Advice wanted re Heat Pumps

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#2022791 26-May-2018 09:45

hi guys,

advice on heat pump wanted :)

we are in Auckland, never had heat pump, always lived in warm apartment. Recently moved to 3 store townhouse and for past 2 nights its been little cold :( 16-17 degs first level with garage and my office, 17-19 degs second level (lounge + open kitchen), and 18-20 degs top level (2 bedrooms).

I was thinking to install heat pump in the lounge ~40 sq m. used couple calculators and looks like 5kW heat pump should be enough for our lounge and heat will travel 2 bedrooms. is this a good deal? https://www.kiwiheatpump.co.nz/product/fujitsu-astg14lucb-54kw-heat-pump-installed-p-44/

there's ceiling and walls insulation, but no double glazing.

helping others at evgenyk.nz

Jase2985

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#2022922 26-May-2018 11:56

i would go bigger, maybe a 7kw unit

better to over spec it slightly than under spec it and have to struggling

timmmay

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#2022997 26-May-2018 14:15

kobiak:

hi guys,

advice on heat pump wanted :)

we are in Auckland, never had heat pump, always lived in warm apartment. Recently moved to 3 store townhouse and for past 2 nights its been little cold :( 16-17 degs first level with garage and my office, 17-19 degs second level (lounge + open kitchen), and 18-20 degs top level (2 bedrooms).

I was thinking to install heat pump in the lounge ~40 sq m. used couple calculators and looks like 5kW heat pump should be enough for our lounge and heat will travel 2 bedrooms. is this a good deal? https://www.kiwiheatpump.co.nz/product/fujitsu-astg14lucb-54kw-heat-pump-installed-p-44/

there's ceiling and walls insulation, but no double glazing.

5kw is about average size, but if you buy slightly larger it will probably end up on less and using a little less power. We have a 7kw Daikin for our kitchen which is probably 30 square meters, it's enough, but I probably wouldn't want a lot smaller. However, on a new house and further north it might be ok.

You probably won't regret a few hundred dollars to buy slightly larger.

My Daikin (10 years old) is quite a bit quieter than my Fujitsu Nocria (5 years old). That's probably changed by now, but indoor unit noise is a pain at times. If you have to put it on "low fan" or "super quiet" it reduces efficiency.

One thing we find very effective is turning it on at 5am (free hour with Electric Kiwi) and turning it off 10pm, so the house never really gets cold. On really cold nights we just leave it on. We haven't worked out exactly how much more it costs, because our power bill is still low enough we don't really care.

Handle9

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#2022998 26-May-2018 14:26

kobiak:

hi guys,

advice on heat pump wanted :)

we are in Auckland, never had heat pump, always lived in warm apartment. Recently moved to 3 store townhouse and for past 2 nights its been little cold :( 16-17 degs first level with garage and my office, 17-19 degs second level (lounge + open kitchen), and 18-20 degs top level (2 bedrooms).

I was thinking to install heat pump in the lounge ~40 sq m. used couple calculators and looks like 5kW heat pump should be enough for our lounge and heat will travel 2 bedrooms. is this a good deal? https://www.kiwiheatpump.co.nz/product/fujitsu-astg14lucb-54kw-heat-pump-installed-p-44/

there's ceiling and walls insulation, but no double glazing.

5kW will do the lounge fine. You won't really heat the bedrooms effectively though. Because heatpumps don't overheat the space you don't get a huge amount of spill heat like you do from a fire.

timmmay

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#2023027 26-May-2018 14:31

I know our heat pump (10kw) does heat the bedrooms, which is a total of maybe 50 square meters on the same level, but it takes some time. I suspect the bedrooms will get a bit of heat especially if you keep the heat pump on for extended times (all day), but not huge amounts and not so much if you don't heat the house for long.

madcarue

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#2023039 26-May-2018 15:42

I think you may need to go a bit larger my room is 50 sq m and I have installed a 9kw and so far doing the job OK and only at ½ power, also volume needs to be taken into account I have 2.7M stud approx, so 135 cu M. I am dreading the first bill.

Aredwood

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#2023149 26-May-2018 22:36

kobiak:
hi guys,

advice on heat pump wanted :)

we are in Auckland, never had heat pump, always lived in warm apartment. Recently moved to 3 store townhouse and for past 2 nights its been little cold :( 16-17 degs first level with garage and my office, 17-19 degs second level (lounge + open kitchen), and 18-20 degs top level (2 bedrooms).

I was thinking to install heat pump in the lounge ~40 sq m. used couple calculators and looks like 5kW heat pump should be enough for our lounge and heat will travel 2 bedrooms. is this a good deal? https://www.kiwiheatpump.co.nz/product/fujitsu-astg14lucb-54kw-heat-pump-installed-p-44/

there's ceiling and walls insulation, but no double glazing.

