Heat Pump Options

BurkeO'Neal

I have received proposals from two reputable HVAC contractors, one specifying Amana MDASZ60361E and the other Mitsubishi SUZ-KA30NAHZ. The Amana option is a couple thousand dollars less and is eligible for a $2,000 tax credit and a $1,200 state-level incentive. Does anyone have an opinion about differences in the equipment? I am in Madison, WI, so it is cold, but it is a well insulated, small house and only needs about 15,000 BTUH at -7 F. Backup is electric. Thanks!

BurkeO'Neal

The one HVAC contractor just sent a follow up email saying the SUZ does in fact qualify for the incentives.

HVACNUT

The Amana is really Daikin. Same assembly line.
Choose the best contractor. Know your warranties and whether you need to register the equipment in order to get those warranties. 

Electric baseboard backup?

One is a 30, and one is a 36. They both can modulate, but is either the correct size? How many indoor heads, and what size are they? What's the square footage of the heated and cooled space?

Hot_water_fan

I personally have the Mitsubishi with air handler, it’s been great. If your heat loss is 15,000btu/h, these are both too big. Get a right sized option, you have backup anyway! 

SuperTech

The installing contractor is more important than the brand name of the equipment.  Proper sizing is key. That being said, I tend to prefer Mitsubishi. 

BurkeO'Neal

These are ducted units, so no heads. Since electric resistance is the backup (ducted), the contractors are trying to get the heat needed at very low temperatures, which is why the units are large. House is 1,000 SF above grade. Heat load calculation is based on backing out the current worst month BTU per HDG natural gas use. It matches the Slant Fin program calculation (that I happened to still have on my computer) pretty well, about 16k BTUH at -7 F. We are disconnecting the gas, since the connection fee is more than the gas use fee and we have the ability to cover the electric with expanding our photovoltaic system. Thanks!

pecmsg

Keep the gas

Jamie Hall

Must be one heck of a PV system... and what do you do in a three day blizzard?

Hot_water_fan

These are ducted units, so no heads. Since electric resistance is the backup (ducted), the contractors are trying to get the heat needed at very low temperatures, which is why the units are large.

That’s bad logic on their part. The 24kbtu unit puts out 18kbtu at -13F. There’s not many hours below that, so the extra capacity is wasted. 

https://mylinkdrive.com/viewPdf?srcUrl=http://s3.amazonaws.com/enter.mehvac.com/DAMRoot/Original/10006%5CM_SUBMITTAL_SVZ-KP24NA_SUZ-KA24NAHZ_en.pdf

Hot_water_fan

Must be one heck of a PV system... and what do you do in a three day blizzard?

@Jamie Hall OP asked for help about heat pump sizing. You don’t have to like solar PV but let’s not get distracted. 

Jamie Hall

But I do like solar PV. Having a 15 KW ground mount system installed. But I don't want someone to be disappointed when it doesn't run their heating system on a cold dark night.

Hot_water_fan

Almost all PV installs are grid connected, so I don’t think people are under the impression the array will power everything all the time. 

BurkeO'Neal

Yes, our PV system is grid connected. We have a pellet stove that can keep the house warm during an extended power outage with backup electricity, so we don't need the natural gas connection that costs over $250 per year just to be connected. I'm not a fan of the utility monopoly here, so would rather spend that somewhere else. The contractor specifying Amana said the next size down is 24k (SZ60241E) for $800 less installed. That unit is rated for 13k at -10, so we would be switching to electric resistance at a warmer point than that, maybe 0 to - 5 F. But still, maybe it wouldn't be a large difference over the winter. Just for background information, I'd like to replace our furnace, anyway, since it is a Heil high efficiency unit over 35 years old with no A/C. I work for a solar energy installer, so can expand the PV system inexpensively. Thanks for sharing all your thoughts!

BurkeO'Neal

Should add that the existing furnace is oversized at 45k BTUH and doesn't modulate at all, but other than a little overshoot when it cycles in the shoulder seasons, it hasn't been too bad. This should be an improvement.