Zinsco is gone!

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charlie b

charlie b

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Lockport, IL
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Semi-Retired Electrical Engineer
I have posted several messages on this topic, and am happy to report that I am finally rid of that monster. The electrical contractor replaced it yesterday, and resolved a number of minor problem areas throughout the house. But he didn't have time to get to everything.

One item he didn't get around to is to install a GFCI breaker (2-pole) for the branch circuit feeding the hot tub. Afterwards, we discussed this, and I'd like opinions on what he told me.

He said that the circuit only had two hots and an EGC (no neutral wire). Apparently, all heater and motor loads must be 240 volt, and the tub's lights must be fed by a step down transformer. He then said that he could not hook up a GFCI breaker, because there would be no way to connect the neutral pigtail attached to a GFCI breaker.

I would think that a GFCI breaker would operate properly, even without a neutral connection. Any difference between the current in the two hot wires should cause a trip. Should I call him back in to change out the breaker, or would it be of no use?
 
It will work fine. Just connect the pigtail to the neutral bar in the panel. The neutral terminal on the breaker is for loads that require a neutral connection.
 
The two pole GFCI breaker requires its neutral pigtail to be connected to the panelboard neutral. When a 240 volt load with no neutral is connected, in turn, to the load terminals of the GFCI breaker, every thing is fine, and all's right with the world.

In this configuration, all the breaker neutral pigtail does is provide for the breaker GFCI electronics. . .nothing more. This is essential, however, for the operation of the GFCI.

When a load with a neutral is connected to the breaker, then the neutral pigtail provides for the GFCI electronics and also carries any load unbalance current, after the current has passed through the breaker GFCI sensor, from the breaker to the panelboard neutral.
 
Charlie
Are you operating on the lowest price is best because the work will all be the same anyway theory? If your guy isn't proficient with the two pole GFCI's, can you rest easily with the other work he has done?
 
I spoke with him this morning. I had misunderstood what he had said earlier. He knew about connecting the pigtail to the panel's neutral bar. But he said the 2-pole GFCI breaker has connection points on the load side for two ungrounded conductors and one grounded conductor. He believed that if you had a 240 volt load that did not also use the neutral, so that there was no neutral wire to attach to the GFCI breaker, then the GFCI would not be able to function.

I suspect he is wrong about that. I think the GFCI would detect a difference in current between the two ungrounded conductors, and would trip. Comments?
al hildenbrand said:
When a 240 volt load with no neutral is connected, in turn, to the load terminals of the GFCI breaker, every thing is fine, and all's right with the world.
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I see that you agree with my view.
 
bjp_ne_elec said:
Did he have his other work inspected?
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The Inspector is scheduled to come by within the next two days.
stars13bars2 said:
Are you operating on the "lowest price is best because the work will all be the same anyway" theory?
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I don't think so, not with a price tag over $4K for the total work package. I don't know how that number looks to electrical contractors, but to a home-ower it is a big number.

Along with replacement of the service panel, he gave me GFCI receptacles for the kitchen countertops (fixing one existing code violation), ran two new circuits for the dishwasher and disposal (they were on the same circuit as kitchen countertop receptacles ? another existing code violation), rewired the water heater (it had #12 NM from a junction box to the heater, with a 30 amp branch circuit ? another existing code violation), and fixed the code violation that I described in this thread: http://www.mikeholt.com/codeForum/viewtopic.php?t=10144&highlight=
 
Perhaps a document would be helpful?

Read page three of this four page Cutler Hammer .pdf document and you will find the following quote:
Double pole GFCIs are designed for use in 3-wire, 120/240V ac circuits, 120v ac multi-wire circuits employing common, neutral and 2-wire, 240V ac circuits obtained from a 120/240V source.
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Comparable documentation is available with other manufacturers.
 
It is my understanding that the two ungrounded and the one grounded conductors all three run through a CT (or something similar). As long as there is no fault, no current will be developed in the CT. If the CT develops a current, the breaker trips.

A 240-volt load with a small fault will cause current in the CT.
 
Just to put a close to the story:
bjp_ne_elec said:
Did he have his other work inspected?
Click to expand...
The Inspector came yesterday, and passed the installation.

As a new home-ower, I have to control my spending by spreading out all the "projects" over a long period of time. But getting someone to install a GFCI breaker for the hot tub is going to go high on the list.

Many thanks for the information.
 
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