Panasonic ASHP for heating and cooling

[Mr Blobby]

Sorry to ask again about my heating system but my M and E consultants are not good listeners. They are proposing two MVHR post-heaters/coolers connected to a Panasonic ASHP.  The UFH to be used for heating only.  I'm OK with the Comfopost post-heater upstairs but they don't want to do UFH cooling downstairs, which seems like a no-brainer to me.  The M and E propsal would have 3 zones, CP1, CP2, and UFH.  This just seems over-complicated, more expensive, and less efficient.

 

Before I go on, I am very grateful to @Dan F who over the weekend has patiently answered my questions and explained his similar setup (with comfopost but a different ASHP vendor) and how mixed circuits can control flow temps on the different "zones".

 

Before I make an ass of myself by telling my M and E people how to do their job, I just want a sanity check here first because the solution below is so much simpler and more effective than my M and E proposal that I think I must be missing something.

 

From the latest manual it looks like Panasonic support 2 mixed circuits out of the box, with each "zone" having a pump, mixing valve and temp sensor.   A single buffer can be set up to be controlled by a temp offset from the heating/cooling circuits flow temps.

 

UK_INSTALLATION_MANUAL_H 2020V11 (002).pdf

 

Here's page 37 from the latest Panasonic manual:

 

 

 

So if I were to replace the radiators above with the comfopost, then I can run UFH and comfopost at different flow temps, say 45,25 heating and 10,18 cooling. 

 

This is far too simple to set up.

Is this the right way to set up my system for UFH and comfopost heating/cooling. 

Have I missed anything? 

Has anyone else set up a Panasonic heat pump in a similar way with mixed circuits for heating cooling, and if so, is it really this simple?

 

[Dan F]

This is exactly what I have set up, apart from the fact that our installer also insisted on installing a (IMO redundant) circulation pump and zone valves.  I don't know exactly what Panasonic supports, but from that snippet it looks like it suppots this setup at least.  I'd also look to see if the Panasonic controller also supports i) use of different (optional) heat curves for different circuits with min/max temps. ii) has dew point monitoring to automatically limit UFH temperature etc.  You may not use these for ComfoPost, but both heat curve and dew point monitoring are useful for UFH

 

On the Comfopost(s), have you looked a the very low heating/cooling output that they provide:  https://www.paulheatrecovery.co.uk/wp-content/uploads/2020/07/ComfoPost-CW6-PAUL.pdf.   I don't know how much glazing/shading you have, but unless you cooling load is very low I would not look at only using comfopost for cooling.  In fact, assuming if you are using UFH cooling downstairs (which I agree is a no-brainer), I would only use Comfopost (vs. fancoils) upstairs if you have comprehensive shading (e.g. automated blinds on most windows). Otherwise the limited output from Comfopost probably just is going to be enough on a hot summers day. 

 

You mentioned your cooling demand is around 3W/m2.  What is your total area?  What cooling power can ComfoPost provide based on flow rates?  Even if Comfopost can meet your cooling load, you still need to consider if you have any rooms without shading which suffer from solar gain and may overheat.  If this is the case, you would need aircon or fancoils in these areas, and you could not depend on Comfopost. PHPP doesn't consider things room-by-room, only the house as a whole.

 

Edited February 14, 2022 by Dan F

[Mr Blobby]

3 hours ago, Dan F said:

Th I'd also look to see if the Panasonic controller also supports i) use of different (optional) heat curves for different circuits with min/max temps.

 

I think it does from what I have read in the manual

 

Quote

ii) has dew point monitoring to automatically limit UFH temperature etc. 

 

I don't think Panasonic support this but I would hope that 18C flow to the UFH would be warm enough to avoid condensation on the manifold umnless RH levels were >95%.

 

Quote

 

You may not use these for ComfoPost, but both heat curve and dew point monitoring are useful for UFH

 

On the Comfopost(s), have you looked a the very low heating/cooling output that they provide:  https://www.paulheatrecovery.co.uk/wp-content/uploads/2020/07/ComfoPost-CW6-PAUL.pdf. 

 

I looked at the conmfo post data, I don't get how the cooling output relies on 100% humidty !

