nuckolls.bob(at)cox.net
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 Posted: Wed Feb 13, 2008 4:46 am Post subject: Fusible Link Question |
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(response to query sent privately. writer identity
filtered to comply with the writer's perceived
wishes).
Bob . . .
I believe I'm going with Z 13 diagram. While studing this diagram and
comparing to Z 12, I see that in Z13 the 5 Amp ALT FLD CB coming off the
Main Bus has a fuseable link before it. In Z-12 the ALT FLD CB comes right
off the Main Bus and no fuseable link. Does it make a difference which way
I go? I would perfer NOT to use fuseable link, but come off the Main Bus as
depicted in Z-12.
Z-13 features fuseblock mounted remotely from the
panel . . . so the bus must be extended to the panel
to accommodate the lonely 5A breaker. The upstream
protection for the bus extension to the panel needs
to be MUCH more robust than the breaker. I.e, the
I-squared * T constant for the upstream protection
needs to be bigger. Crowbaring the 5A breaker does not
pose a nuisance trip risk to a fusible link.
What's your heartburn with a fusible link? They're
an exceedingly mature technology with wide application
and in this particular case, makes for the most elegant
solution.
Another point- I am using fuse blocks instead of bus bars, so if I take the
5 amp CB off the Main Bus as in Z-12, would I install a 15 or 20 amp fuse,
then run 18g to the CB ?
Make it a 30A fuse and then I suppose one would also
up-size the fuse-to-breaker feeder to say 12AWG.
You can see which way this is going. My advice
is to stay with the fusible link. It was a long
considered feature of this architecture.
Lastly, in the Z-13, the SD-8 comes off the Battery Contactor, once again
an 18g fuseable link. Is there any way around that ? "like" starting at the
Battery Fuse block instead of the Battery Contactor (use 7 or 10 amp fuse),
then run 18 g to shunt, etc, etc.?
Leave the wire sizes as depicted. Put a 15A in-line
fuse in there if it makes you feel better.
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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