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How to wire two panels with main breakers and separate meters, but one ground

How to wire two panels with main breakers and separate meters, but one ground

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  #1  
Old 01-04-13, 06:12 AM
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How to wire two panels with main breakers and separate meters, but one ground

200A underground service, with two 100A Square D QO 100A panels (circa 1995) that share a ground to copper rod and copper water pipe. One general-purpose and one time of day (for eventual electric heat and hot water). They have separate meters and both have main breakers (disconnects). Only the first is in use right now. The inspector said to remove the bond screw (big green one) in the general-purpose panel and throw it away.

We had a licensed electrician friend check it out after we added circuits. He said to put back the bond screw, add a grounding bar kit for the ground wire and attach only neutral wires to the neutral bus, and use only one wire per screw. The hardware store owner said to leave out the bond screw, attach only neutral wires to the neutral bus, add the grounding bar kit for ground wires, one wire per screw (20 screws).

Your forum says one neutral or two ground wires per screw. Square D tech support agrees (two ground wires up to size 10).
Also that you can run two cables to one breaker but only if you don't run out of screws on the neutral bus (which we would) and to use junction boxes instead.

2008 Code says to put neutral and ground screws on separate buses, which means both panels need grounding bar kits, not just the pseudo-subpanel. Newer panels come with separate neutral and grounding bars.

Do we or don't we want a bond screw on the second panel?

Can someone explain what removing the bond screw accomplishes (the purpose - added safety?).
 

Last edited by sindikeesan; 01-04-13 at 07:56 AM. Reason: called Square D with questions
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  #2  
Old 01-04-13, 08:42 AM
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Welcome to the forums!

Note: I've started a new thread for your question, to avoid confusion over answers to different questions in the same thread.

Your panels appear from your description to be two separate main distribution panels, and to each contain the first means of disconnect for its service. If so, each should have its own grounding electrode conductor, IIRC. Two separate ground rods and two separate bonds to the cold water inlet, with no bond between the two panels.

Inside each panel, the neutrals and grounds may share the same bus, or buses, which should be bonded to the enclosure.

Check the label on the inside of each panel door to see if it has any specific information regarding the number of wires under each screw on the buses. If not, then standard practice is only one neutral per screw, up to two grounds per screw, and no sharing of a screw by both a neutral and a ground.
 
  #3  
Old 01-06-13, 05:03 AM
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bond screw and ground wires

The previous inspector told us to ground both panels together and remove the bond screw, maybe because the panels are touching? Square D said we could put two ground wires under each screw. We planned to add two 6-screw ground bar kits, but the hardware store ownersays this is not preferable because of possible arc faulting. Couldtwo bare wires in the box also arc fault if not under a screw?So we bought one 20-screw and two 15-screw kits and will see whatfits our box. We had hoped to use two 6-screw kits with two wiresper screw, for 18 circuits.The other panel does not need a ground bar kit because neutrals andgrounds can use the shared bus (with bond screw) but the owner pointedout that if we fill all 20 breaker spaces there will be a neutral wireon each screw, so we will need to add another bar for the ground wires.2008 Code seems to require physical separation of neutral and groundwires (use two different rows of screws on the existing bus, or put thegrounds on an added bus).We should ask the current inspector about the bond screw (in case codehas changed) and two ground wires per screw. Too many opinions.
 
  #4  
Old 01-06-13, 09:47 AM
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Pictures of both the meter socket/sockets and panels would be helpful. You indicate a single 200 amp underground service with two 100 amp panels. I assume you have a single 200 amp rated 2-gang meter socket with each 100 amp position feeding independent 100 amp panels (are there 100 amp breaker disconnects at the meters? You don't say). In my opinion, one ground wire from the 2-gang socket neutral should attach to a ground rod, but each 100 amp panel should have their respective neutrals grounded to the water service entry through separate ground wires and clamps. Both separate panels should have the bonding screw installed. The only reason to remove a bonding screw would be if one panel was a subpanel and you have said that neither is. Again, in my opinion, it makes no difference if the two panels are touching. The only reason to add supplemental ground bars would be if there are too few holes in the respective neutral bars for both branch neutral and branch ground wires.
 
