# [EVDL] Why did all the breakers trip at the same time?



## EVDL List (Jul 27, 2007)

> Michael Hoskinson wrote:
> > Hi all
> >
> > I'm in trouble now with the condo association because of a failure of
> ...


----------



## EVDL List (Jul 27, 2007)

So it blew up after you had let it cool down, when you were unplugging?

I'm going to blame that on using a 125V connector at 208V.

With a catastrophic insulation failure, it's not surprising that
upstream circuit breakers would trip as well, especially if they were
more loaded than the 60A breaker which had already cooled down.

To reduce the risk of this happening in the future, you should get a
"fast blow" circuit breaker, giving the other breakers less time to
trip. Also, change your connector to something that's rated for the
full voltage and current it's going to carry.

-Morgan LaMoore



> Michael Hoskinson <[email protected]> wrote:
> > Hi all
> >
> > I'm in trouble now with the condo association because of a failure of
> ...


----------



## EVDL List (Jul 27, 2007)

> Michael Hoskinson wrote:
> > My Scion xB has a twist-lock plug where the gas filler lived before
> > the conversion. This connects to a PFC-30 which lives under the
> > driver's seat. The failure was in the female twist-lock connector at
> ...


----------



## EVDL List (Jul 27, 2007)

Breakers have a rate speed of disconnect.
If the 60A unit is slower than the 70 and 100A units
then those will trip before the 60A is diconnected.

Also, on a hefty short circuit the current can be
very large (several hundreds of amps) so all
breakers will see an overcurrent and start to disconnect
but it takes a while for each to actually interrupt the
current, so they will all succeed in "breaking" the
circuit at each of the points in the circuit.

Either you need a faster breaker at your charge plug
or you need slower breakers in the sub and sub-sub panels.

Also more room between different breakers - 60 and 70A
will mean that the 70A will usually overload before 
the 60A reaches its limit - it only takes 10A total 
in all the other circuits.

I presume that you have access to the sevice panels, so
the service interruption may have been only a few
minutes?
Why are other tenants so upset over ONE interruption?
Is there a reason they use this to ventilate because
there actually are other underlying issues?

Success,

Cor van de Water
Director HW & Systems Architecture Group
Proxim Wireless Corporation http://www.proxim.com
Email: [email protected] Private: http://www.cvandewater.com
Skype: cor_van_de_water IM: [email protected]
Tel: +1 408 383 7626 VoIP: +31 20 3987567 FWD# 25925
Tel: +91 (040) 23117400x109 XoIP: +31877841130

-----Original Message-----
From: [email protected] [mailto:[email protected]] On
Behalf Of Michael Hoskinson
Sent: Friday, October 31, 2008 11:12 AM
To: [email protected]
Subject: [EVDL] Why did all the breakers trip at the same time?

Hi all

I'm in trouble now with the condo association because of a failure of a
connector between the wall outlet and charger. I have a question for the
electrical gurus as to why when my breaker tripped, all hell broke loose
too.

My Scion xB has a twist-lock plug where the gas filler lived before the
conversion. This connects to a PFC-30 which lives under the driver's
seat. The failure was in the female twist-lock connector at one end of a
15 foot cable which terminates in a 50 amp plug. The wall socket for
this is "protected" by a 60 amp breaker (originally sized for a PFC-50
which I use as an off-board charger. This evening I needed a little
margin in the pack, which was down a little below 50% SOC (these are
TS-160AHA and don't seem to mind being charged only every few days). So
I plugged in and cranked up the PFC30 until it was putting 33 amps into
the pack at about 153 volts, left it for 45 minutes or so. When I was
ready to go out, I turned the charger amps to zero and let it cool off,
then un-twisted the twist-lock. As I was putting the cable down, the
female end banged against a cart and the connector released smoke and
noise. This connector has made its final connection, I said to myself,
noticing that it had also blown the 60 amp breaker on my sub-sub panel.

