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  #1  
Old 01-27-2021, 05:39 AM
rockitdoc's Avatar
rockitdoc rockitdoc is offline
 
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Default E Mags and Ignition Switch

Planning my panel. I have dual EMags. Would prefer to have both EMags wired to ignition switch but have seen other panels where there were separate switches for each EMag.

Do EMags have to have separate switches or can they be wired to the ignition switch like conventional mags?

I would prefer to have fewer switches and am more familiar with the mags being on the ignition switch.

Also, what ignition switch is favored for our airplanes?

Thanks, in advance, as usual.

S
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  #2  
Old 01-27-2021, 07:41 AM
Dave S Dave S is offline
 
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Default

I had Stein Air plan and layout my panel using dual e-mags. They gave me 2 switches as well.

I believe each switch needs to have its own switch in order to test them. Think about the traditional mags with a keyed switch, both mags essentially have their own switch as well. You have the Off, R, L Both position. This allows you you test each mag separately. In order to do the same with a switch instead of a key you would need quite a complex switch.

Thats my limited knowledge, maybe someone else has more in-depth or better information.
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  #3  
Old 01-27-2021, 07:55 AM
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Carl Froehlich Carl Froehlich is online now
 
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You can use a standard, old school ignition switch with pMags if you want. Wire it so the engine starts on both ignitions. I prefer separate ignitions switches and a start button, regardless of the ignition choice.

You do your mag check using the ignition switch just as before. You do the periodic test of the pMag internal generator by pulling the associated pMag breaker with the engine running.

Carl
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  #4  
Old 01-27-2021, 08:00 AM
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The extra switches are for testing the PMag generators during your run-up so you don't have to wear out the breakers, as I understand breakers aren't designed to be used as a switch constantly.

Basically you want to know if those PMag generators are working so when you temporarily disconnect ship power using the switch or breaker from the PMag they should continue running normally, no stumbling, etc.

On my run-up after I test the regular P-Lead ground with the key switch, I then test the PMag generator with the separate switches (about 3 seconds each).

Whether you have a key switch or regular switches doesn't matter too much.

Edit: The PMag test switches are simply inline between the breaker and the key switch, again there just to save the breaker and make it convenient. For example, in my 14, due to my height, I can't reach the breakers without taking off at least my right shoulder strap.
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  #5  
Old 01-27-2021, 08:44 AM
PhatRV PhatRV is offline
 
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Default Question to Carl and bkervaski

When testing the Pmag at runup using the regular keyed ignition switch do you get the same RPM drop as in the regular magnetos, as though one magnetos completely dropped out?

Also, when testing the Pmag generator using a panel mounted switch (or disconnect the circuit breaker), do you also get the same RPM drop as using the keyed ignition swith?

I just finished installed the Pmag wiring yesterday but have no way to test the wiring until many months from now.

Thanks
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  #6  
Old 01-27-2021, 08:57 AM
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Carl Froehlich Carl Froehlich is online now
 
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Quote:
Originally Posted by PhatRV View Post
When testing the Pmag at runup using the regular keyed ignition switch do you get the same RPM drop as in the regular magnetos, as though one magnetos completely dropped out?

Also, when testing the Pmag generator using a panel mounted switch (or disconnect the circuit breaker), do you also get the same RPM drop as using the keyed ignition swith?

I just finished installed the Pmag wiring yesterday but have no way to test the wiring until many months from now.

Thanks
PMag RPM drop doing a regular mag check will typically be less than you see with a standard mag.
Note - for those running a pMag has a standard mag, RPM drop will be different dependent on how you set timing.

When testing the pMag internal generator (pulling the power breaker) the pMag will continue to run as before (the reason for the test is to verify this), as such there is no RPM drop. Recommend at least once a year or so reduce RPM during this check to find out how low you can go and still have the pMag produce enough power to run. This is covered in the installation manual.

Carl
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  #7  
Old 01-27-2021, 09:21 AM
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bkervaski bkervaski is offline
 
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Quote:
Originally Posted by PhatRV View Post
Also, when testing the Pmag generator using a panel mounted switch (or disconnect the circuit breaker), do you also get the same RPM drop as using the keyed ignition swith?
There should be no change when testing the PMag generators by removing ships power. If there is a change, you have a problem.
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  #8  
Old 01-27-2021, 10:39 AM
PhatRV PhatRV is offline
 
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Thanks for all the answers.
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  #9  
Old 01-27-2021, 11:14 AM
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Just to re-iterate, the PMag generators are only guaranteed to work at 900 rpm or above so if you're at idle and disconnect ships power (switch or breaker) then the engine will shutdown as the PMags stop firing.

"... the internal alternator will be unable to support the ignition somewhere below 900 rpm ..." (page 22 of the manual)
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  #10  
Old 01-28-2021, 07:47 AM
PhatRV PhatRV is offline
 
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Quote:
Originally Posted by bkervaski View Post
Just to re-iterate, the PMag generators are only guaranteed to work at 900 rpm or above so if you're at idle and disconnect ships power (switch or breaker) then the engine will shutdown as the PMags stop firing.

"... the internal alternator will be unable to support the ignition somewhere below 900 rpm ..." (page 22 of the manual)
Thanks for the explanation. This makes sense now. I was wondering when looking at pictures of RV panels why there are separate Pmag switches in addition on to the ignition keys. Now I know why they are there and why they are needed.
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