Bosch variable speed compressor heat pump paired with a single-stage gas furnace with A coil - moisture problems?

Question

I live in Seattle where AC is only needed for a handful of days each year. A friend has a 20 year old gas furnace needing replacement, and he would like to update his system, including adding AC. A local company bid a system that includes a 5 ton Bosch (generation 2) variable speed heat pump, a new 80% single-stage gas furnace and an A coil. Am I right to be concerned that while the heat pump is variable speed, the furnace has a single speed blower? My primary concern is that such an approach may result in humidity problems. That said, given that humidity is really only a concern when running the AC (I think), and given the low number of days that AC is needed here, should we be concerned about this approach? - Thanks in advance! - Jim

I should add that he is being quoted a total cost of $15000. He also got a bid for a matched system, by which I mean a variable speed compressor paired with a ducted variable speed indoor air handler, but the costs for the latter system is over $20000 and a bit out of his budget comfort zone.

Answer 1

Let's start with what information you need to choose AC system

Zone: what climate zone do you live in ? I show Seattle to be in zone 3.

Lets assume your home is 3,000 sqft

For that a 5 Ton AC is a good choice

Next: what type HVAC? Super or normal. That is determined by the SEER rating and other gadgets like variable speed compressor. The cost difference in SEER rating is substantial. But higher SEER will save you on electricity so they say. Really ? how much. Here you go. The cost difference btw SEER 15 and SEER 20 is about $5,000. Your electricity saving between Seer 15 and SEER 20 is about $200* per Year ??? How many Years it takes to recover the higher cost ?

Just for clarity the SEER 15 will cool or heat your home at same levels as SEER 20, so it is just the electricity consumption.

Humidity: Seattle is in humid to very humid area. The AC will ONLY remove humidity when the cooling is running. So if you want more constant humidity removal instal a dehumidifier that can run all the time independent of the AC.

Variable speed Fan in the heat exchanger cabinet. It is nice to have but not must have.

To summarize: I recommend 5Ton, SEER 15/16, no variable speeds on anything, it is more simple unit and easier to repair.