Grounding/Bonding portable generators used for Tsunami Relief

[ElectroWeed]

Hi all,

Can anyone supply some good links or info on grounding and bonding portable generators?
In this case I will be using a 5800W portable generator to power a 230VAC 1-phase, 3/4hp pump on a manual starter.
I'm most interested in how the generator breaker would trip on a fault to ground if the frame of the generator was not connected to a grounding electrode. Is the neutral typically grounded to the frame of the generator or is it floating?
Any info to help ensure this application is safe would be appreciated.

Thanks,

 

[BJC]

Small generators intended for stand alone use ( powering tools, pumps, lights etc ) usually have the the neutral connected to the frame. ( at least in this part of the world)
Bonding the frame to the neutral would keep the frame at low touch potential (depending on where the system is "earthed").
Draw a schematic with the hot, neutral and ground (bonding )conductors. Analyze faults at the generator, the load and the wiring in between. You want a good fault return path. The worst thing that people do is have a bonding (green wire ) in parallel with an earth return. The parallel earth return comes about by driving ground rods at the generator and somewhere else downstream and connecting neutral to ground(earth) in two places. It's a violation of the US-NEC but will work safely anyway.

 

[alehman]

The two or three generators I've rented recently have been marked 'caution - floating neutral'. I assume this is because they are intended to have the neutral solidly connected to an existing distribution system, which presumably has a neutral-ground bond.

Be sure to check that your generator has a neutral-frame bond. This will allow the breaker to trip for any fault to ground (ground being anything connected to the generator frame).

The NEC allows the frame of the generator to be ungrounded (not connected to earth) if the generator supplies only "cord and plug connected equipment through receptacles mounted on the generator" and "the non-current carrying parts of the supplied equipment and equipment grounding conductor terminals of the receptacles are bonded to the generator frame".

For your application I would probably go ahead and drive a ground rod and connect it to the frame although it may not be strictly required.

 

[cuky2000]

Below are several links with info on grounding and bonding portable generators. I hope the enclose references could help.

http://standards.ieee.org/colorbooks/sampler/Greenbook.pdf

http://www.cat.com/f2l/servlet/cat.vce.servletProxy.

SecuredFileDisplayServletProxy?m=8703&x=7&fileId=99865&languageId=7

http://www.mikeholt.com/videodisplay.php?id=78

thread242-101725

https://www.nspower.ca/inspections/uploads1/B-28-900.pdf

http://www.imsasafety.org/journal/marapr/ma5.htm

http://www.nyseg.com/nysegweb/webcontent.nsf/Lookup/EmergGen/$file/EmergGen.pdf

http://www.ecmweb.com/mag/electric_grounding_nonseparately_derived/

 

[mc5w]

Drive a 10 foot ground rod about 8 to 9 feet into the ground near the generator. This will give you a way to pull it back out when you need to relocate. Copper clad steel ground rods have to be a minimum of 5/8th inch diameter for grounding of power systems here in the U.S. For your application a 3/4 inch ground rod would be better for repeated driving and removal.

You would then need to connect the ground rod to the generator using #2 American Wire Gauge stranded copper wire - this size is for mechanical strength and durability. In Akron, Ohio, U.S.A. the minimum grounding electrode conductor is #4 solid or #2 stranded. (#4 is 2 sizes smaller than #2)

If you can, use an electrical joint compound such as Ilsco Deox which has no conductive particles or Burndy Penetrox E which has copper particles. Remember to sand your wire strands, ground rod, and the interior of any UNPLATED copper lug with #220 wet or dry silicon carbide abrasive paper.

The neutral needs to be bonded to the generator frame and the grounding electrode conductor. Preferably, the neutral and the grounding electrode conductor should be connected together using a genuine equipment ground bar so as to reduce the number of things that can vibrate apart.

Your conductor size going to the starter should be #12 AWG for both the current carrying conductors and the equipment grounding conductor. This is also a mechanical strength consideration and also accounts for the matter that in your situation you may only have 1/2 of the wire strands conducting.