Ducted Heat Pump - Whole house or Half house with Single Split Unit

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Corcoran

26 posts

Geek

#272106 9-Jun-2020 19:23

Hi All,

Looking for some advice or feedback from anyone who chose between installing a whole house ducted heat pump with 2 zones or ducted system for bedrooms with a separate single split heat pump for lounge/kitchen/dining area.

What helped you make your decision? Are you happy with your decision? Any regrets or things I should be wary of?

Am currently considering between a 16kw heating Fujitsu ducted system with 2 zones for $12,000 or an 8kw Fujitsu ducted system for 4 small to medium rooms and a separate 6kw heat pump for the lounge/kitchen for $9,000.

I like the money saved on the separate heat pump for the lounge/dining/kitchen area but am worried how well it will heat this area. The lounge is approx. 7.3m long and there is a wall separating the lounge and dining/kitchen area. The wall has a normal size doorway at one end (no door) and a 1.6m opening down the other end, near where the heat pump would be installed in the lounge. The total floor area of the lounge/dining/kitchen is approx 50sqm.

Will the heat pump heat these areas effectively? Or will having ducts in the lounge and dining area be more effective?

How efficient is having 2 zones and having the ability to shut one off? Initially I was going to go fully ducted, however now my wife will be working the majority from home so will work out of the dining area.

Thanks for reading.

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991 posts

Ultimate Geek

Lifetime subscriber

#2501719 9-Jun-2020 19:56

I think split the 2 would be best. Ductud systems suck in air which is heated/cooled and then pushed out. This needs to be balanced through the rooms. Zoning this complicates the matter as you would either need to have a return in each zone or have to leave doors open. Then you also need to think about pushing cooking smells etc into the bedrooms.

Would highly recommend going with the cheaper option. In an ideal world there would be a fresh air intake and heat recovery going on but getting that all to work in harmony (especially with zoning) seems rather difficult and costly!

blackjack17

1705 posts

Uber Geek

#2501723 9-Jun-2020 20:13

We have a ducted system and at first we were interested in zoning but then we thought about it and what is the point? Why would you want part of your house cold?

We have one zone, warms the whole house nicely. In the rare event that we wouldn't want to heat a room you can just close off the vents manually.

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mrfee

20 posts

Geek

#2501735 9-Jun-2020 20:50

We are planning to do exactly what you have done OP. We have an existing high-wall heat pump in the open plan lounge/dining/kitchen with a door separating this from the rest of the house. We have been quoted for a range of 8kW heating systems for the four bedrooms.

We chose to do this primarily because of the cost as we already have the high-wall installed and are happy with it. Ducted systems are also less efficient in general so having a separate high-wall unit will generally result in lower running costs for the same heat/cool output.

Setting both units up on timers will result in a pretty integrated experience between the two systems too I would imagine.

Corcoran

26 posts

Geek

#2501748 9-Jun-2020 21:46

blackjack17:
We have a ducted system and at first we were interested in zoning but then we thought about it and what is the point? Why would you want part of your house cold?

We have one zone, warms the whole house nicely. In the rare event that we wouldn't want to heat a room you can just close off the vents manually.

With my two young boys and a wife who now works from home a single zoned ducted system could run much of a 24 hour period.

With my wife working in front of a computer screen in a corner of the dining area it seems inefficient to heat the whole house.

I would have one zone operating while my wife is home, both zones in the evening, then the bedroom zone only over night.

From what I understand closing vents/diffusers manually does not help with energy costs.

Corcoran

26 posts

Geek

#2501773 9-Jun-2020 22:16

mrfee:
We are planning to do exactly what you have done OP. We have an existing high-wall heat pump in the open plan lounge/dining/kitchen with a door separating this from the rest of the house. We have been quoted for a range of 8kW heating systems for the four bedrooms.

We chose to do this primarily because of the cost as we already have the high-wall installed and are happy with it. Ducted systems are also less efficient in general so having a separate high-wall unit will generally result in lower running costs for the same heat/cool output.

Setting both units up on timers will result in a pretty integrated experience between the two systems too I would imagine.

Thanks for the response, the installer did say it would be more efficient and cheaper having this set up over the fully ducted system.

What size heat pump do you have in the lounge/dining/kitchen area? I assume it heats a large area and was wondering if its loud or quite draughty, where I would imagine ducted would not be.

blackjack17

1705 posts

Uber Geek

#2501797 10-Jun-2020 06:54

Corcoran:
blackjack17:
We have a ducted system and at first we were interested in zoning but then we thought about it and what is the point? Why would you want part of your house cold?

