Ducted mini-split???

[zak77]

Does anyone have an opinion or experience with a ducted mini-split system?? I have yet to come across one but they seem like a decent idea as opposed to the heads on the wall or ceiling cassettes.

I'd prefer to have the duct work in the basement vs the attic just so it's not fighting the elements in the attic. Plenty of head room but current heating system is 28 year old oil forced hot water but i burn wood in the winter for heat. No central air or duct work so everything will be newly installed.

My issue with the heads or cassettes is the amount of partitions in the house and my lack of faith in just 2 heads(or cassettes) taking care of the whole house. I understand the cost will be higher but i'd rather do it right the first time. I guess in a perfect world i'd have ducting run to each bedroom(3) and 1 or 2 to the living room/dining room/kitchen(kind of an open floor plan).

 

[finn]

The lack of ducts is what makes a mini split a mini split, isn’t it?

You are describing a central air system as far as I can tell. A coil above the furnace plenum or in an air handler, and a compressor/ condenser outside.

 

[walta]

Read the manuals carefully most of the ducted minis fans are not very powerful so the ducts must be bigger and shorter to work.

In my opinion duct work in the attic is a bad idea and should be avoided if at all possible.

Walta

 

[Ohmthis]

I have installed several. They have worked well, but for the money, a conventional split system is cheaper. Where in the basement would you put the evaporater? I ask because they are fairly large and if used in a mechanical type room a conventional will fit also. Don’t believe that the duct has to be short, it’s all in how the duct is designed. One system has 35’ of trunk and 60 total feet of branch duct. Each supply flows within 5% of the others and supplies the air at the same velocity as a conventional system. I didn’t take any pictures but can maybe get one of the units in the drop ceiling section. Ask questions and I’ll do my best to answer them.

 

[Fixin'Stuff]

Trane makes a ducted mini-split. It looks like a typical updraft furnace and uses a fan that is designed to deal with the high static pressure of a ducted system. I don't know the cost, but I would expect it to be quite high. Trane is pretty proud of their stuff and I've never seen any of the products for sale anywhere other than from a Trane dealer.

 

[yeldogt]

The ducted fall into three main categories. The original is the one you see in many hotel rooms hidden in the entrance hallway --- single intake from hall and single exhaust into room. This first type does not have a fan capable of long ductwork. Manufacturers understanding the need/desire for longer more complex ductwork have developed units with fans able to handle greater static pressures. They can handle quite a lot of ductwork -- even zones and are quite large. The third type looks like a conventional USA air handler and is designed to be installed as we do conventional systems in the USA.

The first two are popular in the city where spaces are tight and floor to floor ducting is difficult -- being able to have a mix with a multihead system allows a lot of possibilities. My current HVAC guy is doing a house with two conventional types and adding a heating coil from a boiler in each .. the house also has radiant heat.

 

[zak77]

I had a feeling the motor for the blower would be an issue trying to supply an entire house off one air handler so i may need more than 1 handler. I'm trying to figure out if it would even be possible to do this or have a conventional FHA system installed. The current boiler is 28 years old so replacement is coming soon. I guess i'll make some calls to HVAC companies when the time comes and just run the numbers.

 

[Trey T]

The world of mini-split, particularly ducted ones, has evolved a lot and is equivalent to the automotive world of electric/gasoline hybrid. Meaning that their ability to provide work can vary based on the wide spectrum of needs, such as zoning, capacity, and/or efficiency. The down side is cost, like double the cost to have it all.

Mini-split is still a niche market for central system because conventional system have been long adopted and their technology is moving toward the efficiency of mini-splits. Another factor is that electricity in many part of our country is very cheap, can be cheaper than natural gas.

For me, conventional central air system is the most feasible alternative.

 

[yeldogt]

Whenever possible I have done properly designed conventional ducted systems -- most often with some zoning. Most of my projects have been partial or full gut rehabs of old building -- often very difficult for ducted systems ... unless a Unico type ... and I don't love them because it's all flex.

Because of the current state of the industry -- mini-splits are not going to be a cheap route. But, they can solve lots of problems that previously had no answer.

 

[chinboys]

I have one installed for an upstairs bathroom as I didn't want the big wall unit to be seen. Would I do it again??? no, the unit sits in a half attic in the heat thus I had to add extra insulation to prevent the extra heat from the unconditioned attic space from heating up the cooler conditioned air. Plus the unit doesn't have the properly sized squirrel cage fan to really force the cold air out. the high-speed setting is more like the slow\medium setting on a wall unit. This is in reference to a 9K BTU LG in duct unit. Next time, I would use the wall unit. I also have their ceiling cassette units hanging off their F series condensers (1 -2 big line sets to a distribution manifold), I am ok with them but nothing beats the wall unit in terms of install and use in my opinion.

