tank less water heater


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Old 09-02-10, 10:12 PM
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tank less water heater

I want to install a tank less water heater, but need some information first. I know I need a 3/4 '' gas line, and it needs it own vent. But is there a maxi on the vent pipe. I don't really want to mount it on the out side wall.
 
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Old 09-03-10, 04:11 AM
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There is not a practical limit on the exhaust (within reason), but keep in mind each 2' section of vent pipe will cost you about $65. Outside walls look very inviting considering this. One of my clients wanted to install one while I was remodeling their basement. Their present water heater was 20 feet away from the outside wall. Gas company guys explained the cost, and she quickly modified my remodel to include relocating the water heater to an outside wall. $650 was almost half the cost of the unit installation itself, and that was just in additional vent pipe!!
 
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Old 09-03-10, 07:16 AM
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Just to expand on what Chandler said the vent pipe is expensive because it has to be special high temperature not the galvanized double wall you use with a regular gas appliance.
 
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Old 09-03-10, 09:26 PM
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You may need larger than a 3/4 inch gas supply pipeline. The size of the inlet connection is not the determining factor. You need to do a calculation of the total developed length (including factors for fittings) of the piping from the meter to the water heater. Far too often, and especially with DIY installations, instantaneous (tankless) water heaters fail miserably due to undersized gas piping.
 
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Old 09-04-10, 09:12 PM
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Originally Posted by chandler
There is not a practical limit on the exhaust (within reason), but keep in mind each 2' section of vent pipe will cost you about $65. Outside walls look very inviting considering this. One of my clients wanted to install one while I was remodeling their basement. Their present water heater was 20 feet away from the outside wall. Gas company guys explained the cost, and she quickly modified my remodel to include relocating the water heater to an outside wall. $650 was almost half the cost of the unit installation itself, and that was just in additional vent pipe!!
Chandler, I though those tank less heaters use plastic pipe for the vent.
 
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Old 09-05-10, 11:20 AM
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No, unlike high efficiency gas furnaces, tankless water heaters don't use 93% of the heat they generate. It would be nice, but not practical. Therefore, they are relegated to using triple wall stainless steel exhaust piping.
 
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Old 09-05-10, 01:15 PM
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One manufacturer of tankless water heaters DOES use PVC vent piping, the condensing Navien tankless water heater.

I have no personal experience with these and when I did some research on them a year or so ago they had quite a few "bugs" that were being ironed out. Their claims are impressive and they have a premium price to match.

http://www.navienamerica.com/product/ts_heater.aspx?skin=ts_heater
 
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Old 09-05-10, 04:01 PM
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Good to know that furd. I wasn't aware of the brand. Worth checking out.
 
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Old 09-06-10, 11:12 AM
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The Navien is a high-end heater. When I checked a year or so ago the prices started around $1,700 and quickly exceeded $2,000. At those prices I don't think it would pay to purchase one for the sole reason that it uses PVC exhaust venting.
 
 

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