Generator GEC

[LRB]

For the grounding of the portable 200 KW Cat Gen set we are installing, Cat makes the following statement:

?In any generator installation, the frame of the generator must be positively connected to an earth ground. This connection is the first one that is made at the installation. This connection is the last one that should be removed ?

They discuss the need for this conductor to be flexible, and then they say that this cable or strap should have at least the current carrying capacity of the largest line lead to the connected load

Why does Cat require such a large grounding conductor tied to the frame of the gen? My GE will be a near by well casing. Is this grounding conductor between the gen frame and the well casing a GE jumper and gen frame part of the GES? What size of conductor do I need to satisfy Cat?s requirement? If the gen frame is part of the GES then my GEC will be a short jumper of 1/0 from gen T0 to the gen frame.

There is a 200 A 1-phase service to the facility that has a single ground rod for GE. The portable gen will be the sole source of power for the 480 V 3 phase. My understanding that the generator is a SDS and I will have to bond the 2 GE together to make one GES. Do I bond from GE to GE or from 1-phase service entrance to gen T0 or gen frame or the well casing? What size conductor for bonding jumper

 

[Pierre C Belarge]

Is the transfer switch 3-pole or 4-pole?

If it is a 4-pole transfer switch, then you have an SDS, if it is a 3-pole, then you do not have a SDS. This distinction will help you to determine how the grounding will occur at the generator.

 

[LRB]

Generator GEC

Pierre:
No transfer switch. Generator is for 3 phase as needed. Utility power is 1 phase.

 

[brian john]

1. Why would you rent a 3 phase generator for a single phase installation?

2. Why not reconnect it for the proper voltage?

3. Depending where you connect into the system and what you do with the neutral in the service answers your question.

4. Most rentals come with the neutral bonded to the frame at the generator.

5. I assume you are going to run single phase 3 wire, (2 ungrounded conductors/hot, one neutral/grounded conductor) and a one equipment grounding conductor EGC.

6. Connect the ungrounded and grounded conductors and connect the EGC to the frame.

7. How long is this temp a temp?

 

[K8MHZ]

In any generator installation, the frame of the generator must be positively connected to an earth ground.

That right there is incorrect.

I can see Cat wanting big stuff because they make big stuff.

Other than that, a single ground rod is pretty useless no matter how large it's conductor is going to be.

 

[LRB]

Brian:
1. Gen is owned by customer.
2. We need 480 V 3 Ph for 100 HP motor.
3. No 3 phase available from utility.
4. No ungrounded conductor will be utilized.
5. Gen neutral (T0) is not bonded to Gen frame.
6. Only interconnection with 1 Ph will be EGC and GES.
7. Read my quote from the Cat installtion instructions. They want the gen frame positively connected to earth ground with cable or strap that should have at least the current carrying capacity of the largest line lead to the connected load. Gen has 400 A 480 V breaker which will require 1/0 GEC. My line leads to 100 HP 480 V motor are 2/0. To satisfy Cat's requirements do I have to run 2/0 from Gen frame to my GE. Also wouldn't this be a GE bonding jumper and make the Gen frame part of the GES?
8. Gen is temp power used by a large farm depending on time of the year locatin of gen will be moved to different job sites.

 

[zbang]

Here's my reading of this-
3-phase generator to run a 3-phase motor (at a well) and nothing else. I assume this is a trailer-mounted generator (see 250.34 and search this forum for more).

?In any generator installation, the frame of the generator must be positively connected to an earth ground. This connection is the first one that is made at the installation. This connection is the last one that should be removed ?

Yep, got to connect the frame to a proper grounding electrode system.

They discuss the need for this conductor to be flexible, and then they say that this cable or strap should have at least the current carrying capacity of the largest line lead to the connected load

That's bogus. Size this GEC as you would any other. However...

Why does Cat require such a large grounding conductor tied to the frame of the gen? My GE will be a near by well casing. Is this grounding conductor between the gen frame and the well casing a GE jumper and gen frame part of the GES? What size of conductor do I need to satisfy Cat?s requirement?

Dunno.
I'd say that from the frame to the GES would be an EGC, but there could be some debate about that.
Forget Cat's requirement, use the table.

My understanding that the generator is a SDS and I will have to bond the 2 GE together to make one GES. Do I bond from GE to GE or from 1-phase service entrance to gen T0 or gen frame or the well casing? What size conductor for bonding jumper

I have a simplistic outlook sometimes- bond it all . Since the generator is a SDS, you'll also need to bond the generator's neutral to the GES using the appropriate sized jumper.

Is there any conceivable connection between the well system and the 1-phase system (water pipes, etc)? If not, one could argue that the two GES's don't need to be bonded at all.

Brian- your mileage may vary. None of the large generators I've rented had a N-G bond on arrival.

 

[brian john]

Brian:
4. No ungrounded conductor will be utilized.

Well then this post is meaningless because you need ungrounded conductors to power any load.

5. Gen neutral (T0) is not bonded to Gen frame.

Then it should be

6. Only interconnection with 1 Ph will be EGC and GES.

FINE

7. Read my quote from the Cat installation instructions. They want the gen frame positively connected to earth ground with cable or strap that should have at least the current carrying capacity of the largest line lead to the connected load. Gen has 400 A 480 V breaker which will require 1/0 GEC. My line leads to 100 HP 480 V motor are 2/0. To satisfy Cat's requirements do I have to run 2/0 from Gen frame to my GE. Also wouldn't this be a GE bonding jumper and make the Gen frame part of the GES?

We hook up temp gensets from Cat all the time and have never seen this from our local Cat rep. But it sounds like you have it. Many rental companies want a rod driven for it's mystical qualities.
.

 

[LRB]

Brian:
Me bad. #4 of my last post should have stated grounded coductors for the 480V 3 phase will not be utilized.

My orginal intent was to land 1/0 GEC and #3 EGC on Gen T0 and run # 3 EGC from T0 to Gen frame but the more I study this the more confussed I become.

Zbang refered me to 250.34. 250.34 (A) and (B) is not applicable to my install. However, 250.34 (A) and (B) is talking about when it is not required to connect the frame of a portable gen to the GE as defined in 250.52 therefore it appears I must follow 250.52 and ground the frame of the Gen to an approved GE. Zbang has given his opinion that this conductor will be an EGC. If so, I have to run a GEC from T0 to GE in addition to the EGC from the frame to the GE. 250.34 (C) is not applicable to me because I do not have a grounded conductor for the 480 V 3 Ph, however, if there were a grounded conductor it would be bonded to the Gen. frame. Dosen't this make the Gen frame part of the GES?

Zbang, You asked if there was any concivable connection between the 1 Ph and 480 V 3 Ph. We will have 1 ph block heater on Cat engine and also a 1 ph winding heater in the 3 ph motor, therefore the EGC's from each system will be common to each other and I believe the GES if both systems must be tied together.

Thanks to all for their inputs.