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Discussion Starter · #1 ·
Last Friday I parked the Volt in my carport and plugged it into the same 120v outlet that I have been using for the last month. An hour later the house experienced a power surge. Seeing that a pair of (ganged) 70 amp circuit breakers that feed the sub panel in the carport had tripped, I went to the carport. There I smelled smoke and saw that a slot, 1 1/2" long and 1/4" wide, had been burned through the steel faceplate of the sub panel.

When the responding fire fighters removed that faceplate we saw that a feed wire had partially melted its insulation and had completely burned through under the slot.

My electrician replaced the burned out feed wire (black, No. 6 size) and determined that the failed wire had been
supplying not only the Volt's outlet, but two air conditioning units, resulting in an imbalance, such that the black side of the circuit was carrying almost 20 amps more current than the red side. The Volt's outlet has now been re-wired to the red side and I have used it for an uneventful charge cycle.

I certainly do not blame the Volt in any way, as it was simply the (big) straw that broke the back of the electical system. Clearly I had too much on one circuit. No one, so far, has been able to tell me why the feed wire burn through occured prior to the circuit breakers opening.

I plan to have an independent electrician review all circuit loads and I offer this only as a cautionary tale to other Volt owners and welcome feedback from this group.
 

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Having a dedicated circuit for charging your car is a cautious step I recommend to anyone planning on charging an electric car.

I created two new circuits in my garage for car charging. A 240 circuit, wired for 30 A, but with a 20 A breaker. The 240 v circuit has an secondary disconnect between the breaker and the Voltec charger station.

I also added a 15 A 110 circuit, for charging with the portable charge cord. The new 110 v circuit has also improved flexibility for tools and appliances, like running the vacuum cleaner.

WVhybrid
 

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I have a 40A 240V subpanel that only feeds the Volt. I did also put a 120V 20A off each sided of the feed to run my comprssor and/or add as a 120V charge circuit in case the 220 unit fails. Also added in a surger supressor and TED to monitor power usage by the Volt.
 

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I for one don't appreciate the shock headline of your post. Are you trying to be like Fox News?

It should read -- I melted some wires and a fuse in my fuse box by overloading my circuits because of incompetent electricians.

Anyone looking at your headline would think the whole car port was destroyed along with your Volt.
 

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I for one don't appreciate the shock headline of your post. Are you trying to be like Fox News?

It should read -- I melted some wires and a fuse in my fuse box by overloading my circuits because of incompetent electricians.
I thought the title was fine and found the subject very interesting. Obviously YMMV.
 

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Two electric circuits using a common neutral must be supplied from two breakers that are on different 120 volt mains. Having a dedicated circuit breaker with a separate hot, neutral and ground wire from the breaker panel to the outlet will avoid the problem.

This issue is critical because X-10 home automation can fail when circuits are on different sides of the two 120 volt mains. Switching the wires in the circuit breaker panel is an easy fix, but can be a disaster if common neutrals are used and two circuits use the same neutral with both breakers on the same main. If one is a hair dryer and the other a toaster, the neutral will overload when both devices are on.

Because former owners of a home may have switched wires in the circuit breaker panel, it is wise to have an electrician check for this as part of home inspection or when adding any high amperage appliance to a 120 volt circuit where the panel has not been checked.
 

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70 amp circuit breakers...black, No. 6 size

I plan to have an independent electrician review all circuit loads
Using http://www.electrician2.com/calculators/wireocpd_ver_1.html and plugging in 50 amps of continuous load shows a 70amp breaker and #4 wire should be used. And if you raise the ambient temperature drop down box or click the box for feeding branch circuits the wire size gets even bigger. I think your plan to have another electrician review this installation is wise. You may have wire that is too small or the 70 amp breaker may be too big.
 
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Glad to hear that was the only extent of the damage and you and your Volt are all right Bill!

Volt Advisor Trevor
Chevrolet Volt Advisor Team
 

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I was charging our Volt in one of the garage outlets for the past month. Everything was fine until one hot day when the central A/C came on while the Volt was charging. About an hour into using both, a breaker tripped and both died. When I poked around, I found that the furnace/air handler shares the same 15 amp breaker as all of the power to the garage.

The house was built in 1984 and the electrician I called said that code allowed that back then. I had him wire a dedicated outlet to a 20 amp 120v circuit and all is well. Of course, the weather has been cool ever since :) He also found that ground from PG&E had broken off, causing my lights to flicker, and it's good that I had ground from the PV system.
 

