Complete system replacement. Cooling always substandard

12 years ago

Two story Colonial just north of New York City requires complete replacement of HVAC equipment. It's my dad's house, and I do not live local.

Current equipment installed in 1991
-Lennox G20Q3E-125-1 125,000 btu 80% furnace
-Lennox HS22-411V 3-ton condenser
-Lennox 3.5-ton cooling coil

House constructed 1968
-Wiring and pad placement indicate cooling added later
-Motorized dampered zones for first and second floor heating. Cooling single zone.
-First floor fed from basement. Basement partially finished after construction, with two registers connected to first floor zone.
-Second floor fed from exposed attic, trunk from basement rising in center of structure. Attic ducts moderately insulated. Rooms have high registers and low returns.
-Low wall returns in entry and second floor halls

Heating comfort is acceptable, but system quickly cycles except on coldest days. Cooling on second floor has always been barely acceptable, with first floor and basement very cold. Must close supply registers in second floor bathrooms and hallway to cool bedrooms.

Heating and cooling loads completed in 1991 using Logic 1000 Residential Loads Analysis software
-Heat 57,620
-Cool 34,161
-1820 sq. ft.
-Manual J7
-Winter Inside 70/Outside 0
-Summer Inside 70/Outside 90
-Basement not included in calculations
-I believe one north facing wall was accidentally not included in the calculation

Heating and cooling loads completed using HeadCAD 2014, based upon 1991 data. Also includes missing wall from 1991 report, window/door changes since 1991, and basement.
-Heat 62,748
-Cooling 34,598
-2413 sq. ft.
-Manual J8
-Winter Inside 70/Outside 12
-Summer Inside 72/Outside 87

For the life of me, I can't figure out why the contractor in 1991 installed such a large capacity furnace when he had such good data from his load report. I believe he was replacing an A/S 125k unit. He was an old school heating guy, for whom I have much respect.

Here are the proposals received so far. Of course, no contractor did an independent load analysis. We shared the 1991 report with all bidders. I did the HeatCAD 2014 report.

Contractor 1 - old school guy, says ducts oversized, thus requiring 5-ton blower for adequate cooling.
Trane TUD2C100A9V5VB
Trane 4TTR3042D100A
Trane 4TXcc043BC3HCB

Contractor 2 - did not provide specific model numbers or coil info
Lennox ML180-110
Lennox XC-13-042

Contractor 3 -
Trane TUD1B080A9361A
Trane 4TTR6036A1000A
Trane 4TXAB031BC3HUB

I'm looking for advice, suggestions and guidance as we go through the bidding and solution selection process. Getting my dad to take action is relatively difficult these days. Making his life simple and easy is my best strategy.

Thank you.

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Comments (3)

tigerdunes
12 years ago
I assume that the reason for the sq footage difference is the basement area was included. Please confirm. Basement area is finished living area? Basement is below grade?

Do not understand why contractor 1 and 2 want to oversize.

Where will furnace be located? Any reason not to install a high efficient condensing furnace which would require piping through outside external wall for venting?

I would want a properly sized 2 stage var speed furnace 95%+ efficiency.

IMO
fbruno64
Original Author
12 years ago
Yes, the increased square footage is due to the addition of the basement, which is only partially finished. Thus, only some of the additional area is conditioned. The basement floor is a slab six feet below grade. Uninsulated block walls for the unheated area, block walls with wood framing, R-11 and carpeting for the finished portion. Uninsulated partition wall between the two spaces. Single pane, metal framed windows from 1968 all around. See attachment for basement floor plan.

Contractor 1 states that basement trunks are oversized and require five ton blower for proper cooling.This is the smallest unit he could find that provided a five ton blower. He choose a two stage unit to best match needed load using first stage.

As stated in my original posting, cooling to second floor has always been poor. Current equipment supports up to four ton cooling, I believe.

I cannot comment on Contractor 2, as I have yet to speak with him.

Furnace is located in the basement.

My father hates making exterior penetrations, and will not permit the running of the PVC pipe required for the higher efficiency units. It's just the way he is. We need to stay with the current flue to chimney routing. Plus, from his perspective, he likely will not live long enough to recoup the higher cost of more efficient equipment.
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bus_driver
12 years ago
HVAC is not my trade. I recently saw a new installation of a gas furnace in an existing house, one story with basement in which the PVC flue pipe was run up the flue of chimney and terminated above the chimney top with a U-fitting on the top of the PVC to prevent rain from running down the pipe. Could not see how the top of the chimney flue opening was sealed around the PVC.