes part of the zone 1 heating circuit. But if it doesn't get enough heat from that, when Zone 1 thermostat reaches temperature, Zone 2 can operate on its own.
5. Switched the heating to flow temperature and then back to Room, to reset the 'learning' process.

Of course, yet another variable has kicked in, because the outside temperature has risen by about 10C, so it is now about 13C. So of course, everything is toasty, and  I won't tell if the current setting is any good until we drop back down to frosty nights. 

 

Thanks for your help. Here's hoping things are a bit better for these changes.