Advice wanted re Heat Pumps

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timmmay

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#2170261 30-Jan-2019 15:44

Look at the efficiency figures for your heat pump, keeping in mind the outside temp is fairly high. I think it's worthwhile regardless. I find I spend less in summer on cooling than I do in winter on heating, with two heat pumps and little tolerance for heat or cold at home.

xlinknz

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#2170408 30-Jan-2019 20:32

madcarue:

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?

How did cool mode go and how long for ?

I ask as yesterday we used our pump for the 1st time (installed 2 years ago) in cool mode and after a while it starting leaking lots of water inside!

The company are coming around tomorrow to look. The drain pipe that goes outside showed no water

I will be interesting to see what the issue is but the service reception said quite a few call outs with the same issue

richms

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#2170409 30-Jan-2019 20:36

If you've never used cool then you might have had something build a nest in the drain pipe. Or its been installed wrong.

In this weather damn the cost.

Richard rich.ms

timmmay

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#2170447 30-Jan-2019 20:44

That can mean the drain was installed incorrectly or has become blocked. We had that because the drain pipe they put in went through a wooden deck, but they didn't drill the whole way through the board.

Agree cost isn't really a factor in our air conditioner use during a heat wave. Monday wasn't all that hot, but that's my latest data, the power cost that day was less than average for the past week. It'll be interesting to see Tuesday's cost, probably tomorrow.

xlinknz

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#2170458 30-Jan-2019 20:53

richms:

If you've never used cool then you might have had something build a nest in the drain pipe. Or its been installed wrong.

In this weather damn the cost.

TQ for the reply

Good point. I just inserted a 1m bamboo stick up it and had a few dribbles comes out (none when it leaked inside) and no debris. I now wonder whether it is not installed correctly and the water has to go up hill to go out the correct way...

Aredwood

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#2170504 31-Jan-2019 00:37

madcarue:
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?

Check the efficiency figures as mentioned above. But the cooling efficiency will almost certainly be lower than the heating efficiency. As the waste heat from the compressor has to be dumped on cooling mode, but is delivered into the room on heating mode.

Myself, I only use the upstairs heat pumps at night. As my house gets lots of sun, meaning that my heatpumps would struggle and use lots of power if I tried running them during the day.

I retreat to the garage during the day if needed. (yes, I have a heatpump in the garage). And the flatmate has the downstairs rumpus room as his bedroom. Which is naturally cooler than the upstairs, and he also has a heatpump as well.

Since electricity use is normally lower in summer. Paying for the extra power usage shouldn't be a problem. Just read the electricity meter before and after running the heatpump for a few hours. If you want to know how much it would cost you to run it.

timmmay

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#2170522 31-Jan-2019 07:09

I just saw the costs for Tuesday, a super hot day where we ran the air conditioner longer than usual. The bill was upper quartile of the last month, but not the highest. We have run the air conditioners most days this summer, but Tuesday usage was much higher usage. Conclusion is power usage isn't that bad.

This is a reasonably well insulated, double glazed, older home, two adults and a toddler, and we use a fair bit of hot water for toddler baths.

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kiwifidget

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#2170610 31-Jan-2019 09:52

Our house has a Mitsubishi ducted heat pump.

It came with the house, so it must be at least 10yrs old, maybe 12.

Night before last I kept it on cool all night, set at 19C.

Next morning, a not necessarily accurate indoor thermometer read 20.5C.

Close enough.

I decided to keep the aircon running all day, closed the curtains and pulled the blinds and spent all day pretty much in the dark.

We also have double glazing with supposed heat reducing properties.

By dinner time the thermometer read 27.7C.

Is this normal for ducted systems, or is something not quite right?

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k14

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#2170646 31-Jan-2019 11:08

timmmay:

I just saw the costs for Tuesday, a super hot day where we ran the air conditioner longer than usual. The bill was upper quartile of the last month, but not the highest. We have run the air conditioners most days this summer, but Tuesday usage was much higher usage. Conclusion is power usage isn't that bad.

This is a reasonably well insulated, double glazed, older home, two adults and a toddler, and we use a fair bit of hot water for toddler baths.

That has been my observation too. We live in Central Otago and regularly use the heat pumps (one in lounge and one in hallway) when the temps exceed 30. From my rough observations it seems significantly cheaper per hour to run the heat pump to cool the house temp to 23-24 when the outside temp is 30-35 vs heating the house in winter to 21 or 22 when the outside temp drops as low as -5. I would estimate between 20-50% of the cost per hour (although haven't done any exact tests because there are so many variables). Whilst the efficiency is lower for cooling the difference between inside and outside temps are greater in winter thus more energy needs to be used to heat vs cool. We have a 10 year old house with double glazing, good curtains and insulation so that makes a big difference too. Having two young kids the heat pumps are a big sanity saver when the temp outside is still over 30 at bed time!

madcarue

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#2170660 31-Jan-2019 11:55

xlinknz:

madcarue:

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?

How did cool mode go and how long for ?

I ask as yesterday we used our pump for the 1st time (installed 2 years ago) in cool mode and after a while it starting leaking lots of water inside!

The company are coming around tomorrow to look. The drain pipe that goes outside showed no water

I will be interesting to see what the issue is but the service reception said quite a few call outs with the same issue

Switched on approx mid day Tuesday outside temp 34degC set temp at 18 then gradually increased temp to 22deg, by 4pm cooled room to 22deg kept setting at 24-5 and off at 10:30, no leaks, I was very impressed and cool. But I have heard that it costs a lot more to cool than to heat??

E3xtc

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#2170674 31-Jan-2019 12:27

kiwifidget:

Our house has a Mitsubishi ducted heat pump.

It came with the house, so it must be at least 10yrs old, maybe 12.

Night before last I kept it on cool all night, set at 19C.

Next morning, a not necessarily accurate indoor thermometer read 20.5C.

Close enough.

I decided to keep the aircon running all day, closed the curtains and pulled the blinds and spent all day pretty much in the dark.

We also have double glazing with supposed heat reducing properties.

By dinner time the thermometer read 27.7C.

Is this normal for ducted systems, or is something not quite right?

We have a smaller (8kW?) Ducted Panasonic unit that services the upstairs section of our house (bedrooms). On super sunny days the house gets absolutely baked and even if we shut 2 out of 3 of the outlets down, leaving my little boys room getting most of the cool air, the temp in that room (after having it on full for a few hours) still holds at around 24. It takes quite a while for the residual heat soaked into the house to dissipate. This is on a 7 yr old house (insulated/double glazing/etc). Without the heatpump the room easily hit mid 30's, so something had to be done and due to the design/location/etc individual high wall units etc were not an option.

But yeah I just think the effectiveness of the ducted systems just isn't quite as good for "hitting the heat" as the high wall units. Also I think the smaller capacity ones probably struggle a bit; so larger one would probably be more "okay"

kiwifidget

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#2170691 31-Jan-2019 12:41

@e3xtc Thank you for sharing your observation.

We had the double-glazing put in after our first summer in this house, when the indoor temp got to 40C or more on an almost daily basis.

The last few summers the indoor temp reaches about 35C max.

We dont normally run the aircon for cooling, due to perceived higher cost.

But with this heatwave, and a growing intolerance for hot nights, I decided I could run the aircon and offset the cost by turning off the spa pool.

Himself is not convinced about the cost offset but has wisely decided to pull his head in at this stage.

I am actually thankful it kept the temp under 30C, so this may be as good as it gets.

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