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Old 11-07-2008, 12:52 PM   #1
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Tankless water heater questions


Hi all

I am considering replacing my current hot water heater tank(gas, 40 gal I believe, and about 25 years old) with a tankless gas water heater in my below-grade basement where the furnace and water heater are installed currently.

But after looking at some other sites I am a little worried.

- Venting -- do I need a "dedicated" vent all the way up thru the roof or can I tie the vent into where the current hot water tank and frunace are vented, up thru a stack thru my roof? I am below grade and plumbing out a seperate horizontal vent would be problematic due to the location. I figured I could just tie into the exhisting stack but the site says "dedicated vent".

- Intake air requirements....going by a chart I found on one site, the models I am considering (Rheem PTG-74PN 7.4 gpm and Bosch 2400ES NG 6.4 gpm) require a 1250 sq ft, 8 foot ceiling room for installation......My HOUSE is only 1300 sq feet! LOL

My furnace room is about 5 feet by 12 feet or so.....the chart also says I can open up two 14"x14" openings to allow for air.......Basically, that would mean removing the door to my furnace room. Or I can plumb in the intake air, but i would have to make a long run to get outside, running the intake from my furnace room , thru my garage and to the outside......or could I use air from my adjoing (integrated) garage?

Or am I just not a good candidate for a tankless water heater?

Thanks folks....

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Old 11-07-2008, 01:13 PM   #2
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Tankless water heater questions


Why don't you get a direct vented water heater, then you do not need to worry about it starving for oxygen, or your chimney... is your basement fully below grade? You can go UP and out with some of these I think.

Direct vent is going to take outside air for combustion too...

Air from garage is no good

You want good clean air. What is the efficiency on those models?

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Last edited by pcampbell; 11-07-2008 at 01:16 PM.
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Old 11-07-2008, 01:49 PM   #3
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Tankless water heater questions


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Originally Posted by pcampbell View Post
Why don't you get a direct vented water heater, then you do not need to worry about it starving for oxygen, or your chimney... is your basement fully below grade? You can go UP and out with some of these I think.

Direct vent is going to take outside air for combustion too...

Air from garage is no good

You want good clean air. What is the efficiency on those models?
I am completely below grade.....and even if I werent, there is a covered concrete patio directly outside/above where I would need to vent it.

Intake air might not be as large an issue if I can pipe from the heater, thru the garage (two car) to the outside wall that is partially above grade....but I know that cant be done for the venting......

I was hoping I could vent right thru the current chimney stack....
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Old 11-10-2008, 10:55 PM   #4
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Tankless water heater questions


There are models that mount external to the house and require no venting.
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Old 11-11-2008, 04:45 AM   #5
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Tankless water heater questions


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There are models that mount external to the house and require no venting.
I live in SW PA......our winters are pretty cold.....not sure that would be a good idea.
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Old 11-11-2008, 02:13 PM   #6
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Tankless water heater questions


Just a little fyi. Im a certified plumber and have been running my oufit since 87. I thought it would be a great idea to put in an instantaneous hwt, figured id save money etc. Prior i had a 50 gall bronze electric which cost me about $20 a month. After the instant hwt my bills shot up to $30 or so for gas, mostly because everyone in the house now knows they can shower for eternity, also the wife doesnt choose time for the washer or dishwasher because theres alwayw hot water. As an added bonus try to shave, the tank senses water flow and if its not significant enough no hot water. But wait it gets better, when your doing the dishes, rinsing etc we are used to waiting once for the water to get warm, with instant if you don't have the tap running nonstop u get large doses of cold and pretty much have to wait every time for it to heat up. Like a heat pump instantaneous requires getting used to. My suggestion Bronze insulated electric or stainless steel. Good pretty much for life
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Old 11-11-2008, 02:18 PM   #7
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Yep, In BC no doubt about hot water lag. Not so much an issue down here in Texas!
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Old 11-12-2008, 05:43 PM   #8
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Tankless water heater questions


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Originally Posted by airwren View Post
Just a little fyi. Im a certified plumber and have been running my oufit since 87. I thought it would be a great idea to put in an instantaneous hwt, figured id save money etc. Prior i had a 50 gall bronze electric which cost me about $20 a month. After the instant hwt my bills shot up to $30 or so for gas, mostly because everyone in the house now knows they can shower for eternity, also the wife doesnt choose time for the washer or dishwasher because theres alwayw hot water. As an added bonus try to shave, the tank senses water flow and if its not significant enough no hot water. But wait it gets better, when your doing the dishes, rinsing etc we are used to waiting once for the water to get warm, with instant if you don't have the tap running nonstop u get large doses of cold and pretty much have to wait every time for it to heat up. Like a heat pump instantaneous requires getting used to. My suggestion Bronze insulated electric or stainless steel. Good pretty much for life
Thanks...is "bronze" a brand? I have a "State" right now.....24 years old or so....gas.

I wont go electric.....in my area that wouldbreak the bank...gas is much cheaper

RE: your tankless...what unit do you have?
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Old 11-12-2008, 08:10 PM   #9
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Tankless water heater questions


Me? I have a Rinnai R74LSI

Check my blog link below for a pictorial on the install...

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