If you heat with natural gas using a 96% efficiency furnace then it is unlikely using the heat pump in the winter will save any money. If you post your natural gas and electricity prices a cost for each fuel can be calculated.

Spending $2000 on a 14 year old heat pump is not a good investment unless you plan to move in the very near future. Put the money towards a new AC condenser.

Was the old heat pump able to keep the house at 75 degrees on hot summer days? If it did then 3 tons is the right size. Don't judge it by how long the AC ran during the hottest part of the day. If it can maintain the desired temperature then you are sized properly. Two stage units only come in whole ton sizes. If your climate is humid it is better to be a little undersized than oversized.

Is there anything wrong with the furnace? I suspect between the heat pump use and your mild winter climate that the furnace does not many hours of run time. The furnace may give you another 5-10 years of trouble free operation. The indoor coil would have to be changed but that should not be an issue.

If you have nat gas fuel and an Infinity 95+% eff furnace, I would replace HP condenser and coil with AC condenser and matching coil. Forget the HP condenser. Second choice replace compressor on HP but only run in AC mode in summer, forget HP in winter mths.

IMO

I forgot to mention my gas is provided by LP and that rate is highly variable. After the trees fell it would struggle to reach the 75 degree on the "normal" days. Usually on the hot days it would not make it to 75, usually getting to about 78.

The one vendor that did the load calculations did say that is I re-insulate to R-19 I would only need 2.75 tons. The quote to drop to the one system to a 3 ton would save about 7% . I am not sure how much the insulation would be to do, since I would most-likely need to remove the old insulation, since it is faced, and the facing is on the top, I have been told no to layer insulation with facing in the middle.

One of the reasons for the furnace replacement is that in order to replace the coils I will need to have the furnace removed and reinstalled, as I have a down flow setup with the furnace resting on the coils.

The proposed system I am looking at the hardest is:

Condenser: 4TWV8048A1

Furnace: TDHMC100ACV4

Coil: 4TXCC008CC3

I just wanted to through that out there for information.

One of the most frustrating things about getting quotes has been so many have just said replace, with x brand without providing any specs or models. When I questioned one with a lower cost, it was for a 14 seer and 80% single stage furnace, single speed. When I asked about going to like equipment to what I have now 16 and multiple stage/variable speed and 96% furnace, the cost doubled. This was an Amana system.

Did your contractor measure your duct work to see if can handle a 4 ton heat pump? I would be skeptical that it could. You are better off adding the insulation to your attic and staying with the 3 ton size.

Were you quoted a 100K BTU furnace? That seems very oversized your house in North Carolina. I thought you said someone did a load calculation?

Have you looked at your utility company's website? They sometimes partner with local state and local agencies to help homeowners replace and upgrade HVAC systems, insulate, etc. There may be tax credits as well, which can change your bottom line decision. Saved me a bundle. Worth a look.

Mike_home,

They did do a load calculation, I am not sure if they were just matching the 4-ton to 4-ton for units. When I look at the heating summary it is only showing just over 40,000 BTU for the heating needs and cooling req total capacity at 0.70 SHR is 3.3 tons.

As far as rebates and incentives we have the town as the utility company and they are not offering any incentives.

Over sizing the AC or heat pump usually leads to an oversized furnace or air handler. You pay for more equipment that, get less efficiency, and a shorter life.

Does the oversizing impact as much with the variable speed compressors as it did with the single and 2 stage systems? I know they have fewer size options that leads to more oversizing than if they provided half ton increments.

As a consumer I have really found this to be a very trying and painful process.

I really appreciate all the assistance.

If you were to buy a 4 ton 2-stage heat pump, the low stage will be about 3 ton. Most of the time you will be operating in the low stage. Their is a big jump in price between 3 and 4 ton 2-stage systems. You would be wasting money on something you rarely use.

Sktn,

That is the direction I started out with but trying to go with the 3-ton HP replacement. But the quote I received for that was a 25HCB636 and CNPHP4821 coil. The cost to install this option was just under 9000 dollars. I thought that was very high. If it had been in the 4-5 range for the condenser and coil I would have been very open to that.

The carrier quote added 2700 to add a 96% performance furnace, not the infinity to match the HP.

Edit: I noticed they had a different HP with the furnace, I am not sure how they did their quote but us is not clear.

Thank you,

Mike_home,

Does the condenser being a variable 25-100% compressor impact the as much as if it were a 2 stage where is around 70% or 100%?

Thank you,

I don't understand the question. Are you asking is it better to buy an over sized variable speed compressor rather than an over sized 2-stage compressor? If that is the question the answer is no and it is a bigger waste of money in my opinion.

$9000 to replace just the HP condenser unit and coil is a total ripoff! The rest of your estimates also seem high to me. I think you need to get more. Go as far a Raleigh and Knightdale (wink) to see if the dealers there are more competitive. And don't discount brands like Goodman, Rheem, etc. They are just as good as Trane or Carrier.

