gas line

corzy

Hey guys, ive got a quick question for the gas fitters out there, i know im gonna get hammered for the lack of info ive got, but just do your best : )
i bought a natural gas furnace from my wifes uncle for 50 bucks, its the type of forced draft furnace that literally came out of a big fire hall he used to work at. i plan to hang it in my garage that hasn't been built yet and was just wondering how you would plumb to this? when i did my hot water heater (on demand) i just ran a 1/2" pipe (about 30') straight from my main (1" line) into the burner inlet...when i ran the pipe for my central furnace for the house i ran 1" right to it (only 8-10')
now i was told that due to long runs if you dont use big enough pipe there will be not enough volume to keep the burner going since there is so little pressure in the NG line....
i know i havent gave the BTU's or anythign of the the furnace but i dont have it yet, i just know its pretty big, about 3.5 feet high, 2 or so feet deep and wide. what would your guess as to the pipe run that i would need to get there? it would be about 30-40 feet or so...i also know that a lot of these furnaces use just a small copper tube to feed them like my small gas fire place, is that what you run up to the furnace? or just like my water heater/main furnace and need to actually run the pipe black all the way to it

thanks guys

hvac benny

Based on the info you've provided, I would call up my gas supplier and have them install an AL1000 meter (or even better, a 3M rotary), then I'd replace all my piping with 2" black iron. This would (hopefully) cover any short falls in your system.

This is a lot of work, and I'm sure you don't want to do all that, so plan B is to:

- leave all doors and windows open 24/7/365(366)

- give every one in your house carbon monoxide alarms to wear around their necks

- let your neighbours know that what they think smells like natural gas is actually aldehydes. (at this point they should probably get CO alarms as well, or keep their windows and doors closed.)

Plan B also sounds like a lot of work, and some of your family/friends/neighbours with more of a survival instinct may not let you go this route, so here's plan C:

- have your gas lines properly assessed and SIZED AS A SYSTEM (this is the proper way to do it, and there are several different factors to consider).

Just to put things in perspective, your 1/2" line to your on demand water heater is most likely undersized. This will result in it being underfired, which will reduce the life of the appliance, higher gas bills, and a production of CO (and aldehydes), which will put people's lives in danger. These comments aren't from someone who makes money off installing house gas lines and appliances. I work for a gas utility installing and maintaining utility infrastructure, but I also respond to customer gas odour and CO emergencies. If you are on my area, you are very likely to be one of my emergency calls.

gregzoll

hvac benny, they plan on using it in their garage. 2" is over kill for the unit they are getting, until they have it in hand, or can find out the actual spec's on it.

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hvac benny

Thanks Greg. If you were to keep reading past the first paragraph of my reply, and be knowledgable about gas, you'd get the gist of what I was saying. If you have any questions after reading my full reply, feel free to ask.

gregzoll

I read through the whole thing, and all you are doing is making assumptions about the other person, and the equipment they currently have installed, and the stuff they are getting.

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hvac benny

I'm making knowledgable comments based on my extensive training and experience, although some of it is admittedly sarcastic and tongue in cheek. Gas safety is how I make a living, and I'm damn good at it. When I see/hear/read someone doing something unsafe, I will point it out. Do you have any questions for me, or any advice for the OP?

gregzoll

No, you are making assumptions.

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hvac benny

Lol, thanks for your input greg. I think the pros who frequent this site would disagree, but you, of course, are entitled to your opinion.

COLDIRON

Greg I agree with you to many assumptions by benny, sounds like he's wired, need to chill and give the information without taking it personal.
The dude was only looking for info not sarcastic tongue and cheek comments from a guy who makes a living at it and is certified and is good at it.

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Jackofall1

I know this is not the question you asked, but 1/2" piping to an ondemand water heater is likely too small.

As for what you should run to a furnace for your garage based on the information you have provided it is likely to require a 3/4" feeder, run in black pipe, but this is purely a guess as you have not stated the BTU of the appliance you connecting.

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HVACTECH96

Benny,sounds like you're suggesting that instead of hacking and cobbling things togther so that it "WORKS", sometimes it better to just spend a few bucks and get a professional.I agree..