Heat pump and air con advice

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Scotty1986

315 posts

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#159907 16-Dec-2014 19:49

So I moved into a new rental in Johnsonville, Wellington about 4 months ago. Towards the end of winter. It has a triangle shaped roof with no insulation, very thin ceiling with a tin roof. So there is little space between the inside of the ceiling and the outside air. It was surprisingly warm compared to our last house in winter. It has a heat pump downstairs. All has been well until the temperature has started to rise. Upstairs in my man cave where I spend most of my time the heat is becoming unbearable. I am running a fan all day. The ceiling is conducting the heat. It is hot to touch, not warm, hot! Today was the worst, and its only the beginning of summer.

Today I ran the heat pump on cool downstairs with the windows closed and it was bliss.

Couple of questions. Does anybody use their heat pump as a air conditioner often? What does it do to your power bill? Secondly, can I run a second unit upstairs off of the original pump, 2 units off one pump. Hopefully the ducting can go far enough. Estimates of cost on a second unit?

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#1198620 16-Dec-2014 19:51

Some systems are designed to have one outside unit, two inside units. Unless the existing one has this design, then I don't think you can simply add an inside unit in.

Whatifthespacekeyhadneverbeeninvented?

blakamin

4431 posts

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#1198621 16-Dec-2014 19:53

In Australia they're called "split-system air conditioners" and hardly anyone uses them for heat.
I'll let you know about about power bill next month as we've just had a big panasonic unit installed 6 months ago. From what I remember of my research, they do use more power cooling than heating. Depends on the unit tho.

Most units are designed for one indoor unit only. You can buy systems with 2 or more, but they're designed for that. Edit: DarthKermit types faster than me :)

sbiddle

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Biddle Corp

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#1198623 16-Dec-2014 20:08

Multiple units can be fitted off a single outdoor compressor but it's highly unlikely you'll have a compressor that's big enough for this - it's something you'd do during the install phase if they were required.

timmmay

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#1198628 16-Dec-2014 20:20

Unlikely, the units that can support multiple indoor units are twice the price. If you can't get the landlord to insulate or provide a heat pump probably best to move - and make sure the landlord knows why you're moving.

I don't know what my air con costs to run, I don't use it that much, house is pretty well insulated here (also JV). However the sun puts out a lot of heat and without insulation a lot will come inside, so to remove it could cost a lot.

Scotty1986

315 posts

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#1198639 16-Dec-2014 20:39

what about a sun reflecting paint? I know they exist, but not sure if its realistic for residential use.

Hammerer

2476 posts

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#1198666 16-Dec-2014 21:04

We found heating in winter was just more than half the cost of cooling in summer in a well-insulated but very sunny room. Your heating bill with an uninsulated ceiling and metal roof would have been high so it might be a similar ratio for you in summer.

blakamin

4431 posts

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#1198732 16-Dec-2014 22:40

sbiddle: Multiple units can be fitted off a single outdoor compressor but it's highly unlikely you'll have a compressor that's big enough for this - it's something you'd do during the install phase if they were required.

Exactly! This is mine... and only designed for 1 indoor unit. (the mess is from the old unit)

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Jase2985

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#1198767 17-Dec-2014 05:40

why not insulate the ceiling?

Scotty1986

315 posts

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#1198771 17-Dec-2014 05:54

It's a rental, and the design of the ceiling won't allow for it. Unless they build a extra layer over top of the existing ceiling. I don't see the landlord wanting to do build work.

timmmay

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#1198810 17-Dec-2014 07:54

blakamin:
sbiddle: Multiple units can be fitted off a single outdoor compressor but it's highly unlikely you'll have a compressor that's big enough for this - it's something you'd do during the install phase if they were required.

Exactly! This is mine... and only designed for 1 indoor unit. (the mess is from the old unit)

That's a heck of an outdoor unit. I was thinking a double unit like that around 20kw might be enough for a central heating type unit at my place - not that I'll likely ever get to do it, too expensive.

old3eyes

9120 posts

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#1198848 17-Dec-2014 09:08

Scotty1986: So I moved into a new rental in Johnsonville, Wellington about 4 months ago. Towards the end of winter. It has a triangle shaped roof with no insulation, very thin ceiling with a tin roof. So there is little space between the inside of the ceiling and the outside air. It was surprisingly warm compared to our last house in winter. It has a heat pump downstairs. All has been well until the temperature has started to rise. Upstairs in my man cave where I spend most of my time the heat is becoming unbearable. I am running a fan all day. The ceiling is conducting the heat. It is hot to touch, not warm, hot! Today was the worst, and its only the beginning of summer.

Today I ran the heat pump on cool downstairs with the windows closed and it was bliss.

Couple of questions. Does anybody use their heat pump as a air conditioner often? What does it do to your power bill? Secondly, can I run a second unit upstairs off of the original pump, 2 units off one pump. Hopefully the ducting can go far enough. Estimates of cost on a second unit?

We use ours all the time in the summer as an aircon. In fact in the user manual (fujitsu) it never mentions the word "Heatpump" only Air Conditioner so I suspect that the term heatpump is a local most likely australian name for it.. Like Ute for pickup truck..

Regards,

Old3eyes

timmmay

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#1198852 17-Dec-2014 09:13

Mildly interesting point Fujitsu's Nocria is "aircon" spelled backwards - AFAIK it's optimised for heating as NZ typically needs heaters far more than air conditioners.

xontech

268 posts

Ultimate Geek

#1198884 17-Dec-2014 10:11

There is specific types of insulation you can get for that type of roof (skillion).
May need a builder involved to confrm the thickness allowed, as there are air gaps required.
Other challenge is installation, basically involves either removing the ceiling or roofing to install.

wasabi2k

2096 posts

Uber Geek

#1198943 17-Dec-2014 11:01

Cost depends on a bunch of factors (size of room, airflow, age and model of heatpump etc) - I'd suggest using it for a week around the end of the month and then extrapolating.

If you've got a smart meter you should be able to see daily usage online with your power provider.

We use our heatpump to cool in summer, but not every day - cost does add up. We used it almost constantly through winter for heating and it was roughly $1 a day or so.

blakamin

4431 posts

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#1199494 17-Dec-2014 20:11

timmmay:
blakamin:
sbiddle: Multiple units can be fitted off a single outdoor compressor but it's highly unlikely you'll have a compressor that's big enough for this - it's something you'd do during the install phase if they were required.

Exactly! This is mine... and only designed for 1 indoor unit. (the mess is from the old unit)

That's a heck of an outdoor unit. I was thinking a double unit like that around 20kw might be enough for a central heating type unit at my place - not that I'll likely ever get to do it, too expensive.

Biggest domestic unit we could find at the time... :)
When you have 5 days over 42° like we did last year, you want big.
It just idles along quite nicely at 40°, so we'll see how she goes in summer.

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