Dan,
I have a successful wing aux tank setup.
It consists of the following hardware:
2xFacet Fuel pump - ACS # 40108 3xFloat Switch - ACS # 6905-400 3x12v Electrical switches 1x12v Relay Tubing, hoses, and fittings as required
Each aux tank gets a pick-up tube (with screen), fuel pump and separate fuel line to the top of the main tank. The line must enter the tank at the top to prevent siphoning. For vent ideas, look at how the RV crowd does theirs.
The wiring is done thus: Battery buss to the system switch to the float switch mounted in the top of the main tank. The float switch is installed to turn off when the main is full so you cannot over fill it. The power from the float switch then goes to trigger the relay as the float switch can't carry the amps required by the pumps. The relay gets its power from the system switch. Relay power then goes to the individual pump swiches. One pump swich for both pumps will not do as these pumps do not like to run dry. One aux tank will empty before the other.
The remaining two float swiches are installed into each tank as low as you can get them. They serve to tell you when the aux tank runs dry. Mine are hooked up to warning lights. They remind me to turn off the pump on that tank when it is dry.
I found a relay that can be set with a time delay. I set mine at three seconds. They delay switch keeps the system from rapidly cycling when you are in rough air and fuell is sloshing in the main tank.
Operationally, I take off and climb on the main. When I level off, I switch on the system and the fuel pumps. As the fuel burns down, the pumps cycle on and off to keep the main full. When the aux tanks are depleted and the warning lights illuminate, I turn the pumps and system off. I do not manually tranfer the fuel, the system does it for me. Since the aux tanks are on the CG, I normally don't have to trim once the cruise is set. I monitor the transfer by watching the main tank fuel gage.
I know this is a lot of bubble gum to chew. Any further questions, just ask.
_________________ Bob Highley
N711SH
SN 835
KLAL
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