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Replacing Gas Heater

Posted by bobpratt (My Page) on
Tue, Nov 15, 11 at 11:36

I am just getting started on shopping for a new gas heater only. My 4 ton A/C system is all new. I do have my first quote which raised additional questions. I live in Tulsa, the house is all brick, built in 93, 1900 sq ft. There is no nameplate on the excising unit.

ONG is offering a $550 rebate for HE units over 96%

The equipment in installed in my attic and I have read many comments here about problems with HE units installed in attics, but no explanation.

My first bidder mentioned that he had to oversize the heater to 100k in order to get enough airflow for the 4T A/C. If this is true; I think I should be looking at variable speed units.

Trane XV95 $3814
XR80 $2688

I am starting to lean toward a 80%, VS unit.

Comments please.

Follow-Up Postings:

RE: Replacing Gas Heater

HE furnaces (90%+ efficiency) produce condensate. Unless sometimes extreme measures are taken, there is a chance that freezing could occur with leakage (ceiling damage) or possible shut down.

From the Trane website: "The XV95 is rated with up to 96.7% AFUE". This means that CERTAIN (could be only 1) size(s) can reach that value. You need to have your contractor verify that the proposed unit meets the spec. in order to get the rebate.

The term variable speed refers to the ability of the blower motor to ramp up as the static pressure increases (filter clogging, etc.), not the output (and hence, the blower speed) of the furnace. The XV-95 is a 2-STAGE furnace, with a variable speed blower. So, under normal circumstances, the furnace stage will be selected by the (hopefully) 2 stage thermostat, along with the corresponding blower speed.

Did your a/c cycle frequently during the season, and only run (almost) full time on the hottest days.

Depending on your actual house heat loss, and the degree of oversizing of the furnace, it may never run in second stage. A loss of comfort, and the value you are paying for.


RE: Replacing Gas Heater

the XR80 and XV95 both come in 80K btu 4 ton drive furnaces. The XR80 even comes in a 80K btu 5 ton drive. But as far as the HE furnace, according to the info I have only the Trane XV95 in the 60K btu 3 ton drive is 96.7% AFUE. All the rest in that series are less than 96% AFUE.

But size of your heat and size of your ac should not be a quessing matter. Does oklahoma require a load calculation before install?

RE: Replacing Gas Heater

Thank you for the replys..

>>> Did your a/c cycle frequently during the season, and only run (almost) full time on the hottest days ??

Yes. We had many 110 degree days this past summer. We need and use the 4T cooling.

This house was built in '93 with an Rheem Hybrid package; it has high quality construction and insulation. The HP failed last year and I replaced it with a A/C of the same size (4T). Both my heat and air now depend on the operation of an 18 yr old fan. If it fails, it will cost me $300, $400 to replace and I will still have an 18 yr old heater.

The Trane XV 95 proposal includes an 802 thermostat.

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