Alternator / System Questions
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Fleet Mechanic
Joined: Mar 2012
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From: Land of the Free
Makes sense cause i have dual alts and its 355 amps, so its one of each i guess
Freshman User
Joined: May 2011
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Not sure about the CEL indicator, but definitively it will throw codes and potentially turn on the alternator failure light. With a dual alternator system, Ford uses the one on the passenger side as the "primary" and the optional one as a "secondary". What this means is that the primary will produce ALL of the necessary power until it reaches close to its generation capacity. At that point, the ECM will "turn on" the secondary alternator the assist/complement the primary. If either would fail completely, the other would take over but there would definitively be codes and possibly the alternator light on.
Tuned
Joined: Aug 2010
Posts: 482
Likes: 28
From: Southern Ontario
Tux ...... Rule of thumb is not to overload any part of the electrical circuit beyond 80% for a constant load. In other words for a 25 amp breaker and assuming the wiring is rated for 25 amp you should not present a constant load of over 20 amps. Do so and you risk overheating and possibly fire.
Putting the HD relays in the engine compartment direct connected to the battery and driving them from the upfitters is the wise way to do it. Keep the heavy current out of the cab where ever possible.
Putting the HD relays in the engine compartment direct connected to the battery and driving them from the upfitters is the wise way to do it. Keep the heavy current out of the cab where ever possible.
Thread Starter
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Fleet Mechanic
Joined: Mar 2012
Posts: 1,738
Likes: 7
From: Land of the Free
Tux ...... Rule of thumb is not to overload any part of the electrical circuit beyond 80% for a constant load. In other words for a 25 amp breaker and assuming the wiring is rated for 25 amp you should not present a constant load of over 20 amps. Do so and you risk overheating and possibly fire.
Putting the HD relays in the engine compartment direct connected to the battery and driving them from the upfitters is the wise way to do it. Keep the heavy current out of the cab where ever possible.
Putting the HD relays in the engine compartment direct connected to the battery and driving them from the upfitters is the wise way to do it. Keep the heavy current out of the cab where ever possible.
The heavy current is kept out of the cab either way because the upfitter relay is in the engine compartment.
That being said i doubt the manufacturer rate something at 25 amps with the expectation of only 20 usable.
Nonetheless i have about 15 amps on the circuit utilizing the factory relay and fuse
Rather Be Floatin
Joined: Oct 2005
Posts: 2,468
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From: Marble Falls, Tx.
The heavy current is kept out of the cab either way because the upfitter relay is in the engine compartment.
That being said i doubt the manufacturer rate something at 25 amps with the expectation of only 20 usable.
Nonetheless i have about 15 amps on the circuit utilizing the factory relay and fuse
That being said i doubt the manufacturer rate something at 25 amps with the expectation of only 20 usable.
Nonetheless i have about 15 amps on the circuit utilizing the factory relay and fuse
Tuned
Joined: Aug 2010
Posts: 482
Likes: 28
From: Southern Ontario
Tux.. electrical is not natively designed for a constant 100% load. Most "things" will vary in their current draw and not tax the system at a constant load. Exceptions to this are knowns like headlights and the electrics for them are designed not to exceed the 80% rule.
It's kind of funny actually because most mechanical engineering would over design and under utilize as an operational limit. Electrical world not always the case.
It's kind of funny actually because most mechanical engineering would over design and under utilize as an operational limit. Electrical world not always the case.
Laughing Gas
Joined: Aug 2008
Posts: 832
Likes: 110
Tux,
Did you see how thin the upfitter wires are? Granted they are only running 2 feet or so from the relay, but you adding 10 feet of heavier wire to the front lights with heavy draw would turn that thin factory wire into a mini heater. That is what will pop the factory fuse. This the argument for thin wire to your own auto-reset relay underwood near the battery and a heavy wire from the battery to that relay and a heavy wire from the relay to the lights. To help put the draw in perspective, what wire size comes with the lights or is being recommended by the light mfg?
