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two fuses in a circuit

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kenryan

Joined: 20 Oct 2009
Posts: 426

Posted: Fri Aug 07, 2020 9:02 am Post subject: two fuses in a circuit

There has been some discussion about possible issues related to having two fuses in the same circuit. I'm not sure if this was ever resolved.



My situation has to do with the indicator lights that tell me whether or not each of my two fuel pumps is getting power. Of course the wire that powers each pump is fused. But the wire that powers each indicator light is tied to the same circuit as its respective pump, and that wire is protected separately by a 2 amp fuse.

I have attached a picture of my wiring diagram. Wiring is 100% complete, but airplane has not flown yet. Limited testing has not uncovered any issues.

If the existence of these two amp fuses in my system could cause me to lose power to a fuel pump, I would remove them, unless removing them causes other problems.

See attached and as always, thanks!

Ken

wiring-diagram.jpg

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alec(at)alecmyers.com
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Posted: Fri Aug 07, 2020 9:11 am Post subject: two fuses in a circuit

Noob question... why is a separate fuse for the indicator light a good idea, if the circuit is already protected?



On Aug 7, 2020, at 13:03, Ken Ryan <keninalaska(at)gmail.com> wrote:





There has been some discussion about possible issues related to having two fuses in the same circuit. I'm not sure if this was ever resolved.



My situation has to do with the indicator lights that tell me whether or not each of my two fuel pumps is getting power. Of course the wire that powers each pump is fused. But the wire that powers each indicator light is tied to the same circuit as its respective pump, and that wire is protected separately by a 2 amp fuse.



I have attached a picture of my wiring diagram. Wiring is 100% complete, but airplane has not flown yet. Limited testing has not uncovered any issues.



If the existence of these two amp fuses in my system could cause me to lose power to a fuel pump, I would remove them, unless removing them causes other problems.



See attached and as always, thanks!



Ken

<wiring-diagram.jpg>

user9253

Joined: 28 Mar 2008
Posts: 1921
Location: Riley TWP Michigan

Posted: Fri Aug 07, 2020 9:24 am Post subject: Re: two fuses in a circuit

Those 2 amp fuses are not a problem.  If you want to experiment, you could short out 

an indicator light to make sure that the fuel pump fuse does not blow along with the 2 amp fuse.

_________________
Joe Gores

kenryan

Joined: 20 Oct 2009
Posts: 426

Posted: Fri Aug 07, 2020 9:29 am Post subject: two fuses in a circuit

If the indicator light shorts out I would not want that to take down the pump itself.



On Fri, Aug 7, 2020, 09:18 Alec Myers <alec(at)alecmyers.com (alec(at)alecmyers.com)> wrote:



 	  Quote: 	
		  --> AeroElectric-List message posted by: Alec Myers <alec(at)alecmyers.com (alec(at)alecmyers.com)>

 

 Noob question... why is a separate fuse for the indicator light a good idea, if the circuit is already protected?

 

 On Aug 7, 2020, at 13:03, Ken Ryan <keninalaska(at)gmail.com (keninalaska(at)gmail.com)> wrote:

 

 

 There has been some discussion about possible issues related to having two fuses in the same circuit. I'm not sure if this was ever resolved.

 

 My situation has to do with the indicator lights that tell me whether or not each of my two fuel pumps is getting power. Of course the wire that powers each pump is fused. But the wire that powers each indicator light is tied to the same circuit as its respective pump, and that wire is protected separately by a 2 amp fuse.

 

 I have attached a picture of my wiring diagram. Wiring is 100% complete, but airplane has not flown yet. Limited testing has not uncovered any issues.

 

 If the existence of these two amp fuses in my system could cause me to lose power to a fuel pump, I would remove them, unless removing them causes other problems.

 

 See attached and as always, thanks!

 

 Ken

 <wiring-diagram.jpg>

 

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david(at)carter.net
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Posted: Fri Aug 07, 2020 9:42 am Post subject: two fuses in a circuit

It's not the circuit that is protected by the breaker or fuse, it's the *wire*. If the wire running to the indicator lamp is smaller than the 16 gauge running to the pump, the fuse is appropriate. I don't see the wire size labeled. That fuse should be as near as possible to the junction of the pump wire & the smaller indicator wire. If it's wired according to the diagram, I don't see any way the fuse to the indicator could take out the pump, because that fuse is not in the path of the electrons going through the pump. ---

David Carter

david(at)carter.net (david(at)carter.net)



On Fri, Aug 7, 2020 at 1:13 PM Alec Myers <alec(at)alecmyers.com (alec(at)alecmyers.com)> wrote:



 	  Quote: 	
		  --> AeroElectric-List message posted by: Alec Myers <alec(at)alecmyers.com (alec(at)alecmyers.com)>

 

 Noob question... why is a separate fuse for the indicator light a good idea, if the circuit is already protected?

