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rv8iator
Joined: 11 Apr 2006
Posts: 145
Location: Newberg, OR
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 Posted: Sun Mar 29, 2009 7:49 pm Post subject: E-bus relay |
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Bob...
I see on some Z schematics you are suggesting a relay to switch the E-bus alt. feed. My thought is that this adds another failure mode. I don't know what the drop out voltage is for the 701 relay but might it drop out before the battery goes completely dead when that last couple of minutes of battery life could be crucial? Why wouldn't using a both poles of a two pole e-bus alt. feed toggle switch be sufficient to carry 20 amps instead of the relay?
thanks...
Chris Stone
RV-8
Newberg, OR
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C. Stone (RV8iator) |
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nuckolls.bob(at)aeroelect
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| Posted: Mon Mar 30, 2009 4:43 am Post subject: E-bus relay |
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At 10:46 PM 3/29/2009, you wrote:
| Quote: |
Bob...
I see on some Z schematics you are suggesting a relay to switch the
E-bus alt. feed. My thought is that this adds another failure
mode. I don't know what the drop out voltage is for the 701 relay
but might it drop out before the battery goes completely dead when
that last couple of minutes of battery life could be crucial? Why
wouldn't using a both poles of a two pole e-bus alt. feed toggle
switch be sufficient to carry 20 amps instead of the relay?
|
12v relays will stay engaged long after the battery
is gone. A 12v battery is 95+ percent used up at 10.5
volts. A typical 12v relay drops at under 4 volts.
Further the relay is used to provide REMOTE control
of a potentially, always-hot feeder to the e-bus
from the battery bus. It's like a mini-battery
contactor effecting LOCAL control of the alternate
feed path AT THE BATTERY BUS.
It becomes advisable when the e-bus alternate feed
fuse goes over 7A . . . which is 2A greater
than the "rule from dark places" suggesting: "long,
always-hot feeders should be protected at 5A or less."
The 5A suggestion is in consideration of the
response time for breakers. Fuses are so much
faster than breakers that I've suggested we
can go up to 7A . . . but if you want to go
higher . . . it's up to you and depending on
whence your own "rule" arises.
Bob . . .
----------------------------------------)
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
----------------------------------------
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rv8iator
Joined: 11 Apr 2006
Posts: 145
Location: Newberg, OR
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| Posted: Tue Mar 31, 2009 6:02 am Post subject: E-bus relay |
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Bob...
Thanks for your well reasoned reply.
Chris
| Quote: | >
>Bob...
>
>I see on some Z schematics you are suggesting a relay to switch the
>E-bus alt. feed. My thought is that this adds another failure
>mode. I don't know what the drop out voltage is for the 701 relay
>but might it drop out before the battery goes completely dead when
>that last couple of minutes of battery life could be crucial? Why
>wouldn't using a both poles of a two pole e-bus alt. feed toggle
>switch be sufficient to carry 20 amps instead of the relay?
12v relays will stay engaged long after the battery
is gone. A 12v battery is 95+ percent used up at 10.5
volts. A typical 12v relay drops at under 4 volts.
Further the relay is used to provide REMOTE control
of a potentially, always-hot feeder to the e-bus
from the battery bus. It's like a mini-battery
contactor effecting LOCAL control of the alternate
feed path AT THE BATTERY BUS.
It becomes advisable when the e-bus alternate feed
fuse goes over 7A . . . which is 2A greater
than the "rule from dark places" suggesting: "long,
always-hot feeders should be protected at 5A or less."
The 5A suggestion is in consideration of the
response time for breakers. Fuses are so much
faster than breakers that I've suggested we
can go up to 7A . . . but if you want to go
higher . . . it's up to you and depending on
whence your own "rule" arises.
Bob . . .
----------------------------------------)
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
----------------------------------------
|
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C. Stone (RV8iator) |
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