Home HVAC unit

I have a normal central A/C home heat pump unit with a ducting system in my house.
It has some age on it and the condenser unit sustained damage in the storm.
I'm considering replacing the entire unit with a ductless split unit.
This is a heat pump system that has a central condenser unit outside but rather than ducts running to each room they run the wet lines to a separate air handler evaporator coil that hangs on the wall in each room.

Questions I have...

A normal wet line on a central A/C is say 25 feet.
Is there a limit on how long these lines can be ???
In other words how far is to long ??

Anyone have any experience with these Ductless Mini Split Air Conditioner.

The lines can be as long as you want. You just have to factor in the line size and length to determine the refrigerant charge. Lots of commercial units run a hundred feet or more.

One thing to consider is every additional piece is another potential leak.

Size of lines will depend on unit size.
You can triple that 25 foot length with no Hill effect, on a residential unit,

Pressure drop will be minimal, and no adjusting pressure will be needed.

Split units through the walls, I can't help you with,

Guido.

John, I installed a ductless mini-split system in our house a few years ago, but we have a different situation than you. Our house didn't have central AC, and because it has hot water baseboard heat, there's no ducting. Being a quad-level, adding ducts wasn't really practical. I wouldn't recommend replacing your central air with ductless; if it were my house I would replace the existing air conditioning system with a newer, more efficient central air system.

The ductless systems come pre-charged with enough refrigerant for a given lineset length. (Lineset being the high pressure/low pressure pair of lines.) I don't recall what it is offhand, but it's fairly long, maybe fifty feet total. Note that each unit has its own lineset, so if you have two indoor units, each with 25 feet of lineset, that's fifty feet. If you have more lineset than what the pre-charge is good for, you have to add a specified amount of refrigerant for the additional length. I don't think there's any practical limit beyond that for a typical house.

If you have a particular system in mind, download the installation instructions for that system and it will say exactly how long the lineset can be before you have to add more refrigerant.

Note that the ductless units need to be cleaned regularly to prevent mold and mildew buildup, which is not an easy task. We ended up paying several hundred dollars to have our units disassembled and cleaned after they basically quit working. They make a large funnel you can place under the units and flush them out with bleach; I'll do that yearly from now on.

Mark I understand staying with the normal duct system.
The reason I'm considering this unit is I don't have a attic.
All my ducts run under the house and the vents are in the floor.
While it works I really do not like the system.

Plus with all the kids gone we do not need to heat and cool every room in the house.
I have been using a window A/C in my living room since last summer allowing us to turn the central air way down or off.
This has saved a lot on my electric bill.
I'm thinking this ductless system will allow me to turn on the unit only in the room I am in and need it.

John,
A ductless unit is half of a window unit, evaporator, hanging on the wall with lines connected to it. When you use a squirrel cage to pull air through the evaporator, you will also pull condensation off coil and spray water on the inside of unit causing black mold to grow.

I use window units in my rentals. Each year before I install them, I'll take them apart and clean with bleach. I can't see how you can properly do that with unit hanging on wall.

A conventional central in a house uses an A-coil and you push air up through the coil. Any condensation will fall back on coil and no mold issues.

I would stick with what you have. I would never install a split unit even if it were FREE. Keep in mind I'm cheap.

You probably have more moisture in the air than the rest of us. If you have a friend with a split unit, look inside for black mold. Many times people think it just dirt, it's black mold. Dirt soap will clean. Black mold takes bleach. Even the squirrel cage will be covered with the dirty looking black mold.

If you have duct work on the floor, I would look into installing an air handler and a conventional central.

Theres literally 1000s of them on PEI. Theyre mainly used for heating here in cooler months but most get used for A/C in the summer as well. You can have the indoor units professionally cleaned with a coil jet mini split cleaner and a bib kit to catch the mess. If theres any in your area talk to someone who has one Theres dozens of manufacturers,Fujitsu is a popular brand, an 18 000 btu unit will do a nice size area. If your looking at multi head units youll be looking at at least 24 000 btu and you can run 2-3 heads off of those. Ive seen runs up to 40 feet each and they work good. The disadvantage of a multi head unit is if the outdoor unit fails they are all down.