It turns out that it also tripped the 70 amp breaker on the sub-panel,
and the 100 amp breaker that feeds that subpanel (all of which I paid
for, by the way, when I had the outlet installed in my parking spot
years ago). The angry tenants were those served by Shaw cable, which
(inconveniently for me) had its distribution amplifier plugged into the
sub-panel. This is after the World Series, mind you, and well before any
CFL playoffs, so I'm not sure what all the fuss is about. 
Mind you, some of those had cable-based phone service too, which was
also knocked out, in addition to the security cameras and the fire alarm
monitoring box. Once again, in case I lost you: My little box at my
parking spot has a 60 amp breaker that feeds the car. This little box
connects to a big sub-panel in the electrical room via a 70 amp breaker
in that sub-panel. The sub-panel is fed by a 100 amp breaker in the next
panel up the line. Apart from my 70 amp breaker, that sub-panel has 4 or
5 120 volt 15 amp breakers that were relocated from the bigger subpanel
to make room for the 100 amp breaker that feeds it.

Question to the gurus: Why did a short in one 125 volt 30 amp connector
blow not only my 60 amp breaker but the 70 and 100 amp breakers upstream
from my little panel? Am I overloading that connector way too much by
drawing ~20 to 25 amps at 203 volts?

2nd question: What can I do to prevent any further problems at my end
from affecting other users up the line? I'm thinking that first of all I
should replace my 60 amp breaker with a 50 for the PFC-50 and a 30 for
the PFC-30. That seems to be a prudent thing to do anyway, but will it
prevent the 70 and 100 amp upstream breakers from being affected?


Mike Hoskinson
Edmonton, AB
-where oil is king but electric is cool.

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----------



## EVDL List (Jul 27, 2007)

> Cor van de Water <[email protected]> wrote:
> > Breakers have a rate speed of disconnect.
> 
> >
> ...


----------



## EVDL List (Jul 27, 2007)

----- Original Message ----- 
From: "Josh Wyatt" <[email protected]>
To: <[email protected]>; "Electric Vehicle Discussion List" 
<[email protected]>
Sent: Thursday, October 30, 2008 11:14 PM
Subject: Re: [EVDL] Why did all the breakers trip at the same time?




> > Michael Hoskinson wrote:
> >> Hi all
> <snip>
> 
> ...


----------



## EVDL List (Jul 27, 2007)

Thanks for all the advice.

Some clarification: Before I disconnected I turned down the charger 
output to zero and waited 3 or 4 minutes until the charger's fans 
started slowing down. The charger had been outputting 33 amps at 153 
volts, so its draw from the 208 volt circuit was not putting a strain 
on the 60 amp breaker.

The smoke came out of what looked like a good quality marine-grade 30 
amp 125 volt female connector when it had already been disconnected 
from the car but was still plugged in to 208 volts, as it bumped 
against a cart. When I took the cover off that connector there was 
melted plastic next to the "hot" connections and the insulation had 
been burned off the first half-cm or so of one of the leads. Clearly 
the main issue for me is an under-rated connector, possibly with cable 
connections that were not tight enough.

I would not normally have been charging at full charger output all the 
time - I'd been trying to work around a problem with the PFC-30 logic 
board while waiting for a new one from Rich. The charger was not 
clamping the voltage properly - it would indicate acceptance voltage 
and start the timer, but would allow the voltage to go up and up and 
up (like 20 volts) if the timer did not shut it off first. My 
workaround was to make sure the pack was down at least 60 amp-hours, 
adjust the timer so that it would shut off after one hour, then charge 
at 30 amps, making sure that the timer came on right away.

Last night the replacement logic board came from Rich, so I should be 
up and running with a more reliable charger after the weekend.

Regarding electrical codes and such, the installation was done by a 
qualified electrician to code and inspected by the electrical inspector.

So, I will try to find a fast-blow breaker or two (this is a Siemens 
panel, if anybody has any specific advice). I'll use the twist-lock 
connection only when charging at lowish amps and use heavier stuff 
when I need faster charging. One thought: Connectors intended for 
ranges and driers don't see anywhere near the abuse that we put them 
through plugging and unplugging every day, freezing and boiling the 
insulation when the car is parked outside, and all the other stuff 
that goes with daily EV use. Still, it beats using gasoline.

