sizing gas lines


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Old 05-01-18, 07:11 PM
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sizing gas lines

I have 4 double stack dryers, 199,000 btu a piece so x 4... then 38,000 water heater, then also a tankless water heater that is 190,000 btu... it come in a ft goes up 6ft goes north 2ft tees to east feeding all the dryers continues north 15ft feeds tank waterheater and 2 more ft feeds the tankless (199kbtu) can you please help me... one thing showed using a loop on the dryers so it feeds both ends.??
 
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Old 05-02-18, 04:47 AM
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First you have to know if you are using natural gas or propane. Then an internet search will turn up many charts to size the piping based on the BTU you need to provide.

LMGTFY
 
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Old 05-02-18, 05:03 AM
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It is natural gas. Ive looked through the charts and seen where people had to know the length then the pipe gets smaller as it goes. Which i understand but the gas company is asking what pressure I need so i gave them the above information on the work order and they said ok what one do you need. I just want to makes sure it is going to be enough supply for the units. so i can use as much help as i can get. I can even draw out what I have if that helps thanks so much
 
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Old 05-02-18, 07:21 AM
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You do need to specify the pressure. The information you provided in your post does not contain any pressure data.

For example at my house I have one high usage appliance that needs a 2 psi supply while everything else uses a more common 10 in pressure. So, it is possible that your devices will need different pressures. You need to look at the specs or data plate for each of your devices and see what pressure it needs.
 
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Old 05-02-18, 05:09 PM
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Old 05-02-18, 05:12 PM
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Im going to look for pressure on the items. thanks but there is a picture of what I have if we can get line sizes from that..
 
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Old 05-02-18, 06:37 PM
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they were talking about 6.5 wc or 2psi is that what you need to know? i can get either one supplied.
sorry i dont know more about this or what you need..
 
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Old 05-03-18, 01:00 AM
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If you have 2lbs NG available you'll be able to run smaller pipe. The appliances will come with a gas regulator, but may not be able to handle the 2 lbs, so you may need to add/replace the regulators. Still, it's probably worth the bother to run smaller gas pipe. For example, that load over 50' (@1050 BTU/cu ft) with low-pressure gas would require a 4" main. At 2 lbs it would work with 2".

Gas pipe is sized by BTUs/cubic foot/hour and length of the run. You'll need to know how many BTUs/cu ft the supplied NG is (probably around 1050).

IOWs, go with 2 lbs for that over-a-million BTU load.
 
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Old 05-05-18, 07:22 AM
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im around 30 ft to the furthest appliance. would it still be a 2 in? then would at the first tee (picture above of what I hhave) could i reduce down at the tee? there is only 2 things after tee one 38k btu and 199k btu. the biggest part of the load is with in 15 ft 190k x 4 thanks so much
 
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Old 05-06-18, 12:01 PM
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The gas piping has to be sized as a system. Draw a little map with distances and loads, then you can calculate the size of each run. There are calculators on youtube:

https://www.youtube.com/results?sear...or+natural+gas

If you've never done it, running hard gas pipe is not all that easy, and the equipment is expensive. Done incorrectly it can be dangerous.
 
 

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