Heat pump for a two-storey house: Two systems or single multi-room one?

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neb

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#262083 4-Jan-2020 16:07

Another part of the great Casa de Cowboy refit, we've got a 15+ year old Panasonic heatpump for what's currently the sole floor of the house, or at least the open-plan living area part of it which is the only bit that needs heating, so just a single room. When we extend downstairs we'll need a heat pump for there as well for the office/work area, i.e. another single room. Options are to add a second heatpump (outdoors+indoors units) for the downstairs room alongside the existing one, or to remove the current, rather large and older, one and put in a modern multi-room one, with one indoor unit upstairs and one downstairs. We're assuming that switching to a multi-room setup with a modern heat pump will be better than adding a second system alongside the existing rather old one, but if anyone has any thoughts we'd be interested in hearing them...

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#2385106 4-Jan-2020 18:12

Hi there
Make sure that you choose an outdoor unit that can independently control each of the two wall mounted indoor units if going down that path. That way downstairs can be on heating while upstairs is on cooling etc.

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Handle9

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#2385111 4-Jan-2020 18:41

If the current unit works ok then I would just put a second smaller unit downstairs. When. The upstairs one fails then it can easily be replaced as the piping and wiring should be able to be reused.

The install downstairs will then likely be very straightforward which further reduces your upfront cost. You can then also avoid any complications due to a multi head unit.

timmmay

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#2385120 4-Jan-2020 20:11

Pipes can't always be reused, especially the older ones, and some places want to run new pipes anyway. Should be easier than the initial install though.

I'd go with individual heat pumps unless you want whole house / whole floor heating. Whole house / floor is from about $15K.

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#2385167 4-Jan-2020 21:06

timmmay:

Pipes can't always be reused, especially the older ones, and some places want to run new pipes anyway. Should be easier than the initial install though.

I'd go with individual heat pumps unless you want whole house / whole floor heating. Whole house / floor is from about $15K.

Whole floor/whole house ducted solutions have their advantages (and I recognise this even as someone who went for individual heatpumps with our new house - we didn't design and build and just bought something that was brand new). However, I totally endorse what @Handle9 has pointed out here if anyone wants to go down that route: lots of residential installers have no clue on how to install these properly. I'd further add that one should beware of cowboys who will sell you under-powered solutions just to get you across the dotted line -- witness the recent splurge of "Whole house ducted solutions for circa 7K!" ads on Facebook and other NZ websites. When we were looking for our new home, we targeted high spec small (both house size and land area) houses of circa 130 to 150 sq metres that were either brand new or no more than 3 years old. The number of ducted solutions that we saw where one bedroom on one side of the house was freezing cold whilst another on the opposite side was an oven etc, was staggering.

Even as a non-expert, I could easily see that many solutions had air outlets in places that were wrong/purely there to achieve perceived aesthetic requirements. I am not here to talk anyone out of ducted solutions and there must be people who can do them properly but investigate your solution provider thoroughly before going ahead.

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#2385215 4-Jan-2020 22:14

Yoban: Hi there
Make sure that you choose an outdoor unit that can independently control each of the two wall mounted indoor units if going down that path. That way downstairs can be on heating while upstairs is on cooling etc.

I couldnt find any that do that, its always both have to heat, or both cool, or it alternates between the 2 rooms. No facility to move the heat from one room to the other.

Also got way more total power for minimal extra spend on 2 separate systems, and it gives me redundancy if one of them flakes out I can open both bedroom doors and crank one of them to get the other down to a bearable temperature.

Richard rich.ms

mattwnz

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#2385217 4-Jan-2020 22:17

Yoban: Hi there
Make sure that you choose an outdoor unit that can independently control each of the two wall mounted indoor units if going down that path. That way downstairs can be on heating while upstairs is on cooling etc.

I don't know why anyone would want to do that. Either the house is hot, or the house is cold. I also don't think any of the multi ones that I have seen allow one indoor unit to heat, and one indoor unit to cool, as I was told that was the downside with multi unit systems. But then they said that noone should need to do that anyway. .

richms

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#2385218 4-Jan-2020 22:23

mattwnz:

I don't know why anyone would want to do that. Either the house is hot, or the house is cold. I also don't think any of the multi ones that I have seen allow one indoor unit to heat, and one indoor unit to cool, as I was told that was the downside with multi unit systems. But then they said that noone should need to do that anyway. .

