# Flexible gas line for shop heater



## firehawkmph (Dec 12, 2009)

Richo,
What kind of flexible line did you have installed? Is it the corragated stainless steel with the yellow jacket? If so, that's ok. I would take a look at the specs for your heater. They usually have a page on gas requirements that will tell you what size pipe to use based on how far you are going. I wouldn't rely on the person at the home center. Not sure on your venting question, haven't seen an exhaust that small. If you have a hvac suppier in the area that sells to the trades, they should be able to fix you up with what you need.
Mike Hawkins


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## Richo (Dec 6, 2007)

Yes, it is the corrugated pipe with the yellow jacket.

The gas inlet on the heater is for 1/2" pipe. I will check the manual for the heater to see what it says about long runs.

I think what the guy at the home center was referring to had to do with changes in pressure going from 1/2" to 3/4" then back to 1/2" at the heater.

There are HVAC suppliers that I can check with on the venting. I kind of figured it wasn't going to be a common part.

Thanks for your reply.


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## beenthere (Oct 11, 2008)

Is this furnace an 80 or 90% efficient furnace?


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## Thurman (Feb 9, 2009)

"I think what the guy at the home center was referring to had to do with changes in pressure going from 1/2" to 3/4" then back to 1/2" at the heater."
You WILL NOT, under any circumstances get any increase or loss of _pressure_ due to in increase or decrease in piping sizing. You will only change the flow rate, or volume as in Cubic Feet Per Minute (CFPM) with a gas. Pressure will equalize within any differential of piping size as the gas is fed into the pipe or used from the pipe. That's why I do not like the recommendations of employees at the apron stores. Not that I don't like them personally-they are employees and only employees. Yes, you do find the rare one who used to work in the trades and does know one or more particular areas, but seldom.


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## Richo (Dec 6, 2007)

beenthere said:


> Is this furnace an 80 or 90% efficient furnace?


That I'm not sure about. Is the owner's manual going to say something about that? It's a 10 year old garage heater that hangs from the ceiling.


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## beenthere (Oct 11, 2008)

The owners manual might, the install manual will tell you the vent requirements it has.

Depending on the unit. It may need to vent through SS, not B vent like you have. Some unit heaters that need to be vented through SS, will rot out your B vent if you vent them through it.


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## Richo (Dec 6, 2007)

I had this heater installed in my shop at my previous home for 10 years and I used dual wall sheet metal piping for the vent, never had a problem with that.

I will have to go back to the same place that I got the venting from back then.


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## beenthere (Oct 11, 2008)

Richo said:


> I had this heater installed in my shop at my previous home for 10 years and I used dual wall sheet metal piping for the vent, never had a problem with that.
> 
> I will have to go back to the same place that I got the venting from back then.


Remember. We only have the limited info you post, to give our answers.

The more info you give at one time. The better chance of getting accurate answers.


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## Richo (Dec 6, 2007)

Well the info I'm posting is all of the info I have.

I did grab the installation manual and all it says about gas pipe diameter is that it needs to maintain a line pressure of 7" w.c. and to consult the utility having jurisdiction.

For venting, it is approved for type B-1 double wall vent pipe, which is what I used in the first installation.


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## beenthere (Oct 11, 2008)

Richo said:


> Well the info I'm posting is all of the info I have.
> 
> I meant the part that you had it installed in B vent at your other house.
> 
> ...


How long is the total run from where the flex taps into the gas line to your furnace. 

Better to have a larger then you need gas line, then a slightly small one.


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## Richo (Dec 6, 2007)

There is about 20, maybe 25 feet between the furnace and where the flex line starts. 3/4" makes the most sense I guess since the flex is 3/4" too so I'll plan on going with that.


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## Richo (Dec 6, 2007)

One quick follow up question: I was reading some info online about gas connections and I came across this on the PG&E website.


> If you shut off the gas, there may be a considerable delay before PG&E can turn your service on. Once the gas is shut off at the meter, do not try to turn it back on yourself. If the gas service shutoff valve is closed, PG&E or another qualified professional should perform a safety inspection before the gas service is restored and the appliance pilots are lit.


Now I don't have my service through PG&E but how could turning the gas off at the meter prevent you from being able to turn it back on? 

When I installed this heater at my previous house 10 years ago I ran all of the gas piping from the basement, through the garage and into the shop. I turned the gas off at the meter to be able to tap into the existing pipe and had no issues getting it back on.

I've never heard of not being able to turn it back on yourself. Is PG&E just wording it that way to discourage someone from turning off the gas except in emergency?


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## oh'mike (Sep 18, 2009)

I am sure the gas company is covering its ___.

I am sure that warning is aimed at folks that might not remember to relight pilot lights and check the new work properly.


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## hvac benny (Dec 29, 2009)

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.


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## beenthere (Oct 11, 2008)

hvac benny said:


> 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.
> 
> ...



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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## hvac benny (Dec 29, 2009)

beenthere said:


> 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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## beenthere (Oct 11, 2008)

hvac benny said:


> 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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## Richo (Dec 6, 2007)

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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## firehawkmph (Dec 12, 2009)

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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## beenthere (Oct 11, 2008)

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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## Richo (Dec 6, 2007)

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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## kenmac (Feb 26, 2009)

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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## Richo (Dec 6, 2007)

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


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