  #5  
Old 01-07-13, 06:20 PM
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bond screws and ground buses

Today I called the electrical inspector, who said my terminology was quite understandable. I said I had been practicing at forums and was learning that the same thing can have five names - main or service panel = breaker box, main breaker = disconnect, etc.

He agrees with the previous inspector that we can have only one bond screw, to avoid parallel grounds, with Square D that we can put two ground wires but not two neutral wires or a mix under one ground screw, and that the #6 and #8 ground wires as well as the smaller ones from the individual circuits need to be moved to the new ground bars. For 20 circuits we need 10 screws plus 2 additional screws for the larger wires, so we will put a 7 on each side (no holes for ground bars top or bottom). This is only the third time we will have redone the panel wiring.
 
  #6  
Old 01-07-13, 06:32 PM
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Please re-read and answer the questions in post #4.

In that post, as I understand it, CasualJoe has basically asked where the service entrance bond and the two main overcurrent protection devices are located. The proper way to set up your GEC (or pair of GECs) depends on that.
 
  #7  
Old 01-08-13, 05:26 AM
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bond screw and ground bus

Sorry, I wrote answers to those questions but they somehow failed to post. My partner who worked as an apprentice electrician and is coaching me on this is dyslexic (and also asleep). I am a science translator used to looking up jargon, but electricians seem to have an exceptionally large choice of terms for each concept.

Is 'service entrance bond' same as 'bond screw' or 'bonding jumper' in a main panel? Big green screw that connects the neutral bus to the metal case thereby grounding it (which I think means stray current goes to ground via the grounded case - but where would it go without a bond screw?). We have one bond screw in one of the two panels (closest to the meters).

Overcurrent protection device = circuit breaker
Main breakers are in the electric panels (breaker boxes).

GEC - grounding electric conductor - the big wires going to ground rod and metal pipe?

We have one 200A underground service feeding two meter sockets (?) one of which has a meter in it, the other not yet in use. The meters do not have disconnects (you can only disconnect by removing the meter). First meter feeds a general-lighting electric panel (on the left). The other will feed a time-of-day-rate panel (on the right closer to the meters ) for heat and hot water. Identical panels, with 100A main breakers (service disconnects) and space for 20 1-pole circuits. I am told in Michigan meters do not have separate disconnects and the disconnects are typically in the main panels.

The panels each have a neutral bus with two rows of 9 screws and one of 5 screws. Connected to the 5-screw row are the neutral (very large stranded bare wire) from the large cable entering from the meter (I think), and two large ground wires grounding the panels to copper pipe or ground rod, and to each other. There is no ground bus, possibly because this was not required in 1995 and possibly because we had not added any circuits when we got the main connection inspected in 1995. (We are building a house very very slowly).

Both the 1995 and the current inspector agree that the two panels should be grounded as one unit: #8 wire from 1" copper water pipe to the left meter, #6 wire between panels, #6 wire from right meter to ground rod. They also both said to remove the bond screw (aka bonding jumper) from the left panel to avoid a parallel ground. The hardware store owner agreed, but the licensed electrician thought we should add it back.

Code has changed since 1995 and we now need a separate ground bus (ground bar kits) for at least the panel without the bond screw (left panel), and since we cannot put more than one neutral wire on one screw, we need it for the other panel as well in order to have enough screws to attach the ground wires to. Two #10 or two #12 ground wires per screw are allowed in Square D QO ground bar kits, but only one neutral wire or one larger ground wire (#8 or larger). You cannot mix neutral and ground wires, or two sizes of ground wire, on one screw. Everyone agrees on this, but the hardware store owner thinks one ground wire per screw is somehow safer.

