asb313
New Member
Trying to figure out if an existing NG 1/2" drop is sufficient to run GX390 Honda 7k watt portable gen. It's about 11 HP. Total BTUs for all appliances is about 220k BTUs and that is full load for all appliances. The meter is sized for 256k BTUs. The gen would run during a power outage only so some of the gas appliances would not be used. Water heater (36k BTU) would run and during winter the Boiler (125k BTU).
The pipe layout is as follows (total run about 54 feet of schedule 40 black pipe):
19 feet of 1" pipe from the meter (includes 1 90 degree elbow)
reduces to 3/4" with a total run about 25 feet (include 2 90 degree elbows)
along the first 10 feet of the 3/4" run there are three 1/2" drops for the boiler, hw heater and dryer. All within about 6' of each other. Then the 3/4" continues to the end for about another 15 feet.
At the end of the 25 foot 3/4" run there is a 10 foot 1/2" drop used for a grill. This is the connection I plan for the generator.
According to the charts using the longest method for sizing, the 1/2" drop for the grill will deliver about 42k BTUs. I don't think that is enough to power the generator with 50% load. Question is do these charts ignore the larger pipes up to the reduction of 1/2". In my set up, there is 19 feet of 1" and 25 feet of 3/4" until it reduces to 1/2".
Note: changing this 10' 1/2" pipe to 3/4" would only require replacing the 3/4 to 1/2 reducing elbow with 3/4 to 3/4 elbow and run a new 3/4" 10 foot pipe. This should deliver about 90 BTUs.
Thanks
asb313
The pipe layout is as follows (total run about 54 feet of schedule 40 black pipe):
19 feet of 1" pipe from the meter (includes 1 90 degree elbow)
reduces to 3/4" with a total run about 25 feet (include 2 90 degree elbows)
along the first 10 feet of the 3/4" run there are three 1/2" drops for the boiler, hw heater and dryer. All within about 6' of each other. Then the 3/4" continues to the end for about another 15 feet.
At the end of the 25 foot 3/4" run there is a 10 foot 1/2" drop used for a grill. This is the connection I plan for the generator.
According to the charts using the longest method for sizing, the 1/2" drop for the grill will deliver about 42k BTUs. I don't think that is enough to power the generator with 50% load. Question is do these charts ignore the larger pipes up to the reduction of 1/2". In my set up, there is 19 feet of 1" and 25 feet of 3/4" until it reduces to 1/2".
Note: changing this 10' 1/2" pipe to 3/4" would only require replacing the 3/4 to 1/2 reducing elbow with 3/4 to 3/4 elbow and run a new 3/4" 10 foot pipe. This should deliver about 90 BTUs.
Thanks
asb313
Last edited:
