Replies

1. 
   Patrick_OSullivan | Jun 23, 2019 09:51am | #1

   PVA-A30AA7 is more of a traditional air handler, so the lack of modulation doesn't surprise me.

   A bit more info would be useful. Some general information about the size and shape of your house will be helpful in determining if one or more compact ducted units would be more suitable.

   And though I suspect your sizing might be driven by the heating load, perhaps you can share your Manual J cooling load as well.

2. 
   Jon_R | Jun 23, 2019 10:24am | #2

   Be careful - a wide modulation range doesn't mean much of anything (why do you want it?). It might provide worse dehumidification and worse efficiency than a system with less modulation (or possibly even a single speed system with no modulation).

   Do give some preference to a system that will allow some zoning without creating problems - loads vary and zoning can improve comfort.

3. Expert Member
   Akos | Jun 23, 2019 06:26pm | #3

   John,

   This is your best resource to figure out your options:

   https://ashp.neep.org/#!/product_list/

   If you get a decent duct design done up front (less than 0.4" water drop), you can go with a pair of low profile ducted hyper heat units to get some zoning.

4. 
   ranson | Jun 24, 2019 12:40pm | #4

   Here's the basic house layout.

   The cooling load is 12675BTU @85C design temperature. This is one reason why I want a unit with good modulation. Any heat pump that can heat the house will probably be around 2x oversized for cooling.

   
5. Expert Member
   Dana Dorsett | Jun 24, 2019 01:52pm | #5

   The 2.5 ton mid-static Fujitsu mini-duct unit (has blower power comparable to full-sized air handlers) would cover those loads, with about a 3.5:1 turn down in cooling mode at your 1% outside design temp of ~85F:

   https://ashp.neep.org/#!/product/25351

   The heating capacity margin is a bit thinner than the PVA-A30AA7 & PUZ-HA30NHA5 though:

   https://ashp.neep.org/#!/product/29005

   The 3 ton Fujistu mid-static mini-duct unit has a big bigger modulation range, and a bit more heating capacity than the 2.5 ton Mitsubishi solution at temperatures that matter:

   https://ashp.neep.org/#!/product/25352

   The max static pressure ratings of that series Fujitsu mini-duct cassette is the same 0.8" w.c. as the Mitsubishi PVA air handlers. Duct systems designed for one will work with the other, except for the details at the air-handler/cassette unit itself.

   https://hvacdirect.com/hvac/pdf/36RGLXD.pdf

   http://meus1.mylinkdrive.com/files/PVA-A30AA7___PUZ-A30NHA7-BS_Product_Data_Sheet-en.pdf

6. 
   ranson | Jun 24, 2019 04:00pm | #6

   Thanks Dana.

   The 30kBTU Fujitsu unit looks great. I can't find a technical manual for it, but I found one for the AUU30RGLX, which uses the same outdoor unit. It confirms the maximum heat output at 5F should be sufficient for my needs.

7. Expert Member
   Dana Dorsett | Jun 24, 2019 04:43pm | #7

   While the ARU30 would do, the ARU36 isn't oversized for the heating load- it's only a 1.25x oversize factor using the max at +5F, and that doesn't account for defrost. The ARU36 also modulates about 10% lower than the ARU30 in cooling mode at the temperatures that matter, per the NEEP data sets (which sometimes contain typos and other errors.)

   Even if your Manual-J has slightly inflated load numbers the 3-tonner is probably the "right" one. They both modulate down to the same 9.6K @ +47F - it's not giving up any modulation range in heating mode to go with the ARU36RGLX.

   With either of them you're going to have to run it in "DRY" mode to keep humidity bounded on the stickier days. The COP at minimum-modulation in cooling mode is an insanely high 15+ at 82F, which usually translates into very little latent cooling, and your calculated cooling load isn't much higher than the minimum modulation.