Connecting a 12kw genset

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technoid52

Member
Location
PA
Hello, I am a retired water utility electrician. Over the years I had worked with 3 phase gensets and many controls. Water utilities are not under the code restriction. But we had electrical engineers working with us to keep close to the code as possible. I am installing a home 12kw single phase 240v unit for my trailer. An existing 100 amp manual transfer switch mounted on a power board outdoors with the main panel will be used. The transfer switch does not switch the neutral. I have placed the genset in my garage 100 feet away. From there I will be running #6 in conduit to the transfer switch. Now my question is (I have been out of touch with the code) can I run my 3 each #6 in the exisiting garage sub panel supply conduit back to the switch? Or do I have to install a separate conduit just for the genset? The 1 1/2 conduit has exisiting 4 each #6 for the garage sub panel. There is also a question about the bonding. I will be grounding the genset at the garage with a ground rod. But do I have to run another green from that ground back to the main? Or can I use the garage sub panel green? The sub is also grounded to rods.
 

mcclary's electrical

Senior Member
Location
VA
Hello, I am a retired water utility electrician. Over the years I had worked with 3 phase gensets and many controls. Water utilities are not under the code restriction. But we had electrical engineers working with us to keep close to the code as possible. I am installing a home 12kw single phase 240v unit for my trailer. An existing 100 amp manual transfer switch mounted on a power board outdoors with the main panel will be used. The transfer switch does not switch the neutral. I have placed the genset in my garage 100 feet away. From there I will be running #6 in conduit to the transfer switch. Now my question is (I have been out of touch with the code) can I run my 3 each #6 in the exisiting garage sub panel supply conduit back to the switch? Or do I have to install a separate conduit just for the genset? The 1 1/2 conduit has exisiting 4 each #6 for the garage sub panel. There is also a question about the bonding. I will be grounding the genset at the garage with a ground rod. But do I have to run another green from that ground back to the main? Or can I use the garage sub panel green? The sub is also grounded to rods.


7 #6's is the most you could put in an 1& 1/2" PVC sch 40.

And in you situation, even if they fit, it would be illegal. You need one conduit for your genset feed, one conduit for your controls, and a 3rd conduit for battery conditioning. (disregard the last two if not automatic transfer)
 

RUWired

Senior Member
Location
Pa.
7 #6's is the most you could put in an 1& 1/2" PVC sch 40.

And in you situation, even if they fit, it would be illegal. You need one conduit for your genset feed, one conduit for your controls, and a 3rd conduit for battery conditioning. (disregard the last two if not automatic transfer)

I'm not sure why you said the 7 # 6 can't fit in a 1-1/2" pvc conduit. You can put 9 # 6 thwn c.c.c. rated at 50 amps in a 1-1/2" pvc conduit. (i assume both garage and gen set feeders are rated at 50 amps).

Technoid, Since both are feeders i don't see a problem using a common equipment ground conductor.I take it you are going to use a disconnect in the garage for the generator feeder output and nipple into the sub panel and use that conduit as a raceway back to the manual transfer switch? Does the manual transfer switch feed the outdoor panel?
The grounding electrode conductor from the ground rod should not be tied into the grounded neutral conductor from the generator. It's ok to go to the frame with it but not the neutral. You also have to make sure the bonding jumper in the gen set is removed.

Rick
 

tom baker

First Chief Moderator
Staff member
Water utilities are not under the code restriction.[/QUOTE
Is that a state rule? A water utility has premise wiring, and on the customer side of the service point, you would clearly be subject to the NEC, unless exempted by someone. Electric utilities are clearly exempt, perhaps you are a water and electric utility, but even then the water side would not be exempt.
 

technoid52

Member
Location
PA
Water utilities are not under the code restriction.[/QUOTE
Is that a state rule? A water utility has premise wiring, and on the customer side of the service point, you would clearly be subject to the NEC, unless exempted by someone. Electric utilities are clearly exempt, perhaps you are a water and electric utility, but even then the water side would not be exempt.

