Any plumbers with nat. gas regulator sizing experience on board?
 

Installing a standby gen, and am working on the gas line.

Known variables:
1) gas line will be a length of approx, 15 ft, tee'd right at the meter. Not tapped into existing lines.
2) 1/2" NPT line, with 3-4) 90's
3) 2 PSI system. But I think that since it's a dedicated line, and short one at that, pressure drop in line isn't really an issue??? Just using the normal spec of 1 psi press drop for calculations, thought it doesn't seem to effect the results.
4) Gen requires 5-7" pressure NG. at gen regulator inlet.
(min 4")
5) gas draw is 140 cfh at full load, 77 cfh. at 1/2 load

I've researched the regulators by Maxitrol and think this is the one I need:

325-3L
It meets the requirements as I understand them
http://www.maxitrol.com/PDFs/LPR_MS_EN_09.2011.pdf

using this chart and using 1/2" pipe, 2psi max inlet, 1 psi normal inlet press, 7" outlet press, max 140 cfh, min 77 cfh use:

http://www.2psi.com/regsizprog.htm

The 2 issues I'm unclear about is

1) the press drop. I "think" with the numbers I input, it should have an output press of 6.48"
Is that what is shown?

2) And the gen specs 140cu ft at max draw. Just meets the reg individual load, but under the total load of 250 cu . in.

BTW, I ordered this last nite, just looking for some reassurance that this one will work just fine.
Maxitrol won't give tech help to gen public.
Thanks

The generator does not already have a pressure regulator come with it? In my past experience with them they do.

Yes it does, but isn't 2 psi too much for it? It is a dual regulator, meaning NG and LP uses.
LP is rated at 14". But 14" is 1/2 psi. Wouldn't be a problem if I didn't have the 2psi system, but then I'd have 3" pipe going thru the house. :)

The manual just specs out 5-7" for NG.

Guess I'll call Generac tomorrow and hope they will tell me what I need, and not say gotta have a plumber come out.

That is your best bet, I'll assume the one with it will be sufficient.

Just looked. Sticker on unit at inlet port: "N.G. inlet pressure ...5-7".

Still looking for confirmation on the 325-3L regulator.

Thanks

dont use a maxitrol outside... use an american meter company house regulator approx 30 bucks. you prob have to use a 3/4 to 1/2 bell reducer, do not use bushing style reducers on gas lines!!! Maxi's make great regs non vented type for indoors but some how all the maxis I have used outdoor get water in the vent and freeze up and once frozen dont allow gas to flow. It would suck butt to be in an ice storm with that nice new gen and not be able to use it. American meter company regs are typically what the local utilies use. some authorities will sell them to customer, some wont. just tell them btu in on the gen and 2" to ounces or what w.c.'s and they can set it up.

LC

let me know if u need one......

maybe things are diffrent where you live,but 2psi on natural gas?around here we only see that pressure in com/industral jobs.houses are 2psi @the line side,but reduced to 4-6wc.most of the gen sets i have piped were in the area of 10-25kw.a 15kw gen set burning natural @4-6wc is going to use a 1" blk iron pipe to the gen set,and then reduced to 3/4 or 1/2".i dont have my chart in frount of me but i think 1" will carry around 275k @15ft.hope this helps.

Make sure u use the flex connector included with the gen set. Do not hard tie in.

2 psi is very common in my area residential. Takes a big pipe to flow a whole house on inches.

Maxitrol has a vent protector cap that replaces the vent limiter for outside use. Yes, using the 12" included flex line.

Thanks

Is the flex connector to counteract vibration to the regulator? On generac models the internal regulator is plumbed with flex hose so it wouldnt vibrate very much anyway.