ETL Breaker Tests

14000 Burn Rd
Arlington, WA 98223
USA
Ph [phone]
www.midnitesolar.com
165 VDC ETL TEST STORY
Rev: - Page 1 of 2
The breaker pictured is the MidNite
MNEPV series breaker with the proposed
ETL label installed. As of this writing, the
label has not yet been submitted to ETL for
approval, so production breakers may be
labeled differently
.
Wow!
In my 18 years in the Renewable energy industry as an engineer, I’ve seen a lot of cool blow
ups, flames, sparks and such, but never anything as dramatic as the ETL test conducted on this little circuit
breaker.
MidNite Solar orders custom made breakers for their PV applications from Circuit Breaker Industries in
South Africa. These breakers come with a UL 489A listing of 125VDC with an interrupt rating of 10,000
amps. The UL voltage rating is not adequate for today’s PV systems, so an additional agency listing is
required.
I don’t know where ETL cooked up the test requirements. They seem to go far beyond what we did at
OutBack a few years ago, but we only tested a15 amp breaker back then. This new test we conducted was
brutal to say the least, but it showed just how good these little breakers are.
There are several parts to the ETL test. Our test set up included
thirteen 12V batteries in series, four really big DC power
supplies, 18,000 watts of resistive loads, fuses, high voltage
knife switches, lots of 6AWG wire and of course our MidNite
CBI circuit breakers. Batteries were furnished by Dyno Battery
The first test consisted of applying 165 volts of DC to the 63
amp breaker while running 99 amps of current through it. The
test was done turning the breaker on for one second and then
off for 9 seconds. This was done successfully 35 times. That
was 16,335 watts of high voltage DC the little breaker had to
switch on and off. The first time we ran this prior to ETL being
there, all we got was a melted down breaker fused solid in the
closed position! It’s a good thing we keep a hand on the knife
switch for cases just like this. The breakers are marked with
words stating “+ for DC”. Now we better understand why this
marking exists. We had it backwards and that doesn’t allow the
breakers internal arc shute to work effectively. Engineers rarely
read directions before applying power to equipment. The +
wording on the breaker was added by CBI on my
recommendation years ago.
The second part of the test was conducted directly after the
first with no break or cool down period. It consisted of turning
on the breaker and running 99 amps through it until it tripped
on its own. Every third time, I was required to hold the handle
on to make sure the trip free mechanism worked. This
automatic tripping would take about 30 seconds and was done
15 times. A 1300 volt hi-pot test was conducted on the breaker
after these 50 cycles of testing. After passing the second part I thought we were home free, boy was I
wrong!