 

[eddieK]

The bottom line with mini split systems...almost disposable.

If you are considering doing this much, conventional makes a whole lot more sense, you can get these in fairly high SEER as well, with great warrantees.

 

[zak77]

I can now see that this tech is still young and has bugs to be worked out. One reason i was leaning towards a heat pump was to provide heating and cooling cheap if i were to install solar panels. I'm not getting any younger so burning wood is getting tougher but there are alternatives. When i am ready to replace the old boiler i just may look at getting FHA installed with central air. Yeah it'll be more expensive since ducts will have to be installed but for the benefit, it'd be worth it. Thank Guys!!!!

Any more info, please feel free to share.

 

[yeldogt]

I can now see that this tech is still young and has bugs to be worked out. One reason i was leaning towards a heat pump was to provide heating and cooling cheap if i were to install solar panels. I'm not getting any younger so burning wood is getting tougher but there are alternatives. When i am ready to replace the old boiler i just may look at getting FHA installed with central air. Yeah it'll be more expensive since ducts will have to be installed but for the benefit, it'd be worth it. Thank Guys!!!!

Any more info, please feel free to share.

The technology is not new -- these have been around for years. The conventional air handler units are newish ... all the main USA companies make modulating equipment now. Unless you are combining two of the conventional type units or mixing a conventional with a different mini-split on a central compressor the typical split is more rational.

In a city property -- the space is limited for the compressor. The ability to do various types of heads makes a multihead mini a great way to go. The many different sizes available also makes sizing more accurate for each load. It's often impossible to get proper ductwork into an old house -- and it can eat into valuable space.

 

[Orionrising]

I realllly wish someone would make a good low temp nonsplit heat pump.

 

[justinjoyal]

The bottom line with mini split systems...almost disposable.

If you are considering doing this much, conventional makes a whole lot more sense, you can get these in fairly high SEER as well, with great warrantees.

How are they « almost disposable » when they can last 15+ years ?

Better warranties and better efficiency as well.

 

[LS6 Tommy]

I wouldn't install a cassette in my worst enemy's building...

Tommy

 

[Jackfre]

I have found it exceedingly difficult to install duct work PROPERLY in an existing building. To access the areas necessary and to seal them properly requires a guy who is very very good. some of the vrf systems are good on the air flow, but the smaller 9 & 12 ducted evaps have almost no static airflow capability. They are like a "puff" of air, so positioning and installation are critical to successful operation. Personally, I'm with Tommy in this. On mini-split installs I used to tell my customers who complained about the appearance of the hi wall evaps that, "the longer you live with them the better looking they become." If you did the mini-split package you will run your boiler less. When I represented Fujitsu in New England I had many customers who would only run the boiler when it got really cold. You get to define really cold, but the combination of the boiler and mini is excellent. I see from the weather channel that Monson is sitting at about ground zero on this high temp, unbearable humidity heat plume now. Good luck with your project.

 

[Falcon67]

I wouldn't install a cassette in my worst enemy's building...

Tommy

Yes, yes - please go on. (because I considered a dual cassette system for better air distribution in the shop)

 

[LS6 Tommy]

They have very little air flow, many drip condensation and generally are a pain in the *** to service. The fan motor run capacitor is bolted in during manufacturing, so when (not if) it goes bad your options are to either almost completely disassemble it to get the electrical box out, or just shove the replacement in.

Tommy

 

[yeldogt]

I have found it exceedingly difficult to install duct work PROPERLY in an existing building. To access the areas necessary and to seal them properly requires a guy who is very very good. some of the vrf systems are good on the air flow, but the smaller 9 & 12 ducted evaps have almost no static airflow capability. They are like a "puff" of air, so positioning and installation are critical to successful operation. Personally, I'm with Tommy in this. On mini-split installs I used to tell my customers who complained about the appearance of the hi wall evaps that, "the longer you live with them the better looking they become." If you did the mini-split package you will run your boiler less. When I represented Fujitsu in New England I had many customers who would only run the boiler when it got really cold. You get to define really cold, but the combination of the boiler and mini is excellent. I see from the weather channel that Monson is sitting at about ground zero on this high temp, unbearable humidity heat plume now. Good luck with your project.

I have never done the concealed ---- I'm thinking about having one in my new build (if I can ever get it finished). I have gone and looked at quite a few -- everybody uses flex for connections (not crazy about flex in area that would require the wall to come down to access). That said -- they work .... guess the newer models have more flow and the newest high static models are huge one I saw was 4' wide but they are only about 16" high.

