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Community and Q&A

Heat Pump Replacement Spec for ’87 Contemporary in SE PA

washxhouse | Posted in Mechanicals on

Hi all-


Back with another ‘Rate my Quotes: Heat Pump Edition’ … I have a ~2800 sq ft 1987 contemporary house in Bucks County, PA (NE of Philadelphia, border of zones 4 and 5) with loads of 2-pane casement windows on three faces of the building and 5 sets of sliding doors facing south. There is a 2-story great room on the north side of the building with 3 skylights. It’s 2×6” construction with an unfinished basement.


The current setup includes two 15-year-old Carrier Infinity heat pumps (3.5T downstairs, 2.5T upstairs) paired with oil backup (in-ground tank in the front). One system developed a catastrophic coolant leak recently, precipitating my investigating replacing both systems entirely and taking the opportunity to go all-electric by removing the oil backup and getting rid of that tank.

As far as I know the ducting is reasonable and won’t present any major problems.


Upon moving in in late November of last year, I had an energy audit with a blower door result of 0.58 ACH and 3,437 CFM50. 


Since then I had blown CC insulation done at the band joist and in the attic (HFO blowing agent – thanks to this forum for helping with sourcing that vendor), air-sealed the attic, and I have also added R49 of blown fiberglass *on top of* the existing batts in the attic. I intend to continue to pursue air sealing and insulation projects over time.


As a result of my reading GBA fairly religiously, I’ve begun every conversation with HVAC salespeople with the words ‘Manual’ and ‘J’, to varying degrees of success. 


One vendor came up with: 

3,300 sq ft conditioned area  

26,397 cu ft above grade volume

71,540 Heating BTUH 

44,694 Cooling BTUH

2,200 CFM

41,960 Sensible cooling

2,734 Latent

.939 SHR



… obviously my heating loads are more significant (~3,000 heating hours vs 900 cooling with much larger deltas, IIRC), so my understanding is I should be indexing on heating efficiency over cooling, all other things being equal.


Among many, I have three quotes I’m considering, each from very reputable firms, all much more expensive than I expected, but then I’m looking at communicating variable systems inside and out with efficiency and comfort top of mind. I just bought this house, am fanatical about energy usage, and plan on staying here for a long time.


These aren’t apples-to-apples but I’m hoping to get a gut check and callouts on any ‘gotchas’ from the experts here. Any and all comments welcome.


The coolant runs are probably about 25’ total through an unfinished basement. More or less a straight shot across the ceiling. No difficult issues of access or anything that would complicate the labor.



Quote 1, Mitsubishi Hyper Heat, 1 outdoor unit, zoned:

The team who did those loads are very well-respected in the area. They want to put in one outside unit to replace the two I have now, switching to a zoned configuration.

(1) Mitsubishi MXZ-8C48NAHZ hyper heat (50,680 BTU heat, 47,097 cooling)

(1) SVZ-KP36NA (first floor air handler, variable speed)

(1) EH10-SVZ-M 10kw (emergency heat ,first floor)

(1) SVZ-KP24NA (second floor, variable speed)

(1) EH05-SVZ-M 5kw (emergency heat, second floor)

(2) Honeywell MHK-2 thermostats

4” media cabinets



Notes: Obviously we lose the redundancy we have with two units by going to one outdoors. We also lose the complexity of maintaining two units. These guys are a diamond dealer for Mitsu and you get a 12-year warranty P&L warranty if you keep up service on the units. 


They asked Mitsu engineering about my return configuration because it enters both air handlers with a single drop and thus risks the units drawing on each other’s supply when only one is on and the response was that this should be OK if the units are configured so both fans are always running at the same speed. They say there’s no issue with that but it sounds like there’s hidden complexity in the implications of that.


This is the most expensive quote I’m actually considering but I believe the one with the lowest TCO because of the system’s ability to continue to output ~4 tons of heat at ~5 degrees outdoors, rather than rely on backup resistive electric. This system as configured is only 10 HSPF / 16 SEER but I think keeping that ~10 HSPF in the colder parts of the year *might* meet or beat a more efficient heat pump that starts to roll off to the backup at or around 40 degrees outside. I’m not sophisticated enough with this stuff to do that math, though.


As these guys are also a Carrier dealer I asked about Greenspeed stuff and they said it’d be even more expensive (like $36-37k all in) and that I’d hate the thermostat.



Quote 2, Daikin Fit, 2 outdoor units:

Another very well-reviewed local outfit who are a Daikin diamond dealer.

(1) Daikin DZ17VSA301 2.5 ton heat pump (second floor)

(1) DV36PVCD14 air handler (second floor) 10 kw aux heat

(1) DZ17VSA421 3.5 ton heat pump (first floor)

(1) DV47PVCD14 air handler (first floor) 15 kw aux heat

(2) Daikin one WiFi thermostats


Total: $25,000

Notes: Daikin also offers 12-year parts warranty, but only a 2-year warranty on labor. 


This configuration is up to 17 SEER / 10 HSPF.

Quote 3:

For what seems like an astronomical price, another well-regarded shop quoted Trane equipment in a good-better-best 3-tier quote at roughly $33,000 / $36,000 / $40,000 all-in.


Even if I were particularly excited about Trane’s options over Mitsu or Daikin I wouldn’t really be considering this, but it’s vaguely in contention since I feel like this is a high-quality vendor who have a great reputation and took the spec process seriously.




… OK so that’s the roundup as it stands. Are 1 or 2 good options? Are they priced appropriately? Am I missing any gotchas? Am I thinking about this correctly? Is there someone else I should be talking to?


THANK YOU in advance!

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