Converter relay

[KYAvion]

Can any electrical experts tell me why the factory converter uses a relay to provide power to the 12v fuses? The blue wire provides juice to all the factory fuses except for the “Accessory 1” fuse, which appears to only provide juice to the 12v receptacle or TV antenna circuit. The Accessory 1 circuit appears to be wired straight to the battery (red wire) in the 12v panel.

Why the relay? I’ll be swapping out the converter, which will elimate the relay since the blue and red wires will be connected directly to the positive feed of the converter. I’m just curious why the factory converter operates this way?

[KYAvion]

@Salty ?

[Salty]

I have no good answer for you on this. I can only speculate and pontificate, but in the end you'd be no further ahead. Since, as I understand it, you're changing out the converter,and bypassing the relay it's a moot point.
My trailer had already been converted to 50Amp service with a Parralax power center, which truth be told, was not done very well, so I don't have a factory original converter to refer to. I'm in the process of updating all things electrical myself but am hampered by niggling little annoyances such as weather, work, travel for work and the odd family obligation.
What brand of converter are you going to? 50 Amp service? How many amps @12VDC?

[KYAvion]

Hey Salty. You’re right—it is a moot point since I am going to switch out the converter anyway. I’m just looking for a little speculation to fulfill my curiosity as to why the original manufacturer of the converter designed it this way. As it is, my converter isn’t fully working. Juice isn’t passing through that relay when I’m on batteries only. Thus, if disconnected from shore power, none of the lights, ceiling fans, range hood, etc. work. My TV amplifier does though since it on the Accessory 1 circuit (horizontal fuse in pic) which is wired in the panel straight to the battery and doesn’t go through that relay. I just can’t think of a good reason why all the fuses wouldn’t be wired like the Accessory 1 fuse. Instead, all six of the main fuses are powered via that relay. The 7th fuse from the left is separate, and appears to go to the “power on” light and is wired separate from the relay like the Accessory 1 fuse.

Your speculation is welcome, if you don’t mind?

As far as my upgrades, my new converter is a 45 amp Boondocker, and my new 110v panel is a 50/30 split panel by Progressive Dynamics. My 12v panel will be one my father made for my prior 79 Airstream, and it consists of breakers instead of fuses.

[Salty]

Speculation: The relay had to be enabled by 12 VDC - likely battery power - in order for the balance of the circuits to be powered. If 12VDC dropped below the relay coil threshold, the relay would drop out and you'd lose power to whatever was turned on. This would occur under 2 circumstances: your load was too high - current draw had exceeded capacity and the 12VDC was dragged down to a point that the relay coil couldn't maintain closure. OR.. the batteries had drained to a point that relay coil couldn't maintain closure. in either circumstance, the relay opens and you lose power to the 12 VDC circuits.
Another theory: the relay coil power runs through the CO/LP gas detector and is only turned on in the absence of an alarm.
Why the TV amplifier should be on a priority circuit is beyond me. I would have expected that the CO/LP gas detector would be on that circuit and maybe the afore mentioned relay would enable/disable a gas solenoid and or heater power in the event that there was an alarm by the CO/LP gas detector.

[KYAvion]

Thanks for the conjecture. All are interesting possibilities.