 

 

Quote

You mentioned your cooling demand is around 3W/m2.  What is your total area?  What cooling power can ComfoPost provide based on flow rates?  Even if Comfopost can meet your cooling load, you still need to consider if you have any rooms without shading which suffer from solar gain and may overheat.  If this is the case, you would need aircon or fancoils in these areas, and you could not depend on Comfopost. PHPP doesn't consider things room-by-room, only the house as a whole.

 

 

Coolind demand is ony 500W, but your'e right, there will be parts of the house without blinds that will suffer local overheating.

 

I think I need to speak to my M and E people about using the UFH for cooling. 

 

Edited February 14, 2022 by Mr Blobby

[Dan F]

4 minutes ago, Mr Blobby said:

 

I looked at the conmfo post data, I don't get how the cooling output relies on 100% humidty !

How's that?

[Mr Blobby]

1 hour ago, Dan F said:

How's that?

 

In the Zhender perforance data the ouput air, after being cooled, is at 100% RH, which kind of makes sense I guess because the air has been cooled.  The input air is, if I am reading this correctly,  at 80% RH and water temp input is at 7C.  That seems a little ambitious, I'm not sure the panasonic ASHP can cool below 10C

 

An enthalpy exchanger is relied upon in the technical data to get the extra moisture in the air to transport the heat.  I imagine that otherwise the comfopost heat exchanger wouldn't work so well with dry air.

 

Basically I agree that the comfopost will take some heat out of the air, which will be nice upstairs, but it shouldn't be relied upon as the only means of cooling. 

Edited February 14, 2022 by Mr Blobby

[Dan F]

1 hour ago, Mr Blobby said:

An enthalpy exchanger is relied upon in the technical data to get the extra moisture in the air to transport the heat.  I imagine that otherwise the comfopost heat exchanger wouldn't work so well with dry air.

I don't get this.  ERV has lower output RH from Comfopost simply because RH into Comfopost used is lower I thought.  The total cooling power with HRV is higher isn't it?

 

1 hour ago, Mr Blobby said:

Basically I agree that the comfopost will take some heat out of the air, which will be nice upstairs, but it shouldn't be relied upon as the only means of cooling

We introduced this because of feedback from others with similiar contruction that first-floor can typically be a degree or two higher/lower in hot/cold weather.  But before using Comfopost made doubly sure that fancoils weren't going to be needed and that we weren't going to have localized overheating either.  Our primary strategy to reduce cooling load is Loxone-automated external venetian blinds.

Edited February 14, 2022 by Dan F

[Mr Blobby]

On 14/02/2022 at 19:21, Dan F said:

We introduced this because of feedback from others with similiar contruction that first-floor can typically be a degree or two higher/lower in hot/cold weather.  But before using Comfopost made doubly sure that fancoils weren't going to be needed and that we weren't going to have localized overheating either.  Our primary strategy to reduce cooling load is Loxone-automated external venetian blinds.

 

To revisit this old thread, our primary cooling strategy is also automated blinds so we will rely on the comfopost to do no more than balance out the first floor temperature by just a degree or two.

 

The question is, @Dan F, if you are heating/cooling just the first floor MVHR supply air, then how did you split the MVHR supply to first floor only?  Do you have two MVHR units, one for each floor ?  Or do you have a single MVHR unit with a y-peice in the supply ducting to create two supply branches with a single comfopost on one (the first floor) branch?

 

If the latter, with a split supply from a single MVHR unit, then does the comfopost on one branch create any issues in balancing the ventilation system?

 

[Dan F]

18 hours ago, Mr Blobby said:

The question is, @Dan F, if you are heating/cooling just the first floor MVHR supply air, then how did you split the MVHR supply to first floor only?  Do you have two MVHR units, one for each floor ?  Or do you have a single MVHR unit with a y-peice in the supply ducting to create two supply branches with a single comfopost on one (the first floor) branch?

 

Just one MVHR unit (Zehnder ComfoAir Q600 ERV).  The supply splits for the ground floor and first floor, with the ground floor manifold in the plant room and the first-floor manifold in the loft.  The Comfopost is in the plant room on the first-floor branch.