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Two electric circuits using a common neutral must be supplied from two breakers that are on different 120 volt mains. Having a dedicated circuit breaker with a separate hot, neutral and ground wire from the breaker panel to the outlet will avoid the problem.

This issue is critical because X-10 home automation can fail when circuits are on different sides of the two 120 volt mains. Switching the wires in the circuit breaker panel is an easy fix, but can be a disaster if common neutrals are used and two circuits use the same neutral with both breakers on the same main. If one is a hair dryer and the other a toaster, the neutral will overload when both devices are on.

Because former owners of a home may have switched wires in the circuit breaker panel, it is wise to have an electrician check for this as part of home inspection or when adding any high amperage appliance to a 120 volt circuit where the panel has not been checked.
Common neturals are apotential problem when the load is not ballenced between the phases, and you can get up to double the normal voltage to a circuit if that common netural failes.
 

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Discussion Starter · #13 · (Edited)
Follow Up: Member 719 was indeed correct in that my 6 gauge feed wires were too small for the subpanel load. I have upgraded to 4 gauge wires which the electricians say are good for 85-90 amps. To be conservative I have kept the original 70 amp circuit breaker that protects these wires and also downgauged the breaker that protects the Voltec Charge Cord outlet from 20 to 15 amps (in accordance with the recommendations that come with the cord set).

Bil R.
 

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Last night I found out how bad the wiring really is in my parents' house.
The breaker for the whole house tripped while I was charging last night, leaving the other buildings still powered. It was a 60 amp breaker for the whole house, which powers everything significant such as the 240v dryer, the 240v air conditioner, the 240v oven and the 240v range, and everything 120v such as the plug in the carport where my Volt was charging from.
At the time it tripped, we were using the air conditioner, plus grilling steaks on the electric range, had 2 desktop computers running, a fan or 2, the TV, aquarium, numerous lights, and my Volt was charging. We might consider the Volt the straw the broke the camel's back in a sense. (The Volt's load wasn't significant compared to the A/C or the range.)
Plus side: the steaks came out better from having cooked slower from the power being out for a while. :)
The 240v 60A double breaker had to cool down before I could get it to turn back on. When I did turn it back on, there was power to everything except the living room and one bedroom. One of the sides of that double breaker didn't engage.
The house is loaded very unevenly. The living rm and one bedroom is on one branch while everything else 120v is on the other branch. I will need to have the breakers rearranged to load evenly. I'll probably put the carport on the less loaded branch so my Volt can't be blamed for tripping a breaker, plus replace the main 60a breaker since it is kindof worn out and the side that was barely loaded, wouldn't engage easily.
I'm still concerned that they might run the dryer, A/C, and oven or range simultaneously tripping this breaker again, without my Volt even being in the equation. And most outlets are not grounded. At least the carport outlet that I recently replaced is, so my Volt 120v charger doesn't reject this particular outlet.
 

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First of all, I'm glad the problem did not result in a fire. So if the meltdown was caused by an inbalance between the two phases, would this have been averted if a 240 VAC charger was used?

The second unrelated thought I had is the emergence of EVs will place a heavy demand on residential wiring, so it may be a good idea to have it professionally checked by an electrician to make sure it is safe before bringing the EV home. Finally, this makes me wonder about the suitability of the future "perfect" battery that will hold a 300 mile charge and be capable of being charged in a few hours.
 

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So if the meltdown was caused by an inbalance between the two phases, would this have been averted if a 240 VAC charger was used?
I'm not sure if you are asking me about the event at my parents' or if you're asking Bill R. who started this thread . . .
But probably in both cases it would depend.
In both cases it was a sub-breaker box that one of the 2 branches was overloaded. The 240v charger loads both branches evenly. If the 240v charger was wired to a breaker in that sub breaker box, it would be loading the branch overloaded by the 2 air conditioners by about the same amount that the 120v charger did. (maybe about an amp more) And in the case of my parents, it would load the branch that is already overloaded from all the lights, computers, deep freezer, refrigerator, fans, including the central air handler, and A/C and range. So a 240v charger would probably cause the same thing to happen if wired that way.

But most likely if a 240v charger were to be installed, a professional electrician would foresee the potential of an overload and give the charger it's own breaker in the main breaker box, like what was done in my house, so if any overload happened, the 240v Volt charger would not have contributed to the overload whatsoever.
 
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