Breaker sizes, Vin Max vs Hyper VOC

[Vic]

Just ordered a Classic 150.

Several questions:

Guess that the CC to Battery Breaker should be 100 Amps ?
Operating Vin Max is 150 VDC
What is the definition of Hyper VOC,  and how is this parameter applied -- how do I use this information ?  Is this the real max Vin.
In a system with Classic plus an MX-60 or an XW POS CC how are the DC returns wired ?

Thanks for the front and side drawing of the Classis.  I would bet that there are two knockouts in the bottom as well (?).  What is/are the diameter of all of the knockouts,  1-inch max ?

Finally a curve:  I am loooking for a smallish enclosure for an Airpax E Frame breaker (think CarlingSwitch also made this size-IIRC breaker is 5.80" high X 1.026" W).  Something like the MNDC Quad,  but for four or so of these larger breakers,  as used in the old Xantrex DCCB-L.  My layout works better with the breakers on the left side of the inverters,  and the DCCB is on the right,  so would like to put the PV/Battery DC breakers on the left end of the SW inverters.   Any pointers ?

EDIT:  Off to the mountains,  will check back in a week  Thanks ...

Thanks  HH  Vic

[Robin]

If you have a 12V battery bank, then a 100 amp breaker may be required depending on PV in voltage. Look at the graph on the home page of our website. Normally an 80 amp breaker will do. You will need 4AWG wire for the 80 or 100 amp breaker. The breakers both cost the same if you are getting the MidNite breakers. ($20 each).
The Classic 150 has an operating voltage of 150V. You get to add the battery voltage to the operating voltage as a dafe area (HyperVOC). The unit will shut off beyond 150V though.
1" knockouts on the bottom and sides. 3/4" knockouts on the back. The E-frame breakers are an old style breaker. We do not use them because of the size and cost. There is no box made for them. It may be less expensive to get our MNEDC breakers and the Quad box?
Robin

[Vic]

Hi Robin,

Thanks for the info ... OK,  the Hyper VOC is just safety margin for non-operating Vin above 150 VDC,  at least,  this is my understanding.  My systems are all 48 V.

OK on the E-Frame Breakers.  Was just hoping that there was some breaker box product around that someone might know of.

It does sound like the MN Classic will accommodate #4 AWG wire,  at least for the CC to Battery wires.  And nice  selection of knockouts,  as well.

I am currently using the DC Quad box and a variety of your Panel Mount DC Breakers.  Guess that am going to use the E-Frame breakers in the DCCB.  For some reason I do like the 'feel' of the E-Frames. 

QUESTION:  Is therer a spec for using  the MNEDC breakers used as a switch,  switching about 60% of its rated DC current ?  I'd bet that this is very HARD on a breaker.  I do try to switch them fast,  but guess tahat this is beyond the spec for longevity.  This particular application is switching sections of a DC Load Bank onto the battery bank,  as an aid in discharging a bank in preparation for high-rade recharging.

AND regarding the DC Return from the CC to the negetive bus of the battery.  Does the GFP &/ot Arc Detector require that the battery DC return be handled in any special manner?  And,  lets say that one was using the XW SCC in the same system as the MN Classic,  what is the suggested approach in wiring the DC return,  as the XW SCC seems to usurp the DC Return.

Know you folks are busy  Thanks again,     Vic

[niel]

vic,
you bring up a good point and i'd be curious to know the possible lifespans for breakers used as switches if that type of info is available. this is a common thing to do in the industry as breakers tend to be cheaper than actual switches and you get an added benefit from a breaker if a current overload occurs. i used one of my murray breakers as a switch and it did not last long as a result. the actual purpose of a breaker really wasn't meant to be used as a switch, but if it is made well there shouldn't be a problem with using it as such. i know now murray breakers are not long lasting in a switching application and i'm concluding that it may not last long if it kicks out often when used as a breaker.

[Vic]

And Robin,  just found the manual on your site. Looks GREAt! Congratulations on shipping the first units 12/23 !

And niel,  you are correct on using breakers as switches.  In the olden days,  worked at an industrial site,  where there were NO light switches.  Every day,  the breaker panel was used to turn on/off lighting.  The story was that some breakers were "switch-rated",  and could survive the mechanical and electrical sterss of daily switching,  but most others would not.

Some of the front-mound DC (and AC) breakers have a long travel handle,  and a two step contact (perhaps over-center) engagement.  This leads me to bellieve that they are better suited,  mechanically,  to be used as switches.   BUT,  switching many amps DC is often very stressful on the contacts.  Especially if the make/break occur slowly -- causes any arc to be sustained.  Am no expert on this.  Switching DC currents (under load)  is an ugly thing.

