Message-ID: <000001bdf6f2$e30adb60$2cd652c3@default>
Reply-To: "JENS PETER JENSEN" <jenspeter@get2net.dk>
From: "JENS PETER JENSEN" <jenspeter@get2net.dk>
To: "Lancair Builders Mail List" <lancair.list@olsusa.com>
Subject: Fuel Tank Float Switches
Date: Tue, 13 Oct 1998 21:39:37 -0000
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I have followed the extensive and interesting discussion on different header tank float switches.
I have been a pilot since I was 18 years old and do not have any technical education, besides building my "Lancair 320i" including my own designed Automatic Fuel Transfer. 
But here is my humble contribution.
I try to keep things as simple as possible, which means as few components as possible to go wrong.
In my transfer system I use only one of the 30$ float switches mentioned by Marv, - but I turn it upside down. 
It is probably not the way it was meant to be used, but it has worked without problems for more than 200 hours airborne time.
Test with a meter how high you have to lift the float with the switch in the inverted position before the connection is broken and position it according to that. I can't give you any measures because I have built my own header tank with straight walls that holds almost 12 gallons when topped up.
The float switch will only handle about 600ma so I use a couple of the mentioned 30 amp Bosch relays to run the pumps.
The system is controlled by two 3-position switches with AUTO-OFF and Manual. In AUTO the float switch control the pumps, and the MANUAL position is wired directly in case the float switch or any of the relays should fail. Above each switch I have one of the flat green lights earlier delivered as gear lights from Lancair, to indicate when the transfer pump is running or more correctly,  when there is voltage to it. 
The pumps are actuated at an 8 gallon level and stops at almost 11 gallons, so between that, plus whatever unbalance I can accept is what I will have of endurance should a transfer pump fail.
I have landed my 320i with an 8 gallon unbalance without any problems.
Here in Europe we don't have the wide open spaces where you fly for hours without seeing an airfield, so I find that very sufficient. 
I have added a couple of inches of extra foam to the float to increase buoyancy, and find that I have to fly in  real heavy turbulence before the pumps are actuated unwantedly.
I am sending a photo to Marv for his picture gallery where you might be able to see my set-up.
Jens - flying out of Copenhagen