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  Reply # 508120 17-Aug-2011 17:34 Send private message

timmmay: Why are heat pumps more efficient when cooling? In both cases they're moving heat from one side of the heat pump to another, rather than creating or destroying heat.


When heating, the heat pump has to extract heat out of the air outside which is usually very cold. The fins often freeze up and it has to warm them with a standard heater coil (defrost light) and so if its 10 degrees outside, and you want to warm it up by 10 degrees inside, alot more energy is required to extract this heat.
Its still more efficient than a heater though.

When its hot inside, and you want to cool it, it is easier to extract the heat because there is much more of it there and so it requires less energy to make a difference.




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  Reply # 508121 17-Aug-2011 17:36 Send private message

Anyone remember the california power crisis of ~2001
They were having blackouts because too many people were running air conditioners in the hot summer.

Well that was before we knew enron was artifically lowering the supply of power.




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  Reply # 509190 19-Aug-2011 20:08 Send private message

Part of the cost is plumbing the refrigeration pipes from the indoor to outdoor units, and the installer may try to convince you to plant the outdoor unit in the closest most convenient spot, which is probably also the most ugly. A bit more piping and you can put everything in the best places, and yes there needs to be a drain on the indoor unit too. Unfortunately refridgeration pipes need extra equipment to gas them up and if everything is done properly and wired into thermostats in sensible places it might cost over $2000 to install. Cant remember exactly how much is normal for a home AC, but that sounds reasonable if they know what they are doing.




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  Reply # 509196 19-Aug-2011 20:27 Send private message

wreck90:
mattwnz:
Regs: for comparisons sake, i had a ducted gas central heating unit installed for around $8k. It heats the entire house, not just one room, and i costs a similar amount to run as a heat pump given the 6c/kw gas prices versus 25c/kw electricity prices. i can also turn it on and have the whole house warm in about 5 minutes, and it works in the cold!


It doesn't cool though, unlike a heat pump, and gas prices and availability in the future is probably not sustainable. Also it could be more efficient to set it up with a big heat pump. One of the most efficient heating solutions is underfloor heating in a slab, heated by a heat pump, but initial costs are high and can usually only be done during construction


Don't talk to me about underfloor heating.....my gas bill is $450 a month (in summer it is around $60 a month).

When I complained to the architect (new house, and he told me about the wonders of efficient underfloor heating) they got the uber-experts around to check out the installation...they changed the heating system, maybe helped a little but, definitely very expensive still.?

My total gas+electricity in winter is now around $700 -$800 . ? This is a 3 year old house. I'm really annoyed .?


Should have used a heat pump water heater, combined with solar arrays, as gas is very expensive for such a system. I can imagine how high the costs would be if using gas, and I presume you chose gas as the initial setup costs were less than with ah heatpump system. They should have done a cost analysis before installation, to show you how much different system would cost. I assume you can turn off various zones to cut down the cost so it is a lot cheaper. There is no point in heating rooms you are not in a lot. I believe the good thing about underfloor slab heating, is it is the most efficiency way to heat a house if using a heatpump water heater system. And once the pipes are in the slab, you don't have to use it, it can be used in the future as the buildings use changes. Alternatively you can use radiators connected to a heatpump heater, which has a faster heating time than a slab.

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  Reply # 509198 19-Aug-2011 20:29 Send private message

hellonearthisman:
The South Island with an energy supply problem. Yeah right...

As for heatpumps cooling, they use a lot less (40% my guess) power in cooling mode than in heating modes. Open a window is nice when there are not heaps of bugs wanting to get in to drink your blood.


The country as a whole does. Does the south island have priority on power just because a lot of the hydro generation is down there, I don't think so?

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  Reply # 509426 20-Aug-2011 19:37 Send private message

You can always request at your own cost to replace the meter. 

Or better yet, get them to check your meter, if something is wrong they will fix or replace for free, if not you pay that investigation fee. 

For the heatpump.  We had a high ceiling and no attic above the lounge area so no insulation.  We usually just had 1 oil fin heater and wear coats while watching TV but if we had 2 heaters and turn them on for lengthy hours so it is warm, yes, we could pay $600 a month, from experience.  The HP now is so much more affordable like $300 and it is just as warm.  Before we were with Contact.  We also got the meter changed at our cost. 

Installation, cost $700-800 back to back wall.  For us we had to route it down stairs (it's a floor standing HP) and then on the garage ceiling it was routed outside to the side of the house.  $1800 installation approx.  Floor standing units are also more expensive for the unit.

