Please help review this proposal

[i g norant]

This is the only proposal I have to date. He is the only guy who ran Manual J. I did not think to ask for the load print out, but he ran it on a laptop in my living room & I hope he saved it. I got sidetracked when he started explaining a possible zone conversion.
He said he had to go with the 100,000 BTU furnace to get the airflow needed for the heat pump, not for the heat load. Does this sound right?
The house is about 1700 sq ft, 2 story, single system in Atlanta. The current A/C is 3 Tons & the 23-year old furnace is 100,000 BTU.
I would appreciate a critique of his spec. No other bids will come in until Monday.
Thanks in advance. This forum is a gold mine of information.

Trane 4TWX4042*100* 3.5 Ton R-410A Heat Pump
Trane TUD100R9V5* 100,000 BTU2 Stage Variable Speed Gas Furnace 21
Trane RXC054S3HP* R-410A Coil 21 Wide
7/8 x 3/8 Line set LS4-50
Outdoor thermostat
Honeywell Touch Screen Thermostat
Dual Fuel Kit
... misc other parts ...
Labor to install complete system (up flow level 1)

[jacob perkins]

Originally posted by i g norant
He said he had to go with the 100,000 BTU furnace to get the airflow needed for the heat pump, not for the heat load. Does this sound right?


sounds confusing...what does it mean?

[coolwhip]

100k seems a bit much for atlanta, however he does have to move quite a bit of air haveing a 3.5 ton a/c.

[dirtyboy103us]

sounds like you got money

[BaldLoonie]

He said he had to go with the 100,000 BTU furnace to get the airflow needed for the heat pump, not for the heat load. Does this sound right?

No it isn't. There is an 80,000 BTU furnace with enough blower for the 3.5 ton heat pump.

Is this 1700 sq ft per floor or for both floors? If 3 ton did the job in the past why go bigger? Or didn't it?

[i g norant]

Jacob - don't know what it means exactly, but that was his answer I thought 100K was too big. He did all calculations, sizing and proposal preparation on his laptop.

Cool - I think that is what he was saying.

dirtyboy - nope, don't have the money to throw at this wastefully.

Bald - 1700 sq ft is both floors, each is 857.
The only thing I remember about his load calc was 95* outside & (I think) 75* inside design temp, 2.5 tons for first floor on slab, 1.5 tons for second floor.
I'm glad to hear that there is an 80K BTU furnace with enough blower. I want to save as much as I can.
The 3 ton would run for 1.5 hr or more set at 79 with outside 92-95. I don't think it could have pulled any cooler. But he never asked how well the current setup worked.

[2hot2coolme]

Boy 'o' Boy, dude does a heat load and still gets slammed....what next?

[BaldLoonie]

1700 sq ft total, 3.5 ton sounds like a lot of cooling. No insulation? Lots of windows?

He may have done a load calc but still seems fishy. 100K and 3.5 ton for only 1700 sq ft and a 2 story to boot so only 857 sq ft of attic. I'm trying to understand this.

We may build our houses that much tighter up here the reason we can get by with lots less capacity. I saw a couple of 2600+ sq ft homes get done this summer with 2.5 ton total. No complaints, the salesman ran his inspection on one of them on a very steamy day. 70 inside.

[dpatty]

In atlanta you will not get much use out of the furnace. As mentioned earlier there is an 80 available and would ask why that furnace would not do. Also mentioned earlier if a 3 ton had done the job why now do you need to upsize? There may be a good reason for this but keep in mind an oversized AC will remove less moisture from the air and will require lower set points to achieve the same comfort level.

The company that gave you the quote may be right in there suggestions but ask a few questions to be sure

[dirtyboy103us]

OK here goes this from memory i live in Fla. mind you

10. kW heat strip is what i would use in a 3 to 3 1/2 ton heat pump ton unit i would look at the house and see how old it was and take a peak in the attic to see the insulation now i would measure the house and go with 500 sq. ft per ton depending on
windows if they were those jealousy windows i would go up a half a ton to make up for it that's what's in the j manual and it works now if is a newer home or has had insulation added then i would go down a half a ton and make sure they went with a higher efficient unit that will pump more of the load and run
longer to pull out the humidity

[Jultzya]

Originally posted by BaldLoonie
He may have done a load calc but still seems fishy. 100K and 3.5 ton for only 1700 sq ft and a 2 story to boot so only 857 sq ft of attic. I'm trying to understand this.


