Heat Pump - Floor vs Wall

Forums › Home Workshop DIY › Heat Pump - Floor vs Wall - R32 vs R410A

Delphinus

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#293531 28-Jan-2022 11:58

I have a 32sqm office at the far end of my house. 3 external walls (insulated) and plenty of double glazed windows. I'm down south so only really care about heating, not cooling.

House is pretty warm in general, so once at temperature shouldn't need more than 1-2kW of heating to maintain it. Got a couple of quotes and all suggestions are around the 5kW mark.

Various readings on the internet suggest a floor console unit is better for heating. High wall units need to push warm air down, which results in more energy, more breeze/noise etc. Is this accurate?

Also suggestions are that R410A is being phased out for R32. Only the Daikin floor units use R410A - should I avoid?

Quotes have come back:

Floor Console: MITSUBISHI MFZ-KW50G

Heating kW: 5.8
COP: 3.79
Minimum: 1.2 kW
Gas: R32
Price: $4528

Floor Console: Daikin FVXS45R

Heating kW: 5.56
COP: 3.83
Minimum: 1.2 kW
Gas: R410A
Price: $3390 - $1100 cheaper than the Mitsi!

High Wall: MITSUBISHI MSZ-AP50VGKD

Heating kW: 6
COP: 3.7
Minimum: 1.4 kW
Gas: R32
Price: $3550

High Wall: Daikin FTXM46U

Heating kW: 5.4
COP: 3.89
Minimum: 0.9 kW
Price: $2830

All seem to have pretty similar COP's etc. Just need to decide between floor vs wall, and do I pay extra for the R32 gas if going floor.

Thoughts and suggestions?

timmmay

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#2857640 28-Jan-2022 12:08

I find that most places seem to over-spec heat pumps. Our ducted unit is 10kw and we could probably have gotten by with 6-7kw, and with ducted having a low minimum output is important. For high walls doing heating it's less important, but means less cycling on and off.

My (limited) experience after owning four heat pumps is R32 based heat pumps louder than the older ones, though I don't know if this is a general rule or just what I've found. The R32 Daikin 10kw is a lot louder than the older 9kw Fujitsu it replaced and the 7kw Daikin we still have. The Panasonic R32 was so loud we refused to accept it and had it removed.

A 5x6m or meter well insulated single room wouldn't need 5kw I'd have thought. How are you heating it now? If a single fan heater is doing the job now then you might just step up from 2kw to maybe 3-4kw. You might choose one from a hardware store and get a third party installer, but make sure you look at features and especially noise.

Floor consoles in theory should be more effective for heating. How much difference it makes I don't know as I've never had one. Check the noise specs as well.

Delphinus

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#2857708 28-Jan-2022 13:10

I thought the spec was a bit overkill as well, but it's the same value that comes out of the healthy homes calculator thing I did myself out of interest. Taking into account the windows and insulation etc.

I've been using a single 2kw convection heater to date, sometimes boosted by an additional 2kW oil column heater (especially during hour of power). They get it pretty toasty if the door to the rest of the house is shut, but I don't mind a bit extra to push down to the rest of the house.

Far end of the house is heated by a fireplace.

Noise levels:

Mitsi: 35 (low) 29 (quiet)

Daikin: 32 (silent)

I have considered just keeping the convection heater, but I do like the idea of something with a bit more accurate temperature control that can be safely left going, that is also more efficient.

Maybe I should go for the Daikin, it's loads cheaper (2-3 years worth of power) and if the R410 is actually better (quieter)..... I assume you mean the indoor unit is loud?

But then the Mitsubishi has a lower minimum (1.2kW vs 1.7) which would be plenty for keeping the place warm.

I should have done better experiments last winter to see what ACTUAL heating kW levels are required.

insane

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#2857710 28-Jan-2022 13:20

I have a 3.5Kw Mitsi doing my lounge, dining and kitchen (because I took a wall down) which would be 45smq and open to the hallway, north facing getting full sun - right in the corner in the worst possible place. It only struggles when we have the 90cm Oven going - otherwise it's probably a little under spec'd if you want to go from warm to cold, or cold to warm quickly, but if you're happy for it to take 30 minutes or so before it ramps down then it's adequate. I've got 6 heat pumps and it hasn't bothered me to the point I'd be needing to upgrade it. If it dies I'll get 4-5KW unit and place it more centrally.

It's R32 for what it's worth and far more quiet than my other 5 Panasonic units. Inside unit is slightly quieter than my other standalone Panasonic 3.5Kw unit, and the outside unit is a lot quieter.

Delphinus

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#2857711 28-Jan-2022 13:30

insane:

I've got 6 heat pumps

Thanks for that info. Are they wall or floor units?

insane

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#2857718 28-Jan-2022 13:54

Delphinus:

insane:

I've got 6 heat pumps

Thanks for that info. Are they wall or floor units?

