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2019 Promaster 3500 Silver high top 159"
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I bet the in-rush current to the refer is much greater than 5a running. Still even if it were 10A that is only a 4% drop. 14 ga should be fine.

@GaryBIS I connected my B2B to the red regular fuse on the fuse block (the up-fitter fuse?). Was that a mistake? Should i have used a separate fuse like your photo shows? So far after a year of use no issues...
 

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2019 Promaster 3500 Silver high top 159"
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608 Posts
Hi,
It looks like the red fuse is 50 amps - so, as long as your wire to the B2B is good for 50 amps, it seems OK to me. If you have other loads on the up fitter connection, they would be adding to the B2B load, and the fuse may blow with the when the B2B is drawing less than 50 amps.

Gary
I don't have any upfitter loads, and my fuse is 70a and the b2b can draw 50a, but in practice I have never seen more than 40.

Thanks!
 

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2019 Promaster 3500 Silver high top 159"
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The fuse will likely blow before the breaker, but, don't overthink this. I have the same DCC50 and I have never seen more than 40A draw. YMMV. Even if it did supply 50A to the house battery, it would only draw a tad more than 50A from the starter. I, personally, think there is no need for the breaker at the DCC50 side of the wire, but it is sure convenient to be able to disconnect the service battery when working on the wiring.
 

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2019 Promaster 3500 Silver high top 159"
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I was looking at the specification sheet for the battery you have. BATT-LFP-12-170.pdf (renogy.com) It is impressive. If you believe their life cycle charts the battery can deliver ~8 mwh cycling 30% DOD! (3 mwh @100% DOD) The battery also has an impressive short circuit specification. Looks bullet proof.

I'll point out my pet OCD issue. The wiring diagram has three control elements in the high current inverter loop. A post fuse, a disconnect and the breaker. That is a lot of connections (each one costs power and voltage drop) and all functions can be served by one breaker replacing the disconnect switch.

Other than that, a super clean design.
 

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2019 Promaster 3500 Silver high top 159"
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608 Posts
I totally get your concern regarding the reliability of the breaker. Quality breakers I looked at are rated for only about 100 cycles. I presume those cycles are over-current events. I guess, one tries to design the system so tripping is an infrequent event.

I struggled with crummy breakers and finally replaced it with a disconnect and fuse - and purchased spares. Now that I have quality breakers (from my testing) I intend to put the breaker back in. I just need to get a "round tuit".
 
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