ductless mini split heating and cooling

[Happyras]

I installed a few systems this summer. One for our barn apartment, which I mounted the outdoor unit under a stairway, hung from the stringers. 12k BTU 120v Costco cheap, Super quiet, rubber foot mounted it though. Also our daughters house had a very poorly installed gas furnace/duct system. It was so bad with leaks it would take several thousand to do right. I installed 2 3 ton 3 head mini splits. One at each end of the house with line sets out to the 6 locations. Either system would heat the home, but this is what they wanted. I re-used 2 circuits from prior 240v hot tubs, replacing the proper breakers, lower amp HVAC rated. They love the systems, each room is so well controlled and so quiet. Their home is so much better balanced, the AC was essential for my pregnant daughter this summer, and now the heat is working so well. We recently had temps in the low teens, unusual for Seattle, but all worked so well no need for their gas leaking duct system to kick on. However, I would argue that at a SEER of 22, these mini-splits are far more efficient than a central HP typical SEER of 16.

 

[Happyras]

I might add that I installed the Mr Cool mini splits. One from Costco and 2 from Ingrams Water and Air, on-line seller to DYI. They make a DYI mini split that has pre-charged line sets with quick connectors. It makes it so easy to install, because you do not have to do a vacuum draw down, or charge the system with refrigerant. Mount, wire, route lines and connect, your ready to start up.

Mr Cool seems to be high enough quality for most home owners, and very low cost. I have bought a lot of equipment from IWAE.com, honest and support warranties quickly.

 

[explanade]

If these are ductless, what are the outside units for?

Do they connect to the outside units by duct?

 

[Happyras]

If these are ductless, what are the outside units for?

Do they connect to the outside units by duct?

Yikes, these are heat pumps. They have line sets (vapor and liquid) between the indoor unit and the outdoor condenser, as well as power and control cables. The heat/cool is directly taken from the indoor coil and distributed by a fan on the indoor unit. A furnance, for example, heats the air and distributes the heat via ductwork, and a return air duct takes cooler air back to the furnace.

Does this help, or is this a goose not a duck.

 

[explanade]

My central air is sitting on a pad in a terrace.

There are control lines and some kind of tubing running underneath the house, crawl space, to the furnace and blower in the garage, which on the other side of the living room.

So ductless means just no air ducts between the AC and the rest of the HVAC?

The tubing is maybe 1/2 inch to an inch in diameter.

Hard to believe it's sending cold air through that to feed the central HVAC.

The system is over 20 years old so I don't imagine it's a heat pump.

 

[Happyras]

My central air is sitting on a pad in a terrace.

There are control lines and some kind of tubing running underneath the house, crawl space, to the furnace and blower in the garage, which on the other side of the living room.

So ductless means just no air ducts between the AC and the rest of the HVAC?

The tubing is maybe 1/2 inch to an inch in diameter.

Hard to believe it's sending cold air through that to feed the central HVAC.

The system is over 20 years old so I don't imagine it's a heat pump.

Well, not what your thinking....ductless is referring to the distribution system inside the house. You have ducts from the furnance. A ductless does not have a central furnace, just dedicated fan/coil units inside the home at one or more locations instead of ducts and registers distributed from the furnace. I do not think I can explain more..... and 20 years is fairly recent. I installed my first Heat Pump in 1982 on the first home I designed as a young engineer in my spare time. That is 40 years my friend. Not knowing what you have, but if you have a furnace it is likely a simple AC system with furnace. The only real difference is in the control and use of a reversing valve on the refrigerant and an expansion valve etc.

 

[Happyras]

Its all in what you know...to me, these things are tinker toys with simple control systems and mechanical features. To most apparently this seems more like rocket science. These systems have tiny refrigerant compressors and simple evaporation coils. When I w#$K'd, a compressor might have 9000 horsepower and and a pump might be up to 1000 hp, driving evaporators made of exotic ss materials standing 140 feet high and 22 feet in diameter, driven by Honeywell distributed plant control systems. So, yeah, pretty simple stuff to us enginurds.

 

[skyking1]

One of the features that make these so efficient is the inverter DC technology. Unlike the old mondo heat pump with the start capacitors, these things spool up quietly and can run at whatever speed is needed. The Old Tech is either off or on.
FYI I have a vac pump and gauge set, and a little R410a in the south sound area if somebody needs a hand. They are really easy, but the Pioneers I installed did require a pulldown, and one of them I had an extra long line set that exceeded the precharge in the outdoor unit. I had to add 6? ounces.

