Recommendations for Air Conditioning expert in Auck ?

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1726 posts

Uber Geek

#2991737 4-Nov-2022 09:25

tweake:

efficiency goes bad when on part loads. it depends a lot on the combo and how its used, but basically its a big compressor trying to run a small head, so it short cycles. eg a 8kw lounge and 3kw bedroom means a 11kw compressor. if your only running the bed room its a 11kw compressor on a 3kw head. big miss match especially if you only need 1 kw output. variable helps a bit, and theres a few tricks that help.

So what are the long term implications of this scenario? IE our bedroom one runs all night, I forget the size, maybe 3kW and the compressor isn't as large as 8kW. Premature wear and tear on the outdoor unit, or just reduced efficiency?

It's been ridiculous how little our winter bill changed since they went in.

For the OP, I put in Mitsubishi, I didn't want any other brand, and contacted them to find an installer. A company called Apple Air did the install and I was happy with it.

NB wifi is absolutely brilliant too. The remotes went in a draw a week after the installation and haven't been used since. It's nice getting your phone out when you're about to leave for home and turn the heatpumps on if it's a crappy winter day.

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timmmay

19638 posts

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#2991759 4-Nov-2022 10:44

mudguard:

So what are the long term implications of this scenario? IE our bedroom one runs all night, I forget the size, maybe 3kW and the compressor isn't as large as 8kW. Premature wear and tear on the outdoor unit, or just reduced efficiency?

It's been ridiculous how little our winter bill changed since they went in.

For the OP, I put in Mitsubishi, I didn't want any other brand, and contacted them to find an installer. A company called Apple Air did the install and I was happy with it.

NB wifi is absolutely brilliant too. The remotes went in a draw a week after the installation and haven't been used since. It's nice getting your phone out when you're about to leave for home and turn the heatpumps on if it's a crappy winter day.

It will be efficient, but the minimum power outdoor output of a large unit might mean your indoor unit can't run on lower power / output. That would mean the unit turns on, runs for a short time on a higher speed, then turns off. If there was a small outdoor unit it might just run constantly at low power.

tweake

1057 posts

Uber Geek

#2991942 4-Nov-2022 16:49

mudguard:

tweake:

efficiency goes bad when on part loads. it depends a lot on the combo and how its used, but basically its a big compressor trying to run a small head, so it short cycles. eg a 8kw lounge and 3kw bedroom means a 11kw compressor. if your only running the bed room its a 11kw compressor on a 3kw head. big miss match especially if you only need 1 kw output. variable helps a bit, and theres a few tricks that help.

So what are the long term implications of this scenario? IE our bedroom one runs all night, I forget the size, maybe 3kW and the compressor isn't as large as 8kW. Premature wear and tear on the outdoor unit, or just reduced efficiency?

It's been ridiculous how little our winter bill changed since they went in.

For the OP, I put in Mitsubishi, I didn't want any other brand, and contacted them to find an installer. A company called Apple Air did the install and I was happy with it.

NB wifi is absolutely brilliant too. The remotes went in a draw a week after the installation and haven't been used since. It's nice getting your phone out when you're about to leave for home and turn the heatpumps on if it's a crappy winter day.

i would say both.

however when i say bad, the worse i've heard of actually been measured was 2:1. ie loose about half the units efficiency. it will vary a lot depending on the setup and how its used.

wear and tear will go up. the hardest thing for a compressor is start up. some compressor setups have maximum number of starts per hour. to many starts it flags an error.

also, depending on the units, some will have poor temp control. to reduce the amount of starts/stops they will let indoor temps change a lot more before starting (to give it more load to make it run longer). sometimes that can create comfort issues.

tweake

1057 posts

Uber Geek

#2991944 4-Nov-2022 16:58

timmmay:

mudguard:

So what are the long term implications of this scenario? IE our bedroom one runs all night, I forget the size, maybe 3kW and the compressor isn't as large as 8kW. Premature wear and tear on the outdoor unit, or just reduced efficiency?

It's been ridiculous how little our winter bill changed since they went in.

For the OP, I put in Mitsubishi, I didn't want any other brand, and contacted them to find an installer. A company called Apple Air did the install and I was happy with it.

NB wifi is absolutely brilliant too. The remotes went in a draw a week after the installation and haven't been used since. It's nice getting your phone out when you're about to leave for home and turn the heatpumps on if it's a crappy winter day.

