Ducted Heat Pump Queries

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shall0w

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#311753 12-Feb-2024 08:57

Morning, I'm looking for some input into a ducted heat pump system that I'm wanting installed.

I've read the pinned thread and a few others, but what I'm being told by the company quoting doesnt line up with what I've read / understand.

A few details, the house is a 1910 villa

3m? stud
walls insulated, ceiling insulated and partial floor insulated
Sash windows - leaky round the edges, some double glazed, heavy insultated curtains floor to ceiling
Large freestanding fire in the main area
Approx 150sqm, wanting to heat 3 bedrooms, bathroom and lounge + dining + kitchen (one room
Ceiling has enough headroom to comfortably standup and walk around in, so in roof unit shouldnt be difficult
Site is dead flat, with easy access
Outdoor unit to roof connection straight up the wall and into the soffit - nothing crazy
House has been rewired - electrical should be straight forward also, easy access to switch board.
Location - wairarapa

Wanting a mitsubishi, with wifi connectivity and zoned so we can heat the bedrooms / bathroom seperately when the fire is in use.

I've been quoted $21k for the following, which seems high given prices I've seen in other threads.

Ducted heat pump system
Supply and installation of a Mitsubishi Electric ducted heat pump with WiFi
Model: PEA-M140
Heating 16.0 kW
Cooling 14.0 kW
Manufacturer’s Warranty Period: 5 years parts & labour on the unit.
Warranty Period for installation parts and materials: 12 months
Indoor unit location: In a central location within the ceiling.
Outdoor unit location: Outside the bathroom.
200mm down-jet supply air ceiling diffuser locations:
Bedroom One x 2;
Bedroom Two x 1;
Bedroom Three x 1;
Dining x 1;
Lounge x 1;
Kitchen x 1.
150mm down-jet supply air ceiling diffuser locations:
Bathroom x 1.
800mm x 400mm return air grille locations:
To be confirmed but two are rquired and need to be in a common area away from supply air grilles (ideally in the
hallway).
All insulated ducting will be R1.0

Sidenote - I had a lossnay system quoted as an addon, was not expecting it to be an addititional $6k!

I asked some follow up questions based off my reading here, answers from the installer in bold

Can you please let me know how you sized the system - I'm surprised that such a small house requires the largest system. I drew a detailed plan of the house, then entered the details (length, width and heaight) into a heat load calculator. I then took into account the type of house and the likely insulation rating. That gave me a required kW and air volume figure. I then checked performance table to see what kw output a particular system will profduce at 2 degrees as all systems have a significant drop in performance at lower temperatures
There doesn't appear to be any reference to zoning? We would want the ability to individually set the rooms via zones and automatic temp control (i.e. not manually adjusting the flow to rooms via diffusers) if possible. At a minimum we'd want to separate the living and bedrooms into 2 zones. We use AirTouch5 Zone Control. It adds around $5k to the quoted price. Please be aware that from industry testing there are little to no power savings achieved from zoning, which is what some people want it for. I can provide a quote for this if you would like one?
Diffusers - what is your opinion on square Multi Directonal Outlet one's - I'm told that these perform much better than the regular round ones. They are generally metal as opposed to plastic and I haven't seen them used residentially. I can't comment on performance differences as I haven't had experience with them.

My questions

Does this seem expensive to anyone who has recently priced a system?
The system feels oversized given the size of the house - thoughts?
I thought the mitsi could be zoned without the need for airtouch?
Does anyone know of another installer in wairarapa they'd recommend so I can get a second quote.Any and all input appreciated

Any and all input appreciated!

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#3194197 12-Feb-2024 09:50

We paid $19.5k in mid 2020 for exact same model Mitsubishi ducted aircon model PEAD-140 (R32), WiFi adaptor, 8 x 200mm outlets, 2 x wired wall controllers, 1 x Lossnay unit (50VRX or ERX model), 1 x lossnay wall controller, 2 x ducted aircon return air grille and 1 x lossnay return air grille in hallways. From memory, Lossnay cost was just under $4k and ducted aircon cost was $15.5k. We have no zoning and did not opt for it to avoid any noise or back pressure issues. It's nice to walk into any room and feel the same tempurature.

