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Facet Boost Pump Fuses

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messydeer

Joined: 13 Feb 2006
Posts: 214
Location: Bellingham, WA

Posted: Thu Jul 15, 2010 6:36 am Post subject: Facet Boost Pump Fuses

Hi!



I'm wondering what size fuse to use for my Facet 40104 boost pump. I talked to somebody in their engineering department  and he said 3 is recommended. I told him I'd heard of a couple people blowing 3A fuses in a 40105. They replaced it with a 5A and had no further problems. For some reason Facet is stingy with documentation. They list 20 or more pumps and give only their psi and gph ranges individually, then lump them all together and say they draw an average of 1.6A. The 04 I have is the smallest, with the 05 only slightly bigger. http://www.facet-purolator.com/index.php?option=com_content&task=category&sectionid=7&id=16&Itemid=31 



I asked if putting a 5A in would work. The Facet dude said it probably would work, but it'd increase the chance of wrecking the coil, but wouldn't get hot enough to start a fire. I have 15-20' round trip of 20awg wire going to it, so I know a 5A fuse would protect the wire. I plan on using this as a boost pump for my mechanical, turning it on before startup,  check the pressure, then some seconds later crank the engine. It would then be turned off at altitude and back on for landing. The boost pump is near the bottom of the cowl, ~1' below the mechanical pump. They are in series with no recirculation, so it would be pumping with no flow until cranking.



The fuses I'm thinking of are the fast ATO/ATC style. I could go with slower 3AG fuses, if there is a any advantage in doing this. I assume that if the Facet is pumping against a closed valve a couple feet downstream it would in a few seconds reach its max current draw. I haven't heard of anyone wrecking their boost pump, just a few that blew 3A fuses. 



I'm waiting for Facet to return my emailed questions. I also could bench test this pump with my VOM and see what the current draw really is. 



Suggestions?

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_________________
Dan

nuckolls.bob(at)aeroelect
Guest

Posted: Thu Jul 15, 2010 1:40 pm Post subject: Facet Boost Pump Fuses

At 09:36 AM 7/15/2010, you wrote:

 	  Quote: 	
		  



Hi!

I asked if putting a 5A in would work. The Facet dude said it 

probably would work, but it'd increase the chance of wrecking the 

coil, but wouldn't get hot enough to start a fire.


	


   That is . . . shall we say . . . no . . . I'll be civil.

   First, supply fuse (at least in an airplane) is never

   intended to protect devices . . . only wiring.

 	  Quote: 	
		  I have 15-20' round trip of 20awg wire going to it, so I know a 5A 

fuse would protect the wire. I plan on using this as a boost pump 

for my mechanical, turning it on before startup,  check the 

pressure, then some seconds later crank the engine. It would then be 

turned off at altitude and back on for landing. The boost pump is 

near the bottom of the cowl, ~1' below the mechanical pump. They are 

in series with no recirculation, so it would be pumping with no flow 

until cranking.


	


    If it's 20AWG, put a 7A fuse in an don't loose

    any sleep over it. Having too robust a feeder

    protection cannot put anything inside the pump

    at risk.



 	  Quote: 	
		  The fuses I'm thinking of are the fast ATO/ATC style. I could go 

with slower 3AG fuses, if there is a any advantage in doing this. I 

assume that if the Facet is pumping against a closed valve a couple 

feet downstream it would in a few seconds reach its max current 

draw. I haven't heard of anyone wrecking their boost pump, just a 

few that blew 3A fuses.



I'm waiting for Facet to return my emailed questions. I also could 

bench test this pump with my VOM and see what the current draw really is.


	


   We had a thread on this topic some months ago. The

   current draw by solenoid pumps is pulsed. I cited

   a number of patents that go back to the 50s or earlier.

   The first devices had mechanical contacts that pulsed

   the coil when the fuel pumping piston approached end

   of stroke thus pulling the piston back against a spring

   for another stroke. The energy consumption of these

   pumps WAS somewhat dependent in fuel flow. You could

   hear the stroke-rate go up as flow increased.



   Modern pumps are all solid state, no switches and

   simply pulse the coil so many times per minute irrespective

   of flow rate. If the flow is high, the piston strokes

   long in the bore. If the flow is low, the piston barely

   moves with each pulsed and tends to stay in the max

   compressed end of the stroke.



   Trying to get any sort of current measurement on

   on of these things by watching a meter is meaningless.

   It will be all over the place.  A true ENERGY

   measurement must be made with some RMS type ammeter

   having a very long time constant . . . or a fast

   data acquisition system that will secure a sufficiently

   verbose data stream to do bit-wise integration of

   current values.



   I've got that on my list of things to do . . . in fact,

   there's a Facet pump on my bench loaned to me by a

   generous Lister for that purpose. I tried to get

   real engineering data from Facet on several occasions

   with no success. I'm doubtful that anyone there

   even understood the question.



   Nonetheless, the have been building a really slick,

   trouble-free product for a very long time. You don't

   have to know how it all works to serve great hamburgers,

   fries and a shake . . . just follow directions. It's

   the ISO way.



   Bob . . .

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jloram

Joined: 07 Nov 2009
Posts: 54
Location: United States

Posted: Thu Jul 15, 2010 6:20 pm Post subject: Facet Boost Pump Fuses

[quote] --

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messydeer

Joined: 13 Feb 2006
Posts: 214
Location: Bellingham, WA

Posted: Fri Jul 16, 2010 10:57 am Post subject: Re: Facet Boost Pump Fuses

Thanks, Bob 



Nice to get some background on how the pump works.



Facet told me in an email 5A would be fine, I see from Table 11-3 of AC43.13-1B a 5A fuse would work, and you say 7A is peachy. So I'm happy and will think no more about this issue.

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_________________
Dan

nuckolls.bob(at)aeroelect
Guest

Posted: Fri Jul 16, 2010 5:05 pm Post subject: Facet Boost Pump Fuses

>     If it's 20AWG, put a 7A fuse in an don't loose

 >     any sleep over it. Having too robust a feeder

 >     protection cannot put anything inside the pump

 >     at risk.

 > 

 Would this reasoning not lead to running "really" robust feeders/fuses, and

 then a fuel pump (or other device) with and internal problem that is

 generating a lot of heat (fire/smoke)?



 I agree that we're not trying to 'save/protect' the pump, rather trying to

 prevent smoking wires, but a smoking load can be a big problem, too. 



     Most devices we use in our airplanes are considered

     not flight worthy if they exhibit any failure mode that

     becomes a hazard source for combustion . . . emitting

     smoke is frowned upon too. The "really robust" feeders

     was more rhetorical than anything else . . . after all,

     with a fuse block, one has the option of selecting the

     optimal fuse for each application . . . and easily

     changing it if later circumstances suggest it's a

     good idea. Specifically, with the FACET being a low

     energy device totally enclosed in a metal box. The

     risks are nil . . .



 [img]cid:7.1.0.9.0.20100716195619.01fe8f38(at)aeroelectric.com.0[/img] 



     Although I seem to recall that G. Richter suggested

     that the entire airplane could be configured with an

     array of one-size-fits-all, self-resetting PTC polyswitches

     soldered to a nifty etched circuit board product he

     offered. But when it's so easy to achieve the elegant

     solution, why not do it?



 

   Bob . . .

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