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Old 01-21-2011, 03:04 AM   #16
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Flexible gas line for shop heater


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Wow! I have so many comments on this thread I hardly know where to begin!

To properly size your gas line, you must start at the system reg, NOT where it tees near the furnace. I'll assume that it's an inches set: measure the gas line from the meter to where the farthest appliance is, or will be. This is what will determine the size of your gas piping. Also, you will need to know what size the pipe you are teeing off of is, the max. btuh that each appliance connected to it can consume, and the size of each existing appliance's pipe. All of this info will allow you to properly size your new gas line and ensure that the existing system is large enough for the demand.

PG&E says to call them for relights if you shut-off your meter because they, and most other gas utilities, want to inspect your gas lines because some homeowners think that it's ok to just tap into a gas line and that their will be no problems (imagine that, eh?). The problem with this, aside from poor connections and materials, is that the lines and/or system will be undersized and the connected appliances could be under fired. Under fired=bad! The entire system must be able to sustain all appliances firing at max. rate at once, and all appliances must be commissioned to fire properly by a qualified gas fitter. All of this work should be inspected by a qualified gas fitter, as even a knowledgable homeowner wouldn't have a clue what to look at (or even an old or seasoned tradesman).

If your piping is too small, you will get PRESSURE DROP, and therefore a drop in "the flow rate, or volume as in Cubic Feet Per Minute (CFPM) with a gas." Too large of a pipe will not result in a over pressurization problem, just a larger install bill.

Your right about the correct way to size a gas line. But since this is a new house. And the gas line is already ran to the point of being in the garage. I doubt he is going to run a new line from his meter out.

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Old 01-21-2011, 03:40 AM   #17
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Flexible gas line for shop heater


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Your right about the correct way to size a gas line. But since this is a new house. And the gas line is already ran to the point of being in the garage. I doubt he is going to run a new line from his meter out.
New house, old house, either way the gas line should be installed correctly. The line doesn't necessarily need to be run from the meter, just as long as everything is sized properly, and that means evaluating the gas SYSTEM, not just hacking in a few lines here and there.
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Old 01-21-2011, 03:53 AM   #18
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Flexible gas line for shop heater


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New house, old house, either way the gas line should be installed correctly. The line doesn't necessarily need to be run from the meter, just as long as everything is sized properly, and that means evaluating the gas SYSTEM, not just hacking in a few lines here and there.
True.

And most likely his installing company already sized the line since they were installing it new.

Unless he asked after they had already ran the line from the meter, in which case he would have been responsible to pay for an entire new line. Or a new line from the meter to the garage. And if he didn't pay for it then. He isn't going to redo it now.
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Old 01-21-2011, 09:24 AM   #19
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Flexible gas line for shop heater


I guess there is a lot involved in this.

Well, from the meter to the "T" is 26' of 1" pipe. From there is will take a pipe run of 43' to get to where the flex pipe starts. The flex pipe is 50' and comes out right where the heater will be. The only pipe I need to install is the 43' run from the "T" to the flex pipe and then connect the other end to the heater.

Since everything was installed by the HVAC contractor during the rough in, one would have to believe that the 3/4" flexible line they ran is going to allow for the proper flow rate over that distance.
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Old 01-21-2011, 04:22 PM   #20
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Flexible gas line for shop heater


Benny,
Good answer and nice explanation. I knew if we hung around a bit an hvac guy would jump in. Moral of the story, make sure somebody is onsite that knows what's going on when messing with gas.
Mike Hawkins
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Old 01-21-2011, 04:28 PM   #21
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Flexible gas line for shop heater


Your 1" pipe is good for roughly 273,000 BTUs, if the 43 foot pipe is 3/4" then its good for roughly 136,000 BTUs, and if the flex is 3/4" gastite, its good for roughly 75,000 BTUs.

You also need to know what your total appliance BTU is.
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Old 01-21-2011, 04:45 PM   #22
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Flexible gas line for shop heater


The main furnace is 80000 BTU and the water heater is 40000 BTU. With the shop heater at 45000 BTU we're at 165000 total which the 1" pipe is easily good for then.

Very helpful....thanks
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Old 01-21-2011, 05:09 PM   #23
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Flexible gas line for shop heater


when you say flex pipe .Are you talking about trac pipe or n appliance connector ? If it's an appliance connector. Per IFGC. The connector can only be 3' in length & in the same roon as the appliance. 3/4 pipe comming off 1'' pipe is plenty of gas for your heater
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Old 01-21-2011, 05:18 PM   #24
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Flexible gas line for shop heater


It's the stainless steel corrugated pipe with a yellow jacket, installed by the HVAC contractors just for this application.

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