Do whatever you want to do man.

timmmay

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#3194199 12-Feb-2024 09:52

A few thoughts:

Heating a reasonably large house with a high stud that's probably fairly leaky will take a reasonable amount of power. However, if you usually want to heat a subset of the house such as just the bedrooms at night the minimum power means you'll have a lot of excess heat or your rooms will heat up REALLY fast. Even with a 10kw system, heating two bedrooms at night, I have Home Assistant interface with the Airtouch to make sure dampers never open more than 50%. You don't use ducted systems like regular heaters, you turn them on an hour or three before you need the house up to heat / cooled. In winter we don't tend to turn it off, we just turn the temperatures down. Sometimes we turn it off say 7am to 3pm on warmer winter days.
You might not want to size to keep the house 100% up to heat even on the very coldest days. If the house is a little cooler than ideal on a few days a year, put on a jumper, or turn off rooms you don't need heated. Given we have 10kw for three bedrooms and a lounge, 16KW doesn't sound crazy, however I'd be shooing for 6-8kw max next time we have to replace the unit. Actually I'd probably look at multi-split, much simpler.
Heating a bathroom means you'll be pushing humidity into the rest of the house. I'm not sure if I'd do it.
Individual room temperature control is essential IMHO, I wouldn't have a ducted system without it. Even with it, individual room units / multi-split has many advantages, including that you can easily heat one room. With a ducted system you have to have vents, and if you're not careful with vent placement heating / cooling one room affects other rooms. For example, cooling our bedrooms also cools our lounge even if the zone is turned off, because of the vent locations and house layout.
You should consider other good brands like Daikin. I had a sub-par experience with Panasonic, they might be fine these days, but I wouldn't touch them personally.
The Airtouch5 will work well, but I think some brands have built in zoning these days which is probably cheaper and more effective.
Send them a link to the MDO square diffusers I talked about on the other thread. Downjet may be better for 3m stud, but those square ones work fine for us in our old house that has quite high ceilings.
Generally that installer sounds like they have limited experience with ducted systems. I'd want someone who's more confident and experienced.
Next time we need to replace our heating we'll seriously consider multi-split. To make Airtouch4 and zoning work for us I do all kinds of tweaks using home assistant. Multi split or individual units are simple - heat or cool the room. Ducted with temperature controlled zones is much more complex.
$21K without zoning sounds a bit high to me, considering it doesn't include zoning. Get another quote.

Seriously consider a multi-split system, or even a couple of them. Simpler, more control, no cutting holes for vents, avoid the complexity of a ducted system and Airtouch, may be cheaper.

timmmay

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#3194201 12-Feb-2024 09:54

billgates:

We paid $19.5k in mid 2020 for exact same model Mitsubishi ducted aircon model PEAD-140 (R32), WiFi adaptor, 8 x 200mm outlets, 2 x wired wall controllers, 1 x Lossnay unit (50VRX or ERX model), 1 x lossnay wall controller, 2 x ducted aircon return air grille and 1 x lossnay return air grille in hallways. From memory, Lossnay cost was just under $4k and ducted aircon cost was $15.5k. We have no zoning and did not opt for it to avoid any noise or back pressure issues. It's nice to walk into any room and feel the same tempurature.

Our first ducted unit was not zoned. The rooms on the north / sunny side of the house ended up 3-4 degrees warmer than the rooms on the south side on sunny but cool days. It was so bad we had the system removed. I think it depends on the house, the location, how much sun you get, etc whether it'll work. A guy at work has a non-zoned system in his house and said it's fine.

TechSol

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Technical Solutions Aust

#3194204 12-Feb-2024 10:03

I know a bit about this topic so:

Does this seem expensive to anyone who has recently priced a system? This seems fair when you are including zone control - I couldn't understand if this was included, but should be at that price. (Side note $6k extra for lossnay is reasonable)
The system feels oversized given the size of the house - thoughts? This seems about right
I thought the mitsi could be zoned without the need for airtouch? No

shall0w

80 posts

Master Geek

#3194220 12-Feb-2024 10:24

Thanks all, my experience is with gas ducted which we have in our primary home but its a very dumb system so still working out the ins and outs of this type of unit for this house.

@timmmay

The house is used only on weekends in winter so would be for pre-heat prior to arrival / maintain turn off come sunday
- (which is also why I think a smaller system might be suitable)
House gets a lot of sun and the warmth / cold shifts across the house
As its a period house thats been finished to a high standard we (wife!) have a requirement for minimal visual intrusion which rules out multi / individual units and cutting up the doors for returns.
I'll have a look at daiken - peoples experience with the app had put me off (remotely starting heating is a requirement)

@Techsol thanks for the input, that price does not include zone control (extra $5k on top for airtouch 5)

@billgates - great info for comparison, given inflation since your install it seems that the price may be reasonable (massive assumption that the install is comparable)

I had decided against the lossnay as the house isnt used enough to justify the cost (and isnt damp currently).

timmmay

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#3194231 12-Feb-2024 10:40

With a ducted heat pump you must have return paths for the air. Undercutting doors is common in NZ, but if you don't want to do that you can put in door / wall vents that I link to in the other thread. If you don't do this you will end up with pressurised rooms and inefficient heating, as instead of returning the air that should return could go outside through cracks in windows, and the return vent could pull outside air in to heat through leaky windows rather than cycling the indoor air. If you can't do a decent return pathway you shouldn't have a ducted system.