 

[Happyras]

One of the features that make these so efficient is the inverter DC technology. Unlike the old mondo heat pump with the start capacitors, these things spool up quietly and can run at whatever speed is needed. The Old Tech is either off or on.
FYI I have a vac pump and gauge set, and a little R410a in the south sound area if somebody needs a hand. They are really easy, but the Pioneers I installed did require a pulldown, and one of them I had an extra long line set that exceeded the precharge in the outdoor unit. I had to add 6? ounces.

Right on, super quiet and run speed as needed. Nice to know someone has a gauge set for R410A nearby, I have been thinking it might be time to Blow the Dough on one, but these new DYI line sets work awesome, until they don't. Thanks for the offer!

 

[skyking1]

oh heck it was cheapo amazon stuff so don't hesitate to ask, Happy.

 

[euro]

My vacation home has 3 bedrooms and a bathroom up stairs. Downstairs is a large kitchen living room and a utility room/bath.

I would have liked to have put a mini-split in when I had to replace my heat pump, but I had all the sheet metal already installed and a new heat pump was cheaper than adding one mini split and a second mini split with 3 head units.
For those that just have a large room: I once had a 16' x 32' den with a PTAC unit like those used in hotels. I'd cut it on when I got home from work, and it'd cool a hot room to comfortable in 10 minutes. And it was very efficient since we only ran it when we were in the room. Any individual can cut a hole in the wall, install the housing in the hole and slip the PTAC unit in. They're not nearly as expensive to buy or install as a mini-split.

No doubt, they work ok, but they are (in my opinion) noisy as heck. I have a fully functioning unit in my mountain cabin and yet, I installed a mini split earlier this year. It is ridiculous how much quieter the mini split is. True, the mini split is a bit more expensive, but a decent PTAC unit will run close to 1k these days, so the difference is not dramatic.

 

[folivier]

About gauge sets for those thinking of BTD on one. I bought one off of amazon and the sealing surfaces on the hoses are teflon. Great, I thought at first until the first time using it kept loosening up. Not like the older rubber or neoprene softer seals that don't loosen. So when using it I have to tighten every time it moves a bit. So in this case newer and improved is NOT better.

 

[Happyras]

About gauge sets for those thinking of BTD on one. I bought one off of amazon and the sealing surfaces on the hoses are teflon. Great, I thought at first until the first time using it kept loosening up. Not like the older rubber or neoprene softer seals that don't loosen. So when using it I have to tighten every time it moves a bit. So in this case newer and improved is NOT better.

Excellent point, similarly, I just got a new CO2 regulator for my Cornelius Keg. It came with the old style plastic washers, but has an o-ring face seal for the tank inlet, something new and improved. I suspect the o-ring will work until it doesn't, and then I will need to use the old style plastic washers it came with......

Back to HP's, I once started up a new 3 ton condenser and when fully charged and tested, took off the gauge set only to have the Schrader valve get stuck open, blasting all the charge out. The ball valves must have been cooked when the line set was soldered. Not so fun, defective valve? Or was it the gauge line connector that jammed the stem, who knows.

These DYI mini splits have a king valve and separate line set shut off valves and quick connects. Since you do not need to solder to the unit, its just a little mo-better.....

 

[skyking1]

I'd say a lot more better. Pretty easy to cut and flare a good connection DIY. Most do not know how to solder a good connection. I can, but then again heating up other stuff is a PITA. Wet rag is your friend, placed around what you don't want to cook.

 

[explanade]

Stayed at a place in Venice where the thing leaked after using it even for a few minutes.

WAs only a couple of nights and they couldn't repair it during this time.

They gave me a bucket and a towel.

Problem was the unit was over the door so every time I left, it would drip onto the floor.

Guess they didn't mind the water damage.

 

[euro]

Stayed at a place in Venice where the thing leaked after using it even for a few minutes.

WAs only a couple of nights and they couldn't repair it during this time.

They gave me a bucket and a towel.

Problem was the unit was over the door so every time I left, it would drip onto the floor.

Guess they didn't mind the water damage.

Well, that's a clogged drain hose - usually pretty easy to fix with a little compressed air.
That said, we had exactly the same thing happen during a stay in Milan, Italy a couple of years ago and of course, I did not have easy access to compressed air......

