/The same board is used for the 40 and 60 Amp versions -
/The board is capable of 60 Amps but the master relay, on
/the board, is only rated at 40 Amps. When 60 Amps is desired,
/you solder three pads together on the board, or buy it already
/done and add a remote master solenoid. Typical wiring diagrams
/are provided.
Master relays should always be mounted within inches of
the battery to minimize the amount of un-protected, always
hot wire between the battery and the master relay. VERY
IMPORTANT . . . the battery master should also control
starter current . . . starter contactors can stick shut
and give you no auxiliary means for shutting off the flow
of power to the starter.
/Any load over 9 Amps will require a regular circuit breaker, or
/heaven forbid, a fuse. So your pitot heat will need it's own
/breaker and switch.
Why is it desirable to put part of your circuit protection
on an expensive, fabricated assembly that is NOT flexible
in terms of future additions that still makes you cover
things like pitot heat and landing lights as a separate
bus and protection system? What's the problem with a fuse?
If the job is done right, the probability of a fuse opening
is very close to zero . . . when it does, there's something
broke . . . and there's no value in fiddling with it it flight.
/If you don't use switch 2 for the alternator field, it's
/available for any 5 amp load.
What are the alternatives? Are you considering an alternator
with a built-in regulator? Granted, they're attractive for
simplicity of installation but cannot be fitted with over
voltage protection. One of my readers smoked several
expensive gizmos in his airplane on the way to Sun-n-Fun
due to failure of a built-in regulator. He planned to modify
the system per my recommendations after Sun-n-Fun but it
didn't last that long. . .
/The remote switch capability is neat in that it allows you to group
/switches as you desire, not as they require.
As long as you're going to dismount the switches, what's
the advantage to be gained with a $250 product that costs
more than two to three times as much as some very practical
alternatives?
/I install a lot of specialty items in buildings
/and since they have started using ptc's our service problems have
/plummeted. I'm just tickled with their performance, besides, I
/no longer have to worry about the location of the nearest radio
/shack for replacement fuses when "I" blow one.
Buildings and airplanes have nothing in common with respect to
electrical systems design considerations. Airplane branch feeds
from the bus DO NOT nuisance trip . . . at least they shouldn't
if they're designed right. The fact that self-reseting breakers
are a boon to anyone's lifestyle is a testament to poor design.
In over 1,000 hours of flying, I've never had a breaker open in
flight on airplanes ranging from C-120 to A-36. If a breaker
ever DOES open, I'm NOT going to mess with it in flight (except
for the 60 amp alternator breaker on Pipers and Cessnas . . .
that one is DESIGNED to nuisance trip). Of the 150,000 airplanes
in the GA fleet and assuming an average of 15 breakers per
airplane, there are over 2 million breakers flying of which
the vast majority will never be called upon to do their job.
Why? because reliabilty is supposed to be designed in.
Hate to be pedantic about this but there are serious
deficiencies with the EXP-Bus design in addition to
failure to meet their advertising hype. I've caught some
flack about posting the 4-page critical design review
on this product to the list . . . yet people among
you recommend this product and at the same time, didn't
read what I wrote about it . . . one fellow told me he automatically
deletes any piece over a few thousand bytes; a "don't bother
me with facts, my mind is already made up" syndrome.
If someone believes in this product, then at least do me the
honor of debating my evaluation, especially if you're going
to recommend it to the less enlightened in such glowing terms.
List-servers are for the disemination of good information and
a forum for weeding out the bad . . .I won't post the design
review again but if anyone cares to read it for information
-or- the purpose of engaging in useful debate, I'll respond
to e-mail requests for copies.
Regards,
Bob . . .
AeroElectric Connection
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