 

 On Aug 7, 2020, at 13:03, Ken Ryan <keninalaska(at)gmail.com (keninalaska(at)gmail.com)> wrote:

 

 

 There has been some discussion about possible issues related to having two fuses in the same circuit. I'm not sure if this was ever resolved.

 

 My situation has to do with the indicator lights that tell me whether or not each of my two fuel pumps is getting power. Of course the wire that powers each pump is fused. But the wire that powers each indicator light is tied to the same circuit as its respective pump, and that wire is protected separately by a 2 amp fuse.

 

 I have attached a picture of my wiring diagram. Wiring is 100% complete, but airplane has not flown yet. Limited testing has not uncovered any issues.

 

 If the existence of these two amp fuses in my system could cause me to lose power to a fuel pump, I would remove them, unless removing them causes other problems.

 

 See attached and as always, thanks!

 

 Ken

 <wiring-diagram.jpg>

 

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ceengland7(at)gmail.com
Guest

Posted: Fri Aug 07, 2020 9:49 am Post subject: two fuses in a circuit

On 8/7/2020 11:58 AM, Ken Ryan wrote:

 	  Quote: 	
		   There has been some discussion about possible issues related to having 

 two fuses in the same circuit. I'm not sure if this was ever resolved.



 My situation has to do with the indicator lights that tell me whether 

 or not each of my two fuel pumps is getting power. Of course the wire 

 that powers each pump is fused. But the wire that powers each 

 indicator light is tied to the same circuit as its respective pump, 

 and that wire is protected separately by a 2 amp fuse.



 I have attached a picture of my wiring diagram. Wiring is 100% 

 complete, but airplane has not flown yet. Limited testing has not 

 uncovered any issues.



 If the existence of these two amp fuses in my system could cause me to 

 lose power to a fuel pump, I would remove them, unless removing them 

 causes other problems.



 See attached and as always, thanks!



 Ken

If you move the lamp connection point (and fuse) back to the source, any 
	


issue disappears. Unless you're using the CB to control the pump, of course.



What pumps are you using? Facets run on about 2-3A; Walbro injection 

pumps expect a 15A protection device (startup surge). The Wabros are 

marked right on the pump.



Charlie



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kenryan

Joined: 20 Oct 2009
Posts: 426

Posted: Fri Aug 07, 2020 11:17 am Post subject: two fuses in a circuit

Thanks everyone.



On Fri, Aug 7, 2020, 09:36 user9253 <fransew(at)gmail.com (fransew(at)gmail.com)> wrote:



 	  Quote: 	
		  --> AeroElectric-List message posted by: "user9253" <fransew(at)gmail.com (fransew(at)gmail.com)>

 

 Those 2 amp fuses are not a problem.  If you want to experiment, you could short out 

 an indicator light to make sure that the fuel pump fuse does not blow along with the 2 amp fuse.

 

 --------

 Joe Gores

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=497559#497559

 

 

 

 

 

 

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finn.usa(at)gmail.com
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Posted: Fri Aug 07, 2020 4:50 pm Post subject: two fuses in a circuit

My GSL393 is marked "20 amp fuse".



Finn

On 8/7/2020 1:45 PM, Charlie England wrote:

 	  Quote: 	
		   

 <ceengland7(at)gmail.com>



 On 8/7/2020 11:58 AM, Ken Ryan wrote:

> There has been some discussion about possible issues related to 

> having two fuses in the same circuit. I'm not sure if this was ever 

> resolved.

>

> My situation has to do with the indicator lights that tell me whether 

> or not each of my two fuel pumps is getting power. Of course the wire 

> that powers each pump is fused. But the wire that powers each 

> indicator light is tied to the same circuit as its respective pump, 

> and that wire is protected separately by a 2 amp fuse.

>

> I have attached a picture of my wiring diagram. Wiring is 100% 

> complete, but airplane has not flown yet. Limited testing has not 

> uncovered any issues.

>

> If the existence of these two amp fuses in my system could cause me 

> to lose power to a fuel pump, I would remove them, unless removing 

> them causes other problems.

>

> See attached and as always, thanks!

>

> Ken

 If you move the lamp connection point (and fuse) back to the source, 

 any issue disappears. Unless you're using the CB to control the pump, 

 of course.



 What pumps are you using? Facets run on about 2-3A; Walbro injection 

 pumps expect a 15A protection device (startup surge). The Wabros are 

 marked right on the pump.



 Charlie




	




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ceengland7(at)gmail.com
Guest

Posted: Fri Aug 07, 2020 5:52 pm Post subject: two fuses in a circuit

Thanks Finn; I'm having a bad memory day (as you probably saw over on 

the rotary list).



