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Grounding Of Fuel Senders

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dvanlanen

Joined: 25 Jul 2006
Posts: 122
Location: Madison, WI

Posted: Thu Dec 11, 2008 4:08 pm Post subject: Grounding Of Fuel Senders

I have attended a couple of forums at AirVenture on the subject of aircraft electrical systems, and the presenters have been consistent in recommending the routing of a return wire from every component to the universal ground bus, to help insure that there are no “ground loops” introduced into the system that can cause electrical problems.  I personally think this is relatively cheap insurance against grounding issues, and I plan to follow this advice.  However, with the VDO fuel senders, the sender is not designed to be isolated from the fuel tank / airframe because the inner mounting ring and mounting screws are in metal-to-metal contact with the fuel tank and sender case, and thus are also connected to the airframe by virture of the grounding strap installed from the fuel tank to the airframe.  And even if the sender were to be isolated from the tank and airframe via use of shoulder washers under the mounting screws, there is no grounding lug on the case of the sending unit itself to attach a return wire to.  Has anyone experienced any “ground loop” or other electrical issues with the senders when grounding via a mounting screw as instructed by ZAC?  Has anyone figured out a simple way to isolate the sender from the airframe and install an attachment to the sender case for a return wire to the ground buss?    

Thanks,  

Dave Van Lanen  

601XL – working on wings          [quote][b]

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dvanlanen

Joined: 25 Jul 2006
Posts: 122
Location: Madison, WI

Posted: Thu Dec 11, 2008 4:08 pm Post subject: Grounding Of Fuel Senders

I have attended a couple of forums at AirVenture on the subject of aircraft electrical systems, and the presenters have been consistent in recommending the routing of a return wire from every component to the universal ground bus, to help insure that there are no “ground loops” introduced into the system that can cause electrical problems.  I personally think this is relatively cheap insurance against grounding issues, and I plan to follow this advice.  However, with the VDO fuel senders, the sender is not designed to be isolated from the fuel tank / airframe because the inner mounting ring and mounting screws are in metal-to-metal contact with the fuel tank and sender case, and thus are also connected to the airframe by virture of the grounding strap installed from the fuel tank to the airframe.  And even if the sender were to be isolated from the tank and airframe via use of shoulder washers under the mounting screws, there is no grounding lug on the case of the sending unit itself to attach a return wire to.  Has anyone experienced any “ground loop” or other electrical issues with the senders when grounding via a mounting screw as instructed by ZAC?  Has anyone figured out a simple way to isolate the sender from the airframe and install an attachment to the sender case for a return wire to the ground buss?    

Thanks,  

Dave Van Lanen  

601XL – working on wings          [quote][b]

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leo.gates

Joined: 29 Nov 2008
Posts: 35

Posted: Thu Dec 11, 2008 8:11 pm Post subject: Grounding Of Fuel Senders

I have had no problem with the fuel sender grounded to the tank and the 

tank grounded to the air frame.



-- 

Leo Gates

N601Z - CH601HDS TDO

Rotax 912UL

Dave VanLanen wrote:

 	  Quote: 	
		  

 I Has anyone experienced any “ground loop” or other electrical issues 

 with the senders when grounding via a mounting screw as instructed by 

 ZAC? Has anyone figured out a simple way to isolate the sender from 

 the airframe and install an attachment to the sender case for a return 

 wire to the ground buss?



 Thanks,



 Dave Van Lanen



 601XL – working on wings

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hills(at)sunflower.com
Guest

Posted: Fri Dec 12, 2008 5:52 am Post subject: Grounding Of Fuel Senders

Wouldn't you want to ground the tank to the airframe, in order to discharge

any static that might try to build up and cause a spark when you open the

filler cap to refill?



Roger





--

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Gig Giacona

Joined: 10 Jan 2006
Posts: 1416
Location: El Dorado Arkansas USA

Posted: Fri Dec 12, 2008 6:16 am Post subject: Re: Grounding Of Fuel Senders

 	  hills(at)sunflower.com wrote: 	
		  Wouldn't you want to ground the tank to the airframe, in order to discharge

any static that might try to build up and cause a spark when you open the

filler cap to refill?



Roger





-- 	




Of course. There is even a tab on the tank for a ground wire attachment. The ground for the fuel sender is separate because it is electrically isolated from the tank itself.



As for running the ground for the sender back to the central ground in the aircraft. I followed the plans and grounded all the electrical items in the wing (Lights and fuel sender) in the wing. I was looking a a Cessna that the local A&P had apart for annual and it lights were grounded in the wing as well.

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_________________
W.R. "Gig" Giacona
601XL Under Construction
See my progress at www.peoamerica.net/N601WR

amyvega2005(at)earthlink.
Guest

Posted: Fri Dec 12, 2008 8:34 am Post subject: Grounding Of Fuel Senders

THAT IS A MUST!



jUAN



--

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dvanlanen

Joined: 25 Jul 2006
Posts: 122
Location: Madison, WI

Posted: Sat Dec 13, 2008 8:32 am Post subject: Grounding Of Fuel Senders

I agree with Gig’s statement that the tank must be bonded to the airframe to prevent static electrical discharge during fueling.  However I disagree with the statement that the sender is electrically isolated from the tank itself.  This is not a guarantee, because the sender mounting screws are screwed directly into a metal backing plate, which is in metal-to-metal contact with the back side (inside) of the fuel tank.  The only way the sender might be isolated is if you get “lucky” and all five of the mounting screws do not touch the sides of the mounting holes in the sender.    

Regards,  

Dave 

  

Time: 06:16:52 AM PST US  

Subject: Re: Grounding Of Fuel Senders  

From: "Gig Giacona" <wrgiacona(at)gmail.com> 

 

  

hills(at)sunflower.com wrote:  

 	  Quote: 	
		   Wouldn't you want to ground the tank to the airframe, in order to discharge  

 any static that might try to build up and cause a spark when you open the  

 filler cap to refill?  

   

 Roger  

   

   

   

   

 -- 

  
	


Of course. There is even a tab on the tank for a ground wire attachment. The ground  

for the fuel sender is separate because it is electrically isolated from  

the tank itself.  

As for running the ground for the sender back to the central ground in the aircraft.  

I followed the plans and grounded all the electrical items in the wing (Lights  

and fuel sender) in the wing. I was looking a a Cessna that the local A&P  

had apart for annual and it lights were grounded in the wing as well.  

--------     [quote][b]

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