The inspector said to move the three larger ground wires (GECs, 2 per panel including the one between the two panels) to the new ground bar, along with the ground wires from the individual circuits. We have 8 1-pole (4 screws) and 1 2-pole breaker on each side - 5 screws, plus 2 GECs on one side. Since our panels accept ground bar kits only on the sides, and it is neater to keep ground wires on the same sides as the related breakers, we need a 5-screw kit on one side and a 7-screw kit on the other, as a minimum.

We can put two black wires in up to 4 of the 1-pole breakers (to avoid using junction boxes) since we will have 4 free screws on the neutral bus (5-screw row) after moving the larger ground wires to the ground bus. This would require up to 2 more ground screws per side, or a 7 plus a 9. Hardware store sells 7s or 15s, so will probably use 15s with one wire per screw.

I hope this makes sense - took an hour to write and will probably take several hours to rewire.
 

Last edited by sindikeesan; 01-08-13 at 05:35 AM. Reason: goofed
  #8  
Old 01-08-13, 05:18 PM
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We have one 200A underground service feeding two meter sockets (?) one of which has a meter in it, the other not yet in use
So, you have two totally separate meter sockets and two totally separate 100 amp main breaker panels. My opinion is that you have two totally separate and independent services and each should be treated the same. Each service should be connected to the appropriate ground rod and water service entry point. It shouldn't be necessary to connect the two services in any manner; they are two totally separate services.
 
  #9  
Old 01-08-13, 07:27 PM
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bond screw and ground bus

Two inspectors want us to ground the two panels together and to ground one to the water pipe and one to the ground rod, rather than ground each individually to avoid a parallel ground. Local hardware store owner agreed.

Maybe your suggestion is also legal but we need to pass inspection here.
 
  #10  
Old 01-08-13, 07:37 PM
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Either the story being painted is incorrect or the inspector is I'll informed. I too think this is two services fed from one socket. Both need to be bonded along with the connection to the rods and water grounds.

Sindi, you and your help continue to exhibit that you need professional help for this project. There is too much at stake to continue down this path.
 
  #11  
Old 01-09-13, 06:53 AM
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bond screw and ground bus

This is one 200A service feeding TWO (meter) sockets, says my partner. On the inside of the house it is two services. You have to size the ground according to the largest feed. So our first service panel in line is grounded as 200A with #6, and the other as 100A with #8 wire. We think it best to do what the two inspectors want. They don't want a parallel ground.

The electric company gave us two separate meter boxes each with one socket (rather than one box with two sockets which they are doing nowadays). We had to jumper the two boxes.

The 200A service (underground) feeds the meter in the socket for the general-lighting service panel, and from that meter the wires go to the time-of-day-rate socket (which has no meter yet).

Each of the two service panels has a 100A main breaker.

The time-of-day-rate panel is physically closer to the ground rod and the meters (on the right nearest the outside wall) but electric company chose to put the meter for the other panel on the right, to help confuse things. We grounded the panel nearest the ground rod (time-of-day rate), on the right, to the ground rod, with #6 wire suitable for 200A, and the other panel, on the left, to the water pipe, with #8 wire for 100A, as specifically instructed by the inspector. And grounded the two panels together with #6.
And removed the bond screw on the left-most general-lighting panel, also as instructed.

The only thing we are supposed to do differently now to meet changed code is to add ground bar kits (buses) to both panels and move to them all the ground wires (for circuits and also the ones going to ground rod, water pipe, and between panels)

Also we should not mix white and bare wires or two sizes of bare wire, or put two bare wires larger than #10 on one screw.
 
  #12  
Old 01-09-13, 08:54 AM
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Again, the instruction you have received are wrong and do not follow the NEC. You have not listened to the questions or advice here nor the other site so I will not waste any more time.
 
