Be specific about your location. Will this be rental property? Nat gas not available? Building will have good insulation properties following remodeling?Who will pay the electric bill? Don't care for that air handler that was quoted. If not the var speed FV series air handler, then at least the high eff FX series. I prefer demand defrost feature. Carrier/Bryant do not offer that. Trane/ AmStd do.

New Heat Pump System

Here is my general spec sheet for new system.

both outside and inside units should be replaced to have a properly matched system.

15 SEER, 12.5+ EER, 9 HSPF

best matching VS air handler

full BTUs in both cooling and heating for your rated size

R-410a refrigerant(same as Puron)

scroll compressor preferred

electronic demand defrost preferred

thermostat with "dehumidify on demand" feature

staged backup heat strips

new and correctly sized refrigerant lineset

10 yr warranty on parts and compressor

you want a thorough inspection of your ductwork system. size, overall condition, supply and return lines, insulation qualities, leak test, etc.

any hot/cold spot issues in your home should be addressed.

My personal recommendation is Trane/AmStd, and Carrier/Bryant.

Depending on your location, I would not purchase a new system that did not have electronic demand defrost.

IMO

Thanks for the response. To answer your questions:

- This will not be a rental property. It will be an office for my husband's business

- No natural gas available. We could have a propane tank in the back, but propane costs have been variable the last few years and at time it's crazy expensive here. Because of that, we're installing all electric.

- It should have good insulation. We're having two layers of batt insulation above the ceiling. Both units will be in conditioned spaces. Ducts will be covered with insulation. The building's side walls are stone, common with adjacent buildings. Front and back walls will be mainly glass and we're spending extra for quality there.

- Husband's business will pay electric, so it basically is out of our pocket.

I've asked for a quote for an upgrade to a var speed FV series air handler. I read good things about that on here since my post this morning.

I don't know what a demand defrost feature is. Is that mainly for really cold climates?

All heat pumps go through a 'defrost' cycle. It is required since the outside condenser will get cold enough for frost to form on the coils, though usually at cooler temperatures and higher humidity ( think 30s and raining/snowing ). Demand defrost means that the unit monitors the load on the condenser and senses when a defrost is needed. The other type is timed defrost which commands a defrost cycle based on run time (whether it is needed or not). Since a defrost cycle uses the emergency heat it requires more electricity. So it would be a power waster if not really needed.

Hope your ext walls will be well insulated. If not you will be disappointed with the comfort of a heat pump for an 1890 building.

IMO

I'm realizing as I research that the air handler can have a variable speed motor and the heat pump can also have a variable speed motor.

The quoted air handler supposedly has a variable speed motor (per my contractor, my sub and the specs). tigerdunes - if I understand your comment above correctly, you think the air handler is not variable speed. Is that correct?

For the heat pump, the quote to upgrade to a true variable speed heat pump (Carrier #25VNA048A003) will be $7500 per unit, so $15,000 total. I understand there's something in the middle, a two-speed heat pump (Carrier #25HC B6). I've asked for a quote for that as well.

Do you think the cost to upgrade to a variable speed heat pump (Carrier #25VNA048A003) will be worth it? I've looked into rebates and tax credits and none apply, so the upgrade cost will be all ours.

What is the location? If the building is well insulated then 3.5 tons for 1300 sq. ft, and 3.5 tons for 1700 sq. ft. seems over sized. Did the contractor do a load calculation?

The contractor has not done a load calculation. The sub told me he based the sizing on 3200 sf (which is the size of both buildings combined, inclusive of spaces that aren't conditioned, like basement stairway, etc.). Then he said we need 1 ton per 500 sf, so 6.4 tons, which he rounded up to 7.0 tons.

I looked at this chart ( http://michaelbluejay.com/electricity/hvac-sizing.html) for sizing and it seems more like we just need 3.0 tons on each side, or maybe 3.5 tons on the larger side and 3.0 on the smaller side.

Both my contractor and his sub told me it's better to go a little big on sizing than too small. The sub also told me he'd go bigger rather than smaller because it's an office vs. residence (so a lot of glazing at storefront, people coming and going through front door, etc.). But everything I've read and my own personal experience makes me think we should continue to evaluate.

