ACS 510 Starter Switch Fuse Sizing

[rockitdoc]

I am using the L-R-Both-Start ACS510 switch.
What size fuse should I place between the power bus and the switch?
Wires to P Leads, starter and ground are 20AWG which would indicate a 5A fuse would work.
What thinks you all?

 

[bjdecker]

I am using the L-R-Both-Start ACS510 switch.
What size fuse should I place between the power bus and the switch?
Wires to P Leads, starter and ground are 20AWG which would indicate a 5A fuse would work.
What thinks you all?

If you are using the Cole Hersee/Littelfuse/Vans ES 24021 relay, you can use a 3A circuit breaker for the starter wire to the switch.

Here's the math -- per the data sheet, the ES 24021 has a 3.8 ohm coil. Assuming 12V system (12.8V for LA/AGM or 13.2V for LiFePo), I=R/V so I = 12.8/3.8 or I = 13.2/3.8 -=> I is 3.36A or 3.47A; Since there is a bit of resistance in the wire, that Amperage will be a little less so a 3A fuse/CB should be fine.

B

 

[Desert Rat]

The whole idea of a fuse is that it becomes the weak link and in the event of a short it will pop before the wire melts and causes a fire.

You should determine the length of your wire run and size the fuse below the capacity off the wire, but above the draw of whatever it's feeding.

Per the industry standard wire gauge chart from AC43.13, a 20 gauge wire 6' long can handle a bit more than 7 amps. If it's 10' long can handle about 5 amps.

Having said that, I agree with the previous poster. I think in this case a 3 amp fuse will be fine, but if not, you could go up to 5 assuming the wire is less than 10'. I can't imagine it would draw more juice than that.

 

[rockitdoc]

Perfect. Thanks Guys

Thanks guys. As usual, your expertise is spectacular.
S

 

[lr172]

I did some testing on my install and the basic ford starter relay that most of us use drew around 4 amps. It is possible that it has an inrush current higher than that, so steer clear of fast blow or electronic fuses too close to that number.

 

[bjdecker]

I did some testing on my install and the basic ford starter relay that most of us use drew around 4 amps. It is likely that it has an inrush current higher than that, so steer clear of fast blow or electronic fuses too close to that number.

Hey Larry -

How is your starter circuit wired?

A.) Buss -> CB -> ACS 501 -> ES 24021 "S" Terminal.
B.) Buss -> CB -> ACS 501 -> ES 24021 "S" Terminal -> ES 24021 "I" Terminal" -> PMGR Solenoid?

I just had a little bit of a panic - mine is now wired as example B, which I think means I'm pulling current for the starter Relay as well as the PMGR through the CB and the switch. Looking for internal relay schematics to confirm wiring on the "I" terminal....

 

[gasman]

With the load of the starter pulling the line voltage down during cranking, would the increased amp draw be too much for the 3A fuse.

 

[Carl Froehlich]

With the load of the starter pulling the line voltage down during cranking, would the increased amp draw be too much for the 3A fuse.

Agree.

I use a 10amp pull breaker and #18 wire for the starter solenoid (using a push button to start).

Carl

 

[lr172]

Hey Larry -

How is your starter circuit wired?

A.) Buss -> CB -> ACS 501 -> ES 24021 "S" Terminal.
B.) Buss -> CB -> ACS 501 -> ES 24021 "S" Terminal -> ES 24021 "I" Terminal" -> PMGR Solenoid?

I just had a little bit of a panic - mine is now wired as example B, which I think means I'm pulling current for the starter Relay as well as the PMGR through the CB and the switch. Looking for internal relay schematics to confirm wiring on the "I" terminal....

The I terminal is a direct patch to the contact disk and will provide +12V AFTER the contactor closes; No resistance added on this output (just a copper strip). The I term draws from the Batt feed and NOT the S term feed, so no panic necessary. What I did: Batt->CB->mom. switch->S terminal. Grd side is from frame. In my test, I went batt to VOM to S term and got around 4 amps. Not a precise activity and don't remember the exact current. Pretty confident mine was off shore stuff and not an actual Cole Hersee, so that may explain the higher current.

 

[lr172]

With the load of the starter pulling the line voltage down during cranking, would the increased amp draw be too much for the 3A fuse.

Probably. However a slow blo 3A fuse should handle 5 amps for 20 seconds, as would a CB. Fast blo is likely a problem. However, I recommend a 5A CB or fuse when using 22 ga wire. SImply no need to go smaller unless unique situations dictate, such as large wire bundles with no air movement. Fuses protect wires, NOT components and fuses should match the wire ga.

 

[bjdecker]

The I terminal is a direct patch to the contact disk and will provide +12V AFTER the contactor closes; No resistance added on this output (just a copper strip). The I term draws from the Batt feed and NOT the S term feed, so no panic necessary. What I did: Batt->CB->mom. switch->S terminal. Grd side is from frame. In my test, I went batt to VOM to S term and got around 4 amps. Not a precise activity and don't remember the exact current. Pretty confident mine was off shore stuff and not an actual Cole Hersee, so that may explain the higher current.

Yup - I found a cut-away drawing of the 24021 -- "I" current is fed via the BFW/Contact disc and NOT the "S" terminal. Panic averted

 

[Ralph Inkster]

I am using the L-R-Both-Start ACS510...
Wires to P Leads, starter and ground are 20AWG which would indicate a 5A fuse would work.
What thinks you all?

Don't know what others do here, but I have never fused these leads. Remember, open circuit means hot mag... blown (or broken) fuse would create an open circuit!
Unless you are using the L,R positions for something else??

 

[PaulvS]

Don't know what others do here, but I have never fused these leads. Remember, open circuit means hot mag... blown (or broken) fuse would create an open circuit!
Unless you are using the L,R positions for something else??

Same here, the only wire that is fused is the +12V lead for the starter contactor circuit. I used 7.5A fuse per the Aeroelectric Connection schematics and I think the wire to and from the switch to the contactor was probably 18 AWG.