Public water shed pump houses where the general public are not allowed to enter are not under the NEC. But the general offices where you would pay a bill or open an account would be. And that is nation wide. Same goes with the power companies. Thank you for your input. We only deliver water at the service point. Not power.
 

technoid52

Member
Location
PA
7 #6's is the most you could put in an 1& 1/2" PVC sch 40.

And in you situation, even if they fit, it would be illegal. You need one conduit for your genset feed, one conduit for your controls, and a 3rd conduit for battery conditioning. (disregard the last two if not automatic transfer)

Thank you for your input. We always put the 3 phase genset feeders in a separate conduit. If they were doubles comming off the breaker then we would use 2 conduits to avoid inductive problems. So I assume this is the same issue for single phase running in a common conduit? I will take your advise and put in another conduit. Thank you.
 

technoid52

Member
Location
PA
I'm not sure why you said the 7 # 6 can't fit in a 1-1/2" pvc conduit. You can put 9 # 6 thwn c.c.c. rated at 50 amps in a 1-1/2" pvc conduit. (i assume both garage and gen set feeders are rated at 50 amps).

Technoid, Since both are feeders i don't see a problem using a common equipment ground conductor.I take it you are going to use a disconnect in the garage for the generator feeder output and nipple into the sub panel and use that conduit as a raceway back to the manual transfer switch? Does the manual transfer switch feed the outdoor panel?
The grounding electrode conductor from the ground rod should not be tied into the grounded neutral conductor from the generator. It's ok to go to the frame with it but not the neutral. You also have to make sure the bonding jumper in the gen set is removed.

Rick

Thanks for you input Rick, Yes, the main load center is on the outdoor panel with the transfer switch. Because its a trailer the main had to be separate along with the well and the garage. Yes I know the genset and all sub panel neutral busses are not to be joined to the sub chasis ground (bond). Only at the main service.
I am going to take the advise of MCClary and install a separate conduit. I seem to recall from the engineers that different line power sources could not be in the same pipe. It makes sense. I am still not sure on using the garage subs green bond for the genset. I think it might have to have its own bond back to the main and ground rod.
 

mcclary's electrical

Senior Member
Location
VA
I'm not sure why you said the 7 # 6 can't fit in a 1-1/2" pvc conduit. You can put 9 # 6 thwn c.c.c. rated at 50 amps in a 1-1/2" pvc conduit. (i assume both garage and gen set feeders are rated at 50 amps).

Technoid, Since both are feeders i don't see a problem using a common equipment ground conductor.I take it you are going to use a disconnect in the garage for the generator feeder output and nipple into the sub panel and use that conduit as a raceway back to the manual transfer switch? Does the manual transfer switch feed the outdoor panel?
The grounding electrode conductor from the ground rod should not be tied into the grounded neutral conductor from the generator. It's ok to go to the frame with it but not the neutral. You also have to make sure the bonding jumper in the gen set is removed.

Rick



I didn't say 7 would not fit, I said 7 is the most you could legally put in an 1& 1/2" conduit. I'm not talking and 9 ccc's for derating, I'm talking about 7 #6 copper thwn is the most you can legally put in a sch 40 1.5" conduit.
 

RUWired

Senior Member
Location
Pa.
7 #6's is the most you could put in an 1& 1/2" PVC sch 40.

And in you situation, even if they fit, it would be illegal.
I didn't say 7 would not fit, I said 7 is the most you could legally put in an 1& 1/2" conduit. I'm not talking and 9 ccc's for derating, I'm talking about 7 #6 copper thwn is the most you can legally put in a sch 40 1.5" conduit.

mcclary, I was mostly replying to your statement that it was illegal and it was the most that could fit. Being the nec is so technical i said that 9 #6 thwn could actually fit at 50amps. All 15 # 6 thwn conductors that table c.10 shows could actually fit at 35 amps. I was asking indirectly why you thought that only 7 conductors were allowed.

Rick
 

mcclary's electrical

Senior Member
Location
VA
mcclary, I was mostly replying to your statement that it was illegal and it was the most that could fit. Being the nec is so technical i said that 9 #6 thwn could actually fit at 50amps. All 15 # 6 thwn conductors that table c.10 shows could actually fit at 35 amps. I was asking indirectly why you thought that only 7 conductors were allowed.