On 8/7/2020 7:45 PM, Finn Lassen wrote:

 	  Quote: 	
		   



 My GSL393 is marked "20 amp fuse".



 Finn

 On 8/7/2020 1:45 PM, Charlie England wrote:

> 

> <ceengland7(at)gmail.com>

>

> On 8/7/2020 11:58 AM, Ken Ryan wrote:

>> There has been some discussion about possible issues related to 

>> having two fuses in the same circuit. I'm not sure if this was ever 

>> resolved.

>>

>> My situation has to do with the indicator lights that tell me 

>> whether or not each of my two fuel pumps is getting power. Of course 

>> the wire that powers each pump is fused. But the wire that powers 

>> each indicator light is tied to the same circuit as its respective 

>> pump, and that wire is protected separately by a 2 amp fuse.

>>

>> I have attached a picture of my wiring diagram. Wiring is 100% 

>> complete, but airplane has not flown yet. Limited testing has not 

>> uncovered any issues.

>>

>> If the existence of these two amp fuses in my system could cause me 

>> to lose power to a fuel pump, I would remove them, unless removing 

>> them causes other problems.

>>

>> See attached and as always, thanks!

>>

>> Ken

> If you move the lamp connection point (and fuse) back to the source, 

> any issue disappears. Unless you're using the CB to control the pump, 

> of course.

>

> What pumps are you using? Facets run on about 2-3A; Walbro injection 

> pumps expect a 15A protection device (startup surge). The Wabros are 

> marked right on the pump.

>

> Charlie

>




	




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kenryan

Joined: 20 Oct 2009
Posts: 426

Posted: Fri Aug 07, 2020 6:30 pm Post subject: two fuses in a circuit

Charlie, the pumps are Walbro. I believe they are GSL395. I was advised to use 10 amp fuse but I will double check. I did go to the Walbro website but couldn't find specs.



On Fri, Aug 7, 2020 at 9:56 AM Charlie England <ceengland7(at)gmail.com (ceengland7(at)gmail.com)> wrote:



 	  Quote: 	
		  --> AeroElectric-List message posted by: Charlie England <ceengland7(at)gmail.com (ceengland7(at)gmail.com)>

 

 On 8/7/2020 11:58 AM, Ken Ryan wrote:

 > There has been some discussion about possible issues related to having 

 > two fuses in the same circuit. I'm not sure if this was ever resolved.

 >

 > My situation has to do with the indicator lights that tell me whether 

 > or not each of my two fuel pumps is getting power. Of course the wire 

 > that powers each pump is fused. But the wire that powers each 

 > indicator light is tied to the same circuit as its respective pump, 

 > and that wire is protected separately by a 2 amp fuse.

 >

 > I have attached a picture of my wiring diagram. Wiring is 100% 

 > complete, but airplane has not flown yet. Limited testing has not 

 > uncovered any issues.

 >

 > If the existence of these two amp fuses in my system could cause me to 

 > lose power to a fuel pump, I would remove them, unless removing them 

 > causes other problems.

 >

 > See attached and as always, thanks!

 >

 > Ken

 If you move the lamp connection point (and fuse) back to the source, any 

 issue disappears. Unless you're using the CB to control the pump, of course.

 

 What pumps are you using? Facets run on about 2-3A; Walbro injection 

 pumps expect a 15A protection device (startup surge). The Wabros are 

 marked right on the pump.

 

 Charlie

 

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kenryan

Joined: 20 Oct 2009
Posts: 426

Posted: Fri Aug 07, 2020 6:31 pm Post subject: two fuses in a circuit

I will check the pump and see if it is marked.



On Fri, Aug 7, 2020 at 6:26 PM Ken Ryan <keninalaska(at)gmail.com (keninalaska(at)gmail.com)> wrote:



 	  Quote: 	
		  Charlie, the pumps are Walbro. I believe they are GSL395. I was advised to use 10 amp fuse but I will double check. I did go to the Walbro website but couldn't find specs.



On Fri, Aug 7, 2020 at 9:56 AM Charlie England <ceengland7(at)gmail.com (ceengland7(at)gmail.com)> wrote:



 	  Quote: 	
		  --> AeroElectric-List message posted by: Charlie England <ceengland7(at)gmail.com (ceengland7(at)gmail.com)>

 

 On 8/7/2020 11:58 AM, Ken Ryan wrote:

 > There has been some discussion about possible issues related to having 

 > two fuses in the same circuit. I'm not sure if this was ever resolved.

 >

 > My situation has to do with the indicator lights that tell me whether 

 > or not each of my two fuel pumps is getting power. Of course the wire 

 > that powers each pump is fused. But the wire that powers each 

 > indicator light is tied to the same circuit as its respective pump, 

 > and that wire is protected separately by a 2 amp fuse.