We have one zone, warms the whole house nicely. In the rare event that we wouldn't want to heat a room you can just close off the vents manually.

With my two young boys and a wife who now works from home a single zoned ducted system could run much of a 24 hour period.

With my wife working in front of a computer screen in a corner of the dining area it seems inefficient to heat the whole house.

I would have one zone operating while my wife is home, both zones in the evening, then the bedroom zone only over night.

From what I understand closing vents/diffusers manually does not help with energy costs.

Despite having a 1920s sieve. Our house is quite warm. We just need to have the ducted heat on for 15-20 in the morning and a couple of hours in the evening and the house stays quite warm.

It is really nice being able to walk through the house at a constant temp rather than having to open doors to fridges like our old house.

We saved a couple of 1000 by going with a single zone non WiFi ducted system. Going for a more expensive system might have saved $10-20 odd dollars a month but the return on investment would not be worth it. Hell we are only saving $60 odd dollars a month from using column heaters and fan heaters.

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Dingbatt

6755 posts

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Lifetime subscriber

#2501804 10-Jun-2020 08:04

We got a 16kW Fujitsu ducted system installed to replace the single 5kW Panasonic Cassette style heat pump about 3 years ago. It is unzoned and services 4 bedrooms, a lounge and an open plan family/dining/kitchen area. It has one wired controller to operate it. At the moment I would like to have wireless control of the system, but there is no solution off the shelf from Fujitsu. There is Pebble, but that only works for IR control.
The advantage, from my perspective, is there aren’t ugly white boxes on the walls, it has centralised control, it is quiet and the whole house is comfortable.

The disadvantage is there isn’t the ability to fine tune temperature within a room beyond adjusting the aperture of the diffuser. That means energy gets wasted and smaller bedrooms can overheat especially with the door closed. The outside unit is also much larger than the older one and as a consequence noisier.

At the moment I am investigating retrofitting zoning. Partly because the control system I have found that will do wireless control for the Fujitsu (Air Touch) is based around zoning. It is likely to cost about 50% of the initial installation cost, so will need to weigh the benefits carefully.

As an additional note I was advised (before fitting the ducted system) to avoid fitting two discrete heat pumps if there is a chance of them interacting. They end up fighting each other if there isn’t centralised control.

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Lostja

239 posts

Master Geek

#2501822 10-Jun-2020 08:46

We ended up going for a Fujitsu split system for our new 2 story house. Ducted upstairs for the bedrooms, bathroom, office, etc and a single head-unit downstairs for the open plan living. It was cheaper to do it this way and it was hard to run ducts to the downstairs. It works well and would it this way again

sen8or

1789 posts

Uber Geek

#2501832 10-Jun-2020 09:17

We have x2 8kw Hitachi ducted systems in our house (180sqm 3bdrm), 1 system heats the living areas (open plan living / kitchen / dining & separate media room) and 1 system heats the bedrooms.

For us this works well, the temperature that you enjoy in the living rooms is not necessarily the same temp that is comfortable in a bedroom (which are much smaller). We run the bedroom system at around 16-17 turning on at around 5am and this provides enough heat to take chill off without becoming stuffy. On the weekend we ran the living area one at just 16 the entire weekend (in Christchurch where it was pretty cold) and this kept the house really comfortable.

It is a new build with insulated external walls and double glazing which helps with heat retention.

Power wise, once up to temp, they run at around 2kw/hour (both systems on), more if the temp is lower like it was on the weekend, then it was around 3-4, so you need to be comfortable with running costs

mrfee

20 posts

Geek

#2502250 10-Jun-2020 14:36

Corcoran:
mrfee:

We are planning to do exactly what you have done OP. We have an existing high-wall heat pump in the open plan lounge/dining/kitchen with a door separating this from the rest of the house. We have been quoted for a range of 8kW heating systems for the four bedrooms.

We chose to do this primarily because of the cost as we already have the high-wall installed and are happy with it. Ducted systems are also less efficient in general so having a separate high-wall unit will generally result in lower running costs for the same heat/cool output.

Setting both units up on timers will result in a pretty integrated experience between the two systems too I would imagine.

Thanks for the response, the installer did say it would be more efficient and cheaper having this set up over the fully ducted system.

