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FireFly Electrics

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henry.voris

Joined: 02 Mar 2007
Posts: 116
Location: Pueo Field, Kula, Maui

Posted: Fri Sep 14, 2007 1:36 pm Post subject: FireFly Electrics

As the fourth owner of my FireFly I am obligated to bring some order to the wiring...



	Quick description of the DC system... A 447 fired  alternator, AC from the light loop runs through two fuses to a KW Voltage Regulator. DC power and ground run from the regulator to a terminal block where it is distributed to three customers... strobes, landing lights, and the fuel pump. Each of the customer circuits has an on/off switch in line. The FireFly's cage is not included in the circuit, so the negative end of each customer circuit returns to the terminal block.



The system works OK... But it seems odd that:



(A) The engine is not ground to the cage (no continuity).



(B) The fuses are on the alternator side (AC side) of the regulator, rather than the customer side (DC side).



(C) The cage is not used as a ground in the DC system. 



	Are these problems... or is it the way we do it with airplanes?



	Thanks in advance...



Henry



FireFly Five-Charlie-Bravo

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Henry
Firefly Five-Charlie-Bravo

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jindoguy(at)gmail.com
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Posted: Fri Sep 14, 2007 3:40 pm Post subject: FireFly Electrics

Henry, You don't say so, but I would guess your 447 has points. My suggestion would be:

1. Get the Rotax manuals for your engine and check their wiring recommendations.

2. Go to the AeroElectric Connection here on the Matronics lists and Bob Knuckolls'  web site. Buy his book and check out Figure Z-17. 

3. Is there a large capacitor in the 12V + line from the VR or do you have a battery somewhere in the system?



Rick



On 9/14/07, henry.voris < henry_voris(at)yahoo.com (henry_voris(at)yahoo.com)> wrote:[quote]--> Kolb-List message posted by: " henry.voris" <henry_voris(at)yahoo.com (henry_voris(at)yahoo.com)>



As the fourth owner of my FireFly I am obligated to bring some order to the wiring...



        Quick description of the DC system... A 447 fired  alternator, AC from the light loop runs through two fuses to a KW Voltage Regulator. DC power and ground run from the regulator to a terminal block where it is distributed to three customers... strobes, landing lights, and the fuel pump. Each of the customer circuits has an on/off switch in line. The FireFly's cage is not included in the circuit, so the negative end of each customer circuit returns to the terminal block. 



The system works OK... But it seems odd that:



(A) The engine is not ground to the cage (no continuity).



(B) The fuses are on the alternator side (AC side) of the regulator, rather than the customer side (DC side). 



(C) The cage is not used as a ground in the DC system.



        Are these problems... or is it the way we do it with airplanes?



        Thanks in advance...



Henry



FireFly Five-Charlie-Bravo 



--------

Henry

Firefly Five-Charlie-Bravo



Do Not Archive





Read this topic online here:



http://forums.matronics.com/viewtopic.php?p=134462#134462 

when you live at the airport.  [quote][b]

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henry.voris

Joined: 02 Mar 2007
Posts: 116
Location: Pueo Field, Kula, Maui

Posted: Sun Sep 16, 2007 9:15 pm Post subject: Re: FireFly Electrics

Rick,

	Nope my 477 doesn't use points.	

	I have the Rotax manuals...

	Thanks for the tip on "AeroElectric Connection here on the Matronics lists and Bob Knuckolls' web site."

	Also, there's no cap or battery... I do plan to install a small battery (to check the electric fuel pump before starting the engine...), but that is a future project. 

	My concern now revolves around the fact that the DC system (everything past the KW Voltage Regulator) doesn't use the cage as a bus for the ground... And there is no continuity between the engine and the cage. I can't think of a reason why this is wrong, it simply isn't the way I would have done it if I had wired the plane from the get-go, so it makes me a bit uneasy.

	Thanks for the help...

Aloha,

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Firefly Five-Charlie-Bravo

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lucien

Joined: 03 Jun 2007
Posts: 721
Location: santa fe, NM

Posted: Mon Sep 17, 2007 5:38 am Post subject: Re: FireFly Electrics

 	  henry.voris wrote: 	
		  Rick,

	Nope my 477 doesn't use points.	