 >

 > I have attached a picture of my wiring diagram. Wiring is 100% 

 > complete, but airplane has not flown yet. Limited testing has not 

 > uncovered any issues.

 >

 > If the existence of these two amp fuses in my system could cause me to 

 > lose power to a fuel pump, I would remove them, unless removing them 

 > causes other problems.

 >

 > See attached and as always, thanks!

 >

 > Ken

 If you move the lamp connection point (and fuse) back to the source, any 

 issue disappears. Unless you're using the CB to control the pump, of course.

 

 What pumps are you using? Facets run on about 2-3A; Walbro injection 

 pumps expect a 15A protection device (startup surge). The Wabros are 

 marked right on the pump.

 

 Charlie

 

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ceengland7(at)gmail.com
Guest

Posted: Fri Aug 07, 2020 7:22 pm Post subject: two fuses in a circuit

Found a link showing the 395 along with the other Walbro gerotor pumps. It shows 130 lph (at) 15 psi, so the 10A fusing sounds more plausible.



 https://walbrofuelpumps.com/walbro-gsl-series-universal-inline-fuel-pumps

 I was expecting either 3-6 psi for a carb, or 40-60 psi for electronic injection.

 Charlie

 Sent from BlueMail 

 On Aug 7, 2020, at 9:36 PM, Ken Ryan <keninalaska(at)gmail.com (keninalaska(at)gmail.com)> wrote: 	  Quote: 	
		   Charlie, the pumps are Walbro. I believe they are GSL395. I was advised to use 10 amp fuse but I will double check. I did go to the Walbro website but couldn't find specs.



On Fri, Aug 7, 2020 at 9:56 AM Charlie England <ceengland7(at)gmail.com (ceengland7(at)gmail.com)> wrote:



 	  Quote: 	
		  --> AeroElectric-List message posted by: Charlie England <ceengland7(at)gmail.com (ceengland7(at)gmail.com)>

 

 On 8/7/2020 11:58 AM, Ken Ryan wrote:

 > There has been some discussion about possible issues related to having 

 > two fuses in the same circuit. I'm not sure if this was ever resolved.

 >

 > My situation has to do with the indicator lights that tell me whether 

 > or not each of my two fuel pumps is getting power. Of course the wire 

 > that powers each pump is fused. But the wire that powers each 

 > indicator light is tied to the same circuit as its respective pump, 

 > and that wire is protected separately by a 2 amp fuse.

 >

 > I have attached a picture of my wiring diagram. Wiring is 100% 

 > complete, but airplane has not flown yet. Limited testing has not 

 > uncovered any issues.

 >

 > If the existence of these two amp fuses in my system could cause me to 

 > lose power to a fuel pump, I would remove them, unless removing them 

 > causes other problems.

 >

 > See attached and as always, thanks!

 >

 > Ken

 If you move the lamp connection point (and fuse) back to the source, any 

 issue disappears. Unless you're using the CB to control the pump, of course.

 

 What pumps are you using? Facets run on about 2-3A; Walbro injection 

 pumps expect a 15A protection device (startup surge). The Wabros are 

 marked right on the pump.

 

 Charlie

 

 -- 

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johnbright

Joined: 14 Dec 2011
Posts: 165
Location: Newport News, VA

Posted: Fri Aug 07, 2020 11:06 pm Post subject: Re: two fuses in a circuit

Walbro 395 flow and current... the Walbro page I found had broken links to the jpg graphs but those broken links contain file names and with the file names one can google and get https://walbrofuelpumps.com/images/flow-charts/



In that file space is "GSL395-Flow-Chart.jpg"... attached.

GSL395-Flow-Chart.jpg

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N1921R links

nuckolls.bob(at)aeroelect
Guest

Posted: Sat Aug 08, 2020 6:57 am Post subject: two fuses in a circuit

If you use an LED indicator, the obligatory

 current limiting resistor for the LED can

 be installed at the 'head end' of the indicator

 feeder where the fuse would be located . . .

 putting the resistor there limits current

 in that feeder to milliamps even when shorted

 to ground. The fuse goes away.



 

   Bob . . .

kenryan

Joined: 20 Oct 2009
Posts: 426

Posted: Sat Aug 08, 2020 7:28 am Post subject: two fuses in a circuit

Thanks for that Bob, and thanks Charlie for the fusing advice.



On Sat, Aug 8, 2020 at 7:01 AM Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:



 	  Quote: 	
		    If you use an LED indicator, the obligatory

 current limiting resistor for the LED can

 be installed at the 'head end' of the indicator

 feeder where the fuse would be located . . .

 putting the resistor there limits current

 in that feeder to milliamps even when shorted

 to ground. The fuse goes away.



 

   Bob . . .

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