Rick



I was working from memory, and once again, it failed me. I have bet money on that until you corrected me. They would "fit", but I still wouldn't do it. You would most likely damage the cables in place when pulling the others in.
 

ty

Senior Member
Public water shed pump houses where the general public are not allowed to enter are not under the NEC. And that is nation wide.
Not around here.
A Licensed Master Electrician would be required. But who cares, that's not what the topic is about.

I have some questions:

What area of PA are you in?
And what type(brand) of 12kW Generator?
Some have different hook-ups than others.
Is the 12kW Generator auto start, or manual start? is there a bettery for the generator?

Why does your transfer switch NOT switch the Neutral?
Is the Neutral bonded in the Generator?

How many wires feed the sub in the garage?

You say it is a 100a manual transfer switch. What size service is to the mobile home from the pole?
 

technoid52

Member
Location
PA
Not around here.
A Licensed Master Electrician would be required. But who cares, that's not what the topic is about.

I have some questions:

What area of PA are you in?
And what type(brand) of 12kW Generator?
Some have different hook-ups than others.
Is the 12kW Generator auto start, or manual start? is there a bettery for the generator?

Why does your transfer switch NOT switch the Neutral?
Is the Neutral bonded in the Generator?

How many wires feed the sub in the garage?

You say it is a 100a manual transfer switch. What size service is to the mobile home from the pole?

I am in Tioga county. The genset is an open frame from emergencypower.com. Here is the link to what I bought...http://www.emergencypower.com/standby-generators/12-kw-diesel-generator/
This genset can be set for auto start or manual. It has a 75 amp breaker on it. This is the only place on my 12kw genset where the neutral would be broken. (On the middle leg of the breaker). The neutral is not bonded in the genset. I do not have an ATS. And after years of on the job trouble shooting them and repairs, I would not want one. Manual transfer only is just fine. The manual transfer switch is designed not to switch the neutral. I have never seen one that did. Why would you want to? In my old job I had worked on 350kw 3 phase units and larger. ASCO, Motorola, old Euclid, etc auto transfer switches, 240v single phase transfer switches, all of them did not break the neutral. My garage sub panel is 240v. Wired with 2 lines, a neutral and the ground. 4 wires total. The main sevice entrance panel load center is 100amp. Everything was inspected to code years ago. I use to have a small 5kw portable gasoline generator that would plug into the panel when needed. But I went bigger now. So this is why I am on here. To get everything on this 12kw wired to code. And I like diesel units. So all expert licensed electrician inputs to me are gladly accepted.
 

tom baker

First Chief Moderator
Staff member
Public water shed pump houses where the general public are not allowed to enter are not under the NEC. But the general offices where you would pay a bill or open an account would be. And that is nation wide. Same goes with the power companies. Thank you for your input. We only deliver water at the service point. Not power.

Lets change "Nation Wide" to nation wide except for Washington State. I do a lot of work for a large class A water utility, and have pulled hundreds of electrical permits, all required by the state, for working in public water shed pump houses. I have one open currently for motor replacement and control system
We have several speciality electricians that are "Pump Installers" and their scope of work is working in pump houses.
What section of the NEC do you feel exempts public water pump houses?
If you get a minute, PM me with what state you were working in...
I did write an article on the 2008 NEC changes for a national well driller magazine, I didn't get any comments about the "NEC not applying to the pump houses we work on".
 

technoid52

Member
Location
PA
Lets change "Nation Wide" to nation wide except for Washington State. I do a lot of work for a large class A water utility, and have pulled hundreds of electrical permits, all required by the state, for working in public water shed pump houses. I have one open currently for motor replacement and control system
We have several speciality electricians that are "Pump Installers" and their scope of work is working in pump houses.
What section of the NEC do you feel exempts public water pump houses?
If you get a minute, PM me with what state you were working in...
I did write an article on the 2008 NEC changes for a national well driller magazine, I didn't get any comments about the "NEC not applying to the pump houses we work on".

