DRS25A-NXT/6 install and fusing

[Bayhouse]

Preparing for my install and reading the manuals. Ship's main is 12v and I bought the Newmar 12v-24v-7a converter.

I've read that both sides of the converter need to be fused and I'd like to make sure I understand this correctly from the radar install manual:

"Use the 15 A fuse for 12 VDC ship’s main. Use the 10 A fuse for 24 VDC ship’s main."

Translation: 15A on the input side of the converter and 10A (in the supplied blade holder) on the output side of the converter.

Do I have this correct?

Also, still waiting for my scanner unit to be delivered so I don't know what the power/LAN cable assembly ends look like. Is this something that can be easily pulled through a relatively full tube? Manual says not to cut so it may be easier to pull a jacketed power and STP through the tube and connect everything up top (I have a raised box on the hard top for the radar).

 

[Quitsa]

I think the installation manual may have confused you a bit because there is one manual for the DRS6,12, and 25A. The DRS6A-NXT can operate on 12 or 24V, while the more powerful units need 24V. So the 12V fuse specification is only for the DRS6A-NXT when powered off 12V supply. You would need a 10A fuse in the 24V supply to the radar pedestal after the Newmar converter. But I think it is prudent to fuse the converter 12V power supply as well.

My cable had to be run through a tower pipe that already had a fair amount of wires in it. You might be able to pull it through on yours, it's not too big. On my boat, the installer cursed quite a lot and ended up cutting the cable at the end that connects to the network switch and power supply. As long as you know how to install a shielded RJ45 ethernet connector properly, it should be fine. I have never had a problem with mine. The power wire connection is simple of course and hard to screw up. It's the end of the cable at the radar pedestal you don't want to cut so the cable has to be fed in from that end.

 

[Bayhouse]

Thanks Quitsa, very helpful.

Agree that it would be prudent to fuse the input side (12v) of the power supply converter - the question is what size fuse? The boat currently has a small breaker panel largely for electronics and darn it if that's the one breaker I can't find a sticker on to figure out it's amperage.

 

[Bayhouse]

My radar unit finally arrived and I'll be installing the DRS25A-NXT this weekend, wanted to close the loop on this question. What size fuse between the ships main (circuit breaker) and the Newmar 12v-24v-7a converter?

Circuit Breaker -> FUSE? -> Newmar 12v-24v-7a converter -> 10amp Fuse ->DRS25A-NXT

 

[Quitsa]

Generally one would expect the 12V current to be double the 24V. Thus since the converter has a maximum output of 7 amps, it would be at 14 amps on the input side. It is not quite that simple because there is less than 100% conversion efficiency and the input voltage is more likely to be around 13-13.6V especially if you have the motors running. or a charger run by a generator.

That being said, I think you could try a 15A fuse on the 12V input but t may need a 20A. I believe the installer used a 20A on my boat with that same Newmar converter and a DRS25A-NXT.

 

[Bayhouse]

Perfect, thanks again Quitsa. I'll start with a 15 but have a 20 ready to go just in case.

 

[gtstang462002]

I have to double check, But I believe I have a 15 amp fuse installed on both of my boats with the same converter running the DRS25A-NXT pedestals.