10 meter bilge blower question?

[yorklyn]

My 10 meter only has one bilge blower on the port side. I am adding a second one (squirrel cage just like origional) for safety. the hull wiring diagram shows two bilge blowers. does anyone know if both blowers can be run off the same circuit and switch? I believe the amp draw on the new one is 12 amps. I'm guessing if two blowers were an option they ran off the same switch as I dont believe I've ever seen a 10 meter with two factory blower switches? I was hoping not to add a switch to the factory panel if its not needed.
Thanks

[S.A.M.]

Todd,

i have two 4" cages and they run off the same switch next to the genny control panel.

[BobCT]

I have a blower on each side, one switch at the helm.

[yorklyn]

Thanks Guys! Thats just what I needed to hear!

[comodave]

Make sure the wiring and switch can handle the current draw from 2 blowers. If the existing blower also draws 12 amps then the total of 24 amps would require a substantial gauge of wiring, depending on the length of run from the battery to the blowers and back to the battery.

[yorklyn]

The wire diagram for my boat shows 12-2 wire to the existing blower on the port side and 10-2 to the one im adding but it does not show if they are two seperate runs or run in a series. I am going to look into this a bit more. This seems like something that should have a relay rather than running full power to the switch. I had planned on hiring someone to check everything that I do and ask for the help for the things I'm not sure of. on the bright side I cut the hole for the new blower and mounted it today!! just need to figure out the wiring!

[Big D]

Todd, it's a pretty simple calculation. Check the amperage draw on the blower motor, measure the length of the circuit; that is, from the power source to the blower and back to ground. Use that length and the amperage draw and a chart that you could find on-line to tell you the wire size, fuse, and switch rating. I consider the blower circuit a critical circuit so you're looking at the 3% voltage drop chart. These charts can be found at http://www.google.ca/url?sa=t&rct=j&q=a ... bs.1,d.dmQ

or other marine wire/electrical manufacturer, or West Marine http://www.westmarine.com/webapp/wcs/st ... arine-Wire.

[yorklyn]

Thanks,
according to the ancor site, a 25 ft run (im guessing, from switch to 1st blower then 2nd blower and back to ground) at 25 amps would require 4GA wire?!?!? the 10% loss chart for the same shows a 12GA wire which is what is on my diagram. I agree that the blower should be on the 3% critical list. may see if I can use a relay to shorten the run.
Thanks for the info!

[Big D]

....from switch to 1st blower then 2nd blower and back to ground....

Careful how you do this. The way you describe it, sounds like you're hooking them up in series. You want these in parallel. If the math works out $ wise for smaller sized wire, run two smaller positive lines; one per blower and two negatives to ground. And consider that the ground doesn't have to be all the way back to the switch/helm area, just a ground source. You could for example have a ground bus bar in the engine compartment for several returns to ground to shorten runs. http://www.bluesea.com/products/2105/Ma ... _Terminals This requires just one heavy ground cable to the bus bar. I use these all the time for both positive and negative feeds. Don't hook everything up to the batteries. The only wires to the batteries should be the main battery cables, no small accessory stuff. Careful planning and layout first will keep costs and headaches down when it comes to wiring.

[yorklyn]

Thats exactly what I plan on doing at the batteries. It was a mess before . I plan on having a neg bus bar in the battery box. Do you have your positive bus in the battery box also ? I was under the impression that I should run a main feed from the positive terminal to a bus bar located by the main panel or somewhere protected inside?
If I run the blowerers seperatly the neg would go to the bus bar in the battery and the positives would run to a single switch rated for over 24amps or to a 30 amp relay that was controled by the switch.

[Big D]

I would not put any hardware, terminal blocks etc in the battery box, it's too corrosive an area, and it usually increases your circuit lengths simply because you're returning all the way back to the batteries. You're better off installing negative bus bars in key locations to accomodate returns for loads you may have in those areas, ie; one in the stern, one at helm, one or two on the bulkhead in front of engines, flybridge, at DC panel, etc. Remember though that these must be considered as part of the return side to all the circuits hooked up to them so the main cables feeding them must be sized to handle total load to the bus bars. You could use a relay to keep wire size down providing the relay location allows for a shorter load wire run. You can run smaller gauge wire to the helm but still requires heavier wire from a source to the relay then to the load/blower. When using relays though, I like fusing both the control and load sides so this doubles your fusing as I see this as being two circuits. You could also use a double pole switch to control two sides at once so each side only has to handle 12 amps each.

I should mention that if you're using relays in the engine compartment, they need to be marine rated/ignition proof.