Did you see how thin the upfitter wires are? Granted they are only running 2 feet or so from the relay, but you adding 10 feet of heavier wire to the front lights with heavy draw would turn that thin factory wire into a mini heater. That is what will pop the factory fuse. This the argument for thin wire to your own auto-reset relay underwood near the battery and a heavy wire from the battery to that relay and a heavy wire from the relay to the lights. To help put the draw in perspective, what wire size comes with the lights or is being recommended by the light mfg?
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Fleet Mechanic
Joined: Mar 2012
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From: Land of the Free
Electrical wiring in North America - Wikipedia, the free encyclopedia
and thin walled cross linked polyethylene is called TXL
Meets SAE J1128 and Ford Specifications....
Rather Be Floatin
Joined: Oct 2005
Posts: 2,468
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From: Marble Falls, Tx.
its 25 amps for cross linked polyethylene....aka XHHW
Electrical wiring in North America - Wikipedia, the free encyclopedia
and thin walled cross linked polyethylene is called TXL
Meets SAE J1128 and Ford Specifications....
Electrical wiring in North America - Wikipedia, the free encyclopedia
and thin walled cross linked polyethylene is called TXL
Meets SAE J1128 and Ford Specifications....
The NEC says overcurrent for #14 is 15A no matter the type. Up to you bro.
Posting Guru
Joined: Jan 2010
Posts: 1,616
Likes: 6
From: Whitecourt AB, Canada
I realized that building electrical code isn't taken into account when designing vehicle wiring harnesses. Check out the cigarette lighter/12V plug wiring on most vehicles these days.
There's the NEC general rules that we go by, eg. 14AWG = 15A, 12AWG = 20A, etc. which include a pretty huge margin for applicability in various situations, but there are ampacity formulas that take into account spacing between adjacent wires, ambient temperature, whether it's enclosed (conduit) or in free space, insulation type (eg. thermoplastic/THHN or thermoset/XLPE or cloth braid)... putting that all together generally yields higher wire ampacity for the same environment compared to following the rule of thumb which always errs on being safer.
I wouldn't say a vehicle interior is a particularly harsh environment where you have to derate everything... but we like overkill here.
There's the NEC general rules that we go by, eg. 14AWG = 15A, 12AWG = 20A, etc. which include a pretty huge margin for applicability in various situations, but there are ampacity formulas that take into account spacing between adjacent wires, ambient temperature, whether it's enclosed (conduit) or in free space, insulation type (eg. thermoplastic/THHN or thermoset/XLPE or cloth braid)... putting that all together generally yields higher wire ampacity for the same environment compared to following the rule of thumb which always errs on being safer.
I wouldn't say a vehicle interior is a particularly harsh environment where you have to derate everything... but we like overkill here.
Thread Starter
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Fleet Mechanic
Joined: Mar 2012
Posts: 1,738
Likes: 7
From: Land of the Free
I realized that building electrical code isn't taken into account when designing vehicle wiring harnesses. Check out the cigarette lighter/12V plug wiring on most vehicles these days.
There's the NEC general rules that we go by, eg. 14AWG = 15A, 12AWG = 20A, etc. which include a pretty huge margin for applicability in various situations, but there are ampacity formulas that take into account spacing between adjacent wires, ambient temperature, whether it's enclosed (conduit) or in free space, insulation type (eg. thermoplastic/THHN or thermoset/XLPE or cloth braid)... putting that all together generally yields higher wire ampacity for the same environment compared to following the rule of thumb which always errs on being safer.
I wouldn't say a vehicle interior is a particularly harsh environment where you have to derate everything... but we like overkill here.
There's the NEC general rules that we go by, eg. 14AWG = 15A, 12AWG = 20A, etc. which include a pretty huge margin for applicability in various situations, but there are ampacity formulas that take into account spacing between adjacent wires, ambient temperature, whether it's enclosed (conduit) or in free space, insulation type (eg. thermoplastic/THHN or thermoset/XLPE or cloth braid)... putting that all together generally yields higher wire ampacity for the same environment compared to following the rule of thumb which always errs on being safer.
I wouldn't say a vehicle interior is a particularly harsh environment where you have to derate everything... but we like overkill here.
heres a great link for circuit calculations:
http://circuitwizard.bluesea.com/
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