 

[skyking1]

if the hose is graded properly it does not need cleaned out. If you install one, pay attention to the grading of the wall unit and the hole through the wall, so you get a good grade on it. terminate it per instructions up off the ground. I've never seen nor heard any condensate on my installs.

 

[NW-Bound]

My central air is sitting on a pad in a terrace.

There are control lines and some kind of tubing running underneath the house, crawl space, to the furnace and blower in the garage, which on the other side of the living room.

So ductless means just no air ducts between the AC and the rest of the HVAC?

The tubing is maybe 1/2 inch to an inch in diameter.

Hard to believe it's sending cold air through that to feed the central HVAC.

The system is over 20 years old so I don't imagine it's a heat pump.

Happyras has already answered the above questions, but I will make another iteration.

Ductless minisplits and central ACs both consist of 2 units: an outdoor compressor and indoor airhandler. The copper lines between the 2 units are for sending the refrigerant (Freon) from the compressor to the indoor unit, and returning it.

The airhandler of a central AC is usually hidden. The air that is cooled (or warmed) is distributed through the house by a duct network, usually also hidden. The airhandler of a minisplit is usually mounted on a wall and exposed. Because there's no ductwork, a minisplit is usually good for just one room or perhaps a larger living space for an open floor plan.

As earlier posters have said, minisplits are quiet, and efficient. Because the minisplit airhandler does not have to push air through an airduct, its motor is smaller than the blower of a central AC. The compressor of a minisplit is nearly always of the inverter variable-speed motor type, the same as a motor of an EV. There's no reason that this motor type can't be used in a central AC, and I think it is available if one looks for it.

Another reason for having a minisplit is that it can be run off a portable 2-kW generator. This will save your skin during a power outage, which happens more and more frequently.

 

[old medic]

I have been wondering about using Mini-splits when we get to that point on our remodel. The old ducted system has to come out completely. Originally from the 70s, the ducts are full of rat and squirl storage. Crackheads stole the outside unit. We always loved the propane heat of the old place, but added AC coil and wired it to heat from the heat pump if outside temps were above 35. At 960 SqFt, 2 bedroom, bathroom and the rest open greatroom/kitchen, use a 4 head unit, includes one for the 640 SqFt garage.
Can someone talk me out of it?

 

[euro]

I have been wondering about using Mini-splits when we get to that point on our remodel. The old ducted system has to come out completely. Originally from the 70s, the ducts are full of rat and squirl storage. Crackheads stole the outside unit. We always loved the propane heat of the old place, but added AC coil and wired it to heat from the heat pump if outside temps were above 35. At 960 SqFt, 2 bedroom, bathroom and the rest open greatroom/kitchen, use a 4 head unit, includes one for the 640 SqFt garage.
Can someone talk me out of it?

If you are going to tear out the existing ductwork then switching to a mini split is a no-brainer. Extra benefit, you can probably ditch propane also - in some mountainous places it can be a bear to convince the propane company to deliver the goods.

 

[folivier]

I've been thinking about the same, switching to mini splits. In my house in Louisiana I'd need 5 inside units. With help from my son I could do the majority of the work and just have an AC guy do the final charge. Probably save money in energy costs especially with the ability to zone cool rooms we're not in all day.
My house is 9 years old and already have had to replace the evaporator (in the attic) and now having an intermittent issue with the electric heater. Food for thought.
In power failures due to hurricanes which could easily last a week or more I'd be able to only cool the room we're in which means a much smaller generator. Most people choose a 20KW whole house generator. I could probably get by with a 4KW if I zone cool.

 

[freedomatlast]

I've had houses with both.

The mini-splits were the best option for an old farm house we owned that had some additions over the years, where there were some rooms with no ductwork.

However, when the temperatures plunged into the into the single digits and below, and it was windy, they could barely keep up. Yes, they were sized appropriately according to the manufacturer. Under those conditions, they ran all out as hard as they could and when they went into the defrost cycle, the room would actually lose a few degrees. And when they run all out, they do consume a lot of electricity. Granted the insulation in these rooms left a lot to be desired but still the mini-splits were challenged at these temperatures. BTW, these were Fujitsu XLTH's rated to -15ºF. Not the typically cheaper made for DYI models.

Also, keep in mind the temperature sensors are built into the inside unit. So if you have rooms with high ceilings and you have these mounted toward the top, you'll need to set the temperature several degrees higher than normal since it's warmer at the ceiling where the indoor temperature is being sensed. You can buy a remote temperature sensor package, but it's expensive and requires some rewiring. Also remember, you have these inside units mounted someplace on your wall which some people consider unsightly.