I have a blueprint right now where the home is 1900 Sq Ft and he told the last guy he wanted a 115K 93% furnace! :rolleyes:

You know the type, the bigger the better!

[Steve Wiggins]

If you want to save money forget about the gas furnace and just go with the heat pump. No need for both. What kind of air filtering system will you have to protect your investment?

[i g norant]

Here are MY measurements for the first floor. Walls are area after subtracting windows & doors.

NE Wall 52.4 sq.ft.
...Window 17.6 sq.ft.
...Window (2) 17.6 sq.ft.
...Window (3) 17.6 sq.ft.
...Window (4) 17.6 sq.ft.
...Window (5) 7 sq.ft.
...Window (6) 7 sq.ft.
...Door 40.5 sq.ft.
SE Wall 177.3 sq.ft.
SW Wall 206 sq.ft.
...Window 17.6 sq.ft.
...Window (2) 17.6 sq.ft.
...Window (3) 10 sq.ft.
...Window (4) 10 sq.ft.
...Window (5) 10.5 sq.ft.
...Glassdoor 37.6 sq.ft. (Double pane)
NW Wall 141.5 sq.ft.
...Window 5.3 sq.ft.
...Door 30.5 sq.ft.

Windows are all, unfortunately, single pane wood frame.

I REALLY appreciate the input!

[edited] Oh yeah, there heavy shade to the south and west. The house is in full sunlight about 9:30 - 1:30

[Edited by i g norant on 10-21-2005 at 11:24 PM]

[Jultzya]

You can do your own load calculation by clicking on the red tab above.

The program is by the developer of this great site.

[i g norant]

I am working on my calculation. I entered something wrong somewhere and am looking for the bad entries now. I'll post what I get after the results look like they may make sense.

But after I get the numbers, I don't know how to mix and match the parts of the system.

[Jultzya]

Originally posted by i g norant
But after I get the numbers, I don't know how to mix and match the parts of the system.

That's the simple part, you find a competent HVAC Company that will size your unit properly.

You'll know if he is close by your calculations.

[i g norant]

Design conditions: Average infiltration (ACH 0.41 summer 0.83 winter)
and Default values
......Indoor:...................... Outdoor:
Summer temperature: 75.....Summer temperature: 92
Winter temperature: 72.....Winter temperature: 22
Relative humidity: 50......Summer grains of moisture: 99
...........................Daily temperature range: Medium

4 people on first floor, 1 person on second floor

Sensible..Latent...Total...... Total
Gain.......Gain..Heat Gain...Heat Loss
24,362....3,403...27,765......47,889
.......................(2.5 tons)

Change only these design conditions:
Indoor Summer Temperature 70....Outdoor summer Temperature 95

29,310....3,983...33,293......47,889
........................(3 tons)

I sent the guy an e-mail and asked for a copy of his load calc results.

[2hot2coolme]

Well, go ahead and put the equipment size you came up with in...this way you have no one else to blame but yourself...sounds to me like you're good to go.

[i g norant]

2hot - 2 weeks ago I couldn't spell refreejurant. Would you trust my calculations??

Steve - he quoted 2 filters. A 5 inch and Trane's Clean Effects. I thought I would start another thread about filters tomorrow ;-)

[Jultzya]

Originally posted by i g norant
2hot - 2 weeks ago I couldn't spell refreejurant. Would you trust my calculations??

No, but you are closer than the guys you have been talking too! :(

[dpatty]

Looking at your first numbers a 3 ton looks ideal. Unless you had problems with the old unit from the start I would suggest going back with a 3 ton. If you go with your second set of numbers you may have to keep the house at 70 deg to be comfortable.

