I've got a manual j that says my cooling load is less than 16k. I think that is high considering that I've got some trees that weren't taken into consideration and lots of air sealing was done. The ach for the manual j was on the high side. I would rather plan for a load of about 10 or 12k, and in a humid, mixed climate I need a lot more humidity removal than cooling. For my building I have really old ductwork that either needs to be redone if I go with a small heat pump, or I could take it out altogether and do ductless minisplits with a few radiators for backup. I'm at a crossroads. Anyone have experience with EITHER of these who also lives in a similar mixed climate (zone 5 here)? I have heard some hvac people just absolutely trash ductless split systems for humidity removal but I'm not sure I trust them because they're biased. If I opted to redo all of my ductwork and I went the other route, would a 1.5 ton heat pump serve me better than a 1.5 ton ac? Other than a hp providing heat, is there a real difference in their ability to cool and/or remove humidity? Wall insulation is about R30, attic R 60 and foundation walls R 12. None under the slab right now but I might put some in when I do a new basement floor someday.

we just finished a house in zone 6 where we used minisplits (Mitsubishi Hyper Heat ductless)- they were installed in Dec. Can't say enough good things about them - quiet, unaobtrusive, inexpensive to buy & install, inexpensive to use, they heat the house very well even with temps below zero & high winds. Other builders I've spoken to who have used them say the same things.

There is no air exchanged between the minisplit and the outdoors so i don't think they have anything to do with humidity levels. Look to your ERV or HRV to deal with humidity.

If you are cooling interior air down, you have the chance for condensation. Putting "open" drains on my ductless minisplit heads was not as small a job as it sounds.

Posted By Bob I on 04 Mar 2013 09:54 PM
we just finished a house in zone 6 where we used minisplits (Mitsubishi Hyper Heat ductless)- they were installed in Dec. Can't say enough good things about them - quiet, unaobtrusive, inexpensive to buy & install, inexpensive to use, they heat the house very well even with temps below zero & high winds. Other builders I've spoken to who have used them say the same things.

There is no air exchanged between the minisplit and the outdoors so i don't think they have anything to do with humidity levels. Look to your ERV or HRV to deal with humidity.

I was told the general rule of thumb (I know that's blasphemous) that a 1 ton (12,000 Btu) mini-split is good for around 500 sqft of living space.

Have you ever installed or used a LG Unit?

How many square feet was the home (1 story or 2 story)? How many mini-splits were used?

I was looking at the Mitsubishi Dual Zone Unit (20,000 Btu) with one 9,000 Btu unit and one 11,000 Btu unit.  Is it more efficient to have TWO outdoor units running one zone each or having ONE outdoor unit running two zones?

"general rule of thumb (I know that's blasphemous) that a 1 ton (12,000 Btu) mini-split is good for around 500 sqft of living space."
obviously that depends on your envelope. We used three 12000 Btu units in our 2400 SF two story cape style home; two heat the house fine but we added one for more even distribution.

Posted By Bob I on 05 Mar 2013 06:30 AM
"general rule of thumb (I know that's blasphemous) that a 1 ton (12,000 Btu) mini-split is good for around 500 sqft of living space."
obviously that depends on your envelope. We used three 12000 Btu units in our 2400 SF two story cape style home; two heat the house fine but we added one for more even distribution.

So you have 1 ton per 800 sqft but you say that you are able to run it with 1 ton per 1,200 sqft. Are you at Zone6? What are your insulation values on the wall and roof?

Rules of thumb suck, but a ton per 500' usually works for current code-min housing, not so much for high-R houses.

The Mitsubishi ----FE18NA mini-split would cover the load with some margin to spare in a US zone 5 location. (In heating mode it can deliver ~22,000BTU/hr @ +5F, 15K @ -13F.) The --FE12NA might be cutting it close, but maybe...

If the room by room heating & cooling loads and floor plan call for more than one head, there are some ~20K 2-head multi-splits out there that would cover it, or a pair of 3/4 ton units.

What are your 99% and 1% outside design temps?

http://www.energystar.gov/ia/partners/bldrs_lenders_raters/downloads/Outdoor_Design_Conditions_508.pdf

Posted By Dana1 on 05 Mar 2013 11:57 AM
Rules of thumb suck, but a ton per 500' usually works for current code-min housing, not so much for high-R houses.

The Mitsubishi ----FE18NA mini-split would cover the load with some margin to spare in a US zone 5 location. (In heating mode it can deliver ~22,000BTU/hr @ +5F, 15K @ -13F.) The --FE12NA might be cutting it close, but maybe...

If the room by room heating & cooling loads and floor plan call for more than one head, there are some ~20K 2-head multi-splits out there that would cover it, or a pair of 3/4 ton units.

