Outside heat pump element in the inside (well, so to speak): should this work?

[Garald]

  On 04/12/2022 at 16:12, SteamyTea said:

Just put in one, larger shower, large enough to squeeze two bodies into.

Been years since I have had someone scrub my back, one disadvantage of living alone.

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Right, I'll have a large shower, but recall that my parents will come for long visit, and the home office in the ground floor will become their bedsit (with shower and kitchenette) then.

 

[SteamyTea]

  On 04/12/2022 at 16:19, Garald said:

but recall that my parents will come for long visit,

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I put mine up in a cheap hotel.

That stopped them visiting.

[Garald]

  On 04/12/2022 at 16:21, SteamyTea said:

I put mine up in a cheap hotel.

That stopped them visiting.

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No, you see, I *want* them visiting. Plus, a cheap hotel near Paris? That exists?

[SteamyTea]

  On 04/12/2022 at 16:25, Garald said:

Plus, a cheap hotel near Paris? That exists?

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Stayed in a place on the left bank, no A/C, was 34°C at 2 AM.  That was cheap.

But got to see the end of Le Tour nice and early.  Still got my Le Tour cap.  Pedro Delgardo won, well his chemists won really.

[Garald]

  On 04/12/2022 at 16:36, SteamyTea said:

Stayed in a place on the left bank, no A/C, was 34°C at 2 AM.  That was cheap.

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That would no longer be cheap. I know of a place there that's quite all right and wouldn't break my budget, but it was full this time around.

[HughF]

  On 04/12/2022 at 05:42, Garald said:

All right, here is my sheet. Tell me if I have done something wrong.

 

I am getting:

[Heat loss if known kW                  6,6 - no idea where this came from; what is this?]

Heat loss calculator figure kW     8,5kWh

Heating flow temperature C         45

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)

 

Then I get: "your heat pump is expected to provide 69% of your hot water. You will need additional heating to provide 31% of your hot water."

 

Should I take this seriously? I thought Hitachi Yutakis and Panasonic Compact Aquareas had big, nice water tanks. What is the limitation here?

 

(Also, what about cooling? Yutaki, Panasonic, etc. are reversible.)

 

309760954_Myheatinglossworksheet.xlsx 3.16 MB · 2 downloads

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The 6.6 is the figure for my heat loss that I copied over into that cell from the heat loss sheet. If you replace that with your 8.5kW value, the costings should make sense.

[Garald]

  On 04/12/2022 at 09:41, SteamyTea said:

The legionella cycle is going to take up that difference I would have thought.

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The difference between what and what? Should I set my unit to heat water to 50C or more for a while, once every couple of days?

 

At any rate, how should I eyeball how much power I need, given that my heating needs would apparently be covered by 6kW? Would a total of 7kW be enough? 8kW?

In the other direction: would 10kW be already grossly inefficient? (Some brands have nothing between 7kW and 10kW, for example.)

[HughF]

  On 06/12/2022 at 21:37, Garald said:

 

The difference between what and what? Should I set my unit to heat water to 50C or more for a while, once every couple of days?

 

At any rate, how should I eyeball how much power I need, given that my heating needs would apparently be covered by 6kW? Would a total of 7kW be enough? 8kW?

In the other direction: would 10kW be already grossly inefficient? (Some brands have nothing between 7kW and 10kW, for example.)

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There is something amiss in your spreadsheet data because the heat load graph isn’t drawing properly, and the DHW side isn’t working correctly, hence why you are only able to satisfy 69% of your hot water requirement.

 

The spreadsheet I uploaded was populated with all the values for my house, so the cylinder size was set to as closely match my 150ltr slimline as I could find.

 

You need to choose a machine that has enough overhead to recover the required heat loss from the building in the period that it is not doing your hot water cycle. But at the same time modulate low enough so that it isn’t short cycling too much.

[Garald]

  On 07/12/2022 at 07:20, HughF said:

There is something amiss in your spreadsheet data because the heat load graph isn’t drawing properly, and the DHW side isn’t working correctly, hence why you are only able to satisfy 69% of your hot water requirement.

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Thanks for spotting that. I just went over it, and couldn't find the mistake. Do you think it is somewhere in the cells feeding into the DHW calculation? Which ones are those?

[HughF]

  On 07/12/2022 at 10:04, Garald said:

Thanks for spotting that. I just went over it, and couldn't find the mistake. Do you think it is somewhere in the cells feeding into the DHW calculation? Which ones are those?

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I’m flat out at work at the moment but if I get half an hour this evening, I’ll try and figure out what data in what cell is causing the issue.

[Garald]

  On 07/12/2022 at 10:30, HughF said:

I’m flat out at work at the moment but if I get half an hour this evening, I’ll try and figure out what data in what cell is causing the issue.

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Thanks in advance!

[Garald]

Do you think it's essentially correct? I have no clue as to how debug a spreadsheet.

[HughF]

  On 09/12/2022 at 21:52, Garald said:

Do you think it's essentially correct? I have no clue as to how debug a spreadsheet.

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Yes. I had a quick look and couldn’t see why the graph was not drawing. I changed the occupancy figures for the hot water tank to something more reasonable (250ltr, 4 persons) and that fixed the dhw requirement being low.

 

I would cross check the heat loss with heatpunk (I know it’s more work, but you need to get this right) and then move on to how you’re going to find a machine that will work for you in your physical location. I know you’re looking into the options for that.

[Garald]

  On 10/12/2022 at 07:54, HughF said:

Yes. I had a quick look and couldn’t see why the graph was not drawing. I changed the occupancy figures for the hot water tank to something more reasonable (250ltr, 4 persons) and that fixed the dhw requirement being low.

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Thank you. Wait, I thought I had input 4 persons (since that's the realistic maximum)? I don't see where there is a cell where more was stated. (Perhaps that will give us the key to the issue.)

 

  On 10/12/2022 at 07:54, HughF said:

 

I would cross check the heat loss with heatpunk (I know it’s more work, but you need to get this right) and then move on to how you’re going to find a machine that will work for you in your physical location. I know you’re looking into the options for that.

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Sure, and the installers will come up with their own calculations. One of them already did something back-of-the-envelope and was of the opinion that a 7kW Saunier-Duval would be best. That would be great, but it surprises me a little, given that I am getting a 6kW heat loss (greater on cold waves, obvs), there's DHW, and the "7" in "7kW Saunier-Duval" is optimistic (at all temperatures, and in particular at the intended temperature of 45 C). I'll make sure to insulate as well as possible the door opening into the lower level of that small but damaging uninsulated stairwell leading to the attic.

[Garald]

  On 10/12/2022 at 07:54, HughF said:

I would cross check the heat loss with heatpunk (I know it’s more work, but you need to get this right) and then move on to how you’re going to find a machine that will work for you in your physical location. I know you’re looking into the options for that.

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I am getting very different results from Heatpunk, as in, 50% higher in every room. What can be the reason?

 

Example - take the library(/music room/everything else):

9.2m by 3.9m

average ceiling height: 2.8m

One of the long walls and one of the short walls are internal;

the other ones are insulated up to U=0.23.

Total window area = 7m^2,  iwith a value of U=1.4, say (new, high-grade double-glazing with PVC frame)

0,6 air changes per hour

desired temperature: 21C

Outside design temperature: -1.8C

Heated rooms above and below (this is a first floor)

 

Then, from the spreadsheet, I get a heat loss of 1034,2 W, whereas Heatpunk gives me a heat loss of 1533W.

What gives? Which result is right?

 

----

(BTW, the default choices for windows and the like in Heatpunk are starting to show their age - but that is another matter.)

 

 

[Garald]

PS - the last five hours of my life, which should have been devoted to sleep, where spent on this instead. I am not made for GUIs.

PPS. I can't ask Heatpunk's default values for things such as ventilation frequency, heat and ceiling insulation, etc. Perhaps the problem resides somewhere there?

Edited December 11, 2022 by Garald

[HughF]

  On 11/12/2022 at 04:13, Garald said:

PS - the last five hours of my life, which should have been devoted to sleep, where spent on this instead. I am not made for GUIs.

PPS. I can't ask Heatpunk's default values for things such as ventilation frequency, heat and ceiling insulation, etc. Perhaps the problem resides somewhere there?