 

This doesn't present any issues with balancing the system, no.  There will be a small amount of pressure loss through the ComofoPost, but if the system is balanced/commissioned with the Comfopost in place this won't be an issue.

 

I've been proponent of Comfopost for "trimming" first-floor temperature when overheating has already been designed for via overhangs and automated shading, and I still beleive this is a realistic approach in combination with ground floor heating/cooling via UFH.  But, in practice, for some reason the heating/cooling power to Comfopost (measured with a heat meter) doesn't appear to come close to what was in our M&E spec or the manufacturers data-sheet.  I'm not sure what the issue is and need to look into this further, but the delta-t is very low .

Edited May 16, 2022 by Dan F

[Mr Blobby]

1 hour ago, Dan F said:

 

I've been proponent of Comfopost for "trimming" first-floor temperature when overheating has already been designed for via overhangs and automated shading, and I still beleive this is a realistic approach in combination with ground floor heating/cooling via UFH.  But, in practice, for some reason the heating/cooling power to Comfopost (measured with a heat meter) doesn't appear to come close to what was in our M&E spec or the manufacturers data-sheet.  I'm not sure what the issue is and need to look into this further, but the delta-t is very low .

 

Thanks very much @Dan F for replying.  Your setup is pretty much the configuration I am looking to install, split the manifolds with a comfopost upstairs.

Do you have the enthalpy heat exchanger?  That would add some humidity into the air to carry the heat, but I guess you know that already.

I'd be really interested to hear any updates on performance before I commit to this, it's not a cheap option!

[Nickfromwales]

1 hour ago, Dan F said:

 

Just one MVHR unit (Zehnder ComfoAir Q600 ERV).  The supply splits for the ground floor and first floor, with the ground floor manifold in the plant room and the first-floor manifold in the loft.  The Comfopost is in the plant room on the first-floor branch.

 

This doesn't present any issues with balancing the system, no.  There will be a small amount of pressure loss through the ComofoPost, but if the system is balanced/commissioned with the Comfopost in place this won't be an issue.

 

I've been proponent of Comfopost for "trimming" first-floor temperature when overheating has already been designed for via overhangs and automated shading, and I still beleive this is a realistic approach in combination with ground floor heating/cooling via UFH.  But, in practice, for some reason the heating/cooling power to Comfopost (measured with a heat meter) doesn't appear to come close to what was in our M&E spec or the manufacturers data-sheet.  I'm not sure what the issue is and need to look into this further, but the delta-t is very low .

Interesting.

My main thoughts are if the supply air is branched over two floors and the Comfopost is supposed to deliver 'some' heat or cool effect, then surely the main unit would have to go into a semi or full boost flow rate to facilitate that? If the upper floor was the one needing the extra help, then the whole house would receive additional airflow whilst the upper floor was serviced, as trying to shift any kind of heat energy via MVHR would be utterly useless at 'trickle' flow rate? How were you 'sold' this idea?

[Dan F]

4 hours ago, Mr Blobby said:

Do you have the enthalpy heat exchanger?

Yes

 

4 hours ago, Mr Blobby said:

I'd be really interested to hear any updates on performance before I commit to this, it's not a cheap option!

I probably need to call Zehender and see if their technical team can give me any pointers. Without the heat-meter it would be very hard to know what was going on.  I didn't think the Comfopost was particularly expensive, it does means you have to insulate all your first-floor ducting though.

[Dan F]

4 hours ago, Nickfromwales said:

Interesting.

My main thoughts are if the supply air is branched over two floors and the Comfopost is supposed to deliver 'some' heat or cool effect, then surely the main unit would have to go into a semi or full boost flow rate to facilitate that? If the upper floor was the one needing the extra help, then the whole house would receive additional airflow whilst the upper floor was serviced, as trying to shift any kind of heat energy via MVHR would be utterly useless at 'trickle' flow rate? How were you 'sold' this idea?

 

Boosting helps increase the transfer, but transfer will still happen at standard flow rates.  Our first-floor non-boost flow rate is 145m3/h which should equate to 1.5kW/1.8kW cooling/heating.  If this is "useful" or not, will depend on the specific build and your goals.