What size heat pump do you have in the lounge/dining/kitchen area? I assume it heats a large area and was wondering if its loud or quite draughty, where I would imagine ducted would not be.

The lounge/kitchen/dining area is approx 6.4mx5.6m and the heat pump we have is a Mitsubishi MSZ-GE50VA (5.8kW heat) which was installed a couple of years ago by the previous owners. In terms of noise and draught, you can definitely hear it in a quiet room but not when the TV is going for example. If there was furniture nearby I imagine there would be a draught but we don't so it isn't really an issue. To be honest, we like the heating and cooling that it provides so aren't bothered by any noise or draught that may be present. I imagine in a bedroom where you are tying to sleep any noise or draught would be quite a lot more annoying than it is in the kitchen/lounge/dining area.

Corcoran

26 posts

Geek

#2503948 13-Jun-2020 08:58

tanivula:
I think split the 2 would be best. Ductud systems suck in air which is heated/cooled and then pushed out. This needs to be balanced through the rooms. Zoning this complicates the matter as you would either need to have a return in each zone or have to leave doors open. Then you also need to think about pushing cooking smells etc into the bedrooms.

Would highly recommend going with the cheaper option. In an ideal world there would be a fresh air intake and heat recovery going on but getting that all to work in harmony (especially with zoning) seems rather difficult and costly!

Thanks Tanivula, this is the option I have chosen to go with.

Can you tell me how min and max capacities affect heat pumps? What does it mean for 2 heat pumps, one 6kw and the other 7kw, to have the same min and max heating capacities?

Froglotion

208 posts

Master Geek

#2503954 13-Jun-2020 09:18

I'd struggle to not have a fully ducted system, after having one so long. Ours is four zones, a little overkill, but the zones do get used. Mrs doesn't like a warm bedroom at night so that gets turned off, while my office stays heated.

A high wall unit is going to heat a large, obstructed area less efficiently than a ducted system that is providing air to all areas equally via ceiling ducts.

I tend to run it on low fan mode 95% of the time which is more than enough to heat the whole house.

SomeoneSomewhere

1802 posts

Uber Geek

Lifetime subscriber

#2503964 13-Jun-2020 09:46

Corcoran:
tanivula:

I think split the 2 would be best. Ductud systems suck in air which is heated/cooled and then pushed out. This needs to be balanced through the rooms. Zoning this complicates the matter as you would either need to have a return in each zone or have to leave doors open. Then you also need to think about pushing cooking smells etc into the bedrooms.

Would highly recommend going with the cheaper option. In an ideal world there would be a fresh air intake and heat recovery going on but getting that all to work in harmony (especially with zoning) seems rather difficult and costly!

Thanks Tanivula, this is the option I have chosen to go with.

Can you tell me how min and max capacities affect heat pumps? What does it mean for 2 heat pumps, one 6kw and the other 7kw, to have the same min and max heating capacities?

Inverter units can run at a range of capacities, rather than simply 'flat out' and 'off'.

When you need less heating/cooling than the minimum capacity, it will have to resort to cycling between low and off.

I am less sure about why maximum capacity is higher than rated. I think this is something of a short-term overload condition.

Corcoran

26 posts

Geek

#2504718 14-Jun-2020 23:46

Thought I had made a decision but now having second thoughts!

I have ruled out the zoning, but I haven't ruled out the single zoned fully ducted yet as my wife has decided to move her workstation to a smaller bedroom, which should be about to retain alot of heat so not need much heating while she is home.

I have read alot about rooms overheating with a ducted system when the doors are closed. Should I request return vents in every bedroom at the install, or see how it goes first to see if they are required or not?

timmmay

20578 posts

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#2504727 15-Jun-2020 06:25

The way you use your home will change over time, I suggest you design for flexibility.

We find that bedrooms if at least lightly heated during the afternoon / evening need very little heat at night even in the middle of winter - a 1000W oil heater spends most of its time turned off even in my very old but fairly well insulated house. A high wall heat pump in another room can put some heat into a bedroom, not heaps but stops it from being really cold.

I was considering putting the smallest ducted heat pump in for our bedrooms, but we only use two bedrooms most of the time and I guess the smallest is around 6kw, which is way more than we'd need. It would have to be zoned with other rooms heated, and the ability to turn off rooms dynamically so we don't end up heating the whole house all night which would be inefficient.

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