7.5 amp fuse in 12v refer ciruit keeps blowing

[tlundell]

In the 2015 Grand Tour, the refrigerator and freezer share a 12v circuit for non-shore power use. Recently the 7.5 amp fuse has blown on three separate occasions, though I'm not sure at what point that occurs (e.g., turning on the appliances while not connected to shore power or disconnecting shore power while they are already running). This was not a problem earlier on, so not sure why it has developed all the sudden. Simple or complex problem?

[NOLA_russ]

After looking up the current draw for the refrigerator and the freezer in the manual (12 amps) I replaced the 7.5 with a 15. It hasn't blown and the coach hasn't burned to the ground. As a bit more reassurance on page 5-18 of the 2015 manual it lists Circuit 6 for the Grand Tour (on right side) as 15 amp, Red. I think they messed up the panel labels on the coach itself.

The only other workaround I found was to make sure the inverter is on whenever the fridge and freezer are on, since they run by preference (unintuitively) on 110 AC.

[73shark]

If your frig and freezer are like the Novakool in the non-Grand Tour, then running on the inverter uses more power not only the inverter itself, but the frig converts the 110 VAC to 12 VDC to run on. So unless you're on shore or generator power, it's more efficient to run w/o the inverter unless, of course, you need the inverter for something else.

Someone actually unplugged the AC line so it always runs off the house battery.

[Boxster1971]

I was one of those that unplugged my refrigerator AC plug. The wiring diagram I received from Airstream shows the refer AC to be on a shore power circuit, but that is not how mine was wired. It had the AC for the refer coming from the inverter. So that placed an additional load on the inverter that made no sense. I just disconnected the AC cord so the refer always runs directly fro the 12V house battery.


- - Mike
2013 Interstate Lounge EXT on 2012 Sprinter

[lewster]

I would NOT upgrade any fuse without knowing the wire size coming from that fuse position. You are fusing to protect the WIRE, not the device!!


Lew Farber
RVIA/RVDA Nationally Certified Master Tech
Master Tech Energy Systems, Inc.
AM Solar Certified Installation Center
Lifeline Batteries**Magnum Inverters
541-490-6357

[Protagonist]

Originally Posted by tlundell

In the 2015 Grand Tour, the refrigerator and freezer share a 12v circuit for non-shore power use. Recently the 7.5 amp fuse has blown on three separate occasions, though I'm not sure at what point that occurs (e.g., turning on the appliances while not connected to shore power or disconnecting shore power while they are already running). This was not a problem earlier on, so not sure why it has developed all the sudden. Simple or complex problem?

According to my owner's manual, the fuse for a non-Grand Tour Interstate is 8 amps to run ONE Nova Kool refrigerator/freezer. I suspect that to run two units simultaneously creates more load than your 7.5-amp fuse can handle. But as Lewster points out, there's no guarantee that your wire gauge for that circuit isn't too small as well, so simply going to a larger fuse isn't necessarily a fix. Starting an electrical fire because you're tired of blowing fuses is a case of the cure being worse than the disease.

As for why it developed all of a sudden, it could be air temperature related. Two Nova Kool units running together generate a lot of heat at the coils, and if the temperature of the air around those coils is already hot, there's no place for the heat in the coils to go. This means that your units run inefficiently, more so than they do in cooler weather when there's a proper temperature gradient between coils and air. If possible, park so that the side of the van where the Nova Kools are is in the shade to minimize heat transfer from outside, and open a cabinet door or drawer to allow air-conditioned air to get into your galley cabinets around the Nova Kools.

[tlundell]

As has been pointed out, the fuse panel is contrary to the most recent Owners Manual, which, for both the 2015 and 2016 model GT's, show a 15 amp fuse for the refer circuit, with the load chart showing 8.62 amps at 12v. Understand about not taking risk by substituting higher rated fuse (how about just inching up to a 10 amp?), but how to reconcile documentation with the actual setup?

[lewster]

For a DC run from the fuse panel to your fridge connection, you would need 14AWG wires for a 15 amp fuse, and 16AWG wires for a 10 amp fuse.

You can always use a smaller fuse than the current carrying capacity (ampacity) of a wire......but not a larger one. On newer Airstream trailers, I regularly see 15 amp fuses used on all of the 12AWG circuits, which are rated to use 20 amp fuses. Older trailers have the 20 amp fuses on the same 12AWG DC wires.

[rmkrum]

Verify the size of the wire to the fridge is at least 14 gauge. Then a 15 amp fuse is fine.


Sent from my pocket Internet using Airstream Forums

[NOLA_russ]

The wire from the fuse panel is the same gauge as the other 15 and 20 amp circuits, and larger than the 5 amp circuit. I'll leave it to someone else to pull apart their interior to verify the full circuit is 14 gauge. Given the circuit diagram and manual agree it's 15 amp, combined with the load from the refrigerator, freezer, and propane valve far exceeding 7.5 amp, and the fact that I changed this months ago and have used it heavily since, I'm assuming the panel is mislabeled. If others are more risk averse just make sure the inverter is on before you turn on the fridge and freezer when disconnected from shore power or buy a lot of 7.5a fuses.

Of course you can also have your dealer's service department sort it out.