 

[yeldogt]

I wouldn't install a cassette in my worst enemy's building...

Tommy

I know you say this -- An my oldest mitsubishi are only about 3 years old -- but they work great. And they have lots of flow ... mine are 12k. I have two of them and one 12k wall on a 30k compressor

 

[LS6 Tommy]

I know you say this -- An my oldest mitsubishi are only about 3 years old -- but they work great. And they have lots of flow ... mine are 12k. I have two of them and one 12k wall on a 30k compressor

That's good to hear. Maybe they've worked those issues out.

Tommy

 

[danski0224]

Does anyone have an opinion or experience with a ducted mini-split system?? I have yet to come across one but they seem like a decent idea as opposed to the heads on the wall or ceiling cassettes.

I'd prefer to have the duct work in the basement vs the attic just so it's not fighting the elements in the attic. Plenty of head room but current heating system is 28 year old oil forced hot water but i burn wood in the winter for heat. No central air or duct work so everything will be newly installed.

My issue with the heads or cassettes is the amount of partitions in the house and my lack of faith in just 2 heads(or cassettes) taking care of the whole house. I understand the cost will be higher but i'd rather do it right the first time. I guess in a perfect world i'd have ducting run to each bedroom(3) and 1 or 2 to the living room/dining room/kitchen(kind of an open floor plan).

The high end multi zone systems require a great amount of detail be paid to piping practices.

I had a feeling the motor for the blower would be an issue trying to supply an entire house off one air handler so i may need more than 1 handler. I'm trying to figure out if it would even be possible to do this or have a conventional FHA system installed. The current boiler is 28 years old so replacement is coming soon. I guess i'll make some calls to HVAC companies when the time comes and just run the numbers.

HVAC retrofits are not uncommon, it is done all the time. Mostly, people have unreasonable expectations for mechanical equipment space and the cost of a decent job.

If the boiler is piped properly, it will last for much longer than a conventional furnace.

Small duct high velocity systems are another option. If they are properly designed and installed, they are not noisy.

I can now see that this tech is still young and has bugs to be worked out. One reason i was leaning towards a heat pump was to provide heating and cooling cheap if i were to install solar panels. I'm not getting any younger so burning wood is getting tougher but there are alternatives. When i am ready to replace the old boiler i just may look at getting FHA installed with central air. Yeah it'll be more expensive since ducts will have to be installed but for the benefit, it'd be worth it. Thank Guys!!!!

Any more info, please feel free to share.

I'd keep the boiler heat.

A heat pump is possible with a conventional forced air system, and possibly the high velocity systems.

So called mini splits are inverter based, and there are inverter based condensers for conventional forced air systems- but those almost always require a proprietary thermostat to use all available stages of cooling.

 

[yeldogt]

That's good to hear. Maybe they've worked those issues out.

Tommy

Well -- obviously I hope ..... time will tell.

 

[AEAdam]

I know this is an old thread, but I have a related question:

I’m interested in a ducted mini split to distribute primarily air conditioning into multiple bed rooms, a bathroom, and a small living room. The space isn’t really large enough to have multiple individual wall units. If I had one centrally located wall unit, sized for the space, could it practically make all these rooms comfortable?

Is this the reason for ducted systems?

 

[danski0224]

I know this is an old thread, but I have a related question:

I’m interested in a ducted mini split to distribute primarily air conditioning into multiple bed rooms, a bathroom, and a small living room. The space isn’t really large enough to have multiple individual wall units. If I had one centrally located wall unit, sized for the space, could it practically make all these rooms comfortable?

Is this the reason for ducted systems?

I can really only see physical size, and multiple evaporators from one condenser as a possible advantages for these ducted "mini split" systems. I have only seen them installed in commercial applications so far.

Why not do a Unico system? If they are installed properly, they are quiet.

 

[walta]

I know this is an old thread, but I have a related question:

I’m interested in a ducted mini split to distribute primarily air conditioning into multiple bed rooms, a bathroom, and a small living room. The space isn’t really large enough to have multiple individual wall units. If I had one centrally located wall unit, sized for the space, could it practically make all these rooms comfortable?

Is this the reason for ducted systems?

Yes, that is a very good reason to select a miny ducted system.

The question is can you find a way to locate the equipment and ductwork inside the conditioned space and avoid the stupid idea of equipment & ductwork in the hot attic?

As I said before this ductwork needs to be designed with a computer program that calculates the pressure drops and avoids overloading the small fan.

