electrical subpanel question

[brackishdude]

This is for my new-to-me swimming pool pumphouse, but I believe addresses a few points applicable to folks running a new subpanel for their reefs. Just replace the word pool with tank everytime you see it below. It works. I swear.

I am replacing the simple on/off switch for the pool pump with a timer, and had to open the subpanel to run a neutral and ground out to the adjacent timer since the old switch was just a light switch wired into the hot for the pump circuit.

I discovered that the subpanel was wired with ground and neutral on a common bus, which, after consulting the internet, I discovered is not appropriate for a subpanel. The subpanel feeds several other devices/lights/etc already wired in inappropriately.

The problem is that the main feed only has the two hots and a neutral, no ground. It enters the pool pumphouse housed in a metallic pipe with metal fittings and comes underground from the house.

If I establish electrical continuity between the subpanel housing and the pipe as it enters the ground, can I just put in a new bus, screw it into the housing, and wire into it all of the ground wires currently on the neutral bus ? i.e. does the ground bus on the sub panel have to be in continuity with the ground wires of the main panel?

Thanks. Goooooooo reefs!!!

[MC Lighting]

there is nothing wrong with neutral and ground being bonded on the same bus this is common practice in many installations. The ground is being provided by the metalic conduit as it should be securly bonded to the panel housing. If you wish to add another panel you can either run the ground back to the main panel or install a new ground by instlalling a ground rod.

[MC Lighting]

and sorry to answer the rest of your question yes you can install a ground bus bar in the panel if there is one supported for you model and ground it like stated above with either a ground rod or use the existing conduit if the conduit is metal and is continuos back to the other panel then the panels will be of the same ground potential as the are "bonded" via the conduit. Hope this helps

[hllywd]

IMO you should pound in a new ground rod for the pump house. For the cost you then have the peace of mind knowing it is 100% correct. It may be acceptable to rely on the conduit but would leave some doubt in the back of my mind.

I don't know the NEC well enough to quote but I didn't think you could run the ground and neutral to a common bus...

Tim

[wife no likey]

http://www.mikeholt.com/mojonewsarchive/GB-HTML/HTML/Grounding-versus-Bonding-Part-5-of-12~20050304.php


"What if there's no equipment grounding (bonding) conductor run to the building or structure disconnecting means? In such a case, you can bond the disconnecting means to the circuit grounded conductor (neutral). But this is only permitted only where there's no continuous metallic path between buildings and structures, and ground-fault protection of equipment isn't installed."

[BeanAnimal]

<a href=showthread.php?s=&postid=9537560#post9537560 target=_blank>Originally posted</a> by MC Lighting
there is nothing wrong with neutral and ground being bonded on the same bus this is common practice in many installations. The ground is being provided by the metalic conduit as it should be securly bonded to the panel housing. If you wish to add another panel you can either run the ground back to the main panel or install a new ground by instlalling a ground rod.

NO!

YOU CAN NOT BOND NEUTRAL TO GROUND IN A SUBPANEL!!!!!!!! YOU MUST RUN A GROUND FEEDER TO THE MAIN PANEL AND ISOLATE NUETRAL FROM GROUND THE ENTIRE DISTANCE!

Some types of conduit can be used as the earth ground, if they are properly bonded. Some local codes prohibit this!

[MC Lighting]

really then I guess the comercial electrical install that I just did that was passed by an electrical engineer and the city inspector is wrong?

[BeanAnimal]

<a href=showthread.php?s=&postid=9537582#post9537582 target=_blank>Originally posted</a> by MC Lighting
and sorry to answer the rest of your question yes you can install a ground bus bar in the panel if there is one supported for you model and ground it like stated above with either a ground rod or use the existing conduit if the conduit is metal and is continuos back to the other panel then the panels will be of the same ground potential as the are "bonded" via the conduit. Hope this helps

If the building where the sub panel is located, is detached from the building where the main panel is located, then a ground rod should be set and attached only to the ground bar. This is a MUST (even if the conduit is bonded AND a ground feeder is run to the main panel). Notice again, that NUETRAL is NOT to be bonded to GROUND.

Bean

[BeanAnimal]

<a href=showthread.php?s=&postid=9541226#post9541226 target=_blank>Originally posted</a> by MC Lighting
really then I guess the comercial electrical install that I just did that was passed by an electrical engineer and the city inspector is wrong?

I have no idea what "was passed" but what you said is not correct.