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  Reply # 509625 21-Aug-2011 15:37 Send private message

It was interesting catching some of the talk on the morning show about grey power raising concerns on heat pumps and their tendancy to freeze up when cold then using elements to heat the out side unit.
Concerning using a heater to warm the outside unit the only brand I have heard of that does that is Mitsubishi. There may be others but my understanding is that most just use a very small amount of the warmth from the inside system to dry the coils.
We purchased our first heat pump three years ago. We did find that it tended to spend quite a bit of time in defrost mode. We got a couple of crowds in found that the initial company had undersized the heat pump by 1/2. We had a 6kw heating unit when we should have had a 9kw heating unit. As we wanted a second unit in the hall we moved the under size unit into the hall and put the larger unit in the living area. Have not had any icing issues since even when we had all the snow during last week (Wainuiomata).
I think there are two issues happening. A lot of people are going to brick and mortar stores and sizing the units themselves and therefore under size by a large margin or are having pros come in and do the quotes but either because the pros are not doing their home work well enough or due to cost are going for units that are too small. End result a solution that does not work as expected.
Key piece of info that people should keep in mind is that heat pumps should never have to work at their max outputs. They are only ever able to do so for a short amount of time.







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  Reply # 509630 21-Aug-2011 16:07 Send private message

In Wellington, Noel Leeming sent over a tech from Wasabi Air.  They did the measurements and recommended a HP .... but they don't have the govt subsidies ....

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  Reply # 509649 21-Aug-2011 17:31 Send private message

Has anyone put their outside unit in the attic, out of the way and where the air is often warmer?

With the underfloor slab heating you need it running all the time even when you're not there - seems a bit inefficient; not surprised the power bills are high. We have a 3-phase 18kW electric central heating. We only run it when we need it - an hour in the morning, 2 or 3 hours in the evening, and our powerbill is $350-$400 more in winter than in summer (in Wellington). The thing I really like about this heater is it pumps a massive amount of warm air (rather than a small amount of hot air) and that makes it a really comfortable and even heat.




 

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  Reply # 509664 21-Aug-2011 18:42 Send private message

TinyTim: Has anyone put their outside unit in the attic, out of the way and where the air is often warmer?


You can't do that. Heat pumps just move heat around. The room would cool down to below zero and it'd become ineffective. It's also vibrate like anything.

Don't attach a head pump to the side of a house. A friend did it and it made a heck of a racket.




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  Reply # 509666 21-Aug-2011 18:56 Send private message

you might also need a pump.  the outside unit generally should be on a lower level to work better i was told.

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  Reply # 630235 25-May-2012 10:54 Send private message

Hi,

I'm looking to get a heat pump. I have a ~ 1900 cottage in Auckland (2 bedrooms - 90sqm in total).
Roof is fully insulated and it seems to be underfloor insulation as well (from previous owners). I'm not sure about the exterior walls but I should assume they are not. Normal windows with wooden frame.

Could you please recommend an installer in the AKL region in the $750 range?
I haven't decided on the heat pump size/manufacturer so I'm open to suggestions.

An interesting thing about: http://www.consumer.org.nz/reports/heat-pumps/what-size-heat-pump

I've put the following:
- ceiling (insulated) - 90sqm
- floor (slab on ground)- 90sqm
- external walls (I took a wild guess at 95sqm). I achieved it by adding the perimeter of the house (10 + 9 + 10 + 9) (it's a 10x9m house), multiplying by 3 (height) and reducing 20% which are windows.
- windows - 19sqm (as above)
- internal walls - 45sqm (about 15m x 3m height)

and it came out with a wobbling requirement of 11.12kW. Obviously I did something wrong but I'm not sure what.

Any advice is appreciated.

Thanks.

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  Reply # 630240 25-May-2012 11:02 Send private message

Best to have someone come over and do a evaluation, alternatively the Energywise website has a calculator I think with the size of the room and it may ask if your house is insulated or not. 

$750 is the cheap side.  If you wanna go cheaper go for a high wall mount unit, also you need a few hundred for the installation that is extra.  But a higher wall units may require access to the exterior wall, if the room is a bit larger you may want it in the centre of the room - heats quicker.  But those are more $$ to purchase. 

Also remembering that the HP is only for one room.  We just jump around the house thru closed doors over Winter.  If you want better coverage it may mean a extra one for the corridor...

For better heating and cheaper HP price it means closed doors IMO.  One for the lounge and one for the corridor with the bedroom doors open so it filters thru ... and preferably a door that shuts at the end of the corridor or something like thermal drapes and of course shut other doors there like the bathroom, laundry etc ..

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  Reply # 630243 25-May-2012 11:05 Send private message

Hi,

I'm looking for a high-wall mount unit and the $750 was for the installation, not for the heat pump. Depending on the size I'd like one around the $2,000 mark.

The wall where I'd like to put it is an exterior one so it would be a 'back-to-back' installation. As it's a small house I'm pretty confident that the heat in the lounge should reach the bedroom as well.

If you know someone that could come for an evaluation, please let me know.

Thanks.

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  Reply # 630250 25-May-2012 11:13 Send private message

Get a few quotes and compare. We got them off a govt website, might have been Energywise b/c they offered subsidies...

I think we have a 5kW, we have a high ceiling thou like near 3m.  Floor standing unit mounted to lower wall.  Was near $4000 unit itself.  We got a Daikin.  Mitsu is good too so is Fujitsu.  Higher wall units tends to consume less power I think but we needed a floor standing one in centre of room by the wall.

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