Heatpump replacement options for existing house

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KellyP

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#300621 22-Sep-2022 17:35

Hi team,

Just organising a heatpump replacement for my parents.

Thier house is a 1996 built 3-bedroom Townhouse, single glazing with HRV (4 ducts). 2 heatpumps split systems. Mitsubishi (back-to-back in living room) and Panasonic (in hallway for heating rooms off hallway)

My parents are wanting to replace the Mitsubishi as it's nearly 20 years old and it is slow to heat the room.

Initially I was thinking just to replace it with a new equivalent however I do wonder, is a ducted option worth it? The Panasonic is 15+ years old.

Edit: It's in Christchurch, concrete floor.

Thanks

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#2971810 22-Sep-2022 17:54

Have a read of my ducted heat pump guide. They're not for everyone, they're pretty expensive, and you need individual room temperature sensors otherwise they're terrible in my experience.

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tweake

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#2971816 22-Sep-2022 18:06

I really detest the heat pump in the hallway setups. they are a cringe worthy bandaid.

I would look at heat pumps per room or go ducted.

Trouble with ducted is your typically putting the indoor unit outdoors ie in the ceiling. The insulation on the ducts are not great. So they do tend to loose efficiency in colder areas.

Part of it is how they are going to use it. There is a big human factor with this and its often insulting (rather then insulating). A lot of people, especially oldies, tend to use heat pumps like its a fireplace which is not good. they are really meant to keep a house warm not heat the house up from cold. ie you leave it running all the time and you heat the whole house constantly. This is where ducted works best.

Is the mitsi not performing well, is it undersized or is it human factor? I would run the house through one of the heating calcs and work out the recommended heat pump for each room.

insane

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#2971875 22-Sep-2022 23:45

I've gone with highwall units throughout my house (just added another this week) 4 via a single multi-split unit, and 3 standalone.

The one installed this week was a 5kw standalone Panasonic unit to replace a 3.5kw Mitsubishi unit that just wasn't keeping up after we took a wall out and opened up the space it was in.

While it was previously only struggling at the hight of summer and winter, the new unit is performing much better and the room is heated far more evenly.

If they are happy with the placement, a new unit will likely be far more efficient, and physically smaller. Might be able to get a larger rated unit for the same running costs

timmmay

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#2971897 23-Sep-2022 06:56

Can anyone give examples of how much multi-split units cost, installed, compared with individual units? I'm considering getting a multi-split for my kitchen/office, which can't go on the ducted system for two reasons 1) Kitchen smells 2) Office is an extension and I can't easily get a duct in.

@James Bond have a look at that guide I linked to and come back with questions.

tweake

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#2972161 23-Sep-2022 14:26

timmmay:

Can anyone give examples of how much multi-split units cost, installed, compared with individual units? I'm considering getting a multi-split for my kitchen/office, which can't go on the ducted system for two reasons 1) Kitchen smells 2) Office is an extension and I can't easily get a duct in.

@James Bond have a look at that guide I linked to and come back with questions.

try to avoid multi-splits setups if possible. they are fine for doing multi heads in one big room but run worse when the heads are in separate rooms. even worse when there is a big difference in size. also the more heads the worse it gets. you get a situation where its a small head being run by a big compressor and it will short cycle badly. tho just two heads is not to bad, especially with variable compressors, even better if you can keep both heads similar sized.

dazzanz

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#2972171 23-Sep-2022 15:01

timmmay:

Can anyone give examples of how much multi-split units cost, installed, compared with individual units? I'm considering getting a multi-split for my kitchen/office, which can't go on the ducted system for two reasons 1) Kitchen smells 2) Office is an extension and I can't easily get a duct in.

I had a multi split Daikin system with 1 outdoor unit and 5 Daikin Vogue wall units. They have been running throughout winter without a problem. They are in 4 bedrooms and 1 entrance way, all rated the same (I think 2.5kw or whatever is the lowest they sell). Works perfectly so far, heats all of the rooms and we usually have a variation in temperatures. They also work with Home Assistant as they have WiFi built in. Unfortunately I can't give you an install price as I had a family member do it for cost, total was about $7k with about half the price being the outdoor unit and the other half the indoors. They are also quite nice looking units compared with the Mitsubishi we used to have.

timmmay

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#2972173 23-Sep-2022 15:14

Thanks tweake, dazzanz. I was hoping to do a split with about 7kw in the kitchen and about 3kw in my office, to save having multiple outdoor units.

tweake

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#2972175 23-Sep-2022 15:24

timmmay:

Thanks tweake, dazzanz. I was hoping to do a split with about 7kw in the kitchen and about 3kw in my office, to save having multiple outdoor units.

it depends a lot on how it get used. worse case is office being run on its own. however 3kw from a 7kw unit is not to bad if its a variable compressor. the 3kw will run like its a fixed speed compressor.

make sure you run it through the calcs and get the size right. one of the problems i have is my office and bedrooms ones are to big and they are basically the smallest i can get. keep in mind that smaller ones have quieter fans.

