Current draw

[Helmsman]

Installation questions:

With limited breaker positions in my DC panel, I plan to combine certain Furuno products on breakers. I am having trouble finding actual current draw for the products.

1) Is there a source for actual max current draw for each product you build?

I have searched the literature for amperage draw for a TZT3 16” and 12” MFD. The fuse size is recommended at 7.5 and 4.0 amps respectively. I plan to combine the two, and also add the DRS4D-NXT (5.0 amp fuse and current draw of 2.5 amp max per other forum post) to one breaker.

2) In lieu of having actual max current draw, would you add the three fuse sizes and use that for breaker sizing?

I have a NavPilot 300 to install. The one way power run to the Octopump (pump oct 16-12) is approximately 38 feet from the preferred FAP3012 processor location. On another forum post, the suggestion was to use a 20 amp fuse on a 10-12. The 16-12 max amp draw is stated at 18 amps.

3) The tentative plan is to use either 4 or 6 awg wire between the units for the 38 foot run. Which would you suggest?

4) Should I use a 20 amp breaker or 25 amp breaker for the NavPilot system?

 

[hiccup]

The fuses for the individual devices should remain intact. This means that the breaker you're referring to is to protect the wiring and connections between the breaker and the device fuses. Sizing the circuit so that it can supply all devices their fuse rating would be a conservative approach.

So if the fuses add up to, say, 17A, size the circuit & breaker for, say, 20A. When I say size the circuit I am referring to any and all wiring (+12v & ground), connections, bus bars, etc.

 

[FishTech]

Hiccup is right. The breaker is essentially your on/off switch when the fuses remain in play.

I would move the pump closer to the processor and make the hydraulic hoses longer. The proper answer for wire size, without taking into consideration the distance from the power supply to the processor, is 2AWG. 76' for 18 amps @ 3% loss is 2AWG. Hydraulics won't care about 40 more feet.

Or do I not need to double the 38 because you already doubled 19?

 

[Helmsman]

Hiccup is right. The breaker is essentially your on/off switch when the fuses remain in play.

I would move the pump closer to the processor and make the hydraulic hoses longer. The proper answer for wire size, without taking into consideration the distance from the power supply to the processor, is 2AWG. 76' for 18 amps @ 3% loss is 2AWG. Hydraulics won't care about 40 more feet.

Or do I not need to double the 38 because you already doubled 19?

Thanks. I didn’t double.

I spoke with the manufacturer of the Octopump 16-12 after I posted this. He told me that the 16-12 averages 5 to 7 amps with a max of 17 amps. Interestingly, he was thinking 10 AWG wire for that length. I asked about the Blue Seas cable chart and he said they would know more about the size than he would.

What I can do is move the processor back closer to the pump. I will need to run additional wire forward to the Safe Helm 2, which calls for 22 gauge wire and installation close to the lower helm. I will upsize that 22 gauge wire after looking at the length I will need. I will try to get the processor to within 32 feet (round trip now). That would bring the wire size down to 8 AWG. May use 6 AWG

 

[Helmsman]

The fuses for the individual devices should remain intact. This means that the breaker you're referring to is to protect the wiring and connections between the breaker and the device fuses. Sizing the circuit so that it can supply all devices their fuse rating would be a conservative approach.

So if the fuses add up to, say, 17A, size the circuit & breaker for, say, 20A. When I say size the circuit I am referring to any and all wiring (+12v & ground), connections, bus bars, etc.

Thank you. Will take your advice. I thought that was the right way to go, but good to hear the same thing from someone else.

 

[Helmsman]

Hiccup is right. The breaker is essentially your on/off switch when the fuses remain in play.

I would move the pump closer to the processor and make the hydraulic hoses longer. The proper answer for wire size, without taking into consideration the distance from the power supply to the processor, is 2AWG. 76' for 18 amps @ 3% loss is 2AWG. Hydraulics won't care about 40 more feet.

Or do I not need to double the 38 because you already doubled 19?

Furuno recommends a 15 amp fuse. The processor won’t push the pump that high. After re-reading this, and looking at the numbers, here is where we are. The round trip of the circuit is 44 feet. That is from the breaker panel, to the AP computer, to the pump and return to the panel. It doesn’t matter where along that wiring I place the processor, because the overall round trip remains the same.

Unless, in reality, the path from the breaker to the processor is one circuit, and the path from the processor to the pump is another, which would create a lower calculation for wire size.

I could also move the pump closer to the computer. The boat comes with hydraulic tees at the ram for the pump, and a place to fit the pump, and I wanted to be able to use the fittings there to attach the pump.

 

[gtstang462002]

Most installations you will find the pumps tapped in under the helm. (Sea star type of units) it is simply “T” connections in the hard place plastic lines coming off the helm pump to the AP pump. This allows the AP computer to be in a location that in generally dry and keep the pump close to the computer.

 

[Helmsman]

Most installations you will find the pumps tapped in under the helm. (Sea star type of units) it is simply “T” connections in the hard place plastic lines coming off the helm pump to the AP pump. This allows the AP computer to be in a location that in generally dry and keep the pump close to the computer.

That is what I usually see, also. However, the boat I am taking delivery on already has the lines plumbed for the pump in the back. The majority of those boats have the pumps there. Per Furuno, a 15 amp breaker will be acceptable for as much as a 15 meter run, so I should be ok with the plan.