	I have the Rotax manuals...

	Thanks for the tip on "AeroElectric Connection here on the Matronics lists and Bob Knuckolls' web site."

	Also, there's no cap or battery... I do plan to install a small battery (to check the electric fuel pump before starting the engine...), but that is a future project. 

	My concern now revolves around the fact that the DC system (everything past the KW Voltage Regulator) doesn't use the cage as a bus for the ground... And there is no continuity between the engine and the cage. I can't think of a reason why this is wrong, it simply isn't the way I would have done it if I had wired the plane from the get-go, so it makes me a bit uneasy.

	Thanks for the help...

Aloha, 	




This isn't necessarily bad. One drawback of using the cage as the ground is magnetization that can occur to the tubes due to the current flow through them. This can give you fits trying to get your compass to work . This was a problem on my titan.



Though this is usually only a problem if you've got electric start where a whole bunch of current goes through the frame.



Otherwise, as long as everything shares the same ground, IIRC, you should be ok whether it's the frame or not....

(unless you need more than one ground, but I can't think of a situation where you need that?)



LS

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Titan II SS

jindoguy(at)gmail.com
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Posted: Mon Sep 17, 2007 7:12 am Post subject: FireFly Electrics

Henry, I can't find a wiring recommendation for the KW regulator, but the Rotax installation manual shows a 2000uf 25V capacitor used for either of their rectifier/regulators when no battery is installed. See pages 18-3 figure 39 for the 866 080 R/R and page 18-5 figure 42 for the 264 870 R/R. 

I have the KW on my 582 and I run a 20,000uf /50V cap on the 12V output WITH a battery. In this application it's used to kill the high pitch squeal in the radio that rises and falls with alternator revs.

I was thinking of those little diodes in the CDI units that take the ignition secondary voltage if a plug is ungrounded (why you should use an ignition spark tester when checking for spark) when I asked about points.  

As far as putting the fuses on the AC side of the alternator output, that would be a good question for Bob. Perhaps the builder was thinking of a poorman's protection against a runaway alternator. Have you checked the size of the fuses? Are they rated for AC current?  



Rick



On 9/17/07, henry.voris <henry_voris(at)yahoo.com (henry_voris(at)yahoo.com)> wrote:[quote] --> Kolb-List message posted by: "henry.voris" <henry_voris(at)yahoo.com (henry_voris(at)yahoo.com)>



Rick,

        Nope my 477 doesn't use points.

        I have the Rotax manuals... 

        Thanks for the tip on "AeroElectric Connection here on the Matronics lists and Bob Knuckolls' web site."

        Also, there's no cap or battery... I do plan to install a small battery (to check the electric fuel pump before starting the engine...), but that is a future project. 

        My concern now revolves around the fact that the DC system (everything past the KW Voltage Regulator) doesn't use the cage as a bus for the ground... And there is no continuity between the engine and the cage. I can't think of a reason why this is wrong, it simply isn't the way I would have done it if I had wired the plane from the get-go, so it makes me a bit uneasy. 

        Thanks for the help...

Aloha,



--------

Henry

Firefly Five-Charlie-Bravo



Do Not Archive





Read this topic online here:



 

"Ya'll drop on in"

takes on a whole new meaning

when you live at the airport.  [quote][b]

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henry.voris

Joined: 02 Mar 2007
Posts: 116
Location: Pueo Field, Kula, Maui

Posted: Fri Sep 21, 2007 2:50 pm Post subject: Re: FireFly Electrics

Sorry about dropping out... Problems with my wireless source took me off the internet...



Lucien,



	I will ground the engine to the frame and use the cage as a ground bus. The total load running through it is small. And on Maui, where the area is small and the landmarks well known, the compass is mostly for looks.



	

Rick,



	I have the drawing that comes with the KW rectifier and there's no sign of a cap. Also I recall their ad saying that they no longer require a cap. or load...(distinguishing them from the Rotax rectifier setup...)

	

	Bob contacted me by back channels and explained the capacitor set up to can the RFI... Also he thinks the fuse between the KW and the alternator is to protect the alternator...



Thanks Guys...

Aloha

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Firefly Five-Charlie-Bravo

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