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Old 08-07-18, 03:38 PM   #1
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Default Central air vs other

I recently went to the Wisconsin State Fair. I was browsing the random seller's booths and happened upon a HVAC booth. He was showing off a mini split unit as well as others. I asked him how the mini splits were selling, and he said decent. I told him I had considered putting two in my own home, one for upstairs and one for downstairs. He commented that it would be cheaper to install central air. His price would start at a mere $2600 which I thought was incredibly inexpensive. He said this is because I already have forced air, so its simply installing the outdoor unit, and the coil in the duct work. Granted, its probably not the most efficient outdoor unit. But, I was expecting more like $5k installed.

I'm not looking to install central air right now, but the price shocked me and I can definitely see doing it in the future. Right now, we have no air conditioning. If it gets really hot, I throw a window a/c unit in my bedroom window for a few weeks during summer. However, the thought of having the air dehumidified is very appealing. This summer has been really muggy.

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Old 08-08-18, 02:24 PM   #2
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How about if you get a small heat pump for the central air, to only slightly dehumidify and/or cool the whole house, then use the window unit when needed (=less often)? Make it low power with a large heat exchanger, to boost efficiency.
The"central" HP would also help with heating in the winter.
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Old 08-08-18, 11:00 PM   #3
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$2600 for what type of unit though, a 13 SEER builder grade unit without high/low pressure switches? The cost to install also usually will need a new 240v electric run with disconnect box to the outdoor unit plus the lineset running towards your air handler. Add permitting costs too. If you have a simple install with an easy to reach electric service panel and an unfinished or otherwise easily accessible basement and air handler for the lineset, I could see that cost being reasonable. Usually that's about the cost of replacing an existing unit though, I would have figured another $500-1000 more. For a new condensing furnace and 1.5 or 2 ton 16 SEER AC unit(with pressure switches, not builder's grade) with new disconnect box and lineset, my expected quote is around $6k after tax credits. This includes haul away of the old equipment and evacuation of the R22, which they will probably reuse and make money by selling to someone else regardless of the legality or contamination risk to the equipment it might be put into.

My personal consideration was to leave my existing unit in place and do a DIY mini-split install of a very high SEER in my bedroom placed in a way where I could leave the door open and have it shoot through the door across the hall and essentially cool the upstairs with natural convection making the whole house reasonably cooler at the same time and using the old 8.5 SEER junker on the hottest days similar to how more heat strips get used with heat pumps when they are over their capacity. After that consideration I've had housemates move in and they run computers 24/7 and heat up the lower half of the house, so the central A/C makes more sense now plus the electrical cost is split between the housemates so I'm less motivated by cost to do it now. Once they eventually move out, I figure that just having the bedroom cooling is probably enough since I spend most of my time in the bedroom including using the computer, reading, and watching movies and tv. Usually I don't mind if it's hot in the house as long as I keep the dew point below 55 in the house, it's sleeping that I feel the need for cool air. If I sell the house, I'd likely take the unit with me.
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Old 08-09-18, 07:52 AM   #4
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As with other members before you, it's possible to do a self upgrade on what you have for pennies on the dollar. Most new outdoor units come precharged with refrigerant, so the job basically consists of building a base for the outdoor unit, fitting whatever you need indoors, and rigging a lineset between the two. Electrical has high voltage and low voltage components that need to be commissioned as well. Total out of pocket price mainly depends on what you want and where you procure it. Sweat equity is also a good way to drive cost down.

Everywhere HVAC equipment is installed, there exist licensed techs who will come and do a final inspection and sign off on the paperwork (and possibly do finishing touch ups) for a small fraction of what they would charge for a complete job.
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Old 08-09-18, 08:12 AM   #5
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I'm never going to install a central A/C.
No central A/C is efficient as one that's turned off.
The big advantage is rooms where the split is off don't get heated or cooled.
Sure you can block off rooms but the system is sized to cool the whole home so when you block vents you mess with system efficiency, unless it's done on the cheap and way undersized.
I kind of like decentralized systems, that way if one fails it's not a huge household emergency.
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Old 08-09-18, 08:27 PM   #6
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Quote:
Originally Posted by oil pan 4 View Post
I'm never going to install a central A/C.
No central A/C is efficient as one that's turned off.
The big advantage is rooms where the split is off don't get heated or cooled.
Sure you can block off rooms but the system is sized to cool the whole home so when you block vents you mess with system efficiency, unless it's done on the cheap and way undersized.
I kind of like decentralized systems, that way if one fails it's not a huge household emergency.
In Wisconsin, it's uncomfortable if the air conditioning goes out and some people don't even have air conditioners in their houses and just live with a bunch of fans. We do get temperatures in the 90s up here though but some people just deal with those days. It's probably like in New Mexico if you lose your heat in the winter, it's probably not a huge deal if you are in the lower areas. Up north, the biggest hazard is that our air is wet and we have basements that people install drywall in and they develop mold if the moisture isn't kept in check. If a furnace goes out on the coldest day of winter and there isn't an alternate heat source, the house will be uncomfortable(to most people) after just a few hours and if it isn't fixed within a day, sometimes less time, even with insulation meeting today's building standards, the pipes freeze.
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Old 08-10-18, 05:28 AM   #7
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i just put in a new central air system. i put in the air handler and installed the outdoor unit ran all the electric and the line set. i then had a friend that is a HVAC tech come over and braze the line set pull vac and make sure the pressures were all good. he then registered both the indoor and out door unit for warranty purposes. his services only cost 180$. i purchased the indoor and outdoor unit from ingrams water and air for 3500~ plus a few other odd and ends i think total cost was 4200 installed. i now have a 16 seer 2 stage heat pump with a variable speed blower. also this is a 3 ton unit.

smaller units are cheaper.
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Old 08-11-18, 02:43 AM   #8
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It regularly gets to 0F most winters in this part of NM.
The coldest I have seen was 6 days straight of lowes at night -10F to -17F with highs hitting +20F.
This is why I was looking for to global warming.
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Old 08-12-18, 11:28 AM   #9
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Quote:
Originally Posted by oil pan 4 View Post
I'm never going to install a central A/C.
No central A/C is efficient as one that's turned off.
The big advantage is rooms where the split is off don't get heated or cooled.
Sure you can block off rooms but the system is sized to cool the whole home so when you block vents you mess with system efficiency, unless it's done on the cheap and way undersized.
I kind of like decentralized systems, that way if one fails it's not a huge household emergency.
The multi-split units suffer the same penalty. When the outdoor unit is only feeding a single zone, the energy efficiency is heavenly, as the compressor is running slow and the heat exchanger transfers heat at a super low Delta T.

As more zones come online, the compressor speeds up, and the heat exchanger has a harder time moving energy. At full capacity, the compressor is drawing full power and the outdoor HX is operating at Max Delta T. At this point, the system is running at close to the same rating as a ducted central air system.

The thing about your statement that bugs me is that the new central air systems employ variable speed compressor and zone control and expansion valve technologies that the vintage systems did not. If you're trying to keep total system initial cost low, then yes, the generalization does apply, because these technologies are sacrifices made to save money at the getgo. But modern central split units have come a long way since the 80's.

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