What are your 99% and 1% outside design temps?

http://www.energystar.gov/ia/partners/bldrs_lenders_raters/downloads/Outdoor_Design_Conditions_508.pdf

-4 and 90 What do I do for humidity removal? Should I get the smallest portable dehumidifier I can find? A huge operating expensive from my experience though.

If -4F is your 99% design temp you could go with a 1 ton or 1.25 ton Daikin Quaternity (FTXG15HVJU/ RXG15HVJU), which is unique in that it can dehumidify to  an RH setpoint as well as a heating or cooling setpoint.  If you have an ERV/HRV you can run it on dehumidistat control for 6 months out of the year (the cooler months) and duty-cycle it the rest.

Like other air conditioners, all mini-splits dehumidify (but not to an RH setpoint like the Quaternity) in cooling mode, and if the latent load gets ahead of it (rare, in zone 5 climate) most will also have a "dehumidify" mode, (the Mitsubishi's do, and I'm pretty sure Fujitsu Halcyons do too, as well as non-Quaternity Daikins) which runs the blower at low speed and dehumidifies (again not to a setpoint) until you put it into normal cooling or heating mode.

If you get a portable dehumidifier, don't go any smaller than an Energy Star 70-pint version. The smaller portables will still handle the load, but run at considerably lower efficiency.  In winter it converts the latent load to sensible heat (it raises the temperature of the room), which isn't necessarily a bad thing if you already have adequate ventilation, but in summer it just adds to the overall cooling load.  They're all pretty noisy,10s of dBA louder than a mini-split head.

I am having trouble controlling humidity in my new, well insulated, tight house, and have a good energy star dehumidifier, but I hate using it because it is VERY noisy. Seek another solution.

If I didn't have a new heating system I would look at the Daikin Quaternity.

-Rosalinda

Ok I am an idiot. I don't understand how a minisplit can remove humidity without running air over coils and draining the condensation. Does the quaternity have a condensate drain line?

I like the indoor cassette units by Mitsubishi because you have more options where to put them, hide them, etc. LG's art cool line looks nice but there are some negative reviews.

Are there any good small ducted heat pumps that can operate at reduced speed (modulate) to account for the mostly latent load?

we're zone 6, doing R20 under the slab, R30 basement walls, R37 house walls, R64 roof, triple pane windows, very tight.

Does the quaternity have a condensate drain line?

Yup. Drain pan and drain line.

Posted By strategery on 05 Mar 2013 07:55 PM
Ok I am an idiot. I don't understand how a minisplit can remove humidity without running air over coils and draining the condensation. Does the quaternity have a condensate drain line?

I like the indoor cassette units by Mitsubishi because you have more options where to put them, hide them, etc. LG's art cool line looks nice but there are some negative reviews.

Are there any good small ducted heat pumps that can operate at reduced speed (modulate) to account for the mostly latent load?

At your loads, no.  At 2-3 tons there are some options, but a SFAIK versions with guaranteed output at -20C/-4F are very limited.   Mitsubishi may have something ducted & variable in the sub-2 ton range, but IIRC the smallest Carrier Greenspeed is 2 tons, (and oversized for your stated loads.)  IIRC the Bryant Extreme is the same hardware under the paint.

All mini-splits have condensate drain lines. Most set up the drain in the same conduit as the refrigerant lines and control/power cabling between the interior and outdoor units.  In cold climates where you would still use the Quaternity's dehumidification function while in heating mode it's important to route the drain where it won't freeze.  But anybody installing a Quaternity in your neighborhood would/should be hyper-aware of that issue (after the first irate-screaming-customer "training session", anyway. )

Posted By Dana1 on 05 Mar 2013 06:07 PM
If you get a portable dehumidifier, don't go any smaller than an Energy Star 70-pint version. The smaller portables will still handle the load, but run at considerably lower efficiency.  In winter it converts the latent load to sensible heat (it raises the temperature of the room), which isn't necessarily a bad thing if you already have adequate ventilation, but in summer it just adds to the overall cooling load.  They're all pretty noisy,10s of dBA louder than a mini-split head.

I'm not worried about the noise at all. It put it in the basement and I won't ever hear it. I currently have a 40 pint energy star dehumidifier and I only run it when the RH is above 60% which is usually only during the summer months. During the shoulder seasons I usually open basement windows which help to lower the humidity for free. The dehumidifier I bought in 2004. You think it would be a good idea to replace it? What brands of dehumidifiers do you like? Are there any that can operate at a low fan span continuously for higher efficiency? The drawback to going with a bigger one with larger coils is that it may short cycle.

I have the GE ADER50LN, but I don't run it continuously. I have read reviews about how it freezes up with continuous use. I am also not crazy about the dehumidifier, and imagine there must be better ones out there. On the plus side it does run efficiently, and has several settings/features.

-Rosalinda