You can not bond neutral to ground in a subpanel. We can certainly get the NEC out if you wish.

[MC Lighting]

i don't disagree that a ground rod should be driven it is a safety net you cannot beat and as stated is a cheap $38 insurance policy.

[MC Lighting]

all I am asking is you are telling me that a city inspector, a electrical engineer and an C10 electrician are wrong?

[BeanAnimal]

<a href=showthread.php?s=&postid=9541282#post9541282 target=_blank>Originally posted</a> by MC Lighting
i don't disagree that a ground rod should be driven it is a safety net you cannot beat and as stated is a cheap $38 insurance policy.

It is required, not an option :) Actually, I beleive the new code states (2) ground rods need to be installed at detached locations. I would have to look that one up though.

[MC Lighting]

ahhh wait I see where you and I are getting mixed up your assuming in the sub panel and I am assuming in the main panel the way I read his original post is sounded like the main panel and sub panel were one since many people call them subpanels if their is a main disconnect located at the meter probably should clarify main panel and sub panel.

[BeanAnimal]

<a href=showthread.php?s=&postid=9541306#post9541306 target=_blank>Originally posted</a> by MC Lighting
all I am asking is you are telling me that a city inspector, a electrical engineer and an C10 electrician are wrong?

It happens every day... all day :) Give me 10 inspectors and 1) subsection of code, I can give you 10 different interpretations!

Honestly... without knowing the details of the wiring, I have no idea what your setup is and why or how it is approved. I do know that the NEC requires that sub panels have isolated ground and nuetral buses.

[MC Lighting]

well iif two are required then as I stated a C10 contractor, electrical engineer and a city inspector are all in the wrong...

[BeanAnimal]

Lets step back here...

Thre are instances when the neutral and ground can be bonded at the sub panel. In those cases, NO OTHER metal or material capable of carrying current can connect the two buildings. THE PANELS MUST NOT BE IN THE SAME BUILDING. You will find the other criteria and relevant information in 250.32/B2 If the criteria are met, the neutral can be bonded and ground rods at the outbuilding must be set. We tend to not count any of these cases, because they are usually not a good idea. Instead we only look at scenarios where the sub-panel is fed by a EGC and therefore the neutral MUST be isolated.

Here is the PROBLEM (and why MOST inspectors and localities will NOT ALLOW IT). If the neutral becomes OPEN, then the grounding path back to the main panel will become the current carrying conductor. (In the OPS case, this would be the conduit). bad news to say the least. Ground rods are not effective means of protection. Yes they are a good idea, but should NOT be counted on to save your life. It is also not a good idea to have more than 1 grounding reference in a system.

In the case of the OP. The CONDUIT is a METAL PATH back to the MAIN PANEL (or building that houses the main panel) and therefore the NEUTRAL MUST BE ISOLATED. PERIOD!

Sometimes even things that "pass" code are not good ideas.

If you want to discuss "how many" certified and qualified people it takes to notice a mistake... we can have that discussion also.
Your setup may very well meet code.

Sorry to be so BOLD but 99% of the time subpanel NUETRALS should not be bonded to GROUND. The other 1% of the time, it is NOT a good idea.

[hllywd]

:D
I thought I knew a little about neutrals and grounds. thanks for the confirmation Bean!

Tim

[gary faulkner]

<a href=showthread.php?s=&postid=9541659#post9541659 target=_blank>Originally posted</a> by BeanAnimal
Lets step back here...

Thre are instances when the neutral and ground can be bonded at the sub panel. In those cases, NO OTHER metal or material capable of carrying current can connect the two buildings. THE PANELS MUST NOT BE IN THE SAME BUILDING. You will find the other criteria and relevant information in 250.32/B2 If the criteria are met, the neutral can be bonded and ground rods at the outbuilding must be set. We tend to not count any of these cases, because they are usually not a good idea. Instead we only look at scenarios where the sub-panel is fed by a EGC and therefore the neutral MUST be isolated.

Here is the PROBLEM (and why MOST inspectors and localities will NOT ALLOW IT). If the neutral becomes OPEN, then the grounding path back to the main panel will become the current carrying conductor. (In the OPS case, this would be the conduit). bad news to say the least. Ground rods are not effective means of protection. Yes they are a good idea, but should NOT be counted on to save your life. It is also not a good idea to have more than 1 grounding reference in a system.

In the case of the OP. The CONDUIT is a METAL PATH back to the MAIN PANEL (or building that houses the main panel) and therefore the NEUTRAL MUST BE ISOLATED. PERIOD!