 

Our whole-house cooling load is just 330W so, along with UFH on the ground floor, 1.5kW is enough to "trim" things on the first-floor on the hottest days of the year.   Our total heating load is around 3.5kW, which can easily be covered with UFH but having some output on the first floor helps avoid befrooms getting chilly on the coldest days of the year.  What we found this winter is that even with MVHR on low at night the air suppy (after heat exchange) is enough to lower bedroom temperature to 17/18C even when ground floor is a nice 21C.

 

This approach was based on feedback from others with MBC builds that were very happy with just ground-floor UFH as primary source or heating/cooling, but commented on the fact that on the hottest/coldest days of the years bedrooms could be a few degress higher/lower than the ground floor which wasn't always ideal.

[Nickfromwales]

4 hours ago, Dan F said:

 

Boosting helps increase the transfer, but transfer will still happen at standard flow rates.  Our first-floor non-boost flow rate is 145m3/h which should equate to 1.5kW/1.8kW cooling/heating.  If this is "useful" or not, will depend on the specific build and your goals.

 

Our whole-house cooling load is just 330W so, along with UFH on the ground floor, 1.5kW is enough to "trim" things on the first-floor on the hottest days of the year.   Our total heating load is around 3.5kW, which can easily be covered with UFH but having some output on the first floor helps avoid befrooms getting chilly on the coldest days of the year.  What we found this winter is that even with MVHR on low at night the air suppy (after heat exchange) is enough to lower bedroom temperature to 17/18C even when ground floor is a nice 21C.

 

This approach was based on feedback from others with MBC builds that were very happy with just ground-floor UFH as primary source or heating/cooling, but commented on the fact that on the hottest/coldest days of the years bedrooms could be a few degress higher/lower than the ground floor which wasn't always ideal.

Thanks, and agreed.

My ethos is prevention vs cure, so where some designers will give you the option to go 'full throttle' to cool a home, I prefer to simply work on preventative methods to stop it getting hot in the first place.

With successful management ( by using controls with a tight hysteresis ) the runaway should never be more than a degree or degree and a half, eg the uplift over the time taken for the controls to recognise that occurrence and for the system components to have kicked in to respond to tackle said unwanted uplift. A correctly designed system, in a relatively relaxed state, should not struggle to bring that back down in a reasonable timeframe without having to become too aggressive in its response. 

To cool a house down that has been left to runaway to, say, 24oC would almost need air con to drag it back down, given that by then the fabric surroundings would have had time to achieve that new ambient and would be holding on to that heat energy for a much longer / extended period of time, ergo the 'response' would need to dialled up then from a whisper to a shout.

Each dwelling / instance is different, so I review each case uniquely, and on its own merit, in my day to day business. Comments here, however, do sometimes generalise a little, but it is a widely differing crowd on here with varying dwellings / installed systems / wants / needs, so we do our best to cater for all.  

Edited May 16, 2022 by Nickfromwales
Bit of added clarity. It's late, I'm tired.

[Nickfromwales]

I suppose I should add that I found myself, a few days back, wondering about exactly how much wasted ( diverted ) energy would be spent maintaining a "passive" dwelling that had not been designed with some degree of management for unwanted / nuisance solar. I believe it would be significant, eg a shameful waste. Even having excess PV going into that endeavour seems a little grotesque from a design PoV, and it should, instead, be going into other strategic energy storage for self consumption. 

"Fabric first" as always, wins the day.

[Mr Blobby]

On 17/05/2022 at 00:30, Nickfromwales said:

I suppose I should add that I found myself, a few days back, wondering about exactly how much wasted ( diverted ) energy would be spent maintaining a "passive" dwelling that had not been designed with some degree of management for unwanted / nuisance solar. I believe it would be significant, eg a shameful waste. Even having excess PV going into that endeavour seems a little grotesque from a design PoV, and it should, instead, be going into other strategic energy storage for self consumption. 

"Fabric first" as always, wins the day.

 

Would a masonry construction with additinal mass in the walls (and hollowcore floor) help to balance the heat distribution between floors and provide some decrement delay?