Mike Hoskinson


Quoting "Morgan LaMoore" <[email protected]>:

> So it blew up after you had let it cool down, when you were unplugging?
>
> I'm going to blame that on using a 125V connector at 208V.
>
> With a catastrophic insulation failure, it's not surprising that
> upstream circuit breakers would trip as well, especially if they were
> more loaded than the 60A breaker which had already cooled down.
> ...

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----------



## EVDL List (Jul 27, 2007)

Hi Mike an' All;

Guess one of the big issues here was FINDING out that you had wiped out 
alota OTHER circuits, and IF you KNEW it and could access ALL the breakers, 
run over and reset them, before the opther sheeple realized they were down? 
Usually in a condo complex, few , if ANY sheeple know WHERE the damn 
breakers are, or can access the panels?Orthe electrical room is high 
security, needing an act opf Congress or Parliment to get unlocked. Or what 
you MUST have run into? Where/how do I reset?

Boy! I'm spoiled rotten, I just reset my garage breaker, in a short circus 
condition. Never had (Lucky me!) condo or other communal living where an EV 
makes you some kinda outcast? I THINK the Condo(Cheep Cheep , construction, 
like down here?) has wiring issues and I'll bet you PAY enough in Condo fees 
that they could HIRE an electrician to set things right? After all , wiring 
should allow things to default and trip downstrean enough so it's YOUR 
problem, not EVerybody elses?

I plug in my "Monster Charger" and most of Killingworth goes down? Nah? 
Small town, but breakers DO sectionalize things and only I have a self 
imposed blackout, and blown out section of variac coil! Sorta the same 
thing, in larger scale?

Seeya

Bob
----- Original Message ----- 
From: "Michael Hoskinson" <[email protected]>
To: "Morgan LaMoore" <[email protected]>
Cc: "Electric Vehicle Discussion List" <[email protected]>
Sent: Friday, October 31, 2008 10:58 AM
Subject: Re: [EVDL] Why did all the breakers trip at the same time?


> Thanks for all the advice.
>
> Some clarification: Before I disconnected I turned down the charger
> output to zero and waited 3 or 4 minutes until the charger's fans
> started slowing down. The charger had been outputting 33 amps at 153
> volts, so its draw from the 208 volt circuit was not putting a strain
> on the 60 amp breaker.
>
> The smoke came out of what looked like a good quality marine-grade 30
> amp 125 volt female connector when it had already been disconnected
> from the car but was still plugged in to 208 volts, as it bumped
> against a cart. When I took the cover off that connector there was
> melted plastic next to the "hot" connections and the insulation had
> been burned off the first half-cm or so of one of the leads. Clearly
> the main issue for me is an under-rated connector, possibly with cable
> connections that were not tight enough.
>
> I would not normally have been charging at full charger output all the
> time - I'd been trying to work around a problem with the PFC-30 logic
> board while waiting for a new one from Rich. The charger was not
> clamping the voltage properly - it would indicate acceptance voltage
> and start the timer, but would allow the voltage to go up and up and
> up (like 20 volts) if the timer did not shut it off first. My
> workaround was to make sure the pack was down at least 60 amp-hours,
> adjust the timer so that it would shut off after one hour, then charge
> at 30 amps, making sure that the timer came on right away.
>
> Last night the replacement logic board came from Rich, so I should be
> up and running with a more reliable charger after the weekend.
>
> Regarding electrical codes and such, the installation was done by a
> qualified electrician to code and inspected by the electrical inspector.
>
> So, I will try to find a fast-blow breaker or two (this is a Siemens
> panel, if anybody has any specific advice). I'll use the twist-lock
> connection only when charging at lowish amps and use heavier stuff
> when I need faster charging. One thought: Connectors intended for
> ranges and driers don't see anywhere near the abuse that we put them
> through plugging and unplugging every day, freezing and boiling the
> insulation when the car is parked outside, and all the other stuff
> that goes with daily EV use. Still, it beats using gasoline.
>
> Mike Hoskinson
>
>
> Quoting "Morgan LaMoore" <[email protected]>:
>
>> So it blew up after you had let it cool down, when you were unplugging?
>>
>> I'm going to blame that on using a 125V connector at 208V.
>>
>> With a catastrophic insulation failure, it's not surprising that
>> upstream circuit breakers would trip as well, especially if they were
>> more loaded than the 60A breaker which had already cooled down.
>> ...
>
> _______________________________________________
> General EVDL support: http://evdl.org/help/
> Usage guidelines: http://evdl.org/help/index.html#conv
> Archives: http://evdl.org/archive/
> Subscription options: http://lists.sjsu.edu/mailman/listinfo/ev
> 