  #13  
Old 01-09-13, 06:25 PM
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I am a science translator used to looking up jargon, but electricians seem to have an exceptionally large choice of terms for each concept.
As an experienced researcher, I'm sure you're aware that it helps to go to the best source. If you want to know what specific words, terms and phrases mean in the electrical field, you need to refer to Article 100 of the National Electrical Code: Definitions.

Is 'service entrance bond' same as 'bond screw' or 'bonding jumper' in a main panel? Big green screw that connects the neutral bus to the metal case thereby grounding it (which I think means stray current goes to ground via the grounded case - but where would it go without a bond screw?). We have one bond screw in one of the two panels (closest to the meters).
No. The service entrance bond is the mechanical connection of the grounded conductor from the utility to the grounding electrode conductor established on the site. This bond is made at each service entrance, and should be located in the same enclosure as the main overcurrent protection device. It may be made with any number of mechanical means, including screws and clamps, but does not include either a bond screw or a bonding jumper. A common method in residential services is to connect both the utility, or service neutral (the grounded conductor) and the GEC to the same bus bar.

After the service entrance bond is created, all metal parts of the service are bonded to the GEC. This is where bond screws, jumpers and similar devices are used. This is also where you start to create your EGC - your Equipment Grounding Conductor - system, as you tie in the ground wires that run to all of the devices in your house.

You have two separate 100A services. Each could serve a separate dwelling unit as easily as they can serve two different rates paid under a single account. Take a look at the meter bank behind a local strip mall and try to imagine that, because those are all fed from one set of feeders, they are all one service.

That means that
Originally Posted by CasualJoe
Each service should be connected to the appropriate ground rod and water service entry point. It shouldn't be necessary to connect the two services in any manner; they are two totally separate services.
In fact, tying them together would create the "parallel grounds," or parallel paths to ground, that one of your inspectors cautioned you to avoid. Worse, it would allow any power that needed an emergency path to ground to cross from one panel to the other. That does not follow the NEC, as pcboss said.

Sindi, you have had at least three qualified electricians advising you on this, including one licensed master that I know of. We easily have more than 100 years of combined experience in the field, and we do not fail inspections. Our opinions on your service are in consensus. If you choose not to listen to us, or to believe that we don't know what we're talking about, that's OK. It's your house, your service and your liability, not ours.

If you have any questions about the best way to implement the design we have suggested, please post back with those.
 
  #14  
Old 01-10-13, 02:06 PM
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Bond screw and ground bus

I will go over your posts with my partner tonight (busy wiring right now) and we will probably NOT move the larger ground wires to the new ground buses (yet), and will make it very clear during rough inspection how the panels were grounded and confirm that the inspector wants it done the way we think he said and not the way you all said to do it, as two separate services each with bond screw and each grounded to water pipe and ground rod. We will still put in ground bars and move the individual (smaller) ground wires to them.
 
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Old 01-10-13, 03:27 PM
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I will go over your posts with my partner tonight (busy wiring right now) and we will probably NOT move the larger ground wires to the new ground buses (yet)
Did we suggest that? IIRC, what we have consistently said is that, in each panel, the combination ground and neutral bus that came with each panel should have the utility neutral, a large copper connector to the cold water intake, and a large copper connector to a ground rod for that panel terminated to it. Terminating those three conductors - one grounded and two grounding - to that single bus bar establishes and completes the service entrance bond for that panel. All bonding and connecting beyond that is part of completing the EGC system, a low-impedance path to ground that is required as a safety provision inside the house.

We will still put in ground bars and move the individual (smaller) ground wires to them.
Yes, those are necessary steps in completing your EGC system, as I just said. We covered the best way to terminate the individual conductors early in this thread, but I don't remember that we talked much about methods for mounting the additional bars. Here's what we do at work:

After bonding the factory ground/neutral bus to the enclosure, we mark the footprint of the additional bus bar on the inside of the can. Then we use a wire brush mounted in a drill to remove all of the paint within that outline. We mount the new bus bar there, using the screws that came with it. We make a jumper out of a short piece of the conductor used to bond to the ground rods and the cold water inlet to the original bus bar, and use that to bond the additional bus to it. That way, the original combo bus, the added one and the enclosure are all bonded together two ways.
 
