I would fire your contractor for such bad advice.

Go with 80% nat gas furnace with either var speed or high eff ECM blower motor paired with 13-15 SEER AC condensers.

Depending on sq footage on each floor, perhaps there is opportunity to use zoning controls for two floors off one system.

BTW, what is nat gas rate and electric rate for your location in Texas?

Post back.

IMO

tigerdunes, thanks for the thoughts. Why do you say it is bad advice? Is there a reason why a heat pump is a bad idea?

As for rates, here's what I looked up:
Gas: 53 cents per cf (per call Texas Gas)
Electric:
Oct-May: range of 1.8/5.6/7.2/8.4/9.6 cents per kWh, at 500 kWh increments
June-Sept: range of 3.3/8.0/9.1/11/11.4

Yes there is a reason. Relatively speaking, Texas has a short heating season. Plus Texas being an energy rich state has cheap nat gas.

Forget the heat pump. You will never look back if you follow my advice; you always will if you select HP.

And yes, I would send your HVAC sub packing.

IMO

Just to say ... with all the surcharges and fees added the last natural gas bill a family member in TX received was a little over $1 per whatever is the unit of use stated on the bill.

$68.24 for 68 units.

The electric rates you posted don't make sense. Are you sure these numbers include delivery and supply charges?

I agree with Tigerdunes, it makes no sense to get a heat pump when you live in a state that is one of the biggest gas producers in the country. A rate of 53 cents per cu. foot has to be one the cheapest rates in the US.

Another thing to consider the life of a heat pump is hard. It has to operate in a harsh environment for most of the 12 months of the year. The life expectancy is shorter than than that of an AC only condenser who gets to rest during the winter months. A gas furnace has the easiest life and the longest life expectancy. It gets to live in a conditioned environment. I would think in Texas you would have go through two heat pumps before you would need to replace a gas furnace.

Tigerdunes, dadoes, mike_home, thanks for your thoughts. You are confirming my suspicions and gut feeling. That's unfortunate, because I am really tired of "conflict" on this house. Now I need to push for a gas furnace option.

Also, not sure I should "fire" the sub. He just said that this is the option that he proposes. I will have him tell me about a design with natural gas.

Well, just to update, I asked the sub to provide a proposal with furnace instead of a heat pump, but I haven't heard a response yet. Still not sure what to do.

It sounds like he is not interested in installing a gas furnace. He probably may have to hire a licensed plumber for the gas piping which he may not want to do. I suggest you start looking for another HVAC contractor.

Thanks again for your thoughts. Here is the new proposal:

3 Carrier Comfort Series 14 SEER heat pump with Carrier Comfort Series single-speed fan coils with electric auxiliary heat strips, Honeywell Focus Pro 6000 stats, Aprilaire 4" media filters, Broan 80 CFM recessed can vent lights, a bunch of other sundry venting, sealing, low-voltage
(Just noticed they didn't list anything about the tonnage for these systems. Weird.)

Total:$15,500

Optional upgrades: Carrier 15 SEER air condition with Carrier aluminum coils and Carrier Performance Boost Series 96% AFUE two-stage condensing natural gas furnaces, all else same as above, add $2660 (Does that furnace sound like overkill for central Texas?)

Stats to Honeywell Vision Pro 8000 Touchscreen programmable Wi-Fi, add $180.

This sub does a lot of work in the area, and I'm sure he does other houses in nat'l gas, so I would be surprised if it's a concern about gas piping. Maybe they have some heat pumps in stock they want to unload or they get better incentives on those? I don't know. I wonder why they left off the tonnage. It was there for the old proposal, but we changed the system design for 3 systems, with one system split to cover a master suite plus the exposed lower level basement.

Has this contractor done a Manual J load calculation? It needs to be done for new construction in order to properly size the equipment. You do not have a valid quote unless it has all sizes and model numbers.

Your guy does not make sense. he first proposes heat pumps becasue the winters are mild, then he offers the 96% AFUE furnaces. I am not sure if you will every see a return on investment on three high efficiency furnaces

How big is this house and why do you need three systems?

The house is around 3900 sq ft and three floors: main floor, upstairs, and an exposed lower level basement type floor. One system covers the master suite plus the basement floor, another for main public spaces on main level, another for the upstairs.