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----------



## EVDL List (Jul 27, 2007)

Michael;

You may want to change to a different style of plug for the charging
circuit. Meltric manufacturers a line of plugs that have a switch built
into them, and are used in industrial setting. We supply a lot of them for
welders, motors and industrial chargers. I'm the local rep in NY metro
area, but someone at the factory should be able to point you to a local
source, I'm not sure where you are located. The product line is NFPA-70
compliant, and in an industrial setting lets you unplug live power circuits.
No requirement for lock out tag out.

If you have any questions, shoot me an email or call the factory.

Good luck.

Bob

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf
Of Michael Hoskinson
Sent: Friday, October 31, 2008 10:58 AM
To: Morgan LaMoore
Cc: Electric Vehicle Discussion List
Subject: Re: [EVDL] Why did all the breakers trip at the same time?

Thanks for all the advice.

Some clarification: Before I disconnected I turned down the charger 
output to zero and waited 3 or 4 minutes until the charger's fans 
started slowing down. The charger had been outputting 33 amps at 153 
volts, so its draw from the 208 volt circuit was not putting a strain 
on the 60 amp breaker.

The smoke came out of what looked like a good quality marine-grade 30 
amp 125 volt female connector when it had already been disconnected 
from the car but was still plugged in to 208 volts, as it bumped 
against a cart. When I took the cover off that connector there was 
melted plastic next to the "hot" connections and the insulation had 
been burned off the first half-cm or so of one of the leads. Clearly 
the main issue for me is an under-rated connector, possibly with cable 
connections that were not tight enough.

I would not normally have been charging at full charger output all the 
time - I'd been trying to work around a problem with the PFC-30 logic 
board while waiting for a new one from Rich. The charger was not 
clamping the voltage properly - it would indicate acceptance voltage 
and start the timer, but would allow the voltage to go up and up and 
up (like 20 volts) if the timer did not shut it off first. My 
workaround was to make sure the pack was down at least 60 amp-hours, 
adjust the timer so that it would shut off after one hour, then charge 
at 30 amps, making sure that the timer came on right away.

Last night the replacement logic board came from Rich, so I should be 
up and running with a more reliable charger after the weekend.

Regarding electrical codes and such, the installation was done by a 
qualified electrician to code and inspected by the electrical inspector.

So, I will try to find a fast-blow breaker or two (this is a Siemens 
panel, if anybody has any specific advice). I'll use the twist-lock 
connection only when charging at lowish amps and use heavier stuff 
when I need faster charging. One thought: Connectors intended for 
ranges and driers don't see anywhere near the abuse that we put them 
through plugging and unplugging every day, freezing and boiling the 
insulation when the car is parked outside, and all the other stuff 
that goes with daily EV use. Still, it beats using gasoline.

Mike Hoskinson


Quoting "Morgan LaMoore" <[email protected]>:

> So it blew up after you had let it cool down, when you were unplugging?
>
> I'm going to blame that on using a 125V connector at 208V.
>
> With a catastrophic insulation failure, it's not surprising that
> upstream circuit breakers would trip as well, especially if they were
> more loaded than the 60A breaker which had already cooled down.
> ...

