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NYC passes law requiring licensed plumbers to hookup gas appliances
- Thread starter Yikes
- Start date
steveray
SAWHORSE
I wonder if there is any real basis for the law.....But yep...More regulation = More money....
The article says an "illegal hookup" caused an explosion but not who did it and what the specific problem was...So make everyone else responsible instead of the person that caused the problem....
The article says an "illegal hookup" caused an explosion but not who did it and what the specific problem was...So make everyone else responsible instead of the person that caused the problem....
Sifu
SAWHORSE
- Joined
- Sep 3, 2011
- Messages
- 3,507
Not an explosive issue but this demonstrates concern over gas installations.
I want to add a gas line at my new (old) house. The exiting system looked under sized so I decided to check it out. First thing I needed to know was the delivery pressure being supplied by the regulator. Took two visits from the gas company to find out. So now I could figure out the allowable pressure drop. Using the longest length method and the branch length was no bueno because the tables don't provide data for a 2" pressure drop. First gas company technician said no problem, they do it all the time but had no idea what the regulator was pushing. I explained the issue but he glassed over pretty quick. Recommended I call their installation services division (they have a division that will do the install). Yesterday he came out, glanced at it and said no problem. I explained the problems with the sizing to make sure. Once he realized I wasn't the average homeowner he pulled out his book and said yep, its undersized (they use the longest length method, and only with .5" pressure drop) but they would still do it because it will still work and they do it all the time. They just know what works because they never had a problem. I said great, but I still want to run the calc with the 2" pressure drop. It took some real mental gymnastics, stretching my memory and skill of advanced math (at least advanced for me) to run the calculations from the formulas in the IFGC, but the system works (barely). I am a trust but verify kind of guy. So while I trust they know what works, I wanted to verify. The exercise bolstered my faith in the table methods for sizing as being extremely conservative, and since after a few hours of work it does meet the minimum code, I guess my faith in their approach as well. This is a situation where all appliances could be used at the same time pretty easily, so I took no comfort from the idea that would be unlikely.
The point is, in my experience few plumbers and maybe some actual gas purveyors make me feel any better about gas piping installations. Some of the better gas appliance companies have been the best at providing knowledgeable calculations. Outside of that I have found the approach most people use for gas piping pretty dubious, which is concerning.
BTW, the code commentary has a significant misprint in the formula in their simple explanation of how to calculate the data, which slowed me down until I realized it. How do commentary errors get fixed?
I want to add a gas line at my new (old) house. The exiting system looked under sized so I decided to check it out. First thing I needed to know was the delivery pressure being supplied by the regulator. Took two visits from the gas company to find out. So now I could figure out the allowable pressure drop. Using the longest length method and the branch length was no bueno because the tables don't provide data for a 2" pressure drop. First gas company technician said no problem, they do it all the time but had no idea what the regulator was pushing. I explained the issue but he glassed over pretty quick. Recommended I call their installation services division (they have a division that will do the install). Yesterday he came out, glanced at it and said no problem. I explained the problems with the sizing to make sure. Once he realized I wasn't the average homeowner he pulled out his book and said yep, its undersized (they use the longest length method, and only with .5" pressure drop) but they would still do it because it will still work and they do it all the time. They just know what works because they never had a problem. I said great, but I still want to run the calc with the 2" pressure drop. It took some real mental gymnastics, stretching my memory and skill of advanced math (at least advanced for me) to run the calculations from the formulas in the IFGC, but the system works (barely). I am a trust but verify kind of guy. So while I trust they know what works, I wanted to verify. The exercise bolstered my faith in the table methods for sizing as being extremely conservative, and since after a few hours of work it does meet the minimum code, I guess my faith in their approach as well. This is a situation where all appliances could be used at the same time pretty easily, so I took no comfort from the idea that would be unlikely.
The point is, in my experience few plumbers and maybe some actual gas purveyors make me feel any better about gas piping installations. Some of the better gas appliance companies have been the best at providing knowledgeable calculations. Outside of that I have found the approach most people use for gas piping pretty dubious, which is concerning.
BTW, the code commentary has a significant misprint in the formula in their simple explanation of how to calculate the data, which slowed me down until I realized it. How do commentary errors get fixed?
wwhitney
REGISTERED
For a given flow rate through a given type and size of pipe, the pressure drop is linear in the length. So if you have a table for allowable lengths for say a 1/2" pressure drop and a given flow rate, you can just quadruple the lengths for 2" pressure drop. Or if you have a table for allowable flow rates for 1/2" pressure drop and a given length (the way the IFGC makes the tables), you can just use 1/4 your actual length.
This is mostly an effect of discrete pipe sizes, and that the branch length method doesn't provide any allowance for a larger than proportional pressure drop on a given length of pipe when the upstream portion has been sized to provide less than proportional pressure drop due to the discreteness of pipe sizes.
For example, if you need 100 CFH on a given segment, and based on total length from the supply to the farthest outlet supplied by the given segment, you find that 3/4" will allow 83 CFH, 1" will allow 157 CFH, you pick 1". But looking at the table, you see that 1" would actually work for twice the applicable length at 108 CFH. That means your 1" segment will be dropping less than 1/2 its "budget" of your overall pressure drop. There's no prescribed methodology for reassigning the unused budget on that pipe segment to elsewhere in the piping system.
Cheers, Wayne
steveray
SAWHORSE
Online commentary or printed or both?