All highwall units. Outside units are all away on the far side of the house so I don't hear them under normal operation.

My master bedroom is 20sqm and has a 2KW indoor unit. That's probably a better comparison than my first :)

Bedrooms are all part of a single multisplit(x4) 7.1 KW compressor, with the smaller rooms only having 1.6KW indoor units, and even those feel like overkill. 1970s but well insulated house. Floor, walls, ceiling etc

timmmay

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#2857755 28-Jan-2022 15:00

I reckon well insulated bedrooms are ok with 1kw of heating or cooling. Our 1kw oil heater before we got the ducted system was only on 1/4 of the time, so 250w = ie a really bright light bulb but that would keep you awake ;)

In winter you may want to raise the temp 25 degrees from say -5 to 20. In summer you only want to drop it by 3-5 degrees so cooling capacity less important.

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insane

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#2857761 28-Jan-2022 15:12

That's a good point @Timmmay - I just assume everyone's in Auckland and has the same outside temperatures. I'm also at the top-ish of a hill and don't get much mist in the morning. If I were in a valley I might need extra grunt for heating.

For COP, they are different for heating and cooling, so worth looking at the one that matters most. Also the minimal output that was mentioned is important - if it's quite large you'll get bursts of hot and cold depending what it's doing, and not the gentle exact temperature air as you may expect (which I guess is a good reason for not over spec'ing the unit too much)

Delphinus

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#2857777 28-Jan-2022 15:30

insane:

For COP, they are different for heating and cooling, so worth looking at the one that matters most. Also the minimal output that was mentioned is important - if it's quite large you'll get bursts of hot and cold depending what it's doing, and not the gentle exact temperature air as you may expect (which I guess is a good reason for not over spec'ing the unit too much)

Yeah I've been using just heating figures for all my comparisons.

Good point about minimal output. Typo above that I can't seem to edit, the Daikin minimum is 1.7kW (even if you drop to a smaller size eg the RXS35 - Need to go to the RSX25 to get it down to 1.3).

Which might then push me to the Mitsi which can go down to 1.2, which I think feels about right for once the room is warm. Just need to negotiate a better price on it.

Kickinbac

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#2857985 28-Jan-2022 22:17

The transition to R32 is mainly environmental.
R32 has a lower Global Warming Potential (GWP) than R410A. R32 is also slightly more efficient. R32 GWP is 677 and R410A is 2088. (1gm R410A is equivalent to 2090gm CO2)
But R32 is flammable, not really a problem with the small charge of a split system.
ETS levies aka carbon tax means R410A more expensive than R32.

fe31nz

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#2858022 28-Jan-2022 23:52

We replaced an old failed Panasonic in our kitchen with a new R32 model that was the direct replacement. It is a big unit, 7.? kW of heating, and heats the room reasonably fast. Panasonics are are not known for their quietness, but it is fine once the room reaches the setpoint temperature and the fan is set to "auto". There was no discernible difference in noise from the older R410A unit, so I am pretty sure that the refrigerant type has no influence on the noise levels. The noise comes from the fans, not the movement of the refrigerant. It is more efficient and our power bills dropped for a month or two (until the next electricity price increase came along). I am much happier with how the Panasonic works compared to the Mitsubishi Electric units we have in four other rooms. The Mitsubishi remotes do not work nearly as well - you can not set anything without having the unit turned on. The Panasonic allows you to change the settings at any time so you can set things up for when it next comes on without having to turn it on first. We got the Mitsubishis as two of them were going into bedrooms and they were recommended as the quietest units available at the time. That bit is good - they do not wake you up when they need to turn on and off during the night.

insane

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#2858025 29-Jan-2022 00:10

With the Panasonic's, I'm not sure whether it's a design flaw, but the scroll type fan always seems to have a wobble at low speed, no matter what model.

As mentioned above the Auto setting is also somehow the quietest, even quieter I find than the 'quiet' mode as the fans imbalance creates an annoying sound on each rotation that's louder than the additional sound of air on the lowest setting or auto.

And so far it's 6/6 for me, and that's across three different models too across two properties.

Panasonic does have half degree increments which is nice, when they choose to obey the thermostat.

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AACTech

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#2860620 2-Feb-2022 12:54

Note: This reply is assuming a modern fully insulated house.

Definitely floor installation if you have the free wall space. The science is very simple. Hot air rises cold air drops as more dense. So idealy you would want the unit near where you sit in your office. Also bear in mind that placing the unit under or near the window will cut draughts as the cold air from the window, even double glazed, will be drawn to the heat pump and be warmed also most instantly. If the heat pump is installed far from the window the cold air will be pulled between them causing a cold draught across the floor.