UM435 - 6 Amp Blade Fuse?

[tgrevers]

Hello,

I just completed installing a Uniden UM435 Marine Radio into a boat this weekend. The radio came with a slow blow 6A fuse - the vessel is equipped with blade fuses in the power panel. The radio is mounted to the boat's center console, and all powered equipment runs through fuses located at the back of the vessel. Anything powered has its fuses located in the back, so there is no non-fused power running through the length of the vessel.

My question - the radio came with a slow blow 6A fuse. There is no 6A blade equivalent fuse on the market that I could find. Blade fuses are sold as 5A and 7.5A fuses, nothing 6A.

Can this radio be safely run on a 5A blade fuse?

Thanks,

-Ted

 

[mmckenna]

Can this radio be safely run on a 5A blade fuse?

Maybe, but this isn't the right way to do it.

A 25 watt VHF radio may pull more than 5 amps, it depends on a couple of variables:
Individual component tolerances.
Individual radio alignment.
Size and length of wire.
Any splices, connections, etc.

A 5 amp fuse is probably going to give you issues in the long run, and I can almost guarantee that it will be when you need the radio the most.

To really answer this question, I'd need to ask you a few questions:
1. How long is the wire run from the source to the radio?
2. Are you running both positive and negative wires, or relying on a local ground at the radio?
3. What gauge wire are you using? Is it all the same size, or did you make any splices?
4. How many splices/connections in the complete path?

There's a few things you need to be concerned about:
-Long wires will suffer from voltage drop. Voltage drop will result in the radio pulling more current than at higher voltages. If you have a long path from the source to the load, you need to run a suitably sized wire.
-Lots of splices/connections can give you issues. Ideally you want a continuous run of wire from the source to the radio.
-If everything is up to snuff, you could run a 10 amp fuse at the source and use the local 6 amp fuse at the radio. The 10 amp fuse will protect the wire to the radio, and the 6 amp fuse will protect the radio.

It might take some extra work, but it really is worth putting the extra effort into it.

 

[tgrevers]

Thanks for the guidance -

Fortunately, no splicing. The radio has been run on its own dedicated circuit. Ground is at the battery negative terminal through a dedicated 14 gauge run, and positive runs from the fuse block through one continuous 10' 14 gauge wire, to the radio. There are connectors at each end of the dedicated power run, at the fuse end to connect to the panel, and at the radio end, to connect the positive and negative to the wires running from the back of the radio.

The idea of running a 10A fuse is interesting - would it be safer to run a 7.5A, as it's closer to the rating required for the radio?

I appreciate the feedback.

-Ted