 

[u3b3rg33k]

There's plenty of mid static systems out there that can be ducted. Mitsubishi has "american style" "furnace shaped" fan coil units intended for use up to .8" static.

 

[Fav Onefour]

Yes, that is a very good reason to select a miny ducted system.

The question is can you find a way to locate the equipment and ductwork inside the conditioned space and avoid the stupid idea of equipment & ductwork in the hot attic?

As I said before this ductwork needs to be designed with a computer program that calculates the pressure drops and avoids overloading the small fan.

I have a SDHV in the upper floor of a boiler heated home.
The space is long and narrow with four bedrooms. It also has a large living room with three walls of windows. I had looked into mini split setups and took multiple bids for the project. They were all over the place on how many head units and where to place them. In the end it would have required five head units to do whole area properly. Placement would have been a challenge. Plumbing would have been a challenge. I also didn't want the long term issues of all those systems. (I consider each head unit a system)

For the SDHV system, I wanted to keep the unit out of the attic. I was strongly encouraged to install in the attic for better air flow management. The argument made more sense to me when it was installed.
It basically uses a full size plenum to accommodate the coil and airflow. The mini ducts are insulated flexi tube. The mini duct runs should be kept short and straight as possible.

The system has worked quite well in my situation.

 

[u3b3rg33k]

imho, flexduct in attics is



cheap to put in but LOL to achieve any of the system ratings.

"the south" loves them tho:

 

[walta]

If one must put it in the attic burry the ducts in insulation.

Buried Ducts Allowed in 2018 Building Code - Energy Vanguard

Are you confused? In my last article, I said buried ducts are at risk for condensation. Now I’m telling you they’ll be allowed in the 2018 code. What’s going on here? The answer is simple. Yes, when you bury ducts…

www.energyvanguard.com

Walta

 

[AEAdam]

Yes, that is a very good reason to select a miny ducted system.

The question is can you find a way to locate the equipment and ductwork inside the conditioned space and avoid the stupid idea of equipment & ductwork in the hot attic?

As I said before this ductwork needs to be designed with a computer program that calculates the pressure drops and avoids overloading the small fan.

This is a barn conversion and I'm thinking about the ground floor. There is no non-conditioned space. The one I'm thinking of could potentially have ducts that are no more than 8' long. Would I need a computer program for that? One duct might be 8' the others would be 3'.

The other idea I had was install a split wall unit in the hall way and give the bed rooms ceiling fans and 1" gaps under their doors.

The thing about this building is, it has radiant underfloor heat. So beyond a few days in the fall maybe, I don't see the mini splits providing anything but air conditioning (cooling)

 

[danski0224]

"the south" loves them tho:

So does the Midwest.

 

[u3b3rg33k]

So does the Midwest.

I'm fine with ductwork in the attic if it's hard metal, taped, mastic'd, wrapped in R30, and then sleeved.

 

[walta]

The one I'm thinking of could potentially have ducts that are no more than 8' long. Would I need a computer program for that? One duct might be 8' the others would be 3'.

If you make the ducts 18 inches in diameter, I am sure it will be fine If you make the ducts 2 inches in diameter, I am just a sure it will fail.

You are not seeing the point the mini split is sized just large enough to move just enough air thru a will designed duct work. This is done to maximize space and electrical efficiency.

If you are unwilling to do the work of properly designing the duct work but the USA designed equipment it will come with a hugely oversized fan that will move enough air thru whatever duct work Bubba designed on the back of a napkin while he ate lunch an hour before he installed it.

Walta

 

[AEAdam]

I'm just asking the question, would people in my bedrooms be more/as comfortable with their own person wall unit versus a short duct from a zone unit. I know I can run multiple wall units from a single outdoor compressor unit.

If I choose wall units, what about the spaces outside the bedrooms - the hall way, the bath room? I assume the cool dry air in the bedrooms will find its way into the adjacent areas, especially the bathroom which has 2 extractor fans.

To be honest, it's close to a wash cost wise between a single unit with ducts vs a couple wall units. The difference is what happens in the areas not directly served by a wall unit? I feel as tho in buildings I've been in, a single small wall unit covers a lot of space.

 

[u3b3rg33k]

one issues with small rooms full of people is they can get stuffy with no air exchange, even if you cool the air.

I suppose you could do heads and a small balanced ventilation system.

plenty of hallways have no active ventilation and are fine (some have a return).
usually you get some airflow because returns underperform supplies - so a very slow exchange, but also hallways are often between rooms and have little to no outside wall area, and thus minimal heat gain/loss.