Yutaki S Combi vs Panasonic Aquarea Compact All-in-One: questions

[Garald]

Hi,

 

I think by now everybody knows about my recently narrowly averted heat-pump catastrophe. Suffice it to say that I'll be doing my own library research from now on, and will try to find a specialist (hopefully a third party, rather than an installer eager to sell a product and his services, even in ways that make no sense) to check on what I have in mind.

 

I am looking at two heat pumps from companies that my architect and I have looked at in the past - Panasonic Aquarea (High Performance All in One Compact J Generation 1 Phase · R32; 9kW)

and Yutaki S Combi (8kW and 11kW). (This seems to be the right range; the installer who shall not be named convinced my architect that my newly well-insulated triplex apartment (ca. 120m² on which one can stand, plus inhabitable attic space and a big stairwell) that 11kW were needed - I still have to do the heating calculations myself, but common opinion here seems to be that less than 11kW would be fine.)

 

They seem to be both high-quality products. Both of them are apparently compatible with the Aquarea PIV system we are installing (which will provide cooling in summer and supplementary heating in winter). Their inside units are of about the same size (the one by Yutaki is a bit taller, and as a result stores 220L rather than 185L of water), their SCOPs are roughly in the same range (those of Panasonic tend to be slightly better)... The main difference I can see is that the external unit of the Yutaki is quieter by about 5dB. If there are massive differences, I am not noticing them. (Is there anything I'm missing?)

 

One thing that mystifies me is why the Yutaki S 8kW seems to perform worse than the Yutaki S 11kW: it has perceptibly worse COPs and SCOPs, its EER is also a bit lower - and, for some reason, while the sound power of its outside unit is the same (64dB), the sound pressure at 1m is greater for 8kW vs 11kW (54dB vs 49dB).

 

What is the reason? And, should the calculations show that 8kW are enough - will this be a reason to consider getting the 11kW model after all?

 

(The external unit of the 11kW Yutaki model is much taller than that of the 8kW model (or the 9kW Aquarea), since it has two fans instead of one.)

[ReedRichards]

5 hours ago, Garald said:

I still have to do the heating calculations myself, but common opinion here seems to be that less than 11kW would be fine.

 

 

I strongly suspect that the more common opinion is that you should do the heating calculations.  You will doubtless be encouraged to do those yourself but there's no shame if you choose to employ an expert to do them for you.  You don't want to end up with a heat pump that is smaller than you need and there are disadvantages to getting one that is significantly larger also.

[Garald]

I just did the heating calculations (hopefully without making any major mistakes). I seem to be getting that I need at least 8.5kWh. The eyeballing estimate turned out to be in the right ballpark. (The fact that there are two spots we have not been able to insulate (attic sidewalls and the small corner staircase to the attic) is what brings me over 8kWh.)

 

Does that mean:
- 8kW would not be enough

- 9kW would be enough

- 11kW would be... an acceptable overcalculation? Notice that the Yutaki comes only as a 8kW unit (maximum performance: 11kW) or as a 11kW unit (maximum performance: 15.2 kW)

?

1623540008_Myheatinglossworksheet.xlsx

[JohnMo]

Looking at the calc inputs for the rooms, your number of air changes per hours looks very high.  43% impact on heat loss.

 

A property with 7 ach @ 50 pa and with wind loads applied would have an effective air change rate of 0.5.  So 0.5 or better would be more appropriate.

 

If you don't have MVHR the efficiency of that box needs to be set to zero.

 

Correcting the above will half your ventilation heat loss.

 

 

[Garald]

You are of course right - these were the default settings on the spreadsheet -  I see in the actual settings of the MVHR we will install that there are three levels (0.35, 0.5 and 0.6). Let me choose 0.6 to be on the safe side. (There's also a turbo setting of 0.75 or so for a short while - is it when the friend you invited over turns out to have had an active case of COVID? And you burnt the food?)

 

I'll have VMI, which does have heat recovery, but I have no clue as to its sufficiency. I've left it at the 66% setting. How do I find out the right value? It's not obvious from a quick search (perhaps because I don't know what I am looking for).

 

The result is now:

Heat loss calculator figure kW    5,2

1344846824_Haraldsheatlosscalculation-corrected.xlsx

Edited December 4, 2022 by Garald

[JohnMo]

So your heat pump needs to be no bigger than 8kW, with a small buffer. 11 kW would be huge.

[Garald]

8 hours ago, JohnMo said:

So your heat pump needs to be no bigger than 8kW, with a small buffer. 11 kW would be huge.

A "buffer" in this case would be...? The difference between maximal capacity (11kW for the 8kW Yutaki) and nominal capacity (that would be, well 8kW for the 8kW Yutaki model, obviously)? Would that be enough for the scenario of two people showering and another taking a nice hot bath, when it's cold outside?

 

Also, what about cooling? I don't imagine the VMI can really be short of cool water,  but, if I ever put two fan coil units total, will I regret getting only 8kW during the summer?

[Garald]

Another thing I don't know how to take into account is that a 11kW Yutaki is in principle more efficient and a little quieter than a 8kW one, apparently. Or is it the case that a 11kW Yutaki would nevertheless be less efficient in practice  *at the task of heating a place that requires only 8kW*?

 

https://www.hitachiclimat.fr/documentations/telecharger/brochure-yutaki-2-0