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You should be able to change the ceiling insulation level….

 

As for the other questions, I can’t answer. It’s just important that you’ve run the numbers through both systems. There are hundreds of systems installed off the back of the Freedom spreadsheet, and there are no doubt hundreds of systems installed by Midsummer Wholesale off the back of Heatpunk calculations.

[Garald]

But the room I mentioned is on the first floor, so the floor and ceiling figures can't matter. How can I be getting two figures, one of them larger by 50%?

[Garald]

Let me do this by hand, for the room I just described.

 

Outside wall area (U=0.23 W/m^2K): (9.2+3.9)*2.8 = 36.68 m^2

Window area (U=1.4 W/m^2 K; this is the value from the spreadsheet - mine are allegedly a tad better): 7 m^2

Outside wall area minus windows: 36.68 - 7 = 29.68 m^2

Design temperature = -1.8 C, or -2.1C correcting for altitude, aiming to be at 21 C, we have Delta = 23.1

So, heat loss through the envelope:

(29.68*0.23 + 7*1.4)*22.8 = 384.0... W, of which 157,68...W are through the walls and 226.38 are through the windows.

Now I'm already getting a bit confused, since the spreadsheet gives me 263W through the walls and 251W through the windows.

Is the spreadsheet adding some necessary fudge factors, or am I making a mistake?

 

Ventilation losses:

Volume = 9.2*3.9*2.8 =  100.4... m^3

0.6 air changes per hour (this is the medium setting in my PIV)

So, heat loss through ventilation:

100.4*0.6*23.1*0.33 = 459.2... W,

which does correspond almost exactly to the value given by the spreadsheet (458W)

 

Then the spreadsheet adds 60W for heat loss through the floor, which seems reasonable (I'll probably have to give myself more margin in reality: the GP downstairs presumably turns down his heating when he's not there).

 

At any rate, while I can't trust myself yet (as I said, the spreadsheet gives me a value for loss through the envelope different from the one I'm getting), the spreadsheet would seem to be in the right ballpark, and Heatpunk is not.

 

Question: are there some parameters in Heatpunk that I am setting incorrectly, or that are set to default values that aren't right? (I'm a bit frustrated by how non-transparent it is.) That seems to be the most likely explanation. Otherwise, how to account for the difference?

 

 

[Garald]

Perhaps it's that I (truthfully) answered that the house is from 1930 when queried - now Heatpunk may be internally assuming some fantasy values. Of course I would like to see what happens if I insert the fiction that the house is from 2010 (... which is roughly the date of the last renovation before mine), but, try as I may, I do not see how to do that! 

[SteamyTea]

Have you taken the air films and PSI values into account?

 

Air Film

 

 

PSI (thermal bridges) could soon add up on a complicated shape.

 

 

 

SAP-2009-Appendix-K.pdfFetching info...

[Garald]

  On 11/12/2022 at 15:44, SteamyTea said:

Have you taken the air films and PSI values into account?

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I'm taking the air inside the insulation into account (without any excessive optimism) when computing the total R value (the R value of the insulation material alone is 3.8). 

 

Thermal bridges: no, and I entirely believe that the spreadsheet may be including a fudge factor for safety, and that it's right in doing so.

That may explain why it gives a different value for heat envelope loss than I do.

 

What still remains a mystery to me is how Heatpunk gives such high values.

 

 

[SteamyTea]

  On 11/12/2022 at 16:24, Garald said:

at still remains a mystery to me is how Heatpunk gives such high values.

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To oversell a heat pump maybe.

[Garald]

  On 11/12/2022 at 16:32, SteamyTea said:

To oversell a heat pump maybe.

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But third parties here use it as a tool. Most likely there are simply internal parameters that aren't set right (for this project), and now have to be reset (but how?). It's annoying, as it is rather opaque.

[SteamyTea]

  On 11/12/2022 at 18:40, Garald said:

It's annoying, as it is rather opaque.

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That is the secret of propriety software.

Why I start from first principles and make up my own spreadsheets.

They are only glorified graph paper that we used at primary school to do our sums on.

Edited December 11, 2022 by SteamyTea