Another heat pump question

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35 posts

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#3100222 5-Jul-2023 14:14

AklBen:
I am not a fan of split units being used in bedrooms unless there's a strong need for AC in the summer. The reason? You've got a unit that runs with a fan and quite often the fan gets to the point where the air circulation feels cold (it isn't it's just the sensation of breeze).

As Timmay has alluded to over all of these years it's a process to figure out what works best. I would probably start with getting an outdoor unit that can have multi units added to, but start with one or two units in main areas only. I was very surprised how well our single 7kWh unit was able to push heat throughout the house.

My question was about bedroom cooling, we already have a heat pump for the living areas.

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Handle9

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#3100246 5-Jul-2023 15:06

timmmay:
I don't understand why NZ is often called "temperate". I find it fairly warm in summer but quite cold in winter.

In winter in Wellington it regularly gets down to almost 0 - 3 degrees overnight, many days don't get over 10 degrees, though we do have quite a few sunny and warm days in winter as well. We have an old but fairly well insulated house, we end up using heating about 7-8 months of the year and cooling 2-3 months of the year. Part of that is poor house design (i.e. it probably wasn't designed), if it was designed better it could avoid so much solar gain in summer and receive more in winter.

Temperate has a definition. It’s between the tropics and poles. Within that there’s a mild oceanic climate which is what New Zealand has.

Most of the country operates between 5-25 degrees all year. There’s distinct seasons but not particularly big changes in temperature. Contrast that with Northern Europe which swings between -10 and 35 degrees.

concordnz

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#3100257 5-Jul-2023 15:36

Aitchy:
AklBen:
I am not a fan of split units being used in bedrooms unless there's a strong need for AC in the summer. The reason? You've got a unit that runs with a fan and quite often the fan gets to the point where the air circulation feels cold (it isn't it's just the sensation of breeze).

As Timmay has alluded to over all of these years it's a process to figure out what works best. I would probably start with getting an outdoor unit that can have multi units added to, but start with one or two units in main areas only. I was very surprised how well our single 7kWh unit was able to push heat throughout the house.

My question was about bedroom cooling, we already have a heat pump for the living areas.

You need a multi-split, that will be perfect for your requirements,

Don't waste time on ducted, they are nowhere near effective enough specifically for cooling.

With a multi-split, you are only cooling the air required in the room and only to the level required. So they are extremely cost effective.
Your child with the medical issue will love you for it!

My child & I can finally sleep better at night with a multi-split.

timmmay

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#3100264 5-Jul-2023 16:00

concordnz:

You need a multi-split, that will be perfect for your requirements,

Don't waste time on ducted, they are nowhere near effective enough specifically for cooling.

With a multi-split, you are only cooling the air required in the room and only to the level required. So they are extremely cost effective.
Your child with the medical issue will love you for it!

My child & I can finally sleep better at night with a multi-split.

Ducted work well for cooling, but they are more for areas than rooms. I agree that multi-split or even individual room units are better in this case - and in many cases.

tweake

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#3100276 5-Jul-2023 16:28

concordnz:

You need a multi-split, that will be perfect for your requirements,

Don't waste time on ducted, they are nowhere near effective enough specifically for cooling.

With a multi-split, you are only cooling the air required in the room and only to the level required. So they are extremely cost effective.
Your child with the medical issue will love you for it!

My child & I can finally sleep better at night with a multi-split.

i'm not sure where you get that from. ducted aircon is common in usa with millions of people using those systems.

there is some downsides to ducted systems, especially as the unit and ducts are often installed in the ceiling. how much aera is covered does depend on how the returns are done ie don't go via the hallway.

but they can be cheaper to install than running multiple linesets. all depends on the house.

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#3100277 5-Jul-2023 16:31

Why not via the hallway ?

“The modern conservative is engaged in one of man's oldest exercises in moral philosophy; that is, the search for a superior moral justification for selfishness.” -John Kenneth Galbraith

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#3100281 5-Jul-2023 16:37

rb99:
Why not via the hallway ?

In many houses via the hallway is fine, and often better than having a return in individual rooms as it avoids short cycling (air moving from the supply grill straight back into the return).

If you have the doors to the rooms mostly shut that’s when it can be an issue but that’s not how most people live, and especially if you are conditioning the entire house. It really depends on the layout of the space.

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#3100334 5-Jul-2023 17:09

rb99:

Why not via the hallway ?

its adds volume to be cooled, as per concords mention of just cooling those rooms. that can be important if your running a different temp to the rest of the house.

otherwise i would normal say use the hallway and heat/cool the hallway and the side rooms (toilet and bathroom) as a side benefit. close the hallway door if your running the lounge separately.

also i should mention that if the interior walls are not insulated, heat goes through the bedroom walls anyway. so your cooling down hallway etc anyway. i aircon my bedroom lower than the house and if you turn it off, the room heats right back up as its being heated by the rest of the house.