If so then perhaps I need not worry too much about the comfopost for upstairs temps. 

 

Edited May 18, 2022 by Mr Blobby

[Dan F]

36 minutes ago, Mr Blobby said:

Would a masonry construction with additinal mass in the walls (and hollowcore floor) help to balance the heat distribution between floors and provide some decrement delay

I'm not sure.  But, just thinking out loud:

- The masonary construction may help keep first-floor day/night temperature a bit more consistent than with a timber-frame.  We saw a difference of 1C between 6am and 7pm in January in north-facing bedrooms, which reduced to 0.5C in May.  (No Comfopost in use)

- But, I don't think it's necessarily going to help ensure that the first-floor isn't slightly warmer/cooler than the ground floor if your primary heat source is ground-floor UFH.

- With the additional mass in the walls I would assume that it's even more important to keep first-floor temperature in check, as it will be harder to cool down via ventilation/comfopost if you need to cool the mass too.

Edited May 18, 2022 by Dan F
spelling

[Nickfromwales]

35 minutes ago, Mr Blobby said:

 

Would a masonry construction with additinal mass in the walls (and hollowcore floor) help to balance the heat distribution between floors and provide some decrement delay?

If so then perhaps I need not worry too much about the comfopost for upstairs temps. 

 

Motorised Velux / roof lights with automation are a great and cheap option for purge, or for overheat pre-mitigation. 
I would deffo fit post heating / cooling in anything remotely well built. 
My house is shart, and already beginning to become uncomfortable. Air con going in this year ( burning off excess PV ).

The thermal time constant plus the heat energy captive in the interior materials / inner fabric will allow a long swing from temp A to temp B, but probably too long for the upstairs rooms with adverse North > South solar inertia. Depends a lot on glazing as well. Solar reflective coatings work bloody well, so consider that for your strategies. 

[Mr Blobby]

 

2 hours ago, Nickfromwales said:

Motorised Velux / roof lights with automation are a great and cheap option for purge, or for overheat pre-mitigation. 

 

We will have a motorised velux at the highest point (my architect is mad keen on velux for purge cooling) 

External blinds are already designed in.

 

Except for one small bedroom window which I see as a potential issue for overheating....

 

2 hours ago, Nickfromwales said:

 Solar reflective coatings work bloody well, so consider that for your strategies. 

 

... so a coating for the problem window.  I have asked my various advisers about solar coatings but they just look at me like I'm from planet zog.  Any links to threads / products?

 

2 hours ago, Nickfromwales said:

I would deffo fit post heating / cooling in anything remotely well built.

 

Interesting.  That's it decided then, the comfopost stays in the upstairs duct with mixed circuits.

 

 

Edited May 18, 2022 by Mr Blobby

[joth]

1 hour ago, Mr Blobby said:

3 hours ago, Nickfromwales said:

Motorised Velux / roof lights with automation are a great and cheap option for purge, or for overheat pre-mitigation. 

 

We will have a motorised velux at the highest point (my architect is mad keen on velux for purge cooling) 

 

We have this (actually, a Fakro PH window) at the highest point and it works great for cooling. Overnight it's much more effective than the ASHP (via UFH or FCU). Couple notes:

- we also have an opening  rooflight in the ground-floor extension flat roof, opening both together is most effective to create a through-draft

- the open plan area, inc hallway stairwell and landing, all cool down fabulously. However, the bedrooms tend not to benefit much as we keep doors closed (no cats in bedroom policy!) which means I'm still working on designing in some extra mechanical ventilation to push cold air around into those rooms more effectively. (The MVHR, even on bypass and boost in winter, isn't enough to compensate for 2 human bodies in the room)

- I really appreciate the home automation for keeping track of indoor and outdoor temperature, heating and mvhr status, and current rain status, and automating the skylight open position accordingly. 

- originally I just had it "open" or "close" but it's a bit slow to move between end-stops (30secs?) and a bit noisy, so when at the threshold temperature it would clatter all night opening and closing every 15 mins. so now I set the skylight angle proportionally to the amount the house is over target temperature, which very nicely modulates the window down to "closed" as the house cools down, and gradually opens it up as it warms back up.

