Advice wanted re Heat Pumps

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#2023357 27-May-2018 12:39

Batman:
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.

Thanks, I'll check these specs.

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#2023370 27-May-2018 13:24

my fujitsu nocria 6kW has a minimum heat output of 0.9kW and minimum power consumption of 1.34kW according to https://tropex.co.nz/sites/default/files/product_pdfs/Fujitsu%20Air%20Conditioners%20Product%20Range.pdf

so:

1. looks like an overkill heatpump won't over heat and roast you cripsy crunchy

2. but it will likely cost you more in power as the compressor probably can't go below a certain work load

my 200W minimum output unit is a toshiba fancy thing with air cleaning ionizing magic potion.

Batman

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#2023374 27-May-2018 13:28

the middle (3.5kW) or the right (4.5kW) one will suit you. heating range .65-6+ kW.

min power consumption 170W. less than a lightbulb.

http://www.toshibaheatpumps.com/application/files/9914/8468/8607/Toshiba_G2KVP_Brochure.pdf

Technofreak

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#2023382 27-May-2018 13:51

I wouldn't get to het up about what the minimum power draw is and trying to save a few cents on running cost when the heating requirement is low. Anything you save on running costs will be more than eaten up in unhappiness if it's too small at peak demand time.

It's better to be slightly over spec than under spec.

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timmmay

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#2023393 27-May-2018 14:49

Batman:

my fujitsu nocria 6kW has a minimum heat output of 0.9kW and minimum power consumption of 1.34kW according to https://tropex.co.nz/sites/default/files/product_pdfs/Fujitsu%20Air%20Conditioners%20Product%20Range.pdf

so:

1. looks like an overkill heatpump won't over heat and roast you cripsy crunchy

2. but it will likely cost you more in power as the compressor probably can't go below a certain work load

my 200W minimum output unit is a toshiba fancy thing with air cleaning ionizing magic potion.

How does this work? Overheads when going slow? Using 1.34kw to create 0.9kw of heat?! The Nocria should be at least 3:1 heat:power. Mine's the 9/10kw unit and it's fairly loud indoors compared with some others, but the fan seems like it could heat a stadium. Seems fairly good for heating a reasonable sized space.

I'd rather the thing went on higher power for less time than lower power constantly.

Batman

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#2023411 27-May-2018 16:00

timmmay:

Batman:

my fujitsu nocria 6kW has a minimum heat output of 0.9kW and minimum power consumption of 1.34kW according to https://tropex.co.nz/sites/default/files/product_pdfs/Fujitsu%20Air%20Conditioners%20Product%20Range.pdf

so:

1. looks like an overkill heatpump won't over heat and roast you cripsy crunchy

2. but it will likely cost you more in power as the compressor probably can't go below a certain work load

my 200W minimum output unit is a toshiba fancy thing with air cleaning ionizing magic potion.

How does this work? Overheads when going slow? Using 1.34kw to create 0.9kw of heat?! The Nocria should be at least 3:1 heat:power. Mine's the 9/10kw unit and it's fairly loud indoors compared with some others, but the fan seems like it could heat a stadium. Seems fairly good for heating a reasonable sized space.

I'd rather the thing went on higher power for less time than lower power constantly.

Good question! One for the Fujitsu engineers! Maybe the spec sheet is wrong? I have to say I run lots of heat pumps and my power bill is rarely in the 300 dollar bracket. Usually 1-200 bucks a month. We are electric everything.

madcarue

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#2024998 29-May-2018 16:46

This morning was a bit of a shock at -2 deg, heater set to come on at 5:40am 21 deg this has worked OK up to now but at this minus temp it must have gone into de ice mode (6:30pm) and the room was only just warm, I switched it of and went into manual mode at 22 deg but it was about 5 min before it started. brrrrr

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Fred99

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#2025031 29-May-2018 17:48

Batman:

timmmay:

Batman:

my fujitsu nocria 6kW has a minimum heat output of 0.9kW and minimum power consumption of 1.34kW according to https://tropex.co.nz/sites/default/files/product_pdfs/Fujitsu%20Air%20Conditioners%20Product%20Range.pdf

so:

1. looks like an overkill heatpump won't over heat and roast you cripsy crunchy

2. but it will likely cost you more in power as the compressor probably can't go below a certain work load

my 200W minimum output unit is a toshiba fancy thing with air cleaning ionizing magic potion.

How does this work? Overheads when going slow? Using 1.34kw to create 0.9kw of heat?! The Nocria should be at least 3:1 heat:power. Mine's the 9/10kw unit and it's fairly loud indoors compared with some others, but the fan seems like it could heat a stadium. Seems fairly good for heating a reasonable sized space.

I'd rather the thing went on higher power for less time than lower power constantly.

Good question! One for the Fujitsu engineers! Maybe the spec sheet is wrong? I have to say I run lots of heat pumps and my power bill is rarely in the 300 dollar bracket. Usually 1-200 bucks a month. We are electric everything.

LOL - you just need to read it right.

