QO breakers [RE-wrenches]

[William Miller]

Friends:

The subject of QO breakers came up today.  I am forwarding some old posts
that dealt with the subject.

William



>To: RE-wrenches at topica.com
>From: Phil Undercuffler <phil at positivenergy.com>
>Subject: Re: Inverter protection [RE-wrenches]
>Date: Tue, 12 Dec 2000 15:50:02 -0800
>Reply-To: RE-wrenches at topica.com
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>
>Some really good points here by William.  Posts like his make lists worth
>subscribing to.  Some questions, alternatives and rebuttals, however....
>
>----- Original Message -----
>From: William Miller <wrmiller at slonet.org>
>To: <RE-wrenches at topica.com>
>Sent: Monday, December 11, 2000 5:01 PM
>Subject: Re: Inverter protection [RE-wrenches]
>
>
>> 2. The Trace DC Disconnect enclosures are way too small.  So are most
>> electrical enclosures off the shelf.
>> Many RE systems require over sizing wire and that means an off-the-shelf
>> load center or safety switch would have to be oversized to handle the wire
>> as far as lug size and bending radius.
>
>I agree heartily.  It would be interesting to calculate the box volume
>required by 4 4/0 conductors used in a single inverter system, not to
>mention all the other wires we all too often shove into that little box.
>
>> 3. The DC disconnects have no KOs for an AGC fuse holder.  This is
>required
>> for monitor systems.  Not a big deal, I just drill for a chassis mount
>fuse
>> holder.
>
>I often use an inline agc holder (available from Del City) or a 1/4" fuse
>block (Grainger 1cz43 or thru Del City as well), the second 300v rated.  Do
>you have a source for a UL listed DC rated panel mount fuse holder?  I would
>love to mount that accessible without screwdriver
>
> The TC and PM 60s (from Trace and/or
>> Pulse) can be ordered with an integral breaker.  I have seen them wired as
>> input and as output breakers, and I have changed them in the field, as
>needed.
>
>I used to think this was a great idea, until I had to replace someone else's
>TC60 with an internal  breaker wired as the output breaker.  Not much of a
>service disconnect in that installation.  Controllers often fail, and if the
>client has to shut down all power, lose all inverter (and /or meter)
>programming to remove it or risk an impressive fireworks display then we
>have not served them well.
>
>> I do also frequently use the add on breakers in the sides of the Trace DC
>> disconnect enclosure, but this makes the enclosures even more crowded as
>> the breaker can hang over internal equipment.
>
>What I want to see is a stand-alone box made for the Heineman breaker line.
>QO breakers do not have a high enough AIC to use in a battery system without
>current limiting fuses upstream, which is a limitation often ignored.
>Sometimes I will use a 60A class R (oversized relative to breakers and
>loads) and a fuseholder, inside a box with labels stating "no user
>servicable parts inside" to meet safety and NEC
>
>> 5. The tap connection on the Trace DC disconnect breakers is ludicrous.
>It
>> is a code violation (and against common sense) to put two leads under one
>> lug.  Trace would have you put a lug under the bolt head holding the main
>> lug onto the breaker, but this is so difficult to do, especially after
>> wiring 2/0 or 4/0 to the main lug.  I have also stripped the threads in
>> this lug.  I can't imagine the breaker manufacturer condones this
>practice.
>
>I only use the tap connection for powering the meter.  I crimp and solder a
>5/16 (?) terminal on #6 or #4 wire, put it under the bolt BEFORE installing
>the big breaker, and jump to the closest smaller breaker.  If I have
>multiple loads/input breakers, I'll star connect from there.
>
>By the way, has anyone noted that there is a load and a line side to these
>breakers?  And an Up and Down side?  Pull out the glasses and squint at the
>print.  Which brings to mind, if its an array input, which is the load and
>which is the line?  Personally, I always run the battery to the load side.
>
>> I don't particularly mind using a short piece of #6 wire from a battery
>> connection to a circuit breaker.  This wiring philosophy is covered under
>> the tap rule in the NEC.  I've never seen it directly related in print to
>> DC wiring, but the principal is the same:  You can protect a length of
>wire
>> either at the beginning of the wire or at the end.  If the wire is long,
>it
>> is safer to protect it at the upstream end.  If the wire is short and well
>> protected mechanically, it may be as safe to protect it from over-current
>> at the down stream end.
>>
>> 6.  One place to install over-current protection and switch control is in
>> the PV combining box.
>
>I greatly dislike this idea.  Imagine:  if you put the array disconnect at
>the array, and turn off the breaker, what have you accomplished? (other than
>stopping charging)  Both sides of that breaker are still hot (admittedly,
>one side is current limited).  In addition, someone working on the power
>system would have to walk out to the array to disable all power sources.  On
>the other hand, if the array disconnect was grouped with the power
>equipment, especially if it was grouped with the controller disconnect, the
>service equipment (controller) could be disconnected from all power sources
>with one or two hand motions for easy safe service.
>
>I do not like to plumb to an SW
>> inverter via the end panel KOs since this obscures the AC connections as
>> well as the relay and temperature sensor connections, however this is done
>> in the IPPS.
>
>If I could reach up the Zantrax/Anthrax/Prozac/Trace ladder and make two
>changes to their inverters, the first would be to make ALL connections
>accessible from the front of the unit:  straight on, no craning necks, no
>three-handed needlenose and screwdriver manipulations, no looping the temp
>comp from the DC (battery) side around to the AC (who cares what
>temperature) side.  The second would be silent sell, but lets not get all
>hot and bothered on that again.
>
>> Also, I would not relish handling the weight of an IPPS.
>
>Amen brother.
>
>
>
>
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__________________________________________________________________
William Miller
SLO Communications: Communications and Power Systems Consulting
PO Box 50, Santa Margarita, CA 93453
Voice :805-438-5600		Fax: 805-438-4607	VMail: 805-546-4875
email: wrmiller at slonet.org
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