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Posted By: watersparkfalls generators - 01/21/07 05:06 PM
howdy folks have questions about generators I hope you can help with.
with the recent storms we've had out here in the pacific northwest and extend outages everbody wants an auto generator now.
home depot sells a variety from 7kw up propane or natural gas fed.
the 7kw to 16kw come with factory assembled load center and auto transfer switch which
seem pretty straight forward to install.
art 445 seems to be somewhat light though in its chapter, as far as the do's and don'ts. is this a world of electrical which is best left alone (mean learning curve) kinda like factory assembled structure remodels?
some questions that i specifically have are
1. can one put a generator under a two story deck?
2. working clearences the same as panelboards
3. how close to a house may one set gen
4.how close to main service(meter)
5. how close to gas meter(3' typical seperation)
I am sure there are lots I am missisng to ask so if all of your years of wisdom you can think of things that can save the learning curve and insure better installation I would GREATLY appreciate.

thanks,
h20
Posted By: JohnJ0906 Re: generators - 01/21/07 05:46 PM
you should be able to find the answers 3 places- Manufacters instructions, AHJ, and POCO and gas supplier. Between the 3, you should find out what you need. Some requirements will change on your locality.
Posted By: JJM Re: generators - 01/21/07 06:50 PM
I'm going to offer some general answers, but keep in mind local codes and your AHJ will be the final governing authority.

You can install a genset under deck. But keep in mind general clearances, 3 feet all around for servicing and access, and the exhuast 5 feet away from any building openings, such as doors, windows, dryer vents, makeup air for HVAC, etc. CO poisioning is a real issue, so keep that in mind.

I've seen plenty of installs that violate these clearance rules though... not saying it's right though.

It's advisable to keep the genset within a reasonable proximity to services (minimum 3 feet) but the genset can be installed as far away as you want too. Just keep in mind the further away you install the genset, the greater the material costs will be, not just length-wise, but size-wise as well.

You'll need to run much larger wires, which means larger conduit, and you'll need much larger gas lines. For example, you could run a typical 16KW genset with 20 feet of 3/4" pipe. Move the genset 150 feet away, and now you need 1 1/4" piping. Ditto for the cabling. Then these items need to be reduced back to the sizes the genset allows.

The biggest question is whether you'll be using NG, or LP liquid or gas. You may run into issues with NG if the meter doesn't deliver the required volume for the genset and other gas appliances, as well as the regulated pressure, as many gensets require elevated gas pressure, though newer ones are more forgiving. Volume is still an issue though.

Joe
Posted By: Rich Thomas Re: generators - 01/22/07 05:13 AM
What part of the Pacific NW? I'm in Bothell, WA.

Your questions are insightfull. I'll have to be thinking about these issues myself.

One thing different from your questions you might consider is the choice of fuel. You mentioned NG or propane. In addition to NG uncertain capacity and pressure as mentioned, I've been told NG tends to not have consistent BTU content. This seems to be quite variable, regardless of what the gas company says.

Also, King County for example will not use NG for a couple of reasons. One being the BTU content, but another is its availability following an earthquake. The NG supply or service line could be broken during an earthquake leaving a generator fueless, right when it's needed. King County uses diesel.
Posted By: SteveFehr Re: generators - 01/22/07 05:10 PM
I wouldn't say generators are any worse than any other eletrical installation. You just have to be careful with the neutral now that you have two separately derived sources.

The smallest generators I've work with are 200kW, so I can't offer much practical advice about residential installation. We use diesel pretty much exclusively, but it's more for damage control and ease-of-support reasons. Above all, I'd say let common sense prevail! Coordinate with your mechanical subcontractor to make sure your conduit and his/her gas lines aren't interfering. As well as the exhaust, you'll also have to be careful about fuel tank vents- they need to be vented 12' above grade and 5' from any openings.

UFC/NFPA1 offers some more codes that NEC is silent on: http://www.nfpa.org/aboutthecodes/list_of_codes_and_standards.asp