Says on the bid that he conducted a manual j. I haven't seen it or anything.

I would get two systems...

One for main floor and basement with zoning control.

Then a separate system for upstairs.

Of course dealer should have demonstrated qualifications for installing a zoned system.

IMO

I think there are some difficulties in doing just two systems. The house is long, and there is a considerable run from the master suite to the main space, and getting the ducts to work for that were difficult or something. Also, the current configuration calls for a 2 ton (basement+master+study), 3 ton (main), and 2 ton (upstairs) units, so combining the first two might require a much bigger unit. I honestly do not know anything about this stuff. But I really do appreciate the thoughts and advice.

New construction

7 tons of cooling for 3900 sq ft?

I would want to see a load calc for each zone...

And that's nonsense about zoning for basement/main floor...

IMO

Does the 3900 sq. feet include the basement? If so how much? How much of the basement is exposed?

I will ask for the load calc to find out. As for the basement, I call it a basement but it is exposed on three sides; the back wall is a retaining wall with earth all the way up the 9 ft wall. Square footage on basement is around 500 sq ft. First floor 2264 (of which master+study is probably about 930 sqft). And second floor 1150 sf.

So
unit 1 - 2 ton, ~ 1430 sq ft (master, study, basement)
unit 2 - 3 ton, ~ 1334 sq ft (main)
unit 3 - 2 ton, ~ 1150 sq ft (upstairs)

Tigerdunes and mike_home: thanks!

Ok, I now have load calculations and actual model numbers, so I'm hoping you all can take a look at this longwinded reply and tell me where to go from here. Also, while I have multiple pages of load calcs based on a Manual J8, I don't know if I am reading them correctly, so let me know if I get that wrong (there's a page for each system, then a page called "load and AVF summary" so I took the info from the summary page).

Same equipment for each system. 3 ton Carrier 15 SEER/12.5 EER Base series single stage air conditioning and Carrier Performance Boost Series 96.3% AFUE two-stage condensing natural gas furnace. Condenser Model: CA16NA036; Evaporator coil: CNPVP4221A; Furnace: 59TP5A060E17-14. Honeywell Focus Pro 6000 t-stats, one honeywell two-zone damper system, aprilaire fresh air ventilation system (required for foam insulated home), aprilaire 4" media filters. Etc.

System 1 - Main level, main living areas
1350 sq ft; 19933 btuh htg load; 19700 btuh clg load

System 2 - Split between main level master and study, and "basement" level (this is where the controlled damper will go, and two t-stats)
1588 sq ft; 22087 btuh htg load; 18444 btuh clg load

System 3 - Upstairs bedrooms
1228 sq ft; 14266 btuh htg load; 17085 clg load

Does that give enough information? Should I be concerned about the "Base" model AC equipment, and try to upgrade? Would that cost a lot more? I also have some humidity concerns; originally I asked about a whole-house dehumidifier, but was told that it is not necessary for this house.

Thanks for any thoughts!

Well this is lovely. The total heating load is 56,286 BTU but your contractor wants to install 3 furnaces with a total of 180,000 BTU of heating. One furnace would be sufficient to heat the entire house.

It gets more ridiculous for the cooling. The cooling load is 55,229 which is about 4.6 tons. But the contractor says you need three 3 ton units for a total 9 tons of cooling.

He is proposing three systems and on top of this he thinks one system has to be zoned?

Why did he bother doing a load calculation if he is going to ignore it?

Why do you think he is proposing a Carrier Base AC model. Does he have to stay inside an HVAC budget with your builder?

I am not impressed with this HVAC contractor. Do you have an option to work with someone else?

Mike_home, thanks for the input. I honestly don't know what to do. The contractor has all but said he is not willing to work with anyone else because he's used this company for the last 35 years, and they do have a decent reputation in the area. I have spoken with the sub about how they designed the system, and they said that "with a house that is this high end, people are going to want separate systems that control the master suite and the upstairs." he also thought that main level living spaces--which have a lot of glazing and doors--were going to be having a lot different load fluctuations or something and would be better on a separate system. He spec'd the 96% furnace because it does not require a traditional flue pipe (rather, a PVC vent pipe with a concentric vent that also pulls in its own combustion air from outside). I think that was based on space limitations for our HVAC closets.