It will be efficient, but the minimum power outdoor output of a large unit might mean your indoor unit can't run on lower power / output. That would mean the unit turns on, runs for a short time on a higher speed, then turns off. If there was a small outdoor unit it might just run constantly at low power.

efficiency actually drops when they start doing that. they work best if constantly running. thats why you don't want to oversize any heatpump.

i have that problem with two of my bedroom ones. they rarely ever run constantly even in the coldest weather and they are variable compressors. it gets to temp and goes into start/stop mode. my lounge one is sized about right and will run constantly. to give an idea of the difference, it takes about double the time to get a room to temp compared to the bedroom ones. so the bed room ones are double the size they need to be.

SomeoneSomewhere

1127 posts

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#2992267 5-Nov-2022 17:26

Additional reasons why a multi-split can be questionable:

Single point of failure causes loss of multiple indoor units. This could be the difference between having 75% of your house heated if something goes wrong, and no heating.
Lower production & supply quantities leads to worse costs and availability of spare parts.
Obsolete systems likely need to be replaced in their entirety in the event of a major failure, because spare units are unlikely to be available. So you might need 3x new indoors and a multi outdoor, vs just replacing one indoor and outdoor.
Product lifecycles are slower and older. Multi-splits are typically 0.5-1.5 generations behind single splits, with related reductions in efficiency, performance, refrigerant, support lifetimes, and tech level e.g. wifi integration.
A leak is likely to cause a loss of the whole system's charge. Refrigerant is only going to get more expensive.
A bigger system makes fault diagnosis and leak detection more difficult.

The only real advantages are physical space, and theoretically installation & equipment cost, but the latter rarely stacks up here due to low quantities.

mudguard

1726 posts

Uber Geek

#2992270 5-Nov-2022 17:42

SomeoneSomewhere:

The only real advantages are physical space, and theoretically installation & equipment cost, but the latter rarely stacks up here due to low quantities.

Space and installation was my main motivation. Our bedroom is above the lounge, we have a small balcony outside the bedroom. With the split unit we have the outdoor unit in a useful spot, and then the capping runs dead straight up quite a naked external wall. It means the two indoor units line up nicely inside the lounge and bedroom as well.

I'd assume the alternative would have been having two external units and then the installer may have been tempted to install the bedroom's external unit on the balcony upstairs. Which I didn't want.

tweake

1057 posts

Uber Geek

#2992274 5-Nov-2022 17:54

mudguard:

Space and installation was my main motivation. Our bedroom is above the lounge, we have a small balcony outside the bedroom. With the split unit we have the outdoor unit in a useful spot, and then the capping runs dead straight up quite a naked external wall. It means the two indoor units line up nicely inside the lounge and bedroom as well.

I'd assume the alternative would have been having two external units and then the installer may have been tempted to install the bedroom's external unit on the balcony upstairs. Which I didn't want.

no room to install two externals next to each other?

space issues is where multis are useful. but you do see them used even when there is plenty of space because some installers are lazy.

SomeoneSomewhere

1127 posts

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Lifetime subscriber

#2992292 5-Nov-2022 19:57

Mounting them vertically one above the other can be an option.

There can be cost advantages, and if you can get substantial cost savings then it's probably worth it. But for two or three indoors the savings usually aren't there.

concordnz

420 posts

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#2993051 7-Nov-2022 15:08

Highly recommend Gordon Vincent from Vincent Installs, as mentioned in a previous post here.
Excellent communication and will go through all the options with you. I've had install from him and so have friends. Good pricing as well.

Definitely go Single Outdoor unit with Multi head units.
Is much better than ducted.
(people who wax on about 'efficiency are clueless as to all the factors involved and how modern Aircon units work) - (and how ratings are specified)

Multi head unit are normally ' over spec'ed' by up to 40% (more head draw than outdoor unit can technically provide at maximum capacity)
(you also normally won't use a lounge/ office one while you are using the bedroom ones at night so there is pleanty of capacity & because NZ is rarely/never at full cooling/heating requirement there is also heaps of capacity. (we don't live in dubai or central AUS)

Gordon will come and see you - and go through all this...

tweake

1057 posts

Uber Geek

#2993273 7-Nov-2022 20:53

concordnz: Highly recommend Gordon Vincent from Vincent Installs, as mentioned in a previous post here.
Excellent communication and will go through all the options with you. I've had install from him and so have friends. Good pricing as well.