I didn't notice your comment about your gas supply being propane. Given that you don't have natural gas and the fact that our winters are pretty moderate in the Piedmont and Eastern NC, I would probably ditch the furnace and go with straight electric strip backup.

Since OP uses Propane and assuming OP has the ubiquitous Infinity Controller and plans to keep existing furnace which he should, then he probably should keep the HP option. That means either a new matching HP condenser and matching coil, Carrier or Bryant. Second choice is replace compressor but that involves a degree of risk as far as short warranty.. Weigh the two costs and risk between these two options.

IMO

Does the oversizing impact as much with the variable speed compressors as it did with the single and 2 stage systems? I know they have fewer size options that leads to more oversizing than if they provided half ton increments.

complete variable speed systems (variable compressor, otherwise known as inverter systems) operate differently in that they attempt to match the load of the structure.

Which means it will 'almost' always be running, usually in a very slow speed. Due to this my opinion is that it would be impossible to over size the equipment for the structure (negatively)... however, you could oversize the equipment for the ductwork 'if' you are not redesigning the ductwork system.

With that said, an over sized 'inverter system' (full variable speed everything) will never run in the highest speeds as long as you don't set the thermostat to extreme settings.... like 65 or lower as an example... depending on outdoor ambient temperature.

Obviously if you had this extra capacity in my mind you should be able to hit those extreme set points. Oversizing in this regard isn't detrimental necessarily (inverter system only) because the system is always switching gears to find the lowest gear to match the load of the structure.

This in my opinion will give people extra capacity for those really hot days when company comes over, entertaining in the home etc. Just don't forget about the duct system redesign to accommodate such a system. (The system is only as good as the sum of it's parts and 'good' means different things to different people; cost may decide for most people.)

I agree with Tigerdunes. He bought a nice system 14 years ago and can make use of his Infinity furnace and controller.

My recommendation is to add insulation to the attic an buy a 3 ton heat pump. In your prior post you stated the insulation moisture barrier is facing up. If that is true then you have been trapping moisture in your insulation for years. You potentially have a mold problem. Spend the money to correct the problem and then enjoy the lower costs for the next several years.

I agree with Mike on the insulation upgrade and staying with 3 ton sizing. Just replace with new Carrier/Bryant HP condenser and best matching evap coil or just replace compressor on existing HP. Weigh the costs and risk. I think it would be poor strategy to replace a nice Infinity Furnace especially since it is used mainly as an air handler for the HP.

IMO

My current system has the Carrier thermidistat, that can monitor temp and humidity, as well control the HP and Furnace, or at least I think it can. I am not sure where the programming for switch points and such are in my current system, I was a lot more trusting back then.

As far as the duct work I know the supply duct work was redone with the last system and increased in size greatly. The one contractor did check under the house to take a quick look at the ducts.

The reason I was given for the high install price of just the HP and coil was that they would have to uninstall and re-install the furnace to perform the installation. Then it just became the cost of the new furnace while doing the work. I thought it was very high but the quote have all been what I thought to be very high.

I know that I have been concerned about the sizing, as it seemed quite large. I have asked the one contractor about the furnace size and he is going to look at that. He did tell me that they usually just match the furnace to the HP, at the same size since the cooling is more critical here. Also, the furnace can modulate down to a lower capacity to save energy and keep the comfort at a certain level.

I have a feeling that the contractor is frustrated with my asking lots of questions, but I try to be an educated consumer and this is turning out being a larger purchase that expected.

I know that I have tried contacting 3 more contractors and they have not returned the emails or calls, it has been 2-3 days now.

I am not sure how far out I should look for a contractor, Raleigh is about an hour away from me and not sure how many would be willing to travel for the job, or how responsive could they be if a problem arose.

I appreciate everyone's insight and advice.

It is summer and contractors are busy. They like to service customers who don't ask a lot of questions. You are planning to spend a lot of money. You should be asking a lot questions.

Most furnaces have options for different blower sizes. Depending on the model, it may be possible to pair a 60K BTU furnace with a 4 ton AC or heat pump if those are the correct sizes. It takes a little research on the AHRI directory to determine what are the approved combination matches.

I was trying to use the AHRI directory to see how these worked, but I have been less than successful. When I put in the heat pump model it cannot find it.

What is complete mdl number of existing furnace?

I think I have gotten it working, but I am not seeing any configurations with the proposed coil, that are active and not with the furnace I am looking at. Is this something that I should be concerned about?

Tigerdunes,

The current Carrier furnace is 58mvp080-f-17120.

I was also trying to run the numbers on the proposed all 4 ton system, and was not finding anything with the proposed coil. I also did not see any configurations with the 3 ton furnace.

Thank you.

When I ran the AHRI for the equipment all of the furnaces included in the certifications that I could find were the 100k and 120K BTU units of the xc95m downflow units.

None of the coils matched the quoted coil and some of the coils really impacted the efficiencies in a big way. I did find my coil mated to and upflow and it did decently at 11.5 eer 18 seer and 9 hspf. Not sure how the downflow would negatively impact this configuration.