My load bank has two sections each of which draw about 38 Amps DC at 48ish volts.   Have been using the MNEDC Panel Mount 60 Amp breaker as a switch.  This is probably too severe for this breaker to last long.  A solid-state DC relay i s really the way to go for the switching function.  Then the current drawn could even be controlled by a PWM signal  ...  and  so on.  Thanks,   HNY,   Vic

[Robin]

The DC breakers that MidNite suses and sells are UL listed to break rated load at rated voltage for 5000 cycles. Using a 150V breaker at 48 volts is not going to wear them out. The issues people experience are from thermal breakers. Ours are hydraulic/magnetic. They turn off with a spring action, so there is no sustained arc inside. If you ever wear out a MidNite breaker, we will be happy to replace it free of charge. I have been using CBI and Carling breakers for over ten years now. The total quantity of breakers in service exceeds one million. I can count on one hand how many DC breakers have failed. The AC breakers seem to break more often. The quantity that have failed over the years may require me to take off my shoes to count the failures.

[Vic]

Hi Robin,

Thanks for the useful info.   But I had thought that it is possible to "tease" a breaker when it is being used as a switch -- ie making the connection/disconnection slowly,  and cause much more arcing of the contacts than would exist if the breaker was tripping.

I have never had any problems with a Midnite,  or  OB breaker.  I do have a number of the Airpax E-Frame jobs around as we have several X systems which use them.  And, the CF style uses screw compression wire lugs at the top and bottom which I prefer over the lugged rear connections  and so on ...

The Midnite stuff is great and an excellent value.  I really appreciate that MN also offers AC DIN Rail breakers with up to three poles,  also at an attractive price.  Thanks again ... know that you folks are busy !     HNY      Vic

[Robin]

We use the Carling E frame breaker for our 125 amp inverter breaker. That is the only value where it makes sense to me. I designed a plastic adapter to use when you need the 1" wide E frame breakerhttp://www.midnitesolar.com/productPhoto.php?product_ID=253&productCatName=BREAKERS&productCat_ID=16. The adapter allows you to use the smaller and less expensive 3/4" wide C series Carling breakers. They are available now. The E-frame breaker is a very old style breaker. I designed that style into the Trace Engineering equipment 17 years ago or so. The E-Frame was the only solution back then for a DC rated breaker. The thing I do not like about the E-frame breaker other than its ost is the fact tht the design has the plastic under compression and you are carrying current through the threaded studs. This type od design has not been allowed by UL for many years. Putting plastic under compression even when it is a thermal set plastic is not a good idea. Passing current through threads is also not a good idea. I do not understand why Xantrex continued to use this style breaker when designing the XW stuff? They are the only ones that use this style. I made the CD series adapter for those poor soles that bought a Xantrex distribution panel, but then couldn't find breakers for it. I do not know if you can tease an E-frame breaker to continue an arc. I'm pretty sure the C frame and CBI breakers just trip rather than arc. Once again, thermal breakers like in your house distribution panel may allow teasing. They are not very sophisticated. Pop some breakers open some time. There is a lot going on inside a DC breaker. By the way, the CBI QL (AC) and the QY (DC) breakers are built identical inside. People always ask if they can use a DC breaker in an AC circuit. Technically they will work just fine and in the case of CBI they are identical. The markings on the breaker will be wrong though and no inspector would ever allow a DC breaker to be used in an AC circuit. It can come in handy for temporary or emergency installs though. 

[Vic]

Hi Robin,

Thanks for the great additional info ... sorry for the delay,   been at the remote site with NO internet.

Yes,  the threaded studs are a poor idea.  It is fairly common to wind up with the bottom nut (the one against the plastic) loose,  and I always wonder just how tight to  torque it.  Too much,  and the palstic will crack,  too l ittle,  and there is prob a poor connection.

BTW,  there is now a "CF" sytle breaker in the Airpax 209 line,  with front facing solderless wire comperssion type connectors.  This hould resolve the issues with loose nuts,  and they are easily wired from the front without removing the breaker.

Personally,  I do not like stud connections -- they require the user to make bullitproof lug connecitons.  And many DIY types (like me) do not have the $600-800 crimpers.

I inadvertantly teased one of the MN CBI Panel Mount breakers which was flowing about 40 Amps DC.  It made the ZZZZZZZzzzzzzssssshhhhhTTTT sound.  This lasted for a couple hundred MS.  Breaker did not trip,  and still works fine,  but that cannot be good for the contacts.  Was switching the 60 Amp low mounted breaker while standing up from a crouch.  It was stupid to do ... always try to quickly switch breakers which are carrying load currents.  Usually dry to switch them while carrying no current at all,  if possible.

I do like your CBI Breakers,  and use quite a lot of them.  They have always worked great,  and are very cost-effective.  I just got used to the E-Frames from the days gone by.

No need to reply,  know that you folks are busy!   Happy New Year,   Thanks,    Vic