You may want to have the contractors you deal with look at what you have input to verify that you did not miss anything

[Edited by dpatty on 10-22-2005 at 01:03 AM]

[Black Adder]

Ditch the furnace, variable speed airhandler with back up electric strip. In your climate I don't see you using the back up heat very often. 90% variable speed Trane is going to cost bongo bucks. Same unit in a Heil 2 stage 90 variable would be considerably cheaper if you are still convinced that you need to go the furnace route. 100k furnace is way oversized for your conditions. Trane does make a 4 ton in 80,000 btu. You will definetly pay a premium for trane or American Standard. It is good equipment but I often wonder if the cost is justified especially in a climate like yours where the furnace will be mainly used as an air handler.

[i g norant]

Originally posted by dpatty
If you go with your second set of numbers you may have to keep the house at 70 deg to be comfortable.

You may want to have the contractors you deal with look at what you have input to verify that you did not miss anything


I don't really want it at 70 deg. The contractor said he had set up his computer for Atlanta too long ago & did not remember the design temps. I was just trying to get a higher load after I saw his. ;-) Are the first numbers (closer to what I will actually do) OK for Atlanta?

I will talk over my calc with the others that did not do calcs after their bids are in next week.

Thanks for your help.

[i g norant]

Originally posted by Black Adder
Same unit in a Heil 2 stage 90 variable would be considerably cheaper if you are still convinced that you need to go the furnace route.
We have several nights in the 20's, some in the teens and some days when it is never above freezing. Sorry, but I don't have the number of days. That is why I am thinking furnace. My original idea was to keep the 23 year old dinosaur (100K BTU 60%) as backup. Wouldn't I save money on the labor by replacing everything now and increase both heating & cooling efficiency? (Bold item added in edit) :confused:

Originally posted by Black Adder
You will definetly pay a premium for trane or American Standard. It is good equipment but I often wonder if the cost is justified especially in a climate like yours where the furnace will be mainly used as an air handler.
I agree. But I can't sem to find any contractors except the "big advertiser" brand names. If anyone can recommend a contractor, I will absolutely contact them.

[Edited by i g norant on 10-22-2005 at 11:54 AM]

[i g norant]

I found a publication that has data for each Trane model 4TWX4 018-060, ratings with auxiliary devices, etc.
Now I am really dangerous :D
but not stupid enough to specify models myself. ;)

[Freezeking2000]

I would go back with what you had is size. I would also install a heat pump with gas backup for the coldest nights.

If you said your a/c ran for 10 hours and never reached setpoint i would say go larger, but the longer it runs the more effecient it is. Ideally a cooling unit should never shut off at design temp,same with heating, but you should never reach the design in atlanta since you have to size the blower for cooling.

[i g norant]

When doing load calc for dual fuel systems, should you not run two calculations?
First for the heat pump. Set the design temps to the usual summer values to figure cooling load. But set the outside temp to the balance point to figure the heat pump heating load?
Then for the fossil fuel backup. Use the normal outside design temp but set the inside temp to ... what??

[Steve Wiggins]

Yeah and you should also run a calc for when your kids move away to go to college. And then one for when you have a lot of company coming over. And then one for when you cut down your tree in the front yard. And one for in the morning. And one for in the afternoon.

So you start to see how these calcs leave a lot up to judgement and rely less on facts. They are a general guideline guys, could you relax a little about it please?

[i g norant]

I received the contractor's load calculation summary.
I ran the load again with only these changes to the design conditions of my earlier post:
Removed original 75%-85% shading for all windows (from trees on south and SW sides).
Removed indoor shading for all windows (blinds or drapes).