John, the ductless systems are much better than window units. They're very quiet and most are very efficient. If you don't want to cool your whole house, then it does make sense to install ductless units just in those rooms you want to cool. Our system is Mitsubishi, and if I was to buy another system it would be Mitsubishi as well.

Mark,
How are split units better than window shakers beside being quiet? Before split units, I've seen people cut a hole in wall and install window AC's
Another option are units like used in motels. I know a man who has 3 of these units in his insulated pole barn. Those units can be pulled out and taken outside an sanitized.

I think the biggest issue is pulling water off the evaporator causing a health issue, black mold.

I think you mentioned the biggest disadvantage too, only cooling a few rooms. Same will apply to heat pumps.

My brick house was built in 1942, I remolded in 1991.
In 1942 the duct work ran both a hot air and return air in each room. You can close a door and room temp doesn't change. All my rooms are at the same temp because of a cold air and return air in each room. My bigger rooms I have 2 of each.
Today's standards, you one or 2 large cold air returns, close a door and you are in trouble heating and cooling..

Without proper air circulation no cooling system will work well. Just my opinion.

Thanks guys.
You have given me just what I need.
I do know one person with a mini split in a rental.
He has never mentioned a cleaning issue.
I will have to ask him about that.

George not all central A/C are updraft.
My unit is downdraft and pulls air threw the coil.
Everything has to be right or it pulls wet air right out the drain pan.

Like I said the main reason I am even asking about a mini split is for control over what rooms to heat or cool.
Window units can solve the cooling but I'm not real keen on putting in a window unit with heat.
Plus I'm thinking the mini split will be more efficient than a window unit.

Now I will better informed when talking to the HVAC contractor.
Not a fun process dealing with contractors.
But throw a insurance adjuster in the mix and it becomes a nightmare.

I feel I need to address the black mold statements and then some of the other comments both good and bad. Black mold occurs when the unit is(choose one or more). Unit not sitting so condensation is draining out the back, drain plugged, excess humidity range(way in excess of 65% when not in operation), not being cleaned, outside air vent open allowing outside air to come in, outside drain plugged so over flow fills inside pan. There may be a few others but those are the main ones I have personally experienced. At the hotel I worked at and at the Hospital we would occasionally have one that got mold and we would put a pill in the tray of the evap. and no more mold. Do not put a wall mount sleeve in. I used to maintain close to 500 different ones of those over the years and you will not be satisfied. Like a window A/C they do transfer noise from the compressor to the inside, and if the drain plugs moisture will drain inside the house. Mini splits work good(still need a drain, usually goes out with the line set) and we have a couple at the hospital I would say have at least 50 feet of line set, a couple with three or more heads. The hospital they get abused do to lack of maintenance (not enough techs) and there is one that what appeared to be mold but the drain was plugged and it was in a elevator machine room so black does not always equal mold( we have to test when suspicious).
So back to the OP question- a long way if you choose to do it. Contractors like to have the unit close due to it cost more to install and make it look nice.
Observation: have you had any one look at the existing install as that would be my first course of action to see if there was something missed and it is not up to par.
With any install there is going to be some drainage in A/C and that needs to be addressed, Proper cleaning is important in any install whether it is a window or mini split.
I know George has had a mold problem and I have been curious about it, Professionally I'd like to look at it. I don't for a minute say that it cannot be a problem as I have seen it before but am wondering what steps have been done to correct it, I kow he is located ion a humid area so it is more of a problem, but that is not the original post. A mini split is a good second choice.

My AC went out of my house three years ago, They wanted $11,000 to replace it. I bought a sennville 24,000 btu mini split heat pump installed it myself for $2,500. Other than cleaning it has been great. Cools in the summer heats in the winter has a 21 seer rating. Electric bills went down $50 to 60 a month. If I had to do over I would get two indoor units instead of one but it keeps my 2000 sq ft house cool except the master bedroom on the other end. I will probably get a small one when the window unit goes for that.