You can have a small return in each room, that will increase the cost though as more ducting and diffusers will be needed. The advantage of vents is they can be low down, the diffuser putting air into the room is high up, so air is drawn across the room and down. Source and return on the ceiling risks the ceiling area being heated but the floor staying cold, you would need to account for that with your diffuser selection. It's an option, but not a great option.

Since source diffusers would be in the ceiling, having the return vent at floor level can make the system draw air down rather than letting the heat rise. You still need a large vent, but sometimes you can use a centrally located cupboard in a hallway or similar, or that plus a ceiling return. I'm not sure if NZ HVAC people have gotten onto this yet.

The Daikin app I have for my small heat pump is fine. If you use an Airtouch you don't use the native app, you only use the airtouch app. The Airtouch app is good for turning on heating remotely or basic scheduling. Given the house gets a lot of sun and you say hot / cold shifts I think you'd need an Airtouch or similar.

tweake

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#3194406 12-Feb-2024 18:06

shall0w:

Location - wairarapa
I asked some follow up questions based off my reading here, answers from the installer in bold

Can you please let me know how you sized the system - I'm surprised that such a small house requires the largest system. I drew a detailed plan of the house, then entered the details (length, width and heaight) into a heat load calculator. I then took into account the type of house and the likely insulation rating. That gave me a required kW and air volume figure. I then checked performance table to see what kw output a particular system will profduce at 2 degrees as all systems have a significant drop in performance at lower temperatures

that alone tells me the guy doesn't know what hes doing. 2 degrees is auckland temp, not wairapa. sounds like hes using the real basic calcs that do not use location data.

first thing i would do is go use one of the better calcs (remember they are simplified). you will need to know measurements of house/rooms, window sizes and insulation levels. be careful if it asks for type of house because houses with major reno's done to them will not be the same. your going to have to guess a bit depending on whats been done to the house.

loosney, generally speaking waste of money on older homes, unless its been well air sealed from the reno. it also would not dry a home (assuming erv). a standard positive pressure system will work just fine.

i would draw up a plan of it, or get any installer to do so. i'm wonder why they need 2x200mm outlets in a bedroom.

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johno1234

2823 posts

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#3195387 15-Feb-2024 09:04

timmmay:

billgates:

We paid $19.5k in mid 2020 for exact same model Mitsubishi ducted aircon model PEAD-140 (R32), WiFi adaptor, 8 x 200mm outlets, 2 x wired wall controllers, 1 x Lossnay unit (50VRX or ERX model), 1 x lossnay wall controller, 2 x ducted aircon return air grille and 1 x lossnay return air grille in hallways. From memory, Lossnay cost was just under $4k and ducted aircon cost was $15.5k. We have no zoning and did not opt for it to avoid any noise or back pressure issues. It's nice to walk into any room and feel the same tempurature.

Our first ducted unit was not zoned. The rooms on the north / sunny side of the house ended up 3-4 degrees warmer than the rooms on the south side on sunny but cool days. It was so bad we had the system removed. I think it depends on the house, the location, how much sun you get, etc whether it'll work. A guy at work has a non-zoned system in his house and said it's fine.

Does closing the grille dampers work? I do wonder how leaky those things are, and if closing off all but a couple of rooms works well.

I have priced up a ducted heat pump system to install in the basement of the house we recently moved into. There's an existing diesel burning central heating system so we'll just see how that goes this winter before committing to a new system as so far the house is comfortable in the summer week since we moved in. The diesel tank is huge - about 600L estimated and is about 1/4 full. Will be interesting to see how fast that drops when running it.

