Need natural gas line info.......

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Old 03-29-11, 08:53 AM
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Need natural gas line info.......

Want to change out a standard tank water heater for a Noritz tankless NR83 with minimum 18,000 btu and max 180,00 btu rating. I know that the gas line will have to be 3/4 instead of 1/2. The Noritz unit will be just on the other side of the concrete foundation wall from the meter...about a 4 foot run max. Can a "T" just be added after the meter and before it goes to the main line into the house? Should I assume that the natural gas supply coming straight from the meter will be a pressure suitable for the Noritz? Why does the pipe coming out of the meter start with 1 inch, then reduce down to 3/4 inch, THEN go UP to a 1 1/2 inch main supply pipe for the house? The plan is to add the T at the 1 inch pipe before it reduces to the 3/4. I keep hearing that the MAIN problem everyone has with tankless is incorrect gas pipe/pressure issues. THANKS!
 
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Old 03-29-11, 10:01 AM
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I know that the gas line will have to be 3/4 instead of 1/2.
The Noritz has a 3/4 inlet. You cant have any pipe smaller than 3/4 as long as you get the btu x distance.

Can a "T" just be added after the meter and before it goes to the main line into the house?
Yes it can. Add a shut off there also.


Should I assume that the natural gas supply coming straight from the meter will be a pressure suitable for the Noritz?
Yes.

Why does the pipe coming out of the meter start with 1 inch, then reduce down to 3/4 inch, THEN go UP to a 1 1/2 inch main supply pipe for the house?
Gas is based on volume and the larger pipe gets you the volume and btu's required. I would change that small section of 3/4 to 1". It may have been 3/4 but the meter is 1" most likely. The installer was probably too lazy or did not have the correct fittings on the truck.

You can add a 1x1x3/4 tee at the meter outlet and run 3/4 to the Noritz. That will give you 360,000 btu at up to 10 ft. You cant go smaller because the Noritz inlet is 3/4. Change that small section of 3/4 to 1". You will need to break down from the meter to the 1 1/2 then work back to the meter accordingly.

Mike NJ
 
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