Because someone in one room with sun coming in is feeling hot, and someone on the other side of the house with no sun is feeling cold? Or my room with the PCs in it never needs heating, but the other bedroom often does, so it would leave one of them to get too hot while the other one was being heated up.

Richard rich.ms

Yoban

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#2385219 4-Jan-2020 22:24

Here we go: https://www.daikin.com.au/our-product-range/multi-split-air-conditioning

timmmay

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#2385263 5-Jan-2020 07:10

Separate units give more flexibility. A single outdoor unit can either heat or cool, not both at the same time.

jjnz1

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#2385267 5-Jan-2020 08:00

Our house is 120m2 and we have have a Panasonic ducted 10kw, which works perfectly at 0c and 32c. We have it set so the bedrooms are slightly cooler than the living rooms.

I highly recommend a full house ducted unit if you want to replace your existing.

Ours was installed for $8k by HRV, with wifi control.

It is the BEST to have a house that is always @ 20c.

*$15k for a ducted system seems way over priced, unless your house is 220m2 and not insulated?

neb

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#2385398 5-Jan-2020 15:35

Handle9: If the current unit works ok then I would just put a second smaller unit downstairs. When. The upstairs one fails then it can easily be replaced as the piping and wiring should be able to be reused.

A further note, explaining why we'd looked at multi-head, the existing outdoor unit will need to be moved because it's currently under the house where we'll be building. Adding a second system would mean relocating the current outdoor unit and then plonking a second outdoor unit next to the existing one. I'm also not sure how reusable the piping and wiring is, they can be rather system-specific so might need to be replaced if/when we replace the old system.

So there are additional considerations at play, e.g. fitting a single multi-head now while everything is open during construction - we can just run the plumbing through the open spaces - will be a lot easier than replacing the older unit later. It's a bit of a balancing act, not as straightforward as it seems.

neb

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#2385399 5-Jan-2020 15:37

Replying to multiple comments about heating and cooling at the same time: We'd never need to do that, we run the heat pump in winter for heating, very, very rarely on particularly hot days for cooling, and otherwise it's off. So it'd be either all heating or all cooling, never both, and only for two rooms in the house, not a whole-house system.

mattwnz

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#2385404 5-Jan-2020 15:53

richms:

mattwnz:

I don't know why anyone would want to do that. Either the house is hot, or the house is cold. I also don't think any of the multi ones that I have seen allow one indoor unit to heat, and one indoor unit to cool, as I was told that was the downside with multi unit systems. But then they said that noone should need to do that anyway. .

Because someone in one room with sun coming in is feeling hot, and someone on the other side of the house with no sun is feeling cold? Or my room with the PCs in it never needs heating, but the other bedroom often does, so it would leave one of them to get too hot while the other one was being heated up.

If it was the winter and cold outside, then it is very unlikely that the room would ever get so hot from solar gain, that you couldn't open a window or door to cool the room down. Or using sunshades in the room, or shading outside the room to reduce the solar gain. eg treating the cause rather than the symptom. If it was the summer and hot outside, then it is unlikely that a room would ever need heating. I have a split multi system, and have never come across the need to both heat and cool at the same time, and when I discussed this with the manufacturer as I did ask them whether it was an issue, and they said they had never come across people who have needed to do that. But you can also have a split system to most of the house, and a single heatpump in a problem area that gets a lot of solar gain or heat loss.

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#2385569 5-Jan-2020 19:06

Re hot and cold, we have that problem. Our living area has a lot of glass (most of 2 walls), and the sun even in winter makes it too hot in there (we don't have/use curtains).

And our bedrooms are not cold but normally a good temp.

We just put our ducted unit into into fan mode, and it makes the bedrooms warmer and the living areas more bearable.

If it gets too hot, we blast the cold for 20 mins then back to fan.

We have no issues.

timmmay

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#2385571 5-Jan-2020 19:10

jjnz1:

*$15k for a ducted system seems way over priced, unless your house is 220m2 and not insulated?

Verbal estimate from two different heat pump installation companies, about four weeks ago. I got a quote for single systems, and just asked how much whole house would cost. This is for a regular sized but very old house, about 120 square meters not counting extensions that wouldn't need anything, double glazed and fairly well insulated.

$8K seems really cheap. What brand is it, and who sold / installed it?

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