..........Sensible...Latent...Total......Total Loss
First .....21,444....2,514.....23,958....31,909
Second..12,541.......895....13,436....16,008
Whole....33,980....3,403....37,383.....47,889[/B]
........................................(3 Tons)
Previous Totals.................27,765.....47,889
........................................(2.5 T)

Contractor conditions:
...Indoor........Outdoor
Summer 72.......95
Winter 70.......23

............Sensible...Latent....Total.......Total Loss...A/C.....Furnace.......Elec Furnace
First.......16,504.....4,951....21,455.....27,921. .....2.0 T....27,921 BTUH.....8.2 KW
Second...11,123.....3,337....14,460.....18,794.... ..1.5 T....18,794 BTUH.....5.5 KW
Both floors listed Capacity Multiplier 1.00

I don't know which program he used.
I agree with everone on the 3 tons. Do you guys take drapes & shading into consideration? I know I keep them closed on the shady side in winter & sunny side in summer.

[i g norant]

My Duct Loads (with below 120 temp and R2 insulation):
.................. Gain .. Loss
First........ 3,574 .. 4,162
Second.... 2,090 .. 2,088
Whole...... 5,664 .. 6,250
Contractor's Duct loads:
................. Gain .. Loss
First.......... 3,809 .. 6,443
Second...... 2,567 .. 4,337
................ 6,376 . 10,780

I don't know what my duct insulation value is. I didn't want to tear a hole in the covers. I guessed R2 because the metal ducts are encased in something which appears to be like the shiny barrier on attic insulation fiberglass bats.
Does this seem a reasonable assumption?

[i g norant]

Another Trane system proposal from a different company just came in by e-mail. Again proposing 100K BTU furnace.
Which 80% furnace could I use to get close to the numbers from the load calc?

4TWX4036
TUD100R9V5 + RXC03783

[AAone]

OK, if you had a 3 ton (I assume 3 ton straight A/C) before and you told him it would only maintain 79 degrees on a 92 degree day, he probably added 1/2 ton capacity to the system based upon this and also because you will now have a heat pump and the added capacity would be a bonus.
That is a very nice furnace,if you are going dual fuel then I would say go with the 80 percent. The furnace will get little use anyway. Are all the contractors giving you quotes on similar setups?

[i g norant]

Originally posted by AAone
OK, if you had a 3 ton (I assume 3 ton straight A/C) before and you told him it would only maintain 79 degrees on a 92 degree day, he probably added 1/2 ton capacity to the system based upon this and also because you will now have a heat pump and the added capacity would be a bonus.
He didn't ask about how it ran now. He ran load on the first floor & said it was 2.0 T. Then he ran the second floor & said it was 1.5 T. I think his laptop selected the models. He did almost no typing after the second load calc.

That is a very nice furnace,if you are going dual fuel then I would say go with the 80 percent. The furnace will get little use anyway. Are all the contractors giving you quotes on similar setups?
I have received only these two quotes. I had hoped to get 3 today (as two others said they would send it electronically today).
I sure am glad I'm having so much fun with this purchase :rolleyes: ;)

[AllTemp]

Originally posted by i g norant

Originally posted by AAone
OK, if you had a 3 ton (I assume 3 ton straight A/C) before and you told him it would only maintain 79 degrees on a 92 degree day, he probably added 1/2 ton capacity to the system based upon this and also because you will now have a heat pump and the added capacity would be a bonus.
He didn't ask about how it ran now. He ran load on the first floor & said it was 2.0 T. Then he ran the second floor & said it was 1.5 T. I think his laptop selected the models. He did almost no typing after the second load calc.

That is a very nice furnace,if you are going dual fuel then I would say go with the 80 percent. The furnace will get little use anyway. Are all the contractors giving you quotes on similar setups?
I have received only these two quotes. I had hoped to get 3 today (as two others said they would send it electronically today).
I sure am glad I'm having so much fun with this purchase :rolleyes: ;)




[Edited by AllTemp on 10-25-2005 at 02:37 AM]

[i g norant]

I can't find an ARI number for this contractor's combination:
4TWX4036
TUD080R9V4 + RXC037S3
I found some with the XL16i. Is the proposed combination too new, just not tested or not sanctioned by Trane? :confused:

[Edit] The combination came from Trane's Unitary Product Group CD. I guess that makes it a valid configuration for warranty purposes.

[Edited by i g norant on 10-25-2005 at 07:02 PM]