Another heat pump question

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#3099116 3-Jul-2023 15:52

You're right, in winter on a warm night they'll not be doing a lot, but in summer they'll be used pretty heavily in two of the rooms that end up in the mid to high 30s.

timmmay

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#3099122 3-Jul-2023 16:02

Once you bring the temperature down they tend to just tick over slowly unless it's crazy hot. We used air conditioning extensively last summer, didn't cost much compared with winter heating. I figure that in winter we're raising the temperature by 20c, in summer we're just taking it down a few degrees. Might be more where you are, compared with Wellington.

tweake

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#3099131 3-Jul-2023 16:19

timmmay: I figure that in winter we're raising the temperature by 20c, in summer we're just taking it down a few degrees. .

quite right. same thing here. winter is $40/month, rest of the year its $20/month.

tweake

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#3099133 3-Jul-2023 16:26

timmmay:

rscole86:

We're connecting 2x2kW and 1x2.5kW to a 5.4kW outdoor, Mitsubishi Electric kit.
2/3 are double glazed, two are currently bedrooms and one an office, so they'll not always be used concurrently. Even if all three were bedrooms then the 5.4kW outdoor should be fine, unless we push the units to their limit.

Before our ducted system went in we had 1.2kw oil heaters in each bedroom. Once the rooms were up to heat we found the oil heaters ran about 1/4 of the time, so in effect they used about 300w of heating.

Sometimes the minimum output of a heat pump is more important than a maximum.

similar on one of mine.

had 2000w oil heater which heated the office with ease. the calc said about 1500w required. i asked for a 2kw heat pump which was the smallest i could get at the time but the installer brought (for the same price) a 2.5kw.

consequently its way to big, short cycles and overshoots the temp.

getting sizing correct on heat pumps is important and its better to be a bit undersized than oversized.

mattenz

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#3099134 3-Jul-2023 16:26

A central heat pump should work a lot better for equalising temperature from solar gain that one of those heat transfer set ups, but that's assuming a sensible return set up, which is certainly not a given with your typical NZ install!

Handle9

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#3099138 3-Jul-2023 16:32

tweake:
timmmay: I figure that in winter we're raising the temperature by 20c, in summer we're just taking it down a few degrees. .

quite right. same thing here. winter is $40/month, rest of the year its $20/month.

Sigh. I can only dream of those sorts of bills. Saying that I’ve got around 60kw of cooling and it’s forecast to hit 41 today.

tweake

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#3099142 3-Jul-2023 16:46

Handle9:
tweake:

quite right. same thing here. winter is $40/month, rest of the year its $20/month.

Sigh. I can only dream of those sorts of bills. Saying that I’ve got around 60kw of cooling and it’s forecast to hit 41 today.

yet many kiwis are sitting in million dollar properties saying "its to expensive". 🤬

its to expensive to heat/cool but we don't want to build houses that are cheap to heat/cool. it does my freakin head in.

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Handle9

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#3099324 3-Jul-2023 21:44

tweake:

Handle9: Sigh. I can only dream of those sorts of bills. Saying that I’ve got around 60kw of cooling and it’s forecast to hit 41 today.

yet many kiwis are sitting in million dollar properties saying "its to expensive". 🤬

its to expensive to heat/cool but we don't want to build houses that are cheap to heat/cool. it does my freakin head in.

New Zealand is largely a temperate climate. It doesn't really get that hot or cold in the upper North Island. If an occupant doesn't want to pay to heat or cool their house that's not neccesarily an issue with the house.

There are reasons the way houses are built the way they are and not all of them are bad. Often capitalising thermal performance doesn't make much sense.

tweake

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#3099457 4-Jul-2023 09:34

Handle9:

New Zealand is largely a temperate climate. It doesn't really get that hot or cold in the upper North Island. If an occupant doesn't want to pay to heat or cool their house that's not neccesarily an issue with the house.

There are reasons the way houses are built the way they are and not all of them are bad. Often capitalising thermal performance doesn't make much sense.

that excuse is complete nonsense.

even winterless north gets below freezing a few times every year and the odd touch of snow in rare cases. then everyone else in nz builds the same. until last month or so, the difference in new builds between northland and southland was minimal. quite often houses in northland got upgraded to south island spec. thats recently changed for new builds, finally start to catch up with the rest of the world.

i know Canadians who have lived in auckland and thats the coldest house they have ever lived in.

kiwis make excuses because they don't want to spend money on heating/cooling, don't want to spend money on building something decent, but they want to maximise the profit on their homes when they flip it. average length of kiwi home ownership is now down to 5 years. kiwis flip the family home for profit, hence they spend the least they can get away with on the house.

i kinda like it when i see posters here asking about making homes better.