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#3100342 5-Jul-2023 17:40

If we ever do anything, it'll almost certainly be just for heating / ventilation, not cooling.

I guess also, while zoning sounds attractive to me, if you have all the doors open, which I'm pretty sure we will (indoor doors of course), I guess there isn't a lot of point to it ?

“The modern conservative is engaged in one of man's oldest exercises in moral philosophy; that is, the search for a superior moral justification for selfishness.” -John Kenneth Galbraith

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#3100346 5-Jul-2023 17:52

rb99:
If we ever do anything, it'll almost certainly be just for heating / ventilation, not cooling.

I guess also, while zoning sounds attractive to me, if you have all the doors open, which I'm pretty sure we will (indoor doors of course), I guess there isn't a lot of point to it ?

It really depends. Loads differ depending on the number of people in the spaces, solar gain, other heat sources etc.

Zone kits are all a cheap kludge solution to using a constant volume fan coil to supply variable volumes to different spaces. They can range from effective to hopeless. It all depends on your spaces.

Ducted units usually are designed to supply a fixed or three different volumes of air. They aren’t designed to supply a variable volume system. Properly designed variable air volume (VAV) systems are widely used commercially but they need different plant, more sensors and careful commisioning.

Having an energy source in each room will give you the best temperature control - you can apply exactly what each room needs and not affect the other rooms. Typically in New Zealand this means high wall units, either a multi head or individual units.

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#3100379 5-Jul-2023 18:57

Thanks for the info. Must admit, its a bit depressing though - everytime you read about something that sounds great, you see something else that points out some flaw.

Not exactly confined to heatpumps of course...

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#3100382 5-Jul-2023 19:06

rb99:
Thanks for the info. Must admit, its a bit depressing though - everytime you read about something that sounds great, you see something else that points out some flaw.

Not exactly confined to heatpumps of course...

I understand. I’ve worked in HVAC control for a long time and the whole thing is a compromise. If you had unlimited money you’d have a ducted unit for every room but it’s an expensive way to go. If I was living in my house in NZ I’d have small multi head cassettes or high walls for the bedrooms and a ducted unit in the open plan kitchen living space.

In my house in Dubai I have 4 ducted units for a two story four bedroom house. I’ve got one bedroom which is a problem as it has the carport underneath it and the unit serves two bedrooms and the upstairs lounge. We’ve been able to make it better with balancing dampers but it’s still a compromised system. It’s all a compromise as to change it requires significant civil work as well as HVAC work.

You can make most plant work ok, it’s about finding a contractor who is competent, will work with you and explain the compromises.

eonsim

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#3100384 5-Jul-2023 19:16

If you are looking to put a heatpump in a couple of bedrooms I'd also recommend multi-head unit. I would suggest that you use better quality head unit's inside, in particular choosing ones that are known to be low noise or have a Silent or Quiet mode that can be set at night. Some of the cheaper heads units can be a bit noisy.

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#3100390 5-Jul-2023 19:30

eonsim:

If you are looking to put a heatpump in a couple of bedrooms I'd also recommend multi-head unit. I would suggest that you use better quality head unit's inside, in particular choosing ones that are known to be low noise or have a Silent or Quiet mode that can be set at night. Some of the cheaper heads units can be a bit noisy.

i would add do not oversize, if anything go undersize. typically they use the same fan as the more powerful units but run the fan slower which is quieter. good brands will have rpm and sound level listed.

also quiet mode can be a bit different between cheap and fancy model. quiet on my basic model on is just a low speed. quiet mode on the up spec one will run slow speed but will run slower again when its not heating/cooling.

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#3100393 5-Jul-2023 19:36

Don't know how you find someone who's competent. I can ask questions, but being in Whakatane, we've had two guys / companies turn up, one of which who actually gave a quote (fully ducted for the top level plus ventilation, lets just say it begins with a 2).

They say when it comes to fitting things in roofs we'd need two heatpumps, and associated ducting etc etc. They say one unit for a largish living room plus study and the other for another living room / kitchen plus two bedrooms. Perhaps would be better to make one unit bigger to do all living areas and the other smaller for the two bedroom (unless that makes the big unit too big...).

The silence of ducting has a certain appeal, but I seem to sleep lightly and a head unit in a bedroom might be good for white noise cause rain on a tin roof at night is not good for me. But still silent heating...

I can, and do, go round in circles with stuff like this for months...

“The modern conservative is engaged in one of man's oldest exercises in moral philosophy; that is, the search for a superior moral justification for selfishness.” -John Kenneth Galbraith

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