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Old 01-10-13, 06:03 PM
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This is one 200A service feeding TWO (meter) sockets, says my partner.
I'd like to see this, can you post a picture of the two separate meter sockets? I'd like to see how you terminate a 200 amp service lateral to two 100 amp meter sockets. Even if you are using 200 amp rated meter sockets, I'd like to see it.
 
  #17  
Old 01-10-13, 07:45 PM
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I am seeing a 200 amp cable into the socket with two 100 amp tails out to two service panels. A picture is going to be the only way to get this straightened out. The OP does not have the knowledge or terminology down to explain this.

This is for reference:

Owner-builder electrical questions - InterNACHI Inspection Forum
 
  #18  
Old 01-10-13, 08:40 PM
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Thanks for the reference. I was wondering what you meant when you said
Originally Posted by pcboss
You have not listened to the questions or advice here nor the other site...
Now I know.

Answer shopping? . . . . Yep.
 
  #19  
Old 02-08-13, 07:43 PM
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Two panels with main breakers and separate meters; time-of-day heat/hot water

Sorry, have not checked this site recently.

We have wired the downstairs lights and switches, the outside, cellar, crawlspace, porch and attic outlets and lights and motion sensors, and the downstairs outlets that won't be surface wired on exterior walls (after the skim coat of thinset over cement board cures).
One room has four 3-way and one 4-way switch and got mixed up a bit until we learned to label both ends of cables with colored tape (blue and yellow) and individual wires with black, white or red. We have 12 3-way switches in three rooms and a stairway, and paired motion sensors.

Next steps are smoke detectors and baseboard heaters, doorbell, phone, ethernet.

A friend who is an electrician will stop by soon and look at our work and make sure the panels are properly grounded and things are properly wired (they all work, and we used an outlet tester). Thanks for instructions how to add ground bars - We did not remove paint from the box, or run a #6 or #8 ground wire between the two ground bars, and will ask him about that (since I think removing the bonding screw was supposed to separate the connection between things - will also ask the inspector). We left all but the smaller ground wires to the circuits on the original bus.

I don't have a photo of the meter boxes. The 200A service goes to one meter socket with a meter in it (the other is still empty) and the cable from there to the one box that is already in use. We have not wired the time of day box .
yet for 30 gal 240V water heater or 120V hydronic baseboard heaters.

We will wire the water heater with a 120V relay to be used with a 120V mechanical timer and also a 24-hour in-wall timer (for time-of-day meter). The second timer has to be ON for the first one to work, i. e., to take a shower, you wait until after 7 pm then turn the first timer to 10 or 15 minutes and it heats the top third of the tank. This reduces standby losses. In winter the water heater can be on continuously and heat the bathroom in mid-day as it loses heat. (storage heater)

We may also use one timer per space heater, in series with a cheap non-programmable line-voltage thermostat, to turn off the heat automatically from 11 am to 7 pm. Since we have R-35 in the walls and about R-60 in the ceiling it won't cool much.

The timers use about 3W each but in non-heating weather we can simply turn off the breakers to the heat circuits.

The Tork 711AA 24-hour mechanical timer is currently about $6 at ebay, and the cheapest line-voltage thermostat $5. A programmable one is currently at least $25 and all I need is timed on/off. Do mechanical timers wear out faster than programmable thermostats?
The Tork can go on/off every 30 min 48 times a day. It goes up to 15A. There is a 701A for 20A. Our heaters will be 1000W or 1250W and could go on a 15A circuit, but we have lots of 20A single-pole breakers left over from replacing them with GFCI and AFCI breakers when code changed. Can we put them on a 20A circuit (No. 12 wire) and still use a 15A timer?