I think the only variable speed heat pump condenser is the top of the line Carrier Greenspeed. I think that would be ALOT more money than a simple 14-SEER unit. Unless you live in a cold climate (upstate New York, Minnesota, etc), I'm not sure it would be worth the money.

Does 'middle of the country' mean Kansas, Nebraska, Oklahoma, Missouri, Iowa or maybe outside Nashville?

Both Trane/AmStd offer var speed HP condensers. Plus beside Carrier's Greenspeed and sister company's Bryant extreme, both brands offer other var speed HP condensers as well. I suggest you look at these brands' website. And for the OP, the air handler FB series is Carrier's builder grade bottom of the barrel air handler. Pay attention to my earlier post. If Carrier or Bryant, you want the var speed air handler, FV series. You never did say your location as I requested twice. Look at the minimum specs I listed. I would want minimum 9 HSPF heating efficiency. An 8 rating as you were quoted is poor. Your dealer is not giving you correct information. And to be clear, the equipment quoted initially is low end, definitely not what you should be considering.

IMO

"Both my contractor and his sub told me it's better to go a little big on sizing than too small."

Actually for AC sizing it is better to be a little undersized especially if you are in a humid climate. Using a rule of thumb of 500 sq. feet per ton and then rounding up almost always results in over sized equipment. You need to find a HVAC contractor who will do a proper load calculation.

The load calculation needs to take into account the number of people in the building and heat producing equipment.

Sorry, wasn't intentionally holding out location. We're in southern Missouri. We're in a rural area (next real city is 2 hours away/whole town is smaller than the high school I went to). Building and land values are low. The resell value of our building will be less than what we're paying to remodel it, and the same will be true with our house. We're spending the money, even though it's not great from an investment standpoint, because that's the only way to get an office and house we like.

So, what I'm trying to figure out, is if there is a level above what I was initially quoted that is worth the extra expense (given our area and low building values) and that would be correctly installed (given that we're in a rural, lower-income area and low end equipment is by far the norm).

Specifically,

- would you bother spending $800 to go from 14 SEER/8 HSPF Carrier # 25HCD442A003 to 15 SEER/8.5 HSPF Carrier units, #25HBC542A003? Or is the bump in efficiency so little it's a waste of money?

- would you spend $5600 more to get a 16 SEER/9.5 HSPF two stage air pump (Carrier Performance 25HCB6), knowing that your HVAC person--who is very experienced in this area--has only installed it twice?

I will follow up again with our sub about cost to upgrade the air handler and sizing.

Thanks for your help! I feel like our office is good experience for when we build our house in the spring. I'm learning--slowly--but definitely making some progress.

I think the 2-stage Performance series would be the best choice for your application, but a $5600 upgrade charge seems over priced. I think this is happening because he is quoting two 4 ton heat pumps. This is compounding his over sizing mistake. You have to go back to the beginning and get an accurate load calculation. Load calculations are generated by software specifically designed to do this type of work. You may have to hire someone to do this for you if the HVAC contractor does want to do it.

"Getting the jumpers set right on the control board and setting up the better thermostat takes reading the instructions"

We read about many installers who don't do this. Proceed with caution and get more quotes.

The prices do seem high. We have a Carrier 14 seer HP/air handler that is brand new and never installed (we had to switch to a high velocity AC after the original unit was bought and could not be returned). We have had trouble selling the unit in our area (Toronto, ON) as heat pumps are not used here often. Sure wish we could pass along this bargain to you.

Good luck in your decision.

Carol

Unless one just has deep pockets, I see no reason for a 2 stage HP condenser for a business property. Get a correctly sized single stage HP condenser 15 SEER /9 HSPF minimum with var speed air handler. I would want matching Thermidistat as well. If going Carrier, then no lower than their Performance series models, not Comfort series.

IMO

If this is an office environment where workers are sitting at their desks 8-10 hours a day, then spending extra money to make everyone comfortable could be a good investment. It is no fun sitting underneath a ceiling vent where you get a cold blast of air down your neck every time and you have to raise your voice on a speaker phone every time the AC cycles on.

I do agree getting the correct size and quality equipment is higher priority.