bbboomer
Just received my new 22KW Generac, I have a couple questions.
I am running 3/4 PE underground from tank to generator, about 30 feet.
I can locate the low pressure reg either near the propane tank or about 2 feet from the generator.
I have read there may be a benefit to having the length of 3/4 as a reservoir for starting. Is this a good plan and will there be any issue with supply running the whole length at low pressure?
Also I need to run about 80 feet of wire from generator to transfer switch. I plan on using 2/0 for the high voltage and ground, do I need to go  bigger for the control wiring?
Darrell
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Geoff Z
If you have already run 3/4 you may want to stay high pressure. There are guidelines in the installation manual. Don’t have one in front of me but I think you would need 1” at 30’. It is always a good idea to have as much pipe between the step down regulator and the generator. That will help avoid hunting or surging issues. You don’t need 2/0. Generac Wire has #3 current carrying conductors and the #18awg control conductors are good up to 115’

https://www.zillerelectric.com/collections/generator-wire/products/17-22-kw-generac-generator-wire
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bbboomer
Geoff Z,
Thank you for your reply.3/4 should be good for 40' for LP Vapor according to the install manual. Can I just go direct to the generator with a 3/4" flex connector from the meter riser for the PE underground?
I planned on creating a clean out stub at the riser and go direct to the generator from that. The low pressure reg would be at the tank.
I looked at wire sizing charts for amps x distance to decide on 2/0. I had not seen this site until the gen was already ordered or I would have ordered here. I did look at the wire  and noticed the size difference. Can I order that wire without buying the generator here?
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Geoff Z
If that pipe will deliver 3.9gal/hour at 10-12” WC then you are good to go. The generator comes with a built in sediment trap. If that is what you are referring to when you say clean out stub then you don’t need it. You can pipe directly from the gas metal riser into the generator using the supplied flex hose. You certainly can order the wire sold separately. 
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bbboomer
GeoffZ,
Thank you again for your help.
Darrell
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bbboomer
Well I thought I had this figured out but I think I need to make a change.
I will run 3/4 PE underground from tank to riser at generator at standard tank regulator pressure.
Low pressure regulator (11" WC) at riser.  
6 foot 1" flex from regulator to generator.
Will that be enough to avoid starting/surge problems?
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Geoff Z
I would feel good about that. Just do your best to arrange it with as few bends as possible. If you must make a bend make it a sweep not a tight 90.
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78buckshot
I agree with Geoff, you should be ok with primary regulated pressure at 8 - 10psi for the underground and 12" - 13" secondary pressure for the 1in. above grade.
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bbboomer
Thank you Geoff Z and 78buckshot!
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exrace
A friend of mine who runs on LP ran the HP to a regulator that was mounted very close to the 16k genset.
Ran a short input pipe the same size pipe as the rubber supplied line internal diameter, finished with the supplied rubber line for vibration concerns and has no issues with surging.
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78buckshot
Most will run ok with that set-up, it's the occasional one that needs the extra buffer volume.
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Geoff Z
The take away is if the orientation is such to allow it, a reservoir is always a good idea. If your application doesn’t you may never have a problem. 
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Brian Baughman
The installation manual LP pipe sizing chart only covers Sch. 40 black pipe, and only covers low pressure LP from the outlet of the secondary regulator to the generator fuel inlet.  The bigger issue on LP is what type of regulator is being installed, as many appliance regulators are not designed for use on an engine.  The fuel pipe run in this thread is sufficient for the generator.
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