The water heater will be used with a 120V relay which is low amperage and should be okay with the 15A timer.

Any suggestions for better ways to minimize heat and hot water bills?
(Last summer I washed with water from a black rain barrel but hopefully future summers won't be in the 90s more than half of the time).
 
  #20  
Old 02-09-13, 06:54 AM
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We did not remove paint from the box, or run a #6 or #8 ground wire between the two ground bars, and will ask him about that (since I think removing the bonding screw was supposed to separate the connection between things
I still think the bonding screws need to be installed. I am not seeing how the panel boxes and the neutral conductors can be properly grounded with the bond removed. As I recall, neither are subpanels.

I don't have a photo of the meter boxes.
I'd still like to see a picture. BTW, what is your total load calculated to go on the time-of-day panel?
 
  #21  
Old 02-09-13, 08:18 AM
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two panels with separate meters (time-of-day)

The inspector said to leave the bonding screw out, move the smaller grounds to the ground bar, leave the others, and let him look at it before we made any other changes.

100A Time of day panel will control:

1) 30 gal electric water heater (240V 30A breaker, rated at 20A)

2) 7 electric space heaters of 500-1500A each, 120V, probably one per circuit unless it is easier to wire two on some circuits (500+750). 20A breakers. Total calculated heat load at 0F out 70F in -- just over 2000W (sic) but all the heat will go on at once if programmed to be off during peak hours (except bathrooms - fan forced wall heaters). Electric hydronic baseboard 1000 + 1000 + 750 + 750 + 500 = 4000W, and bathroom another 3000 which theoretically could all be on at one time if two people shower at 7 pm.
7000W = 60A

3) HRV with fan (under 100W) - 240V probably 15A breaker. This could just as well go on the main panel but we have more room on this one. I don't plan to run it at all during the summer, when the on-peak rates are much higher, because the windows will be open at night and I will cook on the enclosed porch in hot weather and take showers after opening up (or with the bathroom window open). If a future owner wants to add air conditioning they can get another meter for that and move the HRV to that panel.

About 80A total. We might add a whole-house fan circuit to the panel.

The other 100A panel has 50A breaker for stove, 30A for electric dryer, and several each lighting and outlet circuits. 960 sq ft house. Our current house is 900 sq ft with 60A service (four circuits). And plug-in electric heat, electric stove, electric hot water - works.
 
  #22  
Old 02-09-13, 10:34 AM
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You still have two separate service entrances. Each should be bonded and grounded as though it was the only service entrance on the property.

That means a separate GEC for each service, with the GEC, the utility neutral and the internal EGCs bonded together and to the panel enclosure and no connection between the two services.

If your inspector thinks differently, it would be interesting to hear his reasoning and/or code references.
 
  #23  
Old 02-09-13, 01:05 PM
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The inspector said to leave the bonding screw out, move the smaller grounds to the ground bar
Assuming the neutral is correctly grounded, the panel box, ground bar and smaller branch circuit grounds will not be grounded. You have a definite problem and have been told how to correct it by qualified individuals. You are asking for advice, but evidently you aren't getting what you want to hear. If you want to hear that your method is correct, you'll have to seek yet a third forum.
 
  #24  
Old 02-09-13, 08:25 PM
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Just to highlight something:
You have a definite problem and have been told how to correct it by qualified individuals. You are asking for advice, but evidently you aren't getting what you want to hear. If you want to hear that your method is correct, you'll have to seek yet a third forum.
 
  #25  
Old 02-13-13, 01:14 PM
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Grounding two panels with two meters

A licensed electrician (who sings in the same madrigal group) just spent 30 min poking around our electric panels with a meter and says everything is correctly wired/grounded except that he thinks we should add a wire (#12 is okay) between the new ground bars and the neutral bars. He will straighten out the wires so the inspector can see what goes where - it looks amateur but is all up to code.