Definitely go Single Outdoor unit with Multi head units.
Is much better than ducted.
(people who wax on about 'efficiency are clueless as to all the factors involved and how modern Aircon units work) - (and how ratings are specified)

Multi head unit are normally ' over spec'ed' by up to 40% (more head draw than outdoor unit can technically provide at maximum capacity)
(you also normally won't use a lounge/ office one while you are using the bedroom ones at night so there is pleanty of capacity & because NZ is rarely/never at full cooling/heating requirement there is also heaps of capacity. (we don't live in dubai or central AUS)

Gordon will come and see you - and go through all this...

if the heat pump is rarely or never at full output, then its way oversized. you do not size them for the exact climate, they are always undersized. so it should be running at full output for a part of the season. for the few days or so more output is required, put some clothes on. its simply not worth the cost to have them sized exactly for the climate.

yes you can under spec the compressor for a multi which would help with the miss match in sizing. however then you can run into comfort issues because its far to undersized (eg 40% to small) for the climate. if you do it the other way and oversize the heads, then you end up with short cycling because the room gets to temp far to quickly (a problem i have with a couple of my own). multi's are a trade off.

don't take my word for it, plenty of building science professionals have articles on this including testing actual houses.

TeaLeaf

5118 posts

Uber Geek

#3001245 25-Nov-2022 11:08

Thanks for all the replies. I didnt realise we could keep the Single AC unt for the living areas and then a compressor for the HRV ducting to the bedrooms. How would the system stop air being sent to ducting in the living areas?

This would actually be brillian from the perspective the single Compressor and Head unit installed in the secondary living space (the architect designed it all fairly open so there are no doors as such but enough delineation to know what each area is designed for). That is sort of half the house, but the single unit cools all areas including the main living room nicely. The doorway that access the bedrooms has a sliding door in the wall, with this open and our Master bedroom door open that air con unit even starts to cool our room down, but not quite enough in summer.

We were just going to put another small 3kw single in our bedroom. 2 of the 3 other bedrooms are excellent room temp (and 1 is used for guests) most of the year, never seems to need cooling or heating thanks to a Pohutukawa shading. The house does have excellent thermal design (insulation & dub glazing etc) But if we were to ever need to use the back 2 bedrooms they would need AC as they get a little too warm in summer (some might be ok with it, closing the blinds to the sun and a Fan would prob do enough). We never use the AC for heating, in fact we rarely use the gas fireplace for heating, only a couple of nights a year. It really is only high humidity on the really hot days in summer that we want to fix for the master bedroom. Not wanting to over capitalise in the current economy, even if it is a very livable home.

So keeping the current Single AC for the living areas and Study works, we will just get the secondary 3kw AC for the bedroom at this stage, but will keep in mind a unit for the future that works with the HRV Ducting.

Is there any way to save money on Air Con units and or DIY install?

I will give Vincent Install a ring (2 referrals on here is a good sign) and have OxyAir doing a quote

timmmay

19638 posts

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#3001270 25-Nov-2022 11:58

TeaLeaf:

Thanks for all the replies. I didnt realise we could keep the Single AC unt for the living areas and then a compressor for the HRV ducting to the bedrooms. How would the system stop air being sent to ducting in the living areas?

I don't understand the question. Can you rephrase / expand on it please?

tweake

1057 posts

Uber Geek

#3001350 25-Nov-2022 15:17

TeaLeaf:

Thanks for all the replies. I didnt realise we could keep the Single AC unt for the living areas and then a compressor for the HRV ducting to the bedrooms. How would the system stop air being sent to ducting in the living areas?

don't use the HRV ducting for the heat pump. its a lot easier (and probably cheaper) to simple keep the ventilation and heating systems separate.

in one of the other threads, the person had the ducted heatpump first, then added ventilation to it. which is not bad if done right. however trying to fit a heat pump to a ventilation system has all sorts of problems to the point thats its easier and cheaper to keep them separate.

TeaLeaf

5118 posts

Uber Geek

#3018599 8-Jan-2023 15:22

tweake:

don't use the HRV ducting for the heat pump. its a lot easier (and probably cheaper) to simple keep the ventilation and heating systems separate.

in one of the other threads, the person had the ducted heatpump first, then added ventilation to it. which is not bad if done right. however trying to fit a heat pump to a ventilation system has all sorts of problems to the point thats its easier and cheaper to keep them separate.

Yes I tend to agree.

Have seen one company so far, I want to try a local guy and one recommended on here, not really in a rush, the main heat pump tends to cool the entire house down as it leaks through the hallway etc, which is crazy given its only a 6kw unit, but its not ideal.

Have seen the ceiling unit for split systems, a square shape, that would look good and work well I think. Possibly put one in the 2 main bedrooms currently used and use another 6kw unit at the back of the house and pipes through the roof. Was told can also have them capable of doing their own temperatures etc or 1 turned off etc.

timmmay

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#3018603 8-Jan-2023 15:34

I suggest running any design past us in this thread, there's quite a bit of experience in here, and I think tweake is a professional.

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