Question on Central AC short circuiting - swapping to MrCool DIY


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Old 07-25-22, 09:09 AM
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Question on Central AC short circuiting - swapping to MrCool DIY

Hello.

I have 2 zones on Central AC and the 2nd floor keeps on short circuiting. I have changed filters, and also cleaned the Condensor outside as well as the A Coil in the air handler in the attic.

The system itself is 20+ years old, and i am thinking of doing an upgrade to mini split ductless systems.

I want to install 4 mini splits in the 4 bedrooms upstairs and have the following questions. The setup that I am looking at is 9k, 9k, 9k, 18k.

q1) Is there any system that i can chain up the heads one to another so I dont need to run long lines into the compressor outside? This is becuase one of the 9k and 18k will require about 75 feet run and the other two 9k will need about 50 feet run.

q2) i plan on putting the new compressor on the same slab that the current central ac condensor is on. And since there are already power lines going to the central AC condensor, i want to reuse the same electrical line to avoid re-running new wires (with its own breaker). Any concerns with this? Likewise, i already have power lines going up to the air handler in the attic (with its own breaker) and i plan on re-using to power the heads. Can it be like that or does the heads must be powered from the compressor itself?

q3) What is the general suggestion to the existing AC cover on the ceiling if i install the new ductless? Can i just cover it with a drywall fix?

q4) I saw a system that has a ceiling vent style heads, rather than the entire thing that hangs onto the wall. Are those generally recommended or its too new?

q5) If i get the ductless system in place, can i just get rid of all the ducts thats running all over in teh attic , along with throwing the air handler / compressor away?

thanks!
 
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Old 07-25-22, 10:15 AM
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While I'm a huge advocate of mini-split systems, if you already have decent ductwork installed, it's usually cheaper short and long term to just replace the air handler and condenser. Mini-splits are great if you're saving the cost and hassle of new ductwork, but they are usually more expensive upfront, and due to the electronics supposedly don't last quite as long as their traditional AC counterparts.

But if you decide to go mini-split anyway, I'd suggest looking at Fujitsu first. I personally would only install Mitsubishi or Fujitsu units.

q1) I know Mitsubishi and Fujitsu have distribution boxes that allow one lineset to a box, then branch out from there. I considered them for one install, but they add expense and complexity, so I haven't actually installed them yet.

q2) You need to look at the electrical requirements for the outdoor unit. If it's a 30A requirement, the existing power is probably sufficient. Though some units will require 40A or 50A, which will require rewiring the feed. Are you running heat as well, or just AC?

Most systems only power the outdoor unit. The indoor units are powered and controlled by a 4-wire (or 6-wire) cable from the outdoor unit to the indoor head. Some manufacturers do require indoor power, but you'll have to check out their specs. I believe they would just run on standard 120v@15A circuits.


q3) I would pull out the vents and re-drywall the holes since you won't need the ductwork anymore.

q4) There are heat pump solutions which basically put a single air handler in the closet or attic, and then duct the air to the different rooms. It's the exact same technology, just in a different package. You'll have to figure out BTU and load usage for each room, and ensure the ducts in place support it.

q5) No reason to keep the ducts unless you think you'll need them in the future. You'll need to get an HVAC company in to purge and collect the old refrigerant - it's illegal to let it vent into the air. But otherwise, recycle the copper and old steel ducts and make some money back.
 
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Old 07-25-22, 12:38 PM
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hi.

yes i am looking for both heat/cool solution, and thats why i wanted to move to mini splits.

The existing condensor is a 40A double pole (Each) and both the air handler in attic is shared with a 20 Amps double pole.

I was actually looking at the Mr.Cool units, as they seem to be best bang for the buck. But the 25" feet refrigerant line seems to be a problem for me.

I am only interested in installing this on upper floors for the bedrooms, which means i need 4 heads. Generally, what would be the reason why i want 2 condensor for 4 heads, rather than just 1 condensor for all 4? My btu requirement appears to be 9k, 9k, 12k, 18k.

thanks
 
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Old 07-25-22, 01:11 PM
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With split units.... bang for the buck isn't always the best way to go.
My preference is Mitsubishi.

Typically split units need wiring between them and the outdoor unit.
It was a three wire NM cable. Now most use thermostat cables.

The first thing I'd recommend doing is to get together with a dealer.
Tell him what you want to do. Get his input.
Many installers will not install your equipment due to warranty issues.
 
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Old 07-26-22, 04:15 AM
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The system you speak of with 1 lineset linked to multiple indoor units is called a VRF system, not a minisplit. Itís the big brother of a minisplit system.
The Mr Cool units do not work this way. Youíd have to look into Samsung, Mitsubishi, or other big brands.
The Mr Cool units are not well supported and are basically disposable. As are most DIY minisplits. When they break, there isnít a wide selection of parts to fix them. Nor is there much factory support.
If this system is going to be your primary source of heating and cooling then youíll want something of better quality and support.
 
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Old 07-26-22, 11:50 AM
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Generally, what would be the reason why i want 2 condensor for 4 heads, rather than just 1 condensor for all 4?
There's really no reason for 2 condenser/outdoor units. You'll want one outdoor unit with 4-ports to connect to 4 indoor heads. The only time you need two units is for larger 6+ head systems.
 
 

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