My friend who did the actual wiring understood the explanations of parallel service and ground loops. We have one large meter box with a meter in it, and a smaller box connected to it without a meter in it. We have not one 200A service but a 200A cable coming from underground that goes into the first meter and splits there into two 100A services one of which goes to another meter, and each meter feeds a separate 100A breaker panel.

Removing the bonding screw was to prevent a ground loop - one grounding path only.

My engineer friend doing the wiring said the inspector told him that we should NOT put a bonding wire (or bonding screw) between the ground bar and the neutral in our non-time-of-day box..

My camera battery just went dead so no photo.

We have wired the downstairs except for heat, hot water, and low-voltage, and are running wires upstairs that will be connected later so we can put on the downstairs ceiling.

My electrician friend admired the soundproofing and reminded us to leave 6" wire in each box and said the wires in the wall do not have to look neat (we left an extra foot or two in each run in case we decided to move something later). I have to go help decide where to put a 3/4" hole to run smoke alarm, lighting, and heating feeds upstairs. We have managed to find routes that do not go through ventilation ducts (fire risk), smoke alarm locations not near bathroom humidity, heater locations not under outlets or blocked by doors or furniture, thermostat locations away from drafts, and light fixture locations not in a soundproof ceiling. We have three smoke alarms up already, wearing pink shower caps to keep out the cement dust.
 
  #26  
Old 02-19-13, 12:28 PM
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14-2 and 10-2 black wire with small ground

We have two sizes of black NM cable in which the ground wire is smaller than the white or black wires. Is it legal to use this for lighting (14-2) or for a grounded water heater (10-2)?

We are putting each space heater on its own 20A circuit (though they are only 500W-1000W and we could combine heaters up to 1750A on one circuit). That way a future owner could put in a larger heater.
 
  #27  
Old 02-19-13, 09:13 PM
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Yes, the cable with the smaller wire for the EGC is legal in most jurisdictions. Ask your inspector if that is true where you are.

OTOH, how old is this cable? 14 AWG Type NM-b cable has been white for several decades, and 10 AWG Type NM-b has been orange for about 15 years.

We are putting each space heater on its own 20A circuit (though they are only 500W-1000W and we could combine heaters up to 1750A on one circuit).
A 20A circuit can supply up to 1,920 amps as a continuous load.
 
  #28  
Old 02-20-13, 05:27 AM
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NM cable with smaller ground wire

I don't know how old our cable is but we have been building since 1986 and collecting materials since then, so it could be 30 years old.

We had No. 14 wire not only in black with smaller ground (NM not NM-B) but in white and blue, some of it round rather than flat (14-3). All our No. 12 wire was white.

A local electrician said the smaller ground is okay but I will ask the inspector unless there is some easy way to check in the code book (Michigan uses IRC 2009). We pulled out the black 14-2 we had put in but have more wiring to do and would like to use it. The friend doing the wiring thinks it should be okay for the water heater, which will be already grounded to copper piping.

The black 10-2 is labelled NM not NM-B - does this mean it is 60 C not 90 C wire and if so is it okay for the water heater, which uses 20A of power (on 30A breaker)? One of our space heaters calls for 90 C and the other for 'standard or 60C) wire.

We decided to put all the space heaters on separate circuits (and use more wire but avoid junction boxes in the crawlspace) in case a future owner wants larger heaters. The possible combinations were 750+750 (they might change to two 1000s) and 200 + 1500 (they might replace 200 with 500). Two more wires to pull and hook up to breakers but two less junction boxes to wire and probably safer this way.

Yesterday we came up with a complicated way to combine the outlets in both bathrooms without a separate junction box by going upstairs then downstairs through conduit hidden behind window trim. It helps that my 'electrician' is also the 'carpenter' and likes to be inventive. There was plumbing and ventilation in the way of doing it any other way we could think of except through the downstairs bathroom floor, which is sloped and supposed to serve as a handicapped shower so should not be penetrated. As we understand it, you can run two 12-2 wires through 1/2" conduit if they physically fit and if one end of the conduit is open (which it will be in the ceiling). Correct? The other wire is the laundry circuit (also going upstairs then downstairs because one end of a potential future bedroom will also be a potential upstairs laundry area if we ever get the upstairs done, and in the meantime a downstairs laundry area in the bathroom is required for a CO).
 
