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Old 06-19-2013, 09:18 PM   #1
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80% vs 95% gas furnace and water heater venting


Hello. Resident of Central PA and getting my OLD AC unit and gas furnace replaced. I've had 4 contractors give me estimates...lowest to highest all within $500 dollars of each other and all seemingly reasonable. Now my question. One contractor said a 95% furnace would need to be vented through a wall outside (my old 80% vents via my brick chimney). Fair enough I said. Now...next contractor comes in and I mentioned the venting outside for a 95%. He said I would then need to replace my water heater which also vents through the chimney with one that also vents outside as its against code to have the water heater vent via the chimney by itself. So he suggested just sticking with an 80% which would only be 6 or 7 percent less efficient and not worth the extra cost of a 95% and a new water heater (which is only 3 years new). He suggested the water heater would be fine in the summer venting by itself....but needed the furnace to push the air all the way up in winter, I.e., isn't big enough to do it by itself posing a hazard, thus against code. Now, can anyone point me to where I can find said code? I would prefer to go with the contractor that knows his onions even if a bit more expensive than one who may risk me failing an inspection. Any other comments are welcome. Thank you for your time.

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Old 06-19-2013, 09:27 PM   #2
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80% vs 95% gas furnace and water heater venting


The water tank can stay you just need to line the chimney with a flexible liner. If the interior area of the chimney is within the max size and is an interior chimney no liner is required. 80% gas furnaces are a little easier to install but i recomend a liner either furnace

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Old 06-19-2013, 11:05 PM   #3
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80% vs 95% gas furnace and water heater venting


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Originally Posted by Gorgie
Hello. Resident of Central PA and getting my OLD AC unit and gas furnace replaced. I've had 4 contractors give me estimates...lowest to highest all within $500 dollars of each other and all seemingly reasonable. Now my question. One contractor said a 95% furnace would need to be vented through a wall outside (my old 80% vents via my brick chimney). Fair enough I said. Now...next contractor comes in and I mentioned the venting outside for a 95%. He said I would then need to replace my water heater which also vents through the chimney with one that also vents outside as its against code to have the water heater vent via the chimney by itself. So he suggested just sticking with an 80% which would only be 6 or 7 percent less efficient and not worth the extra cost of a 95% and a new water heater (which is only 3 years new). He suggested the water heater would be fine in the summer venting by itself....but needed the furnace to push the air all the way up in winter, I.e., isn't big enough to do it by itself posing a hazard, thus against code. Now, can anyone point me to where I can find said code? I would prefer to go with the contractor that knows his onions even if a bit more expensive than one who may risk me failing an inspection. Any other comments are welcome. Thank you for your time.
So by that contractors logic the water heater never comes on in the winter unless the furnace is already on??? Haha
Qbert iis right. A chimney liner is all that needs to be done there. And then yo can have a 90%+ vented separately through a wall or wherever
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Old 06-19-2013, 11:20 PM   #4
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80% vs 95% gas furnace and water heater venting


80% gas furnace parallels $.80 of every dollar used to heat your home. 95% efficient gas furnace equates to $.95 of every dollar you spend on gas being used to heat your home, so more efficient as your dollar responds more efficiently to the price of gas, more bang for your buck so to speak.

Question is, how much do you use heat?

I would personally vent intake and exhaust on a 95% furnace away from the water heater, individually, but that's not saying it's mandatory.
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Old 06-20-2013, 05:49 AM   #5
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80% vs 95% gas furnace and water heater venting


Thank for all the responses. Very informative. I guess my main concern remains though, is what the contractor was saying a violation of code regardless if the reasoning behind it may be nonsense? To what authority can I pose this question? State government? County? City? All of the above? Cheers?
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Old 06-20-2013, 06:15 AM   #6
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80% vs 95% gas furnace and water heater venting


call your city or county inspection department. I would recommend venting both away from the chimney.
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Old 06-20-2013, 04:08 PM   #7
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80% vs 95% gas furnace and water heater venting


