Cutler Hammer Service Panel circa 1960

[John Ross]

Cutler Hammer Main Service Panel circa 1960.

Is anyone familiar with these main service panels from that time?

This is a 100 amp service with breakers.

I had some receptacles grounded by running the ground wires back to panel. I had assumed these panels just had a neutral bus and everything was put on that since there were not that many grounds. Indeed, on the top is a horizontal bus that is basically a round piece of copper (like a straw), and all the neutral/ground wires (incuding main house ground) are wrapped around the bar--no screws.

I was surprised when I saw the electrician putting the new grounds on another bus. This one is lower in the panel (also horizontal) and looks like a flat peg board, but this had screws for connections. I didn't get a good look, but it didn't look like there was any wires on it.

Now that I am thinking about this, I am wondering if the two buses are bonded.

In the late 60s or early 70s a central AC/Heater unit was added and they used aluminum wire for it. So now I am wondering if it is more likely that the bus bar with the screws was original or is it more likely it was added when they did the Air conditioning wiring? I was distracted so I am not sure, but I did see a piece of alumium wire around there, but not sure if it was to the breaker or to that bar.

Anyway, has anyone seen this type of Cutler Hammer panel from 1960? What would your take on this be? IF both buses were original, would they have been bonded even though only the top one was used? If the second was added, would the design be such that it would be bonded via the case of the panel?

Obviously, I am new to this stuff, but I hope I was able to describe it, even if I didn't use the correct terms.

-- John

[RBM]

I'm not exactly sure about your descriptions, however there was probably only one neutral\\ground buss in the panel. There should be a bonding screw or jumper attaching the box to the buss. Sometimes it's hard to see through all the wires. Another buss may have been added at a later date, which is fine.

[hallerb]

have you checked ALL outlets in your home for proper grounding both with that plug in tester AND running a 100 watt lamp between hot and GROUND. This will tell you a LOT, about your wiring and doesnt require disturbing ANYTHING!

Its possible for a test lamp to say fine while a 100 watt bulb will glow dimly if at all:)

[John Ross]

So you are saying that if it did originally just have that ONE buss, it would have been connected (by screw or whatever) to the inside of the PANEL? Is this required to ground the actual panel box?

Furthermore, if another bus was indeed added later, then all that was necessary to bond the two was for the second one to make contact with the metal of the panel?

-- John

[John Ross]

The only tester I have is one of those simple plug in things with 2 amber lights and a red one, where they light up or not depending on if there is or isn't a problem.

If I plug that into these outlets, it shows "correct" (i.e. it does indicate a ground).

So, remember, these are connected to the bus bar that does NOT have the main ground for house connected to it. So if the two buses are not bonded, there would be absolutely no grounding for these receps. Would this type of tester show no ground if the ground wire from recep went to the panel and connected to a "ground bus" that had no connection to ground?

I honestly don't get how these testers determine ground, and was wondering how meaningful they were for this sort of situation.

-- John

[Mark Lloyd]

It would have to run a little current through that ground wire. Of course a ground that can handle a neon bulb to two might not handle a

20A ground fault.

BTW, if ground is missing the tester cannot recognize a hot/neutral reversal.

[RBM]

The original buss bar is isolated. A bonding screw or jumper needs to be installed to bond it to the box. This is done for a main service panel, but not a sub panel. Unless you know what to look for and where to look, you may not find it through all the wires. If an additional ground buss is added, it gets screwed or bolted to the panel and becomes part of the grounding system. If you want to connect neutral conductors to it as well, I would run a substantial conductor from it to the original neutral buss

[John Ross]

Not trying to get on your nerves. :)

You kinda lost me with the mention of the "grounding system". IF the panel originally did just have the one bus, used for neutrals and grounds (including main ground), would they have bonded it to the box as you described? I'm still trying to understand if the panel box itself is required to be grounded. Because, if it isn't, why would they bother to bond this to the box (if there was no other bus bar)?

As far as the neutrals, none were added to that other bar--just the new ground wires.

Can this all be determined at the *outlet* by someone if the correct meters were used? In other words, all that has to be determined is if there is a legitimate ground present (the neutrals are not an issue). So if someone who knows what they were doing took a reading from H to G (or whatever you suggest) at the outlet, would the readings (i.e. volts) indicate there is or isn't a legitimate ground? Can that be done?

Thanks!

-- John

[RBM]

At service panels, grounds and neutrals are bonded together. At sub panels they are not. The bonding jumper comes with the panel, but it's up to the electrician to install it if necessary. In your situation it should be installed. If you test your outlet from hot to ground, and get a 120 volt reading, the outlet should be grounded.

[John Ross]

I just read somewhere else about using a 100 watt bulb as a tester in the way you described. Is this a product that can be bought, or a home made type of thing?

-- John