  #29  
Old 02-20-13, 10:26 AM
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I would not waste the time or effort in install wiring that far out of date. The code requirements have changed for the EGC sizing. The old cable with the undersized EGC is scrap.
 
  #30  
Old 02-20-13, 05:42 PM
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old wire in new boxes

Thanks, we will replace the 10-2 with newer 10-2.

I just learned that we need to calculate the sizes of all our electrical boxes, assigning 1 point for each hot wire, 1 for all the grounds, 2 per outlet or switch, and 1 per interior cable clamp, then multiply by 2 (for No. 14) or 2.25 (for No. 12) wire for the number of cubic inches. Boxes are rated for fewer cubic inches than their exterior dimensions. 2x2x4 is rated about 14 not 16 cu inches. This means any boxes with 2 cables going into them need to be fairly large, such as a 3.5" deep box inside the wall, a 4x4x1.5" box on the surface, or a wiremold box (which is wider than a handybox. 14-2 + 14-3 plus two switches = (2 + 3 + 1 + 2 + 2) x 2 = 20 cu inches, too much for a handybox. One more thing to calculate besides number of fixtures per circuit, and a few boxes to replace before inspection.

(Pun on old wine in new bottles).
 
  #31  
Old 09-03-13, 08:43 AM
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passed inspection

July 9 electrical inspector came out for rough inspection. Three of us were there - me, friend who did most of the wiring, and friend who rewired first and wired second main panel.
The latter (who is a retired electrician and used to teach wiring at a junior college) observed that the big green screw that we had been told to remove was present in both boxes so this whole issue is moot. The green had tarnished to brown since 1995. We passed on the first try but are required to add a second grounding rod connected to the first with No. 8 wire, at least 6' away, because code has changed, and I can hook up the second panel for time-of-day service when I need to heat in December.

The inspector hardly looked at anything, including several pages of CAD wiring plans, having apparently realized that we are trying to do things right. He did make sure we knew to put outlets every 4' over countertops.

Low-voltage wiring does not need inspection - phones, internet, doorbells (we will have several bells and buttons so that you can ring either floor from either door, and turn off the bells in each room if you want to sleep, since this is a soundproof house). We also plan on an LED house number that reads the same from both front and back (512 in computer numbers) and little lights to show when each of five doors is locked (in several colors of light, using a switch triggered by locking the door). Also a remote-controlled porch door lock (I forget the terminology). They use various DC voltages so will need to adjust down from the main 12V or 24V. We also want to add a sensor and LED light to keep the porch motion sensor lights from going on on cloudy days.
 
  #32  
Old 09-03-13, 09:55 AM
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Good to read the outcome. Thanks for updating us.
 
  #33  
Old 09-03-13, 11:16 AM
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...but are required to add a second grounding rod connected to the first with No. 8 wire, at least 6' away,...
Are you certain that is what the inspector wants? Under the NEC any grounding electrode wire in a size smaller than #6 requires additional mechanical protection.



Low-voltage wiring does not need inspection...
Perhaps not in your local jurisdiction but many jurisdictions DO require permitting and inspection of low-voltage wiring, including alarm, telephone, television, data and any other signalling and/or control wiring.
 
  #34  
Old 09-03-13, 11:20 AM
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Under the NEC any grounding electrode wire in a size smaller than #6 requires additional mechanical protection.
Also, the conductor from the ground rods must be continuous. It can't break at the first rod.

many jurisdictions DO require permitting and inspection of low-voltage wiring, including alarm, telephone, television, data and any other signalling and/or control wiring.
The ones here do.
 
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