High BTU's for tankless heaters


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Old 08-22-16, 06:32 PM
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High BTU's for tankless heaters

I am looking at an 8.4 gpm tankless that is 180,000 btu's. I have 1 inch black pipe from the meter but the btu/pipe diameter chart says 1 inch of 50 feet only supplies 177,000 btu's. I also have a gas dryer and furnace. Do I really need bigger than 1 inch pipe? I see these installed on the job all the time with 1 inch pipe reduced to 3/4 inch for the tankless stub out.
 
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Old 08-22-16, 06:49 PM
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You need a dedicated line from the meter..

You most likely cant tap off your gas line anywhere.

1" supports 285 k btu. That btu is sized for all your other appliances in the home.. If you add the heater anywhere to that line most likely you'll starve other appliances of gas.. You'll have sooting issues and draft issues.. This may cause CO emissions in the home and you and everyone in the home can die...


I see these installed on the job all the time with 1 inch pipe reduced to 3/4 inch for the tankless stub out.
Yes from the meter I am sure...

The only tankless I would consider is a 199k btu Noritz.. ( But I myself would never waste a dime on tank-less technology..) You save nothing IMO..
 
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Old 08-22-16, 07:03 PM
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Strange. I am working in a development of 67 new homes as a carpenter. Each has 1" from the meter for about 35 feet which then tees 1 x 3/4 x 3/4. 3/4 to the tankless, and 3/4 to the rest of the house for a dryer and range. The houses have passed plumbing inspections (IBC/IRC). The only reason I am considering it for my house is because I have no garage so the tank is in a small laundry room and I'd like to save some space, but not if it will require bigger gas lines, as I just repiped mine with 1".
 
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Old 08-22-16, 07:10 PM
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I am working in a development of 67 new homes as a carpenter. Each has 1" from the meter for about 35 feet which then tees 1 x 3/4 x 3/4. 3/4 to the tank-less, and 3/4 to the rest of the house for a dryer and range.
Its a gas calculation.. Yes that tank-less may work in the situation you state above... It may be a lower BTU too..

It all matters what the farthest appliance is from the meter.. And all btu items in the home.. Then we can test your theory above...

This is based on normal psi meters... Of course there are 2 psi meters out there and this changes all that ...
 
 

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