I thought the residential mini splits were only one outdoor unit and one indoor unit per system?

No. I have seen up to 4 indoor units on 1 outdoor unit advertised.
They size the indoor unit to the room.
So you can get a 18k for the living/kitchen area and two 9k units one for each bedroom.

That is why I asked about line run because you have to reach each room from one centralize location outside.
If you put the unit in the back yard by the back bedroom the front bedroom may be 50 feet away.
If you put it in the front the rear bedroom is 50 feet away.

> How are split units better than window shakers beside being quiet?

Well, George, ain't that enough?

Back in the day, my apartment in Cairo was cooled by three huge Egyptian-made window ACs, mounted in holes in the wall. The noise of those units was deafening, but I was glad to have them. After the first night or two, I slept like a baby with an Egyptian air conditioner bellowing in my ear. But these days I like it quiet, and our mini-split system is nearly silent. You can be outside next to the outdoor unit and you can't hear it over the traffic on I-75 half a mile away.

The other advantage is efficiency. The better mini-splits have SEER ratings of 20 or more, which is considerably better than most central air systems. I've never seen a SEER rating on a window unit, which leads me to believe they all have lousy efficiencies. Now, for rentals you don't really care what the efficiency is, because you're probably not paying the utility bills. But for my own home, I expect decent efficiency from my HVAC system.

> I feel I need to address the black mold statements and then some of the other comments both good and bad. Black mold occurs when the unit is(choose one or more). Unit not sitting so condensation is draining out the back, drain plugged, excess humidity range(way in excess of 65% when not in operation), not being cleaned, outside air vent open allowing outside air to come in, outside drain plugged so over flow fills inside pan.

None of those conditions were present with our system that had a mold problem, with the exception that it was never cleaned. Note that it took about eight years for the buildup to get bad enough to require service. Had I known to clean it every year there would have been no need for a service call.

I suspect the main reason mini-splits are susceptible to this problem is their blowers suck through the evaporator coils, so the blower will tend to pick up moisture.

We have two window a/c units running here in central florida 5 miles from the west coast.
Five years later I am still waiting for the black mold to show up in them.
Maybe the basic window a/c units are built different then the mold makers.I

But when I installed them, I did put them in with a healthy amount of bottom slope down to the outdoors.
I also drilled holes in the lowest points of the floor where water, be it condensation or rain would drain out. Even hung a copper wire in the holes to promote every drop to go away.

We replaced the window unit with a minisplit last year and could not be happier. Our heat pump will handle 3 air handlers, we are only using two. Quiet and efficient with no hot or cold spots. Did I say QUIET! Ours is 100% efficient down to 0 and then it deteriorates at -30. We don't use the heat much, but it works great in a cold spot in the kitchen/dinning room. Supposed to be 30% cheaper than a window AC, but I think the heating part is expensive with our NYS electric prices. Keep in mind the enviro's are going to end fossil fuels, they have no clue how electricity is produced!

I would do it again.

Mark,
For my house I have a 20 year old seer 12 central.
I don't hear a thing.
Are you saying you don't hear the fan on mini splits??

> For my house I have a 20 year old seer 12 central. I don't hear a thing.

Well, since it still works I wouldn't replace it. But if it fails you'll probably replace it with a SEER 16 or so, which is still far less efficient than a typical mini-split. I suppose somebody makes a SEER 20+ central air system, but they're probably prohibitively expensive for most applications.

> Are you saying you don't hear the fan on mini splits??

I'm saying most of the time, the indoor blowers aren't audible, or are barely audible. The outside unit is so quite that you have to be standing right next to it to hear it above ambient noise. And even then it's often so quiet I have to look at the fan to be sure its running.

Note that ductless systems use variable-speed DC motors for their compressors, fans and blowers. They do make a little noise when they're operating at full capacity, but once the rooms are cooled down the ductless systems get ridiculously quiet.