[RE-wrenches] AC disconnect options

[Matt Lafferty]

All,

These "compact pull-out A/C" disconnects are NOT suitable for PV. I don't
believe they should be used for air conditioning disconnects either. The
brand doesn't matter. What kind of quality do you expect to get in a 60A
nonfused disconnect for $7? Or take your pick of fused 30A & 60A models for
$12.  http://tinyurl.com/CheapDiscos 

I've seen too many burned up over the years to consider them reliable or
safe. Fused and unfused. Charcoal in a gray box. Most on A/C units, one on a
PV system. I've wondered for a number of years why they are still listed or
manufactured. My concerns go back to the days before I knew how to spell PV.
Other than payola, the only reason I can conclude for their continued
listing is that something about the listing test process does not adequately
represent real-world environmental and other conditions. Or maybe it is
payola. Either way, they're pieces of crap. 

Or maybe quality wasn't part of the question... So let's look at the utility
aspect. Most utility interconnection "rules" require the utility accessible
disconnect to be: Accessible, Externally operable, Visible blade/break, and
Lockable. These are minimum requirements. I've read quite a few of these
that specifically say "Pull-out Air Conditioning Disconnects are not
allowed."

But there are utilities that don't require disconnects for PV systems up to
a certain kW rating. What about those jobs? I say that we must really get
our heads around and embrace the following fundamental principles. These
principles apply, whether or not there's a building department or a utility.
These fundamentals are about integrity.

Something to remember: Every time we install another PV system, on or
off-grid, we are installing an electric generator. An electric generator
that we promote as safe and reliable for 25 years or so. The safety and
control features we install with our systems are there for a reason. I break
them into three categories: Inherent, Automatic, and Manual. As long as
everything is in a "normal" state, some of them might seem like overkill.
Things are not always "normal". Face it. You and I are not likely to be
onsite when something goes wrong, whether or not it has anything to do with
our PV system. It is under these abnomal conditions that the safety and
control features ABSOLUTELY MUST WORK CORRECTLY! 

Inherent safety and control features provide a primary level protection.
When all else fails or does not respond quickly, the Inherent features may
be the only thing between catastrophe and a simple service call.
Additonally, the Inherent features go a long way toward preventing
undesirable conditions in the first place. Inherent features include
appropriate conductor size and type, quality and type of raceways, suitable
grounding, arrangement & selection of equipment, placarding & labeling, and
most importantly, WORKMANSHIP.  

The Automatic features must do their job in order to
stabilize/minimize/mitigate/eliminate/isolate a potentially hazardous
condition. Among the Automatic features are fuses, breakers, and inverter
controls. I also consider the rotation of the earth to be an important
Automatic feature. Some repairs are best left to darkness and headlamps. 

The Manual features are last-resort. Manual features generally include
switches and breakers. These devices are generally operated for one of two
purposes: Sevice or Emergency. I'll forego a long discourse on
serviceability here and stick to the emergency aspect. Under real or
perceived emergency conditions, all bets are off. From my perspective, an
obvious "Red Handle" is WAY better than some little gray box that somebody
has to 1) Realize it's the switch, 2) Open the cover, 3) Bend over so they
can see under the cover, 4) Figure out that they are supposed to reach
inside and pull on the little plastic handle, and 5) Reach inside and pull
on the little plastic handle. 

Especially when the little gray box just might be the device spewing flames
in the first place! Flame throwers aren't just for snowmen! Reference above
and William K's experience...

For the record, I am personally a staunch supporter of readily-accessible
and visible H-series Square D Safety Switches. I've taken lots of heat for
that over the years... Something about saving $75 on $40,000 PV systems...
It's not a compromiseable position for me. The sturdy, 2-color,
non-conductive handle, interlocking door, arc-suppression cage, and terminal
shield makes me feel better. I know that, no matter what else is going on, a
homeowner/neighbor/passerby/firefighter/utility-lineperson can safely
recognize and operate the switch.

I know most of you/us are thinking: "They should just shut the breaker off."
I am telling you/us that the vast majority of people out there don't know
this. How many installers are honestly giving the customer a thorough
orientation and delivery for every system? Based on the folks I've talked
to, customers and installers, almost none. Even if the original customer
originally knew to use a breaker, there is nothing which ensures that person
remembers and is present (or even still owns the place) when such an event
might occur. I don't believe that opening a service panel door and hunting
for a breaker under duress is nearly as desireable as an obvious "Red
Handle". That's my position, whether or not the local utility requires it.

Be safe. Be ethical. Don't be cheap!

Matt Lafferty