Sometimes even things that "pass" code are not good ideas.

If you want to discuss "how many" certified and qualified people it takes to notice a mistake... we can have that discussion also.
Your setup may very well meet code.

Sorry to be so BOLD but 99% of the time subpanel NUETRALS should not be bonded to GROUND. The other 1% of the time, it is NOT a good idea.



Bean,

Everything that you have stated is correct.

Inspectors make mistakes also but this is a common electrical installation that happens all the time. Most inspectors would catch this mistake.

Sub panels are not to have ground and neutral tied together.

Nuff said ?

[BeanAnimal]

<a href=showthread.php?s=&postid=9541390#post9541390 target=_blank>Originally posted</a> by MC Lighting
ahhh wait I see where you and I are getting mixed up your assuming in the sub panel and I am assuming in the main panel the way I read his original post is sounded like the main panel and sub panel were one since many people call them subpanels if their is a main disconnect located at the meter probably should clarify main panel and sub panel.

No propblem at all.. and again, sorry if I sounded short. I just hate to see anybody get hurt or killed. The bonded neutral subject comes up quite a bit and there is a lot of very bad advice out there. It is safe to say that the only place you should ever bond neutral to ground, is in the main panel (or outby the main panel at the main disconnect). Sub panels, in almost all cases must (or would be better off) with an isolated neutral and ground :)

[MC Lighting]

yup exactly See Bean this is why you and I debate well, thats the problem with the internet sometimes it is hard to understand a subtle detail. Yes lets keep people alive that would be a good idea....

[brackishdude]

Thanks, everyone.


There are instances when the neutral and ground can be bonded at the sub panel. In those cases, NO OTHER metal or material capable of carrying current can connect the two buildings. THE PANELS MUST NOT BE IN THE SAME BUILDING.

Yes, the pumphouse is a separate building and is fed via underground metal pipe, two hots and a neutral (no formal ground). Unknown if the pipe is in continuity with the house main ground. How would I test?


If the pipe/conduit is not tied into the main house ground, you're saying the shared neutral/ground bus in the subpanel is ok, but that I have to ground it too?

And if the pipe is in contiuity with main hous ground, then the shared bus is not OK, and I need to add a dedicated ground bus which will ground through the subpanel housing and thus the incoming pipe?

If so, then I hope the pipe is not in continuity with the main house, because then all I have to do is gound the box, versus putting in a new bus and rewiring. . .

[BeanAnimal]

<a href=showthread.php?s=&postid=9544388#post9544388 target=_blank>Originally posted</a> by brackishdude
Thanks, everyone.




Yes, the pumphouse is a separate building and is fed via underground metal pipe, two hots and a neutral (no formal ground). Unknown if the pipe is in continuity with the house main ground. How would I test? By attaching a multimeter (set on ohms) between the ground in the house to the pipe in the pool house. However, that does not get you out of the woods one way or the other. Also note that telephone wires, plumbing (gas or water) and many other items can be considered conductors between the house and the outbuilding. The area can get kind of grey.. but I would imagine you poolhouse has a spigot and it is from the same metered supply as your house.If the pipe/conduit is not tied into the main house ground, you're saying the shared neutral/ground bus in the subpanel is ok, but that I have to ground it too? The metal conduit is one aspect. You still have to meet the other provisions of the code. I would contact a pro and get their opinion. I simply can not give you that kind of advice. My advice would be to pull in a ground and isolate the neutral bus (if the conduit has enough room).And if the pipe is in contiuity with main hous ground, then the shared bus is not OK, and I need to add a dedicated ground bus which will ground through the subpanel housing and thus the incoming pipe? Well that depends on the classification of that conduit. But the easy answer is still NO, YOU SHOULD ISOLATE THE NEUTRAL. Now if the conduit is bonded and rated and installed as such, then it could take the place of the grounding conductor.

Again, please note that MANY local codes go one step further than the NEC. They totaly phrohibit 3 wire feeders and neutral bonded sub panels. Many local codes also prohibit the use of the conduit as the EGC (Equipment Grounding Conductor). No matter how you roll the dice, you come up with one good answer. That is isolate neutral from ground in a subpanel.

If so, then I hope the pipe is not in continuity with the main house, because then all I have to do is gound the box, versus putting in a new bus and rewiring. . .

Sometimes the easy way is not the safest way. Seeing that WATER is also involved here, you may want to take the high road and pull in the ground conductor.