_______________________________________________
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Usage guidelines: http://evdl.org/help/index.html#conv
Archives: http://evdl.org/archive/
Subscription options: http://lists.sjsu.edu/mailman/listinfo/ev

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----------



## EVDL List (Jul 27, 2007)

I was taught that I should always disconnect an
extension cord by taking it out of the wall plug
first, then worry about the rest.
This prevents for example that you unplug a mower,
drop the female plug in the wet grass and get
shocked as soon as you pick it up again.

Still, with the failure in Mike's cord you would likely
still have a short, the next time you plug it in
and the female end is still shorting from dropping it....

Regards,

Cor van de Water
Director HW & Systems Architecture Group
Proxim Wireless Corporation http://www.proxim.com
Email: [email protected] Private: http://www.cvandewater.com
Skype: cor_van_de_water IM: [email protected]
Tel: +1 408 383 7626 VoIP: +31 20 3987567 FWD# 25925
Tel: +91 (040) 23117400x109 XoIP: +31877841130

-----Original Message-----
From: [email protected] [mailto:[email protected]] On
Behalf Of Bob Brooks
Sent: Friday, October 31, 2008 8:52 PM
To: [email protected]; 'Electric Vehicle Discussion List';
'Morgan LaMoore'
Subject: Re: [EVDL] Why did all the breakers trip at the same time?

Michael;

You may want to change to a different style of plug for the charging
circuit. Meltric manufacturers a line of plugs that have a switch built
into them, and are used in industrial setting. We supply a lot of them
for welders, motors and industrial chargers. I'm the local rep in NY
metro area, but someone at the factory should be able to point you to a
local source, I'm not sure where you are located. The product line is
NFPA-70 compliant, and in an industrial setting lets you unplug live
power circuits.
No requirement for lock out tag out.

If you have any questions, shoot me an email or call the factory.

Good luck.

Bob

-----Original Message-----
From: [email protected] [mailto:[email protected]] On
Behalf Of Michael Hoskinson
Sent: Friday, October 31, 2008 10:58 AM
To: Morgan LaMoore
Cc: Electric Vehicle Discussion List
Subject: Re: [EVDL] Why did all the breakers trip at the same time?

Thanks for all the advice.

Some clarification: Before I disconnected I turned down the charger
output to zero and waited 3 or 4 minutes until the charger's fans
started slowing down. The charger had been outputting 33 amps at 153
volts, so its draw from the 208 volt circuit was not putting a strain on
the 60 amp breaker.

The smoke came out of what looked like a good quality marine-grade 30
amp 125 volt female connector when it had already been disconnected from
the car but was still plugged in to 208 volts, as it bumped against a
cart. When I took the cover off that connector there was melted plastic
next to the "hot" connections and the insulation had been burned off the
first half-cm or so of one of the leads. Clearly the main issue for me
is an under-rated connector, possibly with cable connections that were
not tight enough.

I would not normally have been charging at full charger output all the
time - I'd been trying to work around a problem with the PFC-30 logic
board while waiting for a new one from Rich. The charger was not
clamping the voltage properly - it would indicate acceptance voltage and
start the timer, but would allow the voltage to go up and up and up
(like 20 volts) if the timer did not shut it off first. My workaround
was to make sure the pack was down at least 60 amp-hours, adjust the
timer so that it would shut off after one hour, then charge at 30 amps,
making sure that the timer came on right away.

Last night the replacement logic board came from Rich, so I should be up
and running with a more reliable charger after the weekend.

Regarding electrical codes and such, the installation was done by a
qualified electrician to code and inspected by the electrical inspector.

So, I will try to find a fast-blow breaker or two (this is a Siemens
panel, if anybody has any specific advice). I'll use the twist-lock
connection only when charging at lowish amps and use heavier stuff when
I need faster charging. One thought: Connectors intended for ranges and
driers don't see anywhere near the abuse that we put them through
plugging and unplugging every day, freezing and boiling the insulation
when the car is parked outside, and all the other stuff that goes with
daily EV use. Still, it beats using gasoline.