[This message has been edited by SteveFehr (edited 01-22-2007).]
Posted By: watersparkfalls Re: generators - 01/23/07 12:40 AM
thanks guys for the help.
rich I am in olympia didnt see anything in the WAC even covering art 445.
one more question on the 5 foot rule, what if on first loor(grade elevation) ther are no windows but on second floor there is one.
other then the fact its probably not a good idea to put it here can one do it and suffice code?
this paticular house is on a hill and there is only one practical spot.
thanks,
h20
Posted By: trekkie76 Re: generators - 01/24/07 02:53 PM
I would add that at least on particular brand sold at the Home Depot, doesnt want the genset placed under a deck. This brand comes with a 25' whip from the transfer switch, which is then mated to the liquidtight whip from the genset. I try to place it within that 25' radius, because adding to the whip alters the system, and invalidates the warranty.
I don't have NG here, so we run all the gas gensets on LPG. The gas company requires a min. distance of 10' from the tank, not sure about NG though.
The static pressure required for the newer generation is 10"-12" of water column pressure. The older ones run on 11"-14"W.C. As mentioned earlier, volume is a huge deal, as gas companies seen to unersize the pipe even with the manufacturs instructions right in there face. Min. size is 3/4" pipe up to about 15', depending on 90's which add 2.5' to the length of the run. Also temperature affects the volume tremendously, at least on the LP side. These generators are tested at the factory on NG.
If you dont have the manual, go to www.guardiangenerators.com and you will find all the answers to installation.
Posted By: gfretwell Re: generators - 01/25/07 02:58 AM
I just went through this with my LPG company with a gas pool heater (and a rough in for a genset).
I heard the same setback as Trekkie. 10' from everything on the tank (property line, electrical equipment, structures etc). The regulator and gas lines can pretty much be anywhere.
One thing that might be important to know is a LPG system around here is "high pressure" (around 10 PSI) up to the final regulator where it gets dropped to 10 inches of water (WC). That is in the side of my pool heater and not installed yet on the genny rough. That means you can use a smaller line than the "10 WC" designated size. With Natural Gas you still measure to the final regulator but as I remember this is the one where the meter is.
I discussed this with the gas inspector, "book" (what we call 110.3(B)) in hand. He explained the high pressure thing.
Posted By: Reel-Break Re: generators - 02/13/07 03:21 PM
What are the concerning issues with the neutrals Steve?You bond the neutrals together at the service panel correct? The xfer switch switches only the L1 and L2? I`m asking for some insight for future reference.
Posted By: SteveFehr Re: generators - 02/13/07 04:54 PM
Reel-Break: the key is that you must never have a situation where the neutral is derived to ground at multiple points, as this would allow current to travel through the ground wire. There are two ways to do this:

1) ground the service and the generator neutral one one point (usually the service entrance or the transfer switch)

2) Switch the neutral at the transfer switch

There's some very good information in this thread: https://www.electrical-contractor.net/ubb/Forum1/HTML/007992.html

Edit: you need to check the internal wiring of the generator, too, to make sure the neutral isn't grounded inside the chassis.

[This message has been edited by SteveFehr (edited 02-13-2007).]
Posted By: trekkie76 Re: generators - 02/13/07 09:19 PM
most of the Home Standby generators dont have a switched neutral. So, without the neutral switching, the genset isnt considered a SDS in the NEC sense. The generac line comes with a floating neutral for this reason.
Posted By: George Little Re: generators - 02/14/07 01:41 AM
Trekkie- Did you mean to say that the units with the neutral bonded to the frame are SDS? I hope so. That's the issue here, if the neutral is bonded o the frame at the generator and the utility neutral is bonded at another location, then one would have to switch the neutral and hots at the transfer switch. The trick is to make sure the neutral is lifted from the frame of the generator if the service is bonded (as it would be) so you don't have to switch the neutral.
Generac and Onan do a good job of handling the neutral for this type of installation. Kohler on the other hand does nothing for their customers in the way of assisting them with this issue.
Posted By: markp Re: generators - 02/15/07 03:35 AM
Generac does not bond their generators, but their documentation mentions absolutely nothing about bonding. I had to buy one and hope it was not bonded, or that the bonding could be broken since my transfer switch doens't switch the neutral.

It seems that many residential generators come unbonded, which is my preference.
Posted By: Ron Re: generators - 02/19/07 02:11 AM
Interesting.
The last time I looked at the wiring diagram of one of the Home Depot small generators (5.5kW), the neutral was bonded to the ground at the output (receptacle). That was about 1-1/2 years ago. Mayybe it has changed?
Posted By: iwire Re: generators - 02/19/07 07:45 PM
The Coleman 5 KW model I bought from HD is labeled 'floating neutral'.

I think it depends on who makes it.
Posted By: trekkie76 Re: generators - 03/02/07 10:52 PM
George, I was stating that the neutral is solid, not disconnected at the transfer switch, thus not a SDS by NEC definition. The neutral floats to prevent parallel paths with the ground in this setup.
Posted By: sparkync Re: generators - 03/02/07 11:51 PM
I just got through installing a 7 KW Briggs & Stratton NG automatic generator. Their clearances were 5 ft. on all sides and could not be put under a deck. They had a ATS that would fit inside a stud wall. Worked out great. You'll have to special order the flush cover though if you're going to install it a wall, it comes with a surface cover and the rough edges are not good around where you cut out. It just so happened that the homeowner had a "tapestry" on her wall and they wanted the panel behind it anyway. Everything else worked out great. Their generator comes already "broke in" with oil and a battery in it. You have to order the battery warmer separate though if it will operated under 32F. That cost an extra $ 200.00 where I got mine. Inspector said it was a good job [Linked Image] Steve
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