Different Loads for same situation ?

[mixer440]

Everyone here has been a great help (especially skyheating)

I've pretty well narrowed my choice on a heat pump + furnace to two contractors. The interesting thing is that they're suggesting two different BTU's for the HP and furnace. My location is in the Portland, Oregon area. 2800 sqft single level 1994

Carrier Infinity series (59tn6080e17 2 stage furnace) and a Infinity 16 Heatpump (25hnb648 4 ton 2 stage) with CNPVP4821 coil.
or....
Trane XV95 (TDH2B060A9V3VA 2 stage furnace) and a XL15i Heatpump (4TWX5036B 3 ton) with 4TXCC044BC3 coil

Now the interesting thing is even though both did a Heat/Cooling Loss Calculation, they are suggesting two different sizes for the equipment. I inquired about that and (of course) their both right. Carrier said that it was because the cooling load required the 4 ton HP which required the bigger blower/furnace.

I thought this was all very interesting considering all three used the same software and had the same measurements, etc., that I provided. The other thing is that I'd like to consider fairly the Carrier system, but it seems oversized ? compared to the Trane.

Current System: Coleman 100,000 @80,000 out and HP Coleman 3.5 ton
Carrier Calculations: Heat: 38,122 Cooling: 29,468 (Winter: 22F/70F Summer: 87F/75F)
Trane: (did not provide, but see equipment above)
Independent that I hired: Heat: 34,910 Cooling: 57,500 (Winter: 26F/70F Summer: 87F/75F)

I'd appreciate any comment on the equipment or the heat/cooling load.

Thanks

[jtrammel]

Seems odd that they would be that far off on the cooling calcs. Looks like a heat pump would fit your needs

[mixer440]

Seems odd that they would be that far off on the cooling calcs. Looks like a heat pump would fit your needs

Yes, indeed. Although I think there's an error in the heat load I hired.....at least in the cooling btu. HP for all would probably work here, but I prefer dual heat....especially since NG is so darn cheap. Our Elec rates are going up and up.

Appreciate the comment

[jtrammel]

Yes, indeed. Although I think there's an error in the heat load I hired.....at least in the cooling btu. HP for all would probably work here, but I prefer dual heat....especially since NG is so darn cheap. Our Elec rates are going up and up.

Appreciate the comment

You'll get the best of both world that way, I would recommend the lowest btu input furnace available in 2 stage or fully variable that will meet the fan capacity needed for AC.

[mixer440]

........recommend the lowest btu input furnace available in 2 stage or fully variable that will meet the fan capacity needed for AC.

Yes, and there is the "rub", it appears I can't do that with the Carrier line without going to a 4 ton. At least according to their calculations.

[duckman06]

2 diffrent load cals? Either someone input date wrong or someone fugued to get the numbers where they thought they should be.

Either way if they both supplied you with load cal. Look at it everything and see if the numbers match or inputs for that matter.

You have a (3.5) ton unit and the Trane dealer is suggesting a (3) ton to be honest he must be 100% sure it will work for you because he gains nothing by going down a have size?

Let me explain. A (3.5) ton cost more and that is what is already there so going lower makes no sense unless he is sure the (3) ton will do the job. I am not saying the other dealer is oversizing but since it is 2 stage that he is quoting he had to go up to (4) ton.

Just my 2 cents....

[mixer440]

.......but since it is 2 stage that he is quoting he had to go up to (4) ton.

Just my 2 cents....

You nailed it perfect.

I looked at the specs for the 4 ton hp and the furnace and that's why it pushes it up to the 80K to get the blower to handle the HP. I suppose there's really no issue here. It's not like I can say to the Carrier dealer: "Hey I want you guys to put in a 3 ton with the 60K furnace..." because they don't feel good about it for whatever reason...............

But, that's what ideally I'd like in Carrier equipment.

Side Point: It just shows that load calculations have a lot of gray area, and just having one doesn't guarantee you "jack".

[jtrammel]

You nailed it perfect.

I looked at the specs for the 4 ton hp and the furnace and that's why it pushes it up to the 80K to get the blower to handle the HP. I suppose there's really no issue here. It's not like I can say to the Carrier dealer: "Hey I want you guys to put in a 3 ton with the 60K furnace..." because they don't feel good about it for whatever reason...............

But, that's what ideally I'd like in Carrier equipment.

Side Point: It just shows that load calculations have a lot of gray area, and just having one doesn't guarantee you "jack".

It's your house, you can tell them to put anything you want in, they may have you sign a disclaimer saying they will not change it if it doesn't keep up on hot days. Honestly the temp that load calcs are sized for are ~10% (or less) of the time the unit runs. So would you rather have something correctly sized 90+% of the time or oversized (cost more to install and operate) 90+% of the time.

[duckman06]

You nailed it perfect.

I looked at the specs for the 4 ton hp and the furnace and that's why it pushes it up to the 80K to get the blower to handle the HP. I suppose there's really no issue here. It's not like I can say to the Carrier dealer: "Hey I want you guys to put in a 3 ton with the 60K furnace..." because they don't feel good about it for whatever reason...............

But, that's what ideally I'd like in Carrier equipment.

Side Point: It just shows that load calculations have a lot of gray area, and just having one doesn't guarantee you "jack".

The gray area you talk about is ture but often times the gray area or size can be made worst by input date that contractor is used. Again the company that is telling you that a (3) ton will heat and cool your home has nothing to gain by going smaller.

In other words the contractor recommending the (3) ton must be very sure that it will work. My hat is off to him as he has stood his ground on the sizing and is telling you the (3) ton system will work. It is easy to just say yes we will install a (3.5) ton single stage unit or (4) ton 2 stage!

In my opion this is the guy you want to install your equipment. He is not going by what is their now but ran his load and it showed him that a (3) ton system will do the job. I must repeat he must be very confident in his selection of else he would have told you current (3.5) ton system is not needed but instead a (3) ton system.

You are only looking at it from carrier dealer side. He is either telling you what you want to hear or has some good reason to stick with the (3.5) ton system. The next question would be is what is your duct work sized for? There are some many variables when it comes to sizing equipment and most contractors are scared to size a home smaller then what you already have.

I am not saying that the carrier contractor is wrong but simply you need to talk with both and review over load cal. Just let them explain to you why they are recommending a certain size unit. This is when you will see who is the best for you.