Well like I said in my first blog, I was out of touch with the code. I am going by what I was told in NEC code school from 1995. That utilities were exempt unless local town codes over ruled. I assumed that never changed. My teacher at that time was very good with explaining code. I had worked in Suffolk county on Long Island. Our engineers had the elctrical license. They use to have no code days for us when a particular job was a rush. Even then I was told we were exempt from the NEC at the pump houses. I have been retired now for 3 yrs. So if this has changed I would not know. Now with that said, could you look over all that I had wrote and tell me what is needed to put this 12kw genset in to code? Thank you.

Bill
 

ty

Senior Member
For starters, since this whole set-up is manual, you don't need a conduit for control wiring.

Wait, does it have a battery and charge controller? If so, how does it wire?

I asked the question about your transfer switch breaking the neutral because I wanted to see what you knew about SDS and NON-SDS set-ups.
And yes, there are transfer switches that break the neutral.
Why would you? Well, it depends how the Gen-set is bonded.

It sounds like you should put in a seperate conduit for the gen-set feeder.
4 Conductors. (2hot, 1neutral, 1ground)
Drive a ground rod at your transfer switch and bond to that.

Your Transfer Switch IS SERVICE RATED, isn't it??
 

technoid52

Member
Location
PA
For starters, since this whole set-up is manual, you don't need a conduit for control wiring.

Wait, does it have a battery and charge controller? If so, how does it wire?

I asked the question about your transfer switch breaking the neutral because I wanted to see what you knew about SDS and NON-SDS set-ups.
And yes, there are transfer switches that break the neutral.
Why would you? Well, it depends how the Gen-set is bonded.

It sounds like you should put in a seperate conduit for the gen-set feeder.
4 Conductors. (2hot, 1neutral, 1ground)
Drive a ground rod at your transfer switch and bond to that.

Your Transfer Switch IS SERVICE RATED, isn't it??

No charge control, no wired remote controls, everything is manual. Kiss mode (keep it simple stupid, ha ha) Ok on the separate 4 cond in its own conduit. I will do that. And yes the transfer switch is service rated. Made by Mallard. And there are 2 ground rods 6 ft apart at the service board with the transfer switch. Do I need an additional rod at the genset? The garage load center has 2 rods there already at 6 feet apart. An unbroken #8 bare copper wire in both plus from the sub and attached to the all metal building. The genset is not bonded to the neutral. The neutral is broken at the gensets breaker.
 

ceb58

Senior Member
Location
Raeford, NC
No charge control, no wired remote controls, everything is manual. Kiss mode (keep it simple stupid, ha ha) Ok on the separate 4 cond in its own conduit. I will do that. And yes the transfer switch is service rated. Made by Mallard. And there are 2 ground rods 6 ft apart at the service board with the transfer switch. Do I need an additional rod at the genset? The garage load center has 2 rods there already at 6 feet apart. An unbroken #8 bare copper wire in both plus from the sub and attached to the all metal building. The genset is not bonded to the neutral. The neutral is broken at the gensets breaker.

I would not worry about another ground rod at the gen set. Just pull your 4 wires and bond the frame with the EGC from the switch. In your OP you stated the transfer switch was existing correct? So you have the neutrials together and isolated from the can? And you have the EGC bonded to the can?
 

technoid52

Member
Location
PA
I would not worry about another ground rod at the gen set. Just pull your 4 wires and bond the frame with the EGC from the switch. In your OP you stated the transfer switch was existing correct? So you have the neutrials together and isolated from the can? And you have the EGC bonded to the can?
Neutrals are isolated at the genset. At the MTS the neutral passes through from the meter pan to the main load center. Now my generator neutral will be connected to the main panel neutral on the same buss with the grounds. The MTS was originaly connected that way. At the genset the neutral is isolated from ground.
 

technoid52

Member
Location
PA
Neutrals are isolated at the genset. At the MTS the neutral passes through from the meter pan to the main load center. Now my generator neutral will be connected to the main panel neutral on the same buss with the grounds. The MTS was originaly connected that way. At the genset the neutral is isolated from ground.

I have look but I think there is ground buss inside the MTS. I don't think the neutral is on that buss. Its been awhile since I looked inside.
 

220wire

Member
Is #6 rated for 75a according to your breakers terminal rating? I have a similar job I am looking at w/ a 15kw Cummins /onan setup except with an 80amp breaker on the genset
 
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