Mike Hoskinson


Quoting "Morgan LaMoore" <[email protected]>:

> So it blew up after you had let it cool down, when you were
unplugging?
>
> I'm going to blame that on using a 125V connector at 208V.
>
> With a catastrophic insulation failure, it's not surprising that 
> upstream circuit breakers would trip as well, especially if they were 
> more loaded than the 60A breaker which had already cooled down.
> ...

_______________________________________________
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http://evdl.org/help/index.html#conv
Archives: http://evdl.org/archive/
Subscription options: http://lists.sjsu.edu/mailman/listinfo/ev

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Archives: http://evdl.org/archive/
Subscription options: http://lists.sjsu.edu/mailman/listinfo/ev


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Usage guidelines: http://evdl.org/help/index.html#conv
Archives: http://evdl.org/archive/
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----------



## EVDL List (Jul 27, 2007)

I thought I included a link to the website.

Sorry here it is. http://www.meltric.com/

Bob

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf
Of Bob Brooks
Sent: Friday, October 31, 2008 11:22 AM
To: [email protected]; 'Electric Vehicle Discussion List';
'Morgan LaMoore'
Subject: Re: [EVDL] Why did all the breakers trip at the same time?

Michael;

You may want to change to a different style of plug for the charging
circuit. Meltric manufacturers a line of plugs that have a switch built
into them, and are used in industrial setting. We supply a lot of them for
welders, motors and industrial chargers. I'm the local rep in NY metro
area, but someone at the factory should be able to point you to a local
source, I'm not sure where you are located. The product line is NFPA-70
compliant, and in an industrial setting lets you unplug live power circuits.
No requirement for lock out tag out.

If you have any questions, shoot me an email or call the factory.

Good luck.

Bob

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf
Of Michael Hoskinson
Sent: Friday, October 31, 2008 10:58 AM
To: Morgan LaMoore
Cc: Electric Vehicle Discussion List
Subject: Re: [EVDL] Why did all the breakers trip at the same time?

Thanks for all the advice.

Some clarification: Before I disconnected I turned down the charger 
output to zero and waited 3 or 4 minutes until the charger's fans 
started slowing down. The charger had been outputting 33 amps at 153 
volts, so its draw from the 208 volt circuit was not putting a strain 
on the 60 amp breaker.

The smoke came out of what looked like a good quality marine-grade 30 
amp 125 volt female connector when it had already been disconnected 
from the car but was still plugged in to 208 volts, as it bumped 
against a cart. When I took the cover off that connector there was 
melted plastic next to the "hot" connections and the insulation had 
been burned off the first half-cm or so of one of the leads. Clearly 
the main issue for me is an under-rated connector, possibly with cable 
connections that were not tight enough.

I would not normally have been charging at full charger output all the 
time - I'd been trying to work around a problem with the PFC-30 logic 
board while waiting for a new one from Rich. The charger was not 
clamping the voltage properly - it would indicate acceptance voltage 
and start the timer, but would allow the voltage to go up and up and 
up (like 20 volts) if the timer did not shut it off first. My 
workaround was to make sure the pack was down at least 60 amp-hours, 
adjust the timer so that it would shut off after one hour, then charge 
at 30 amps, making sure that the timer came on right away.

Last night the replacement logic board came from Rich, so I should be 
up and running with a more reliable charger after the weekend.

Regarding electrical codes and such, the installation was done by a 
qualified electrician to code and inspected by the electrical inspector.

So, I will try to find a fast-blow breaker or two (this is a Siemens 
panel, if anybody has any specific advice). I'll use the twist-lock 
connection only when charging at lowish amps and use heavier stuff 
when I need faster charging. One thought: Connectors intended for 
ranges and driers don't see anywhere near the abuse that we put them 
through plugging and unplugging every day, freezing and boiling the 
insulation when the car is parked outside, and all the other stuff 
that goes with daily EV use. Still, it beats using gasoline.