Do some expierments with electric resistance heaters to figure out what the heat loss of the room is. Can a 2.4KW heater heat your lounge? Even if it can't, how much warmer can it get the lounge compared to the outside air temp? Try plugging multiple heaters (on different circuits of course) to find out how many KW is needed.

There is no point in oversizing a heatpump. As larger models tend to have lower efficiency than smaller models. Although you also need to consider aircon load as well. As a lot of the oversizing with heatpumps is partly to make sure that it can easily cool the room as well.

Friends got a quote for a heatpump, the installer recommended a 9KW model for their lounge. Even though they already have a flued gas heater that is rated at around 5KW output. And the gas heater is able to quickly heat the lounge. So that proves for them at least, that a 5KW heatpump will be fine for their situation.

My lounge- A 6KW unflued gas heater can't heat my lounge more than 5-10deg warmer than outside. So a 9KW heatpump is unlikely to be enough. The solution- Have bought a secondhand 14KW ducted heatpump, which will be dedicated just to heating my lounge.

Floor area of my lounge and the friends is similar. So going off floor area alone is unlikely to get the heatpump size correct.

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richms

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#2023161 27-May-2018 00:32

Oversizing also leads to annoying overshooting of the target temperature, and cycling of it as the lowest power it can do is still too much.

Richard rich.ms

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#2023171 27-May-2018 06:51

what kind of house era, what build, open plan or not?

we have a medium sized bedroom at the corner of a house with many glass windows, oversized the heatpump (3.4kW) and still cold. minor roof insulation. 2nd storey. no insulation on the floor.

madcarue

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#2023233 27-May-2018 09:33

richms:

Oversizing also leads to annoying overshooting of the target temperature, and cycling of it as the lowest power it can do is still too much.

Could you please expand on this, I don't understand.

kobiak

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#2023249 27-May-2018 09:48

Thank you all for advice. Looks like a bit over-specs will do fine (6-7kW). Now need to find good deal.

@Handle9, we don't really want to heat bedrooms as it's always 1-2 deg warmer then lounge. Warmer air travels up, there's no insulation between levels. So my theory, it will stay warmer anyway.

@Aredwood, we have no heaters to experiment with

@Batman it's 3 storey townhouse build in 2009. Insulated but no double glazing, no additional ventilation.

it was 10 degs outside during night (west auckland) and inside in lounge it's 18-19 degs at the moment, with no additional heating.

I'd want max 22-23 degs for comfortable shorts + t-shirt outfit.

helping others at evgenyk.nz

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#2023267 27-May-2018 10:16

if you want cheap get a Fujitsu Nocria

tdgeek

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#2023275 27-May-2018 10:30

timmmay:

If you have to put it on "low fan" or "super quiet" it reduces efficiency.

Thanks, I wasn't aware of that.

Aredwood

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#2023285 27-May-2018 10:55

kobiak:
Thank you all for advice. Looks like a bit over-specs will do fine (6-7kW). Now need to find good deal.

@Handle9, we don't really want to heat bedrooms as it's always 1-2 deg warmer then lounge. Warmer air travels up, there's no insulation between levels. So my theory, it will stay warmer anyway.

@Aredwood, we have no heaters to experiment with

@Batman it's 3 storey townhouse build in 2009. Insulated but no double glazing, no additional ventilation.

it was 10 degs outside during night (west auckland) and inside in lounge it's 18-19 degs at the moment, with no additional heating.

I'd want max 22-23 degs for comfortable shorts + t-shirt outfit.

Bunnings have a 2KW fan heater for $17 https://www.bunnings.co.nz/mistral-2000w-fan-heater_p00012654 So it won't break the bank if you need to buy a heater just for testing purposes.

It sounds like your house has good insulation, since you are saying that it is still quite warm even without any heating. Unless you are doing bitcoin mining or something else that produces a lot of heat.

And just looking at the Panasonic CS/CU-PKR series heatpumps for example. The 7.2KW has a 20% lower efficiency compared to the 2.8KW version. And all other brands also have similar drops in efficiency as you increase the size.

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#2023356 27-May-2018 12:36

From what the OP is describing, a 3-4kW heatpump will be more than enough. the lower the output the higher the efficiency. check the COP. my 3.4kW heatpump has a COP of 5, and a lowest power consumption at 200W (presumably delivering 1kW of heat). but disclaimer - YMMW! [i am basing this on your room being closed not open plan]

my 6kW heatpump has a COP of 4.4, can't remember what the lowest power consumption is. the 5-6kW range then to be cheap as they have many sales. presumably 3-4kW also cheap if there are sales. if you are afraid of too overspec, then check the lowest power consumption the high kW heater can do.

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