Makemenuconfig
Member
Hi,
I am close to installing a tankless water heater in my house; I'm planning to install the unit myself and hire out the gas fitting. I am not a plumber, but have done quite a bit of research and reading on this. I am sitting here looking at the international fuel gas code on sizing gas piping trying to determine if my house is going to support the demand as is, or if it is going to need a larger main trunk. I've got a few bids from local plumbers; none of them seem concerned about the size of my gas line; other than switching the existing tank heater outlet from 1/2 to 3/4. However none of the contractors have really done the math here, just have said "yeah, we can do that". If I'm understanding correctly, I think I just barely fall within the acceptable range on the chart in the code but wanted a third pair of eyes before hiring someone and finding out the appliances don't work well.
Attaching a diagram. Gas comes in on a 20' 3/4" line with one elbow and a tee at the end, where an 8' 1/2" line runs to a furnace, and a 7' 3/4" line will run to the tankless location (upgraded from 1/2").
As far as the code goes, the max length is 28' (rounds to 30). When I look at the table, I see that:
30' at 1/2" supports the furnace
30' at 3/4" supports the water heater
20' (segment A) at 3/4" supports both the tankless and the water heater.
Question:
Am I understanding this correctly? When I see people use the longest length approach, it seems segment A would be judged by the 30' row. Why is this? It would seem that segment A only runs 20' and only has to deliver 240 ccf to the tee; so why judge it by the 30' row?
Thanks for the input!
I am close to installing a tankless water heater in my house; I'm planning to install the unit myself and hire out the gas fitting. I am not a plumber, but have done quite a bit of research and reading on this. I am sitting here looking at the international fuel gas code on sizing gas piping trying to determine if my house is going to support the demand as is, or if it is going to need a larger main trunk. I've got a few bids from local plumbers; none of them seem concerned about the size of my gas line; other than switching the existing tank heater outlet from 1/2 to 3/4. However none of the contractors have really done the math here, just have said "yeah, we can do that". If I'm understanding correctly, I think I just barely fall within the acceptable range on the chart in the code but wanted a third pair of eyes before hiring someone and finding out the appliances don't work well.
Attaching a diagram. Gas comes in on a 20' 3/4" line with one elbow and a tee at the end, where an 8' 1/2" line runs to a furnace, and a 7' 3/4" line will run to the tankless location (upgraded from 1/2").
As far as the code goes, the max length is 28' (rounds to 30). When I look at the table, I see that:
30' at 1/2" supports the furnace
30' at 3/4" supports the water heater
20' (segment A) at 3/4" supports both the tankless and the water heater.
Question:
Am I understanding this correctly? When I see people use the longest length approach, it seems segment A would be judged by the 30' row. Why is this? It would seem that segment A only runs 20' and only has to deliver 240 ccf to the tee; so why judge it by the 30' row?
Thanks for the input!