 

 

 

[Dan F]

On 16/05/2022 at 19:58, Dan F said:

Our first-floor non-boost flow rate is 145m3/h which should equate to 1.5kW/1.8kW cooling/heating.

 

I took another look at the datasheet and the quoted cooling power is for 28C air in.  So, if MVHR is actually providing air at closer to 21C, then total cooling power is going to be closer to 1kW (of which 0.3kW is sensible power which matches what I see on the heat meter).   So, it's less than I expected when Comfopost was added to the design, but still 3 times our total cooling demand and is on top of UFH.

 

On 16/05/2022 at 13:33, Mr Blobby said:

That would add some humidity into the air to carry the heat, but I guess you know that already.

 

The datasheet actually shows 25% more total cooling output for HRV vs. ERV.  The assumed humidy for HRV is 80%, where as the assumed humidity for ERV is 55%. (this matches humidy I see on ours)

 

 

 

[NCXo82ike]

This is a really helpful thread and hoping I can learn from the experiences of people on here. Planning an extensive refurb/rebuild of a place with insulation, ASHP, and MVHR. In addition to UFH (certainly on the ground floor, likely upstairs), I'm keen to install a Comfopost, primarily for a little cooling on the hottest days. 

 

It's also great to see that you can have different flow temperatures between the Comfopost and UFH, since I was concerned I'd be running the Comfopost at minimal output to avoid dew point in the UFH system.

 

This may be a silly question, but is there any reason why the Comfopost would require a Zehnder MVHR?

Or could the supply from another MVHR e.g. Vent-Axia be run too the Comfopost, through a Comfowell, and then distributed?

[NCXo82ike]

On 14/02/2022 at 11:19, Mr Blobby said:

 

 

 

 

 

Sorry if I'm just stating something obvious here- I'm quite new to this. 

Just wondering if in the heating setup you've outlined with a 45,25 supply to the comfopost and UFH respectively, are you not heating the whole buffer tank to a greater temperature than your UFH would need and then blending the temperature down, dropping your COP on the whole heating setup for the sake of the additional comfopost heat?

 

I guess the reverse is also true for cooling, but in my mind the comfopost would do a greater proportion of cooling that of heating. I've not done the sums yet and that would naturally vary between installations. 

[Mr Blobby]

Unlike @Dan F I haven't implemented any of this yet, but this configuration comes out of the panasonic box and is what we plan to do.

 

42 minutes ago, NCXo82ike said:

Sorry if I'm just stating something obvious here- I'm quite new to this. 

Just wondering if in the heating setup you've outlined with a 45,25 supply to the comfopost and UFH respectively, are you not heating the whole buffer tank to a greater temperature than your UFH would need and then blending the temperature down, dropping your COP on the whole heating setup for the sake of the additional comfopost heat?

 

Basically yes, but because the MVHR air flow rates are so low and the capacity of the air to transfer the heat from the heat exchanger quite low, then in realoty the temperature difference will likely be smaller, more like 35/25 heat, 15/20 cooling.  I think anything more will result in a very hot or very cold heat exchanger in the comfopost that the air supply in the ducts cannot transfer quickly enough.  At 35 heat and 15 cooling the COP should remain > 3.  For the cooling our solar PV will be powering it all anyway so there is no energy cost.

 

42 minutes ago, NCXo82ike said:

 

I guess the reverse is also true for cooling, but in my mind the comfopost would do a greater proportion of cooling that of heating. I've not done the sums yet and that would naturally vary between installations. 

 

What I am hoping to acheive from the mixed circuits is the ability to tinker with different temps to see what suits us best.  In reality I expect the comfopost to make a small difference upstairs where the UFH will do the heavy lifting in the more important downstairs.

 

1 hour ago, NCXo82ike said:

This may be a silly question, but is there any reason why the Comfopost would require a Zehnder MVHR?

Or could the supply from another MVHR e.g. Vent-Axia be run too the Comfopost, through a Comfowell, and then distributed?

 

Good question.  I don't know.

I do know the Zhender units are not cheap and other MVHR units with heat exchangers are available.