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Mini-Split Heat Pumps


kurt
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I haven't seen that "brand", but the units show up quite often in added sun rooms and Florida rooms around here. I saw my first one about twelve years ago - maybe more? I like them! They're a great way to condition a room when ductwork will either detract from the room or simply isn't practical. The systems are more expensive per ton than conventional units, which is offset to some degree by the lack of the ductwork. I think the elimination of all the potential inefficiencies of ductwork is pretty cool. I'd own one.

I toyed with installing such a system in one of my rentals, but was finally convinced that in the long run it was going to be cheapest to stick with the through the wall and window units. (It's a small home.)

Mitsubishi seems to be the popular brand around here.

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Sorry Kurt but I can't help here.

They were coming into vogue, in some of the old downtown warehouses that were being converted into loft dwellings, about the time I was departing from the 9-5 gig.

I find it interesting that they can run multi-evaps with one condensing unit but haven't spent the time to research.

I take it you've run into a location with them?

Thread drift alert:

Hey, btw, whatever happened to that multi-dwelling unit that had all those condensing units stacked side by side & over and under?

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Good in theory but time will tell how they hold up. One thing to think about is that you now have multiple condensate drains, not sure how they deal with that and provide secondary drains or pans with switches. My guess is they have integral overflow pans and sensors but that is just a guess.

I've not seen one in real life yet.

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I see the wall mount mini-splits all the time in these parts. Mostly used in single room applications like a Florida room (how can you have a Florida room in VA anyway?) and rooms above detached garages. Mostly Fujitsu, Mitsubishi, or Samsung. I've contemplated putting one in my garage but the vent I installed in the plenum that I just turn on or off works just fine.

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I see the wall mount mini-splits all the time in these parts. Mostly used in single room applications like a Florida room (how can you have a Florida room in VA anyway?) and rooms above detached garages. Mostly Fujitsu, Mitsubishi, or Samsung. I've contemplated putting one in my garage but the vent I installed in the plenum that I just turn on or off works just fine.

I installed a ductless split a/c in our master bedroom (bedroom sits over the garage) a while back. I installed a on-delay set for 5 minutes to prevent short cycling and a reverse acting head pressure control for condenser fan low ambient control. I like the bedroom like a meat locker - I keep it 60 degrees in the winter and 64 in the summer. I've run the a/c in 40-50 ambient without any problems.

The thing that's different about the systems Kurt is referring to is multi-evaps and one condensing unit. Imagine a 4 ton condensing unit and only having a 1 ton evap. I'm not sure how they overcome superheat/sub-cooling problems. Will put it on the "to-do list". I feel a vacation coming on first though. [;)]

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Ductless systems started out small in this country. This one is the first one that I've seen that has 4 tons of cooling. It's not a 'mini' anymore.

Earlier 2 to 4 zone minisplits had multiple compressors, one for each evaporator. Kurt's model is 'inverter powered' which means that the alternating current is rectified into direct current first then converted back into AC using MOSFET's or some other electronic switching device. This is similiar to the inverters that anyone can buy at the local Best Buy to convert 12 Vdc from your vehicle battery to 120VAC. I've got one under my truck seat. What sets these ductless inverters apart is that they can change the frequency of the output AC. Since the compressor motors are 'squirrel cage' induction machines, their speed is tied closely to the frequency of the power. By controlling the frequency, the head pressure can be controlled. When one of the themostats calls for cooling, a solenoid valve opens to allow liquid refrigerant to flow to the evaporator (via the TVX or capillary tube) for cooling. The drop in head pressure that this causes is detected by a sensor in the outdoor section and the circuitry responds by adjusting the compressor speed to restore the head pressure to a preset, optimum value. It's not as much an improvement in inverter technology as it is in motor technology.

Each evaporator unit has it's own condensate line. Ceiling mounted units have a condensate pump in them.

After bolting the unit in place, just drill 4 small holes for the vapor refrigerant line, liquid refrigerant line, electric power and condensate line. The thermostat is usually wireless.

Ductless systems are as common in Europe as ducted systems are here. I've never been able to understand why ductless never took off in this country. With the advent of the energy crisis, ductless systems or ducted system that have the ducts installed within the conditioned space are the better choices.

Like Michael B said, they're more expensive per ton than centrally ducted systems. That's about the only hitch to selling them here.

Marc

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Thread drift alert:

Hey, btw, whatever happened to that multi-dwelling unit that had all those condensing units stacked side by side & over and under?

I think the lawsuits are totaling somewhere around 4 million. I'm off the case, but they keep in touch with me. I don't have the courtroom clout of the current advisers. I was the guy that saw it all in the first place, so they still ask me questions.

I've seen plenty of AC mini-splits, and think they're totally in the moment. The heat pump part is what really intrigued me though.

These could be implemented in really interesting ways. It's a whole new way to think about hvac systems.

I have seen 2 heat pumps in my entire career; I would be bad @ inspecting one. Don't know what to think about with these.

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In the Energy Consultation courses I've taken it's always pointed out that ductwork attributes for up to 30% of the inefficiency of HVAC systems, which is pretty sobering. When you ponder what we've seen over the years, it's easy to see why, though.

Thread drift: As Marc points out, we Americans are funny sometimes - very set in our ways (ducted delivery systems). It makes me think of our similar love of the great big refrigerator full of hoarded crap we find ourselves needing to purge of spoiled food every few weeks. Hmmm.. Maybe a little fridge and more frequent visits to the market does make sense. After years of cruising' down the road in our favorite gas guzzlin' beast of a vehicle while lighting cigars with twenty dollar bills, an age of sensibility may finally be upon us? I know I've been thinking quite a bit about all those twenty dollar bills lately....

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I really like the ductless HVAC units. We are really considering adding one to our bonus room as they really are a simple install when compared to a conventional split system. I have not looked at a cost comparison but from what a neighbor told me they are about 20% less than a conventional split system.

We had a speaker at a chapter meeting a few months back who specializes in the ductless units. He said that both of the refrigerant lines must be insulated from the condenser to the air handler/evaporator or you will have major condensation and efficiency problems; this is also a manufacturers requirement. Keep this in mind when you see one on an inspection

The first time I saw one was in Holland about 20 years ago.

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I have not looked at a cost comparison but from what a neighbor told me they are about 20% less than a conventional split system.

Yep, that's what I found when I priced one for that rental - cheaper overall, but only because of no ductwork. I'm betting that we're going to see a whole lot more of them in the future.

Of course, this may be a bad thing for metal workers... NO!.. Not more unemployment!.. [:-weepn]

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OTH - I viewed a couple custom homes being built in a quite pricey part of Dallas. Was taken aback with one in particular:

Metal ducts throughout and very nicely done.

Copper throughout also nicely done.

Pier & Beam that had ~ 3-4 clearance throughout.

Five fireplaces ... no inserts.

Someone had a chunk of change for that one anyway.

I was doing draw inspections on it at the time.

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