Handle9

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#3099693 4-Jul-2023 15:00

You can have whatever rant you like but you can’t make your own facts.

The upper north island doesn’t get below freezing “a few times a year.” If you have any evidence of this I’d love to see it.

tweake

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#3099726 4-Jul-2023 15:42

Handle9: You can have whatever rant you like but you can’t make your own facts.

The upper north island doesn’t get below freezing “a few times a year.” If you have any evidence of this I’d love to see it.

i'll see if i still have the pics of the temp gauge. i've done plenty of mornings with the outside hose frozen solid. pita to go get buckets of water from inside to defrost the car with.

depending on where you are you can be well below what the weather station records. easy enough to drop 5 degrees in the valley.

tweake

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#3099732 4-Jul-2023 15:59

Handle9: You can have whatever rant you like but you can’t make your own facts.

The upper north island doesn’t get below freezing “a few times a year.” If you have any evidence of this I’d love to see it.

just looking at Whenuapai low temp data -2 last year for july, historical average of -1.

i have a pic from last house, but its mid morning, frost was already disappearing and it was just below 0c. so not the coldest.

Handle9

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#3099738 4-Jul-2023 16:07

Right.

The average low temperature in Auckland is 8 degrees. That’s not particularly cold and doesn’t need a particularly high performing building to keep warm. Certainly summer temperatures don’t require anything exotic.

Historically New Zealand had cheap electricity and readily available firewood. That’s why houses are built the way they are, not because people are stupid.

If the payback to retrofit something far more efficient is 10+ years then why would you bother? This is the case everywhere in the world. People don’t spend money on things that don’t have an adequate return.

In very hot or cold climates it’s a different issue. Here in the Middle East it’s 40+ degrees for months, in Europe it’s actually gets below zero for months. You need a different class of performance.

Even heat pumps in NZ can have a marginal business case vs resistive heating. There’s nothing mystical about heating and cooling a house, it’s just energy.

tweake

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#3099747 4-Jul-2023 16:39

Handle9: Right.

The average low temperature in Auckland is 8 degrees. That’s not particularly cold and doesn’t need a particularly high performing building to keep warm. Certainly summer temperatures don’t require anything exotic.

Historically New Zealand had cheap electricity and readily available firewood. That’s why houses are built the way they are, not because people are stupid.

If the payback to retrofit something far more efficient is 10+ years then why would you bother? This is the case everywhere in the world. People don’t spend money on things that don’t have an adequate return.

In very hot or cold climates it’s a different issue. Here in the Middle East it’s 40+ degrees for months, in Europe it’s actually gets below zero for months. You need a different class of performance.

Even heat pumps in NZ can have a marginal business case vs resistive heating. There’s nothing mystical about heating and cooling a house, it’s just energy.

by mem auckland low is more like 4c which we get down to regularly and if i remember right its what we base heating off. 10c is spring temps.

our houses are done that way because they have vested interests. why else would be have double glazing so late. other countries had full insulation and double glazing when we where just starting to put insulation in walls.

even as of last month houses in southland where being built almost the same (and in a lot of cases exactly the same) as in northland. you can't tell me thats not people being stupid.

what annoys me the most is the science is not hard, we know how to do it, its just energy. but kiwi's have been very well taught to put up with a low standard of housing and have other vested interests.

Handle9

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#3099750 4-Jul-2023 17:00

Design conditions for Auckland are typically a low of 5 degrees in a high performance building but it also depends on your internal target temperature. From memory the ASHRAE extreme low temperature is 1.8 dry bulb. That’s not very cold.

“Vested interests” are the supply chain. The reality of construction, as opposed to a fairy tale that everything can change over night, is that you can’t change the availability of building products instantly. You certainly can’t quickly change construction methods. The industry tried that in the mid 90s and it created the leaky homes crisis.

The minimum requirements are different from Southland to Northland, particularly for windows, so if builders are building to the same minimum requirements they aren’t complying.

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