No GES or EGC

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LRB

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Interior Alaska
Good evening
I have inherited a grounding / bonding nightmare.

Let me give you back ground info. Our local farmers co-op grain and fertilizer facility was built by the State of Alaska in 1979 and 1980. The local co-op has leased the facility from the State since construction but negotiated a purchase in the spring of 2016. I have done service calls to the complex for about 5 years but now that the Co-op owns the facility I have been asked to evaluate the entire electrical system.

When the facility was built there was no commercial power available and the site was powered by 150 KW gen set with back-up. In 1983 single phase power was made available and a 200 amp 480 volt 1 phase service was installed with transfer switches.
We have a 25 KVA 1 phase SDS 480 X 240 volt in both fertilizer / office facility and another in the grain facility. When ever running 3 phase equipment, gen set is supplying both 480 3 phase buss and 240 1 phase buss.

Management wants to tie the fertilizer/office SDS directly to POCO to provide more stable power for computers and com equipment. We have an existing spare conduit between generator shed and fertilizer facility.

Now for my grounding / bonding mess.

The only GES I can find is at the Generator shed. There is a ground rod and GEC for one of the Generators and a ground rod for the POCO meter/disconnect. (The other generator is not bonded to transfer switch or generator – both generators have only 3 phase power conductors run to second transfer switch through PVC conduit. Both generators have neutral bonded to generator frame, no EGC or neutral run to transfer switch.) I will bond the two ground rods at the gen shed together (they are about 20 ft apart) and also the frames of both generators.

The conduits feeding the fertilizer plant have dielectric couplers before entering 480 v MDP, therefore the conduits are not an EGC.

There is a small MCC in the fertilizer facility and the ground buss does not have any conductors attached. None of the motor feeders have an EGC run with them and all conduits leaving the MCC are PVC. Therefore none of the 3 phase equipment in the fertilizer facility have an EGC.

The 25 KVA SDS does not have the neutral bonded to anything, but the 120/240 V MDP has the neutral and ground busses bonded. (I installed that bond this spring.)

I am pulling #2AWG XHHW copper for feeders for the 25 KVA step down with a full size EGC. Plan to land EGC on MCC ground buss and then #4 copper EGC from MCC ground to 120/240 MDP ground buss. I am driving 2 ground rods and running GEC from rod to MCC ground buss but I still have to co me up with a EGC for the fertilizer facility 3 phase motors. Short of pulling all new wire for motor feeders what is the best way to achieve this. Can I attach the EGC externally to the conduit.

Sorry for long post.
 
intent

intent

ask yourself this:

If there is a fault in ANY part of this system, will there be a low impedance (bonding) equipment grounding conductor path back to the source (both separately derived transformer and generator or the service) for the fault current to trip any over-current devices?
 
LRB said:
....I still have to co me up with a EGC for the fertilizer facility 3 phase motors. Short of pulling all new wire for motor feeders what is the best way to achieve this. Can I attach the EGC externally to the conduit.

Sorry for long post.
Click to expand...
You need to pull an EGC in the pipe 300.3(B). I don't see why that would mean pulling all new wire to the motors.
 
earlydean said:
ask yourself this:

If there is a fault in ANY part of this system, will there be a low impedance (bonding) equipment grounding conductor path back to the source (both separately derived transformer and generator or the service) for the fault current to trip any over-current devices?
Click to expand...
That IMO should get higher priority then then a grounding electrode system.

How much steel structure is involved can have some favorable impact even if not fully compliant with code on grounding and bonding methods. This is highly likely if grain storage is in steel bins. Fertilizer however can be a different ballgame. Dry fertilizer could very likely be in wood or other nonmetallic structures, liquid fertilizer and steel structures usually have limited life, stainless structures are a good thing - but have a higher price tag.
 
No EGC

No EGC

Thanks for the feed back. Pretty much what I knew but good to have other input. Kwired understands what I am up against. nearly 40 yrs of fertilizer means all metal is corroded, motors on top of 60 ft legs, open pecker heads, screws break off -20 last 2 nites, warmer now + 9 but 20 MPH winds. Motor feeder wires likely undersized, may have to add pull points, ect, ect. I know... sing me a song this is life on the last frontier. Kwired this entire complex was designed by CENEX for the State. The grain complex is steel bins and by the nature of construction is quite well bonded. Fertilizer facility is concrete lower section and transition to wood for upper walls and roof. They have construction prints for concrete and wood framing. Only electrical prints are for lighting, heating and convince outlets. There is a motor schedule but no spec. for wiring.No mention of provision for UFER electrode.

None of the metal conduits have provision for bonding, which i do not believe was required in 1980. Most metal conduits do have lock nuts on both sides of cabinets and I believe this satisfies 250.97 exception 2 (2011 NEC). Am I not correct, if I touch it I have to leave it to current code. The Generators OCP (factory installed) is sized for 150 KW at 208, therefore 500 Amp. which will require #2 awg copper for EGC (please verify me on this.). We have 3 1/2 PVC between Gen and transfer with 350 MCM Al phase conductors. Should be able to get # 2 copper in there but it stars to get crowded in the transfer switch. man I wish they had run metal raceway. There is no way this was to code for 1980.
 
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