Mike Hoskinson


Quoting "Morgan LaMoore" <[email protected]>:

> So it blew up after you had let it cool down, when you were unplugging?
>
> I'm going to blame that on using a 125V connector at 208V.
>
> With a catastrophic insulation failure, it's not surprising that
> upstream circuit breakers would trip as well, especially if they were
> more loaded than the 60A breaker which had already cooled down.
> ...

_______________________________________________
General EVDL support: http://evdl.org/help/
Usage guidelines: http://evdl.org/help/index.html#conv
Archives: http://evdl.org/archive/
Subscription options: http://lists.sjsu.edu/mailman/listinfo/ev

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Usage guidelines: http://evdl.org/help/index.html#conv
Archives: http://evdl.org/archive/
Subscription options: http://lists.sjsu.edu/mailman/listinfo/ev

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Usage guidelines: http://evdl.org/help/index.html#conv
Archives: http://evdl.org/archive/
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----------



## EVDL List (Jul 27, 2007)

Sounds to me like there was a defect internal to the female connector, 
perhaps from design but more likely from hand-wiring.

The overvoltage was probably irrelevant as I expect the connectors are 
overdesigned. I would think that more likely, overdesign exacerbated 
the situation somewhat -- nice short, heavy wires for 50A-rated service 
meant lots of capacity to deliver overcurrent to that short. The 100A 
breaker does not twiddle its thumbs waiting to see if a downstream 
breaker will pop!

Now, about this 120V plug carrying 208V. No! No, no, no! The problem 
is not rating, it's compatibility. I gather your EV has a NEMA L5-30 
male connector on it? That means for the EV to be usable, somewhere in 
the world there must be a L5-30 female connector with 208V on it. 
That's a serious code violation/fire-starter because L5-30 is a standard 
that implies "120V" to every reasonable person.

Use the right connector. Done! In this case probably an L6-30.

You have a point about the durability of dryer connections etc. but the 
machine-shop and marine people have that figured out. I recently wired 
a forklift charger to a perfectly sturdy NEMA L15 connector (480V/3ph).

Robert





> Michael Hoskinson wrote:
> > Thanks for all the advice.
> >
> > Some clarification: Before I disconnected I turned down the charger
> ...


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## EVDL List (Jul 27, 2007)

Mike,

The issue is one of what we in the electrical trade call "selective
coordination". Basically it means that because different overcurrent
protective devices (OCPDs) have different trip response curves they must be
selected to work together under fault conditions. Yes, it does frequently
happen that a short on a branch circuit causes one or more upstream breakers
to trip. This is because the response curves overlap and the devices operate
simultaneously. The latest edition of the National Electrical Code has some
requirements for evaluation of the OCPDs to make sure that the main isn't
going to go out in the case of a branch circuit fault. 

Unfortunately, it can be difficult to implement the protection by means of
device selection and coordination after the fact since residential type
breakers don't offer as many off-the-shelf options as their
commercial/industrial counterparts, which can be custom ordered for the
application. My advice would be to repair your cord and check it
occassionally to make sure that the wiring hasn't come loose internally,
which is another common problem when using fine-stranded conductors in
cords. (The Europeans tend to use a ferrule on the end of the stranded wire
before terminating it on the device to help alleviate the problem.) Because
you haven't had any other incidents my guess would be that you had a
one-time short circuit problem and not an overload problem, and changing the
size of the breakers is not likely to solve it. Fix the source of the
problem and do the necessary maintenance and you'll likely not have any more
problems. Of course you could do an Uncle Sam and declare the you have a
"crisis", commission a million dollars worth of studies, make
recommendations, and then get a military contractor to implement a ten-year
"sweetheart" solution to the "crisis", but I digress! On the other hand you
could buy the neighbors some comic books for those times when the cable TV
goes out! 

If you want more information on selective coordination you can download the
SPD Handbook from cooperbussmann. They used to give it away for free but now
I see that they have a price on it. If you can contact their sales rep in
your area he'll probably give you a complementary copy if you tell him what
you're up to.

Tom Bowes





> Michael Hoskinson wrote:
> >
> > Hi all
> >
> ...


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