The ducted heat pump proposal is based on a 15KW indoor unit and outdoor unit. We would remove all the manufactured rigid metal central heating ducting from the basement. The existing rectangular floor grilles for the central heating are slightly smaller than the air con grills so would require enlargement of the holes in the timber floors so can install new grills there. With staff buying privileges I am able to purchase the air con indoor and outdoor units for a ridiculously cheap price, but the quoted install of the system including "ducted manufacturing. plenums, splitters, boots and grills, return boots and grills, copper, duct saddles and labour" came to an additional $7k plus electrical connection. That's for 9 outlets over 4 bedrooms, office and kitchen/lounge. No zone control, but the technician confirmed that this can be retrofitted later with an airtouch style system. We'd see how the house goes without zone control first.

Does an airtouch system effectively automate closing grill dampers or does it work better than that?

timmmay

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#3195405 15-Feb-2024 09:27

Closing the dampers in the ceiling doesn't completely stop air going through but it reduces it by 95% and you can't feel a breeze. For example, when I turn the lounge heating on with bedroom dampers closed The lounge heats up around 3 degrees and the bedrooms would heat up by around half a degree.

Air touch automates damper opening and closing to reach target temperatures.

You have said grill dimpers, just want to make sure you know these are the dampers in the ceiling inline with ducting. The supply diffusers that you see on the ceiling cannot be closed, at least not the good ones, the old circle ones that don't work very well can be closed.

johno1234

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#3195443 15-Feb-2024 10:19

In our case all the existing central heating outlet grilles (diffusers? Not sure about the correct terminology) are in the floor. These would be replaced by new ones in the floor for the ducted heat pump system and I assumed they would be able to be manually closed off. I would want to avoid heating or cooling the entire house that way if we didn't have zone control?

tweake

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#3196004 15-Feb-2024 19:43

johno1234:

I would want to avoid heating or cooling the entire house that way if we didn't have zone control?

i would heat/cool the entire house. its so much better for comfort, much much better for the house as heat moves moisture and even if you heat just one room your actually heating the house via one room. we have been well taught to only heat the space you use and we need to learn to use whole home heating.

timmmay

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#3196011 15-Feb-2024 20:17

johno1234:

In our case all the existing central heating outlet grilles (diffusers? Not sure about the correct terminology) are in the floor. These would be replaced by new ones in the floor for the ducted heat pump system and I assumed they would be able to be manually closed off. I would want to avoid heating or cooling the entire house that way if we didn't have zone control?

It depends on the vents, I guess.

tweake:

i would heat/cool the entire house. its so much better for comfort, much much better for the house as heat moves moisture and even if you heat just one room your actually heating the house via one room. we have been well taught to only heat the space you use and we need to learn to use whole home heating.

We keep a base level of heating but only really condition the rooms we need now or in the near future. Heating / cooling the whole house could use a lot more energy.

tweake

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#3196022 15-Feb-2024 20:52

timmmay:

tweake:

i would heat/cool the entire house. its so much better for comfort, much much better for the house as heat moves moisture and even if you heat just one room your actually heating the house via one room. we have been well taught to only heat the space you use and we need to learn to use whole home heating.

We keep a base level of heating but only really condition the rooms we need now or in the near future. Heating / cooling the whole house could use a lot more energy.

uses heaps of energy because kiwis build lousy performing housing. we then don't heat our houses properly to save money. using setback/base level on unused rooms is not to bad, but its only a small decrease.

i don't heat the spare room, but it gets heated via the rest of the house as it pulls heat from the rest of the house. so i'm still paying for heating that room, even tho i'm not directly heating it. if i put heater in there, the overall cost would not be much different.

Handle9

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#3196026 15-Feb-2024 21:08

johno1234:

Does closing the grille dampers work? I do wonder how leaky those things are, and if closing off all but a couple of rooms works well.

It's a really bad idea. You will create problems with noise and performance.

The unit is sized to provide a minimum airflow. For example the 16kW unit here is designed for 800-1000L/s. If you introduce a lot more resistance (occlude too many diffusers) that a couple of things will happen. Firstly you will get pressure buildup as the fan will still be trying to spin at the same speed. That can cause all sorts of weird pressure waves and noises, as well as potentially bursting the flexi ducts.

The other thing you run the risk of is freezing the coil when it's in cooling. Basically you can't transfer enough heat into the coil to keep it from freezing condensate, which is the byproduct of passing humid air over a cooling coil.

A well designed and commissioned system has balanced airflows into each zone. Most domestic installers don't do this properly but it's necessary to make a system perform acceptably, especially during high load days. At the end of the day using a single unit to feed a whole house is never going to be perfect, particularly if you have dynamic loads.

johno1234

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#3196042 15-Feb-2024 23:22

If that is all true then isn't airtouch or other zone controlled ducted systems a bad idea too?

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