As for specifying builder grade AC components, I think he was trying to stay as close as possible to the original budget of $15k. The system he proposed comes in at $18k.

I vaguely remember him saying that in certain models, they do not make 0.5 ton increments, only 1.0 ton increments. Perhaps that applies here?

One difference in design condition from the standard defaults, they use 99 degree for outside db (and 75 degree for inside db) when calculating cooling requirements.

What would you recommend here?

When I look at the "Design Information" pages for each system, it shows thinks like sensible cooling equipment load sizing and latent cooling equipment load size. For example, system 1 adds those two numbers to get 24011 btuh equipment total load, and then says req. total capacity at 0.71 SHR is 2.5 ton. I don't know what any of that means, but is that why he spec'd a 3 ton unit perhaps?

AC condensers come in 0.5 increments if they are single stage, 1.0 ton increments if they are 2-stage. The Base model he quoted is a single stage condenser.

The first question would be why is he over sizing the AC by a factor of two?

I still think that the main floor could be one system with 3 zones. This would allow to save money and put it towards better equipment. This assumes this company that has been in business for 35 years (this means nothing, the current owner could have bought the business last week) knows how to implement a proper zoning system.

If you have to use three furnaces, then I think it absurd to use 60K BTU sizes. There are 40-45K furnaces available but the choices are limited. If you got a 60K 2-stages furnaces, they will properly operate in the low stage 98% of the time.

Thanks, mike_home. After some google searching, I found something that says Manual S limit on oversizing is 140% and 115% (heating, cooling respectively). When I looked back over these, looks like this is way, way beyond that limit.

Which you pointed out, of course.

Well, guess I will just have to call again. This gives me 0% confidence in having them do the work, but I don't know if I can make my contractor use someone else.

Ok, they got back to me. For heating, I am told that they need to use the 60k btu furnace because of airflow requirements (40k btu furnace is only rated at 1-2 ton air flow, where as 60k btu furnace is rated for 2.5-3 ton air flow). So we need the larger furnace to provide the air flow necessary for the cooling side.

As for cooling, I guess they are saying that I am reading the information incorrectly. They size equipment based on the sensible load, and none of the systems is oversized on sensible load. E.g., System 1 has a sensible load of 21,456 btu, System 2 a sensible load of 20,219 btu, and system 3 has a sensible load of 18,398, whereas the equipment has sensible cooling capacity at 22,557 btu. For a total difference of only 7,598 btu across all three systems, or just over a half ton.

To drop down to a 2.5 ton per system would result in two undersized systems and one system (system 3) that would have "very little cushion."

I guess I don't know how to read these load calcs. What should I do?

"whereas the equipment has sensible cooling capacity at 22,557 btu"

Where did this number come from? A 3 ton condenser should provide 34-36K BTU. This doesn't make sense.

Attached is the product data for the proposed AC condenser. Look at pages 16-23. You will see furnace, coils, and 2.5 and 3 ton condensers listed. These are all valid matches. Your furnace is not listed, but it should still be a valid match.

You will see the rated capacities for 2, 2.5, and 3 ton condensers. You will see the 2 ton has a capacity of more than 24,000 BTUs in every configuration. It is hard to believe with capacity will be much different with other furnaces.

He should not be adding an extra ton for "cushion". This defeats the purpose of doing a calculation.

You are not the first poster who has been in this situation. The builder and HVAC contractor decided from the beginning you were getting heat pumps and now are making it difficult to make changes.

You could hire another HVAC contractor to design a system that makes sense. Perhaps the builder will give you the $15K credit so you can do it right yourself. Right now both the builder and the HVAC contractor are not helping you. This is something to think about.

Here is a link that might be useful: Carrier CN16A product data

I agree. The HVAC guy needs to go and make sure whoever does it seals the connections with mastic. To have that much ductwork just taped together will leak like crazy in a couple years. Mastic brush on or mastic tape. If nothing else do it yourself while you still can. I prefer the brush on mastic and cheap chip brushes.