Perkynana

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#2972274 23-Sep-2022 18:22

I have a daikin split system. Been in for 5 yrs. The smaller unit in downstairs bedroom, larger one upstairs. Our house split level 2 story. $5400 installed inc gst

Super Multi NX complete system of:
1 x Outdoor unit Model 4MXM68RVMA
1 x Indooe unit Model CTXM25RVMA
1 x Indoor unit Model CTXM50RVMA

works well. I can’t believe how cheap it is to run. Only negative is I’m a light sleeper and I find noise in bedroom a bit off putting if I leave on all night. However I’m Auckland so doesn’t get that cold so I rarely use overnight.

empacher48

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#2972281 23-Sep-2022 18:41

tweake:
try to avoid multi-splits setups if possible. they are fine for doing multi heads in one big room but run worse when the heads are in separate rooms. even worse when there is a big difference in size. also the more heads the worse it gets. you get a situation where its a small head being run by a big compressor and it will short cycle badly. tho just two heads is not to bad, especially with variable compressors, even better if you can keep both heads similar sized.

Having installed Mitsubishi Electric heat pumps into 5 rooms (4 bedrooms @ 2.5kw and lounge @ 7kw) our installer told us to avoid a multi split system for the reasons you explained. Plus he also said the larger outdoor units used are made only in the Japanese factories to keep their technology in house and only produce smaller numbers per year. Where as the AP plus single splits we used are manufactured in other locations as they aren’t so concerned with their tech secrets for single splits to be leaked and can be mass produced in multiple locations. It also makes them cheaper to buy and maintain than waiting for exclusive parts from Japan.

Our installer only deals with Mitsubishi Electric heat pumps as he said in his 20 years running his business the rate of warranty work on them is a lot less than other brands.

tweake

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#2972293 23-Sep-2022 19:10

Perkynana:

I have a daikin split system. Been in for 5 yrs. The smaller unit in downstairs bedroom, larger one upstairs. Our house split level 2 story. $5400 installed inc gst

Super Multi NX complete system of:
1 x Outdoor unit Model 4MXM68RVMA
1 x Indooe unit Model CTXM25RVMA
1 x Indoor unit Model CTXM50RVMA

works well. I can’t believe how cheap it is to run. Only negative is I’m a light sleeper and I find noise in bedroom a bit off putting if I leave on all night. However I’m Auckland so doesn’t get that cold so I rarely use overnight.

now this setup is a little interesting.

the outdoor unit is 6.8kw while the indoor heads together are 7.5 kw. one trick is to undersize the compressor to get around the problems i mentioned. which is better when the building is up to temp, but its undersized for when your running both heads to heat the house up.

Perkynana

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#2972296 23-Sep-2022 19:30

Our house that system is in is pretty small 100sqm 2 bed townhouse . I rarely have to set temp above 18 and house warms up easily.

I don’t feel the system ever runs hard.

From memory the manual talks about a priority room setting where the first room turned on has priority over the other unit f

The two units seem to just toggle on and off as required to meet thermostat temp.

I originally was going for two single units but my installer recommended the split system as better.

It sort of makes sense that one engine is going to be use less energy than two starting and stopping all the time. Also less clutter around outside of house

As I say we’re Auckland and probably use the heating 4 months of the year.

Happy with performance and running cost of the daikin.

Im just a punter with no technical experience but did a bit of research on the daikin vs Mitsubishi.

went daikin as was quite a bit cheaper with what looked like similar performance

tweake

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#2972298 23-Sep-2022 19:49

Perkynana:

Our house that system is in is pretty small 100sqm 2 bed townhouse . I rarely have to set temp above 18 and house warms up easily.

I don’t feel the system ever runs hard.

From memory the manual talks about a priority room setting where the first room turned on has priority over the other unit f

The two units seem to just toggle on and off as required to meet thermostat temp.

I originally was going for two single units but my installer recommended the split system as better.

It sort of makes sense that one engine is going to be use less energy than two starting and stopping all the time. Also less clutter around outside of house

As I say we’re Auckland and probably use the heating 4 months of the year.

Happy with performance and running cost of the daikin.

actually thats not the case. a single big pump is poorly sized for each head (its oversized), where as with two units they are correctly sized for each head. so two headpumps will run constantly and use less energy. they run their best when they run constantly, the pump slows down but doesn't stop. that gives you the most efficiency. which is why oversizing is a bad thing. on auckland coldest days it should be running constantly. if its stopping and starting then its to big.

in bad cases multi's can drop the efficiency in half.

but like a lot of kiwis, your only heating to the barest minimum (assuming the temp is accurate), well under the recommended temp. sadly kiwis are well taught not to use electric heating.

fe31nz

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#2972404 24-Sep-2022 01:55

And smaller heat pumps have higher ratios - up to 6 on the tiny ones for bedrooms now. The best you can get for a large HP such as our 7.2 kW in the kitchen is about 4.5 now. Ours is COP 4.04.

xlinknz

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#2975805 1-Oct-2022 13:39

I know our indoor until has maintenance requirements such as cleaning the filters etc but can anyone comment on whether the outdoor unit require maintenance?

Ours is a Daikin but the manual and web site doesn't say anything on that so does that mean the outdoor until are designed to be maintenance free?

Note ours is one year out of its 5 year warranty

Edit I had a quick look and it appears looking at a couple of companies outdoor maintenance typically consists of

ensuring the outdoor until is free of obstructions such as plants
flush and test condensate drain
Check condition of fan wheel, remove and clean if required (I am not sure if that is indoor or outdoor)
If needed anti rust spay of outdoor casing
refrigerant leak tests

Has anyone found outdoor unit maintenance was worthwhile?

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