Ask Brownstoner: “Should I Buy a Mini Split Air Conditioner?”

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    Reader chukat asks:

    “Trying to decide if we should get air conditioning for our row house. Thinking about buying a mini split system, but we don’t know that much about how they work. Do we need a unit in every room? Where does the piping go? Can the compressor be on the roof or in the back yard? How much does a system cost vs. central a/c?”

    Great question. What is a mini split air conditioner? How does a mini split air conditioner work? How is a mini split air conditioner installed?

    A mini split system has two main parts: an indoor unit that holds the air handler, and an outdoor unit that holds the compressor.

    The compressor in the outdoor unit compresses a refrigerant (which turns into a cold gas) and feeds it through an insulated tube to the indoor unit where it enters a coil. The indoor unit blows air over the coil, and hey presto! the air becomes cool before it enters the room.

    After all that hot air, the refrigerant loses its coolness as it passes through the coil. Then it it’s fed through a second tube running back to the outdoor unit. And the cycle continues.

    A mini-split system could have multiple indoor units in different spaces, and also multiple outdoor units. It’s also called a “ductless system” because — surprise! — it doesn’t have bulky ducts.

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    But there’s also condensation and power to think about. According to heating/cooling expert Steve Fontas of Molten Mechanical Metal Works:

    “Each indoor unit will have a drain that must run either outside or to a drain in the house. Additionally each indoor unit will require 208 volt power which will either come from the outdoor unit or the circuit breaker panel, depending on the system to be installed.”

    Joseph Bellocchio of Iceberg Mechanical Corp told Brownstoner that an indoor unit is required for every closed room. As for the placement of units and tubes, he said:

    “It is most cost effective to try and mount these units on external walls but isn’t required. The pipes can be installed inside of sheetrock and/or plaster walls but expect there to be some carpentry work afterwards to close everything up. The outdoor unit can be placed on the ground, mounted to the back of a brick home, attached to a chimney stack and/or parapet wall on the roof, or in some cases on steel beams.”

    Never place a condensing unit directly on a roof because it is against fire code.”

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    Don’t install a mini-split system on a pad on the roof. Mounting it to a brick wall as above is a-ok

    That all sounds great. Until we get to the cost. But Steve Fontas gave it to us straight up:

    “I’m going to tell you right now that the equipment is expensive. It is much more expensive than window units and marginally more expensive than a ducted system. Here’s the rub though. They are much cheaper to run, quieter, more environmentally friendly, require no dropped ceilings and they add immense resale value to your home. They will also offer you the ability to heat your rooms as all multizone mini-split systems are also heat pumps. I have customers who use the heat to supplement their boilers.”

    Another post in the forum quoted the cost of a mini-split system for a 2,200-square foot house as ranging from $12,000 to $26,000. A reader installed one system in a 1,300-square foot condo for about $5,000.

    Not scared away by the price? Joseph Bellocchio recommends that you move forward by talking directly to a qualified mini split installer:

    “Just be careful in choosing a contractor, the cheapest price sometimes ends up being the most expensive price in disguise because, if not installed correctly, the system will require expensive repairs or reinstallation. Once you’ve done a little research, find a contractor who can make you feel comfortable in moving forward with an installation.”

    If you’ve got a question about your home, post it to the forum.
    If you’re looking for a contractor, check out Brownstoner’s Local Home Pros.

    Special thanks to our heating and cooling experts Steve Fontas of Molten Mechanical Metal Works and Joseph Bellocchio of Iceberg Mechanical Corp.

    Photos of air conditioners via Iceberg Mechanical

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