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Thread: PTAC and ductless air conditioning?

  1. #16
    DIY Member mar3232's Avatar
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    Ok, now I see that some have heating mode and others don't although it really doesn't show much difference in price when I compare. However, I'm really more interested in the best AC for the money so should I go with just the AC only units? Supplemental heat would be a real plus but AC efficiency and RELIABILITY are what I'm after.

    Also, maybe (2) single zone units rather than a dual zone? If one goes down, I still have AC and the pricing seems to actually favor (2) single zone units.

  2. #17
    Retired Defense Industry Engineer jadnashua's Avatar
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    They're not 'like a heat pump' they are! Likely have backup electric resistance heating, but in many climates, you may not need them. You're more likely to need the resistance (heating strip) backup if you setback...you may find it works better with a small or no setback unless you're boing to be away for a long time.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  3. #18
    DIY Member mar3232's Avatar
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    Incredible SEER numbers on that Fujitsu 12RLS -- I'm starting to think of one unit located close to the doorway of my 2 main rooms and do some through wall venting with a fan that cycles on/off.

  4. #19
    In the trades Dana's Avatar
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    Mini-split heat ARE very much heat pumps, but they're ductless, heating/cooling the space with the interior head directly. Inverter drive mini-splits (like those in that third-party test document, and most of the high-SEER units out there) have continuously-variable compressor speeds and controls to adjust refrigerant volumes/flows to precisely match the heat flow through the system to the compressor speed, optimizing efficiency. Some have continuously-variable blowers on the interior heads too, others are 2-speed.

    Most mini-splits do not come with resistance heating of any kind- they handle the defrost cycles by reversing the loop. Since most high-HSPF units have a COP of 2.5 or better at +15F, sizing it for the whole house heat load is often possible size them at 100% or even 125% of the 99th percential design heat load for small to mid-sized homes of reasonable tightness & efficiency in locations with design temps over +10F.

    A 1-ton mini-split is going to be over $3.5K, installed, (my mother was quoted over $4K for a Fujitsu 12RLS, went with a 1.5 ton Mitsubishi instead for similar money). A 2-ton 2-3-head multi- (eg: Mitsubishi MXZ3B24NA, or Daikin 3MXS24JVJU, both with SEER>16, HSPF>9) is likely be cheaper that a pair of pretty-good 1-ton units.

    I wouldn't worry about the reliability aspects- the number of moving parts is lower than old-school heat pumps and the reliablity record of Fujitsu/Daikin/Mitsubishi are all pretty good. Installation by a competently trained techs with experience and backup from local distributors is key. HVAC outfits that only install mini-splits as the 5th line on their their line-card at fewer than 10 units a year aren't in the same class as those who install 25-50/month with an installed base of hundreds still under warranty. It's worth figuring out who is installing lots of them- calling the local distributor is and asking them to recommend a contractor isn't a bad approach- they know more than anyone who is taking them by the dozen, and who keeps calling the tech line with stupid-attack type issues.

  5. #20
    DIY Junior Member JB40's Avatar
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    You shouldn't count out the PTAC unit just yet. There's a reason these are found in most hotels across the country - simplicity. No special refrigeration equipment which means no $125 per hour service calls. Hotel staff doesn't need to rely on 24 hour maintenance contracts, they simply keep 5 on hand at all times. The trades required to install a PTAC unit are a carpenter and electrician. You can expect to get 10-15 years out of them, and when they die you simply buy a new chassis and slide it into the existing wall sleeve. Sound levels contiune to decrease and efficiencies continue to increase. http://www.h-mac.com/brands/cooling-brands/amana.html

  6. #21
    DIY Junior Member emarie15's Avatar
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    Quote Originally Posted by mar3232 View Post
    I have a pretty small ranch house, really just 2 "major" rooms that need cooling and I'm faced with either buying a new outdoor heatpump condensing unit (trane) OR something that may be a "smarter" ? choice.
    I think that a PTAC unit might be the right choice... here is some information to help you decide better. Good luck!

  7. #22
    DIY Junior Member KellyP's Avatar
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    I own a condo in Chicago that has individual room units...PTAC...they are all older units and am looking to replace a couple. The problem is, they are inside mounted units. Nothing shows at all on the outside of the building. Im am sure that the association will require the same type unit as a replacement. Do they have such a thing that is installed only from the inside of the home?

  8. #23
    In the trades Dana's Avatar
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    Quote Originally Posted by KellyP View Post
    I own a condo in Chicago that has individual room units...PTAC...they are all older units and am looking to replace a couple. The problem is, they are inside mounted units. Nothing shows at all on the outside of the building. Im am sure that the association will require the same type unit as a replacement. Do they have such a thing that is installed only from the inside of the home?
    A PTAC always has an exterior grille of some sort- there's no such thing as an air source heat pump that doesn't have access to the outdoor air! A PTAC just has the interior and exterior parts contained in a single module, making it more like a window air-conditioner than a split-system like a mini-split or ducted air conditioner with an air handler.

    You need to figure out how big the opening for the PTAC is in order to find one that actually fits, and whether the exterior side view will change with a new PTAC. Often they are screened from exterior view by architectural elements, or a grille affixed to the building, behind which you can install something of smaller or equal dimensions.

    On the up-side, there are now PTAC units with variable speed scroll compressors & variable speed blowers, which are whisper-quiet and efficient compared to old-skool versions. It's usually worth the upcharge for going with a better, quieter unit rather than replacing it with a legal-minimum efficiency version.

    BTW: Are these AC-only, or PTHP heat pumps that do both heating & cooling?

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