For higher end houses with existing, well designed ductwork, I'd go with a conventional system every time. And when I say conventional system, I don't mean just a conventional heat pump for heat and A/C. I mean one with a flame producing heat source such as oil, natural gas or propane. At very cold outside temperatures, the cooler air coming from the ducts along with the draft they produce from a heat pump only system, just never felt comfortable to me. Even when the resistance element kicks on, it's just not the same as a flame producing heat source, in my experience.

A lot has to do with the geographic location too. The above was written considering a Northeast USA location where it does get quite cold.

In the south were heat needs aren't as high, they make a lot more sense. They do seem to do a much better job providing A/C than heat, in extreme conditions.

 

[euro]

I've had houses with both.

The mini-splits were the best option for an old farm house we owned that had some additions over the years, where there were some rooms with no ductwork.

However, when the temperatures plunged into the into the single digits and below, and it was windy, they could barely keep up. Yes, they were sized appropriately according to the manufacturer. Under those conditions, they ran all out as hard as they could and when they went into the defrost cycle, the room would actually lose a few degrees. And when they run all out, they do consume a lot of electricity. Granted the insulation in these rooms left a lot to be desired but still the mini-splits were challenged at these temperatures. BTW, these were Fujitsu XLTH's rated to -15ºF. Not the typically cheaper made for DYI models.

Also, keep in mind the temperature sensors are built into the inside unit. So if you have rooms with high ceilings and you have these mounted toward the top, you'll need to set the temperature several degrees higher than normal since it's warmer at the ceiling where the indoor temperature is being sensed. You can buy a remote temperature sensor package, but it's expensive and requires some rewiring. Also remember, you have these inside units mounted someplace on your wall which some people consider unsightly.

For higher end houses with existing, well designed ductwork, I'd go with a conventional system every time. And when I say conventional system, I don't mean just a conventional heat pump for heat and A/C. I mean one with a flame producing heat source such as oil, natural gas or propane. At very cold outside temperatures, the cooler air coming from the ducts along with the draft they produce from a heat pump only system, just never felt comfortable to me. Even when the resistance element kicks on, it's just not the same as a flame producing heat source, in my experience.

A lot has to do with the geographic location too. The above was written considering a Northeast USA location where it does get quite cold.

In the south were heat needs aren't as high, they make a lot more sense. They do seem to do a much better job providing A/C than heat, in extreme conditions.

Those concerns are well founded and until recently, I would not have even considered mini splits (or any heat pump systems for that matter) in colder climates. However, I think the technology has matured quite a bit recently and I would not automatically dismiss the option, even in the Northeast. Case in point: my mini split in the NC mountain cabin had no issue at all keeping up with the recent cold snap (granted, I don't think the temperatures dropped to significantly negative numbers like in may Northern places, but definitely came very close).

 

[folivier]

There are lots of improvements in mini splits. There are different types of inside units, some that mount in the ceiling, others that are square and can have a picture mounted on the front. There are also some inverter units that can utilize existing ductwork and are more efficient than typical AC central units.
And IIRC there are some units that the thermostat is in the remote so you can place it anywhere in the room.
I'm hoping that the major AC central unit manufacturers like Lenox, etc. will come out with inverter compressors soon.
But putting the evaporator and air handler in the attic is a horrible idea. The extreme temperatures aren't conducive to longevity.

 

[Chuckanut]

Those concerns are well founded and until recently, I would not have even considered mini splits (or any heat pump systems for that matter) in colder climates. However, I think the technology has matured quite a bit recently and I would not automatically dismiss the option, even in the Northeast. Case in point: my mini split in the NC mountain cabin had no issue at all keeping up with the recent cold snap (granted, I don't think the temperatures dropped to significantly negative numbers like in may Northern places, but definitely came very close).

Two of my neighbors have had a mini-split installed. One had here baseboard heating removed at the same time because she wanted to push furniture up close to the walls. The other had two of the three baseboard units removed, but kept one base board unit that was the farthest from the split's indoor wall unit. I'll give you one guess as to which was happier when temperatures spent about a week in the 20's and very low 30's.

Both report somewhat lower electric bills, but not nearly enough to justify the expense solely on saving money. The added AC capability was the major deciding factor.