Its in the ifgc international fuel gas code tables in rear of book. NO secret the info may even be on the web somewhere
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Old 06-20-2013, 06:34 PM   #8
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80% vs 95% gas furnace and water heater venting


When you replace the htg and a/c you will need to line your chimney with a flex liner.After that and in the future when you need to replace water heater you will only need to replace it with the least expensive unit out there .this unit will be almost exactly like the one you have now except it will have a spark ignition pilot instead of a standing pilot.
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Old 06-20-2013, 08:11 PM   #9
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80% vs 95% gas furnace and water heater venting


I left our water heater in place, after we had our old Octopus furnace that came with the house replaced with a 95% furnace. Just this year, finally replaced the water heater with a power vent Richmond 50gal water heater.

The water heater with tax was around $950, install around $275 for the guy that I use all the time, to do the water heater install. Furnace labor and some materials when we had that done around 2005, was about $1300. At today's prices, I would be looking at around $2200 or so. That was without a/c install, which we had done in 2010, and for that with A-Coil, outdoor unit (13 seer/r-22), lineset, labor, freon & nitro charge, was around $2400.

The furnace we had installed, which we got for free, due to having the oldest furnace during a contest during the home show in 2005, is a Lennox Signature Series. It is a workhorse, and even with the Single stage A/C, it is nice having the furnace running on Stage 1 when needed, to just cool the house off. If it needs to, it will kick up to Stage 2 to cool the house off further, if the furnace cannot keep up.

Our A/c is a Armstrong Air, which is manufactured by Lennox. May want to look at that line. Very quiet a/c unit. Measured it around 38db when running, compared to my next door neighbor's, which I have measured her Lennox 10 seer at around 50db.
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Old 06-20-2013, 08:19 PM   #10
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80% vs 95% gas furnace and water heater venting


I may be wrong so please don't bite my head off; stage one's directory is not mainly to cool but to dehumidify. an air molecule with 30% humidity at 73 degrees holds less heat than an air molecule holding 60%, 70% or higher at the same temperature. Due to dehumification alone it cools. Stage 2 is cooling, blower on full speed. but with a smaller home I can see how stage 2 rarely kicks in.
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Old 06-21-2013, 03:39 PM   #11
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80% vs 95% gas furnace and water heater venting


I ran into the same code problem going from 80% to 95%.
A flue liner was $150-200 in parts, the water heater was ten years old, and a new electric water heater was about $300 including wire, disconnect box, and circuit breaker.

Since I'm on propane and the cost of electric hot water is nearly identical to natural draft propane, it was an easy decision to seal off the chimney and put in an electric water heater.
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Old 06-21-2013, 03:56 PM   #12
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80% vs 95% gas furnace and water heater venting


Quote:
Originally Posted by Gorgie View Post
Hello. Resident of Central PA and getting my OLD AC unit and gas furnace replaced. I've had 4 contractors give me estimates...lowest to highest all within $500 dollars of each other and all seemingly reasonable. Now my question. One contractor said a 95% furnace would need to be vented through a wall outside (my old 80% vents via my brick chimney). Fair enough I said. Now...next contractor comes in and I mentioned the venting outside for a 95%. He said I would then need to replace my water heater which also vents through the chimney with one that also vents outside as its against code to have the water heater vent via the chimney by itself. So he suggested just sticking with an 80% which would only be 6 or 7 percent less efficient and not worth the extra cost of a 95% and a new water heater (which is only 3 years new). He suggested the water heater would be fine in the summer venting by itself....but needed the furnace to push the air all the way up in winter, I.e., isn't big enough to do it by itself posing a hazard, thus against code. Now, can anyone point me to where I can find said code? I would prefer to go with the contractor that knows his onions even if a bit more expensive than one who may risk me failing an inspection. Any other comments are welcome. Thank you for your time.
An orphaned water heater often needs a liner in the chimney. A 3" dilution hood water heater may not be vented into a chimney with greater then a 49 sq in cross section(EG: 7"X7"). If the chimney is on an outside wall, or an outside wall, it will need a liner even if it is only 7X7, to stop condensation.

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