The spec sheet states Input Power heat/cool, then 1.35/1.02 kW, so 1.35kW max on heating.

That will be maximum continuous power use - if it's on a low heat setting it won't be using that - probably not even close, especially these days with inverter pumps.

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#2025034 29-May-2018 17:56

My apologies, I never read things right the first time. Maybe I need to put in my signature.

Aredwood

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#2025192 29-May-2018 21:56

Technofreak:
I wouldn't get to het up about what the minimum power draw is and trying to save a few cents on running cost when the heating requirement is low. Anything you save on running costs will be more than eaten up in unhappiness if it's too small at peak demand time.

It's better to be slightly over spec than under spec.

Agree that you should slightly over spec. Assuming that you know a reasonably accurate heat loss figure for the room. What I'm against is massively oversizing the heatpump.

This will partly depend on the weather patterns in your area as well. Last winter at my house in Auckland, there was only around 10 overnight frosts the whole winter. So even if my heatpump was running at the limit on those nights. I would have the other 355 nights where I will be enjoying peak efficiency and lower running costs.

There will be more than 1 heatpump in the house as well. Plan is to put closely matched and highly efficient heatpumps in my bedroom and the flatmates bedroom. As they will get used the most. While the lounge and the workshop will have bigger heatpumps that I got for cheap/free. As it is more important to me to quickly heat or cool the lounge and workshop. As those rooms don't get used as much in my house.

I want to avoid the bedroom heatpumps constantly cycling on /off, if possible. As that cycling will mean that the rooms will never be a stable temperature. So even if I have to occasionally use an electric heater at the same time as the heatpump on the coldest night of the year. I'm willing to do so. The savings over the rest of the year, and on purchase costs. Will easily pay for a couple of nights of electric heater use. Or I could just run the lounge or workshop heatpumps if needed to help spread the load on the coldest nights.

kobiak

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#2065948 31-Jul-2018 22:59

Aredwood:
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.

I'm back with some details.

At the end of May we purchased el-cheapo 2kW fan heater which we used to heat our lounge and downstairs when needed. the little thing could heat up to 20-21C (we just did not try to heat any more) within 30-45 mins from 18C. Upstairs gets it's usual 1-2C warmer.

We then been out of the country for 6 weeks since mid June and recently came back. Still using the same heater to heat the lounge when at home in the evenings for total maybe 2-3 hours from 4pm. No heating at night and lowest it gets in the lounge 16C (2-6C outside in Waitakere). Heater for 1 hour in the morning and temps is back to 18-19C for most of the day. Our ground level where my office and garage is the coldest at 12-13C when outside is 2-4C.

Currently we are debating if we even need/want heat pump? cost to run this heater is under $50 a month. So missus questions my idea of having costly heat pump + running costs.

Someone is coming tomorrow for free assessment and advice on heat pump installation, I won't be be at home to ask questions. But I'm totally puzzled now, do we need 5kW unit? or will 3.5kW will be more than enough?

helping others at evgenyk.nz

timmmay

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#2065979 1-Aug-2018 06:07

If it's one small room and you only use it a couple of hours a day, in a well insulated house, maybe the fan heater is ok at least not when the weather is mild. Wait until you get into a big storm or really cold night though.

We have the heat pumps effectively heat our whole house. It takes some time to get around corners and into every room, but it gets there. Having the whole house warm is nice - heating one room is a very NZ thing to do.

I wouldn't bother with a 3.5kw heat pump unless it was for one tiny room, it's barely better than a fan heater.

kobiak

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#2066055 1-Aug-2018 08:38

timmmay:

If it's one small room and you only use it a couple of hours a day, in a well insulated house, maybe the fan heater is ok at least not when the weather is mild. Wait until you get into a big storm or really cold night though.

We have the heat pumps effectively heat our whole house. It takes some time to get around corners and into every room, but it gets there. Having the whole house warm is nice - heating one room is a very NZ thing to do.

I wouldn't bother with a 3.5kw heat pump unless it was for one tiny room, it's barely better than a fan heater.

Was that reply to me? if yes, not sure if you read my added details correctly.

we eventually are heating entire townhouse with 2kW fan heater from warehouse. yes it take an hour to get to 18+ (I usually stop it when lounge is at 20C) degrees from 15-16C when it's 2-6C outside at night.

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timmmay

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#2066075 1-Aug-2018 09:00

An hour to heat an entire home to 20 degrees isn't too bad, but we heat our home to 22 or 23 degrees, more quickly. In practice we don't turn the heat pumps off during really cold parts of winter, and it doesn't increase our power bills by all that much. we find there's a big difference between having the air warm, and having the whole house and everything inside it heated through. That would be significantly more expensive with a fan heater, than a heat pump.

If you're happy with the fan heater, use the fan heater. A heat pump will let you get the house warmer, faster.

madcarue

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#2170256 30-Jan-2019 15:27

I am more than satisfied with my heat pump over the winter, and now am using it in cool mode, I have been told it is much more expensive to use in this mode but by how much?

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