NEC 250.34 discusses portable and vehicle-mounted generators. I have read it and I think I understand it but I continue to get questions from employees and various inspectors that seem to interpret it differently. I would like to generate some discussion on a specific situation. We use portable generators (wheel mounted that pull behind vehicles) to operate submersible pumps. Flexible conductors are attached to the lugs provided on the generator and run to enclosed disconnect switches. Flexible conductors run from the disconnect to the submersible pump. Is there any reason or requirement to provide a grounding electrode and grounding conductor to the generator? We rent some of these generators and own some others. Some of them have lugs that are labeled "ground". Why does the manufacturer provide an attachment for a grounding conductor if the unit is not required to be grounded?
Portable Generators and Submersible Pumps
- Thread starter mlittle
- Start date
- Status
- Location
- Massachusetts
Re: Portable Generators and Submersible Pumps
If you are hardwiring the pumps to the generators you are required to provide grounding electrodes.
If the pumps are cord and plug connected no ground electrodes required.
If you are hardwiring the pumps to the generators you are required to provide grounding electrodes.
If the pumps are cord and plug connected no ground electrodes required.
charlie
Senior Member
- Location
- Indianapolis
Re: Portable Generators and Submersible Pumps
What more are you seeking?
What more are you seeking?
- Location
- Massachusetts
Re: Portable Generators and Submersible Pumps
I am sorry I did not see your follow up question.
I can not give you a reason why it is required for one and not the other.
Here is the reply I was typing to your newer post but it got locked before I could post.
Basically if you have to hard wire the pumps to the generator then you must provide a grounding electrode.
If all your equipment is cord and plug connected you do not have to provide a grounding electrode.
From your description it sounds like a grounding electrode is required.
In my opinion you should be as, or more concerned that the generators neutral you are using is bonded to the generators frame and grounding terminals.
If you do a site search here you will find a thread about this subject longer than 120 posts, hope you have some free time.
Bob
I am sorry I did not see your follow up question.
I can not give you a reason why it is required for one and not the other.
Here is the reply I was typing to your newer post but it got locked before I could post.
Basically if you have to hard wire the pumps to the generator then you must provide a grounding electrode.
If all your equipment is cord and plug connected you do not have to provide a grounding electrode.
From your description it sounds like a grounding electrode is required.
In my opinion you should be as, or more concerned that the generators neutral you are using is bonded to the generators frame and grounding terminals.
If you do a site search here you will find a thread about this subject longer than 120 posts, hope you have some free time.
Bob
charlie
Senior Member
- Location
- Indianapolis
Re: Portable Generators and Submersible Pumps
Generally (that is a word that you can get into trouble with ) the smaller generators are protected with a GFCI and serve only plug and cord connected equipment. Grounding is not required because it doesn't do any good.
If it is a larger generator where everything is hard wired, grounding is required. If it is an in between size, it could go either way. Therefore a grounding lug should be provided to allow that flexibility.
I am shooting from the lip on this comment, please correct me if I am wrong.
Generally (that is a word that you can get into trouble with
) the smaller generators are protected with a GFCI and serve only plug and cord connected equipment. Grounding is not required because it doesn't do any good.If it is a larger generator where everything is hard wired, grounding is required. If it is an in between size, it could go either way. Therefore a grounding lug should be provided to allow that flexibility.
I am shooting from the lip on this comment, please correct me if I am wrong.
- Location
- Massachusetts
Re: Portable Generators and Submersible Pumps
When I read both 250.34(A) & (B) my take is generator size is irrelevant and I could build an elaborate distribution system from portable generator Generator to Main Distribution Panel to other panels and finally branch circuits and if all cord and plug connected no grounding electrode required.
What is anyones opinion on this?
What is an in between size?
When I read both 250.34(A) & (B) my take is generator size is irrelevant and I could build an elaborate distribution system from portable generator Generator to Main Distribution Panel to other panels and finally branch circuits and if all cord and plug connected no grounding electrode required.
What is anyones opinion on this?
javiersalas52d
Member
Re: Portable Generators and Submersible Pumps
I am in the military and from what they teach us is that all our generators need to be grounded for safety reasons.
I am in the military and from what they teach us is that all our generators need to be grounded for safety reasons.
- Location
- Illinois
- Occupation
- retired electrician
Re: Portable Generators and Submersible Pumps
I still fail to understand how a connection to earth improves safety of a system powered by generators. The connection to earth only provides protection from lighting and accidential contact with higher voltage systems. I also don't understand how the electrons know if the equipment is hard wired or cord and plug connected. If one requires grounding, then they both should require grounding as there is no electrical difference between a hard wired and a plug and cord connected system. Maybe the intent is for smaller systems not to have a grounding electrode, but the code does not say that. There are 500 amp cord and plug connections available.
Don
I still fail to understand how a connection to earth improves safety of a system powered by generators. The connection to earth only provides protection from lighting and accidential contact with higher voltage systems. I also don't understand how the electrons know if the equipment is hard wired or cord and plug connected. If one requires grounding, then they both should require grounding as there is no electrical difference between a hard wired and a plug and cord connected system. Maybe the intent is for smaller systems not to have a grounding electrode, but the code does not say that. There are 500 amp cord and plug connections available.
Don
- Location
- Bremerton, Washington
- Occupation
- Master Electrician
Re: Portable Generators and Submersible Pumps
There is no standard amoung genset mfgs on when the neutral is bonded to the frame. But 95% of the larger gensets, say above 10 KW, are not bonded. You have to open up the genset and see if the bonding jumper is there or not. And Don is correct that a ground rod does not add any safety, I doubt if it would help much if the genset got hit by lightning anyway.
There is no standard amoung genset mfgs on when the neutral is bonded to the frame. But 95% of the larger gensets, say above 10 KW, are not bonded. You have to open up the genset and see if the bonding jumper is there or not. And Don is correct that a ground rod does not add any safety, I doubt if it would help much if the genset got hit by lightning anyway.
- Status