Master Switch Wiring

[marshawk 82]

Just getting ready to wire the panel on my avid with the ea81 and looking for some help. Luckly my brother is a mechanic but what we want to know is the master switch better to be mechanical or electrical and do you switch the positive or the negative, so we can still run hot to ignition and fuel, is this correct?

Thanks for any input

[SuberAvid 617]

I used a Cesna type split switch for my master switch with one to the solonoid at the battery and one to the alternator. The battery one is a negative if I remember right and it trips the solonoid to energize the battery main positive cable to the positive buss. The alternator switch is positive to send signal power to the alternator. I used two separate single pole switched for my ignitions; one taking positive from the buss and one coming direcly off the battery and bypassing the battery solonoid so I still have ignition power on that ignition if I have to shut down the master switch. Probably a lot of ways to do this but that was my thinking.

[EDMO 1078]

I used a Cesna type split switch for my master switch with one to the solonoid at the battery and one to the alternator. The battery one is a negative if I remember right and it trips the solonoid to energize the battery main positive cable to the positive buss. The alternator switch is positive to send signal power to the alternator. I used two separate single pole switched for my ignitions; one taking positive from the buss and one coming direcly off the battery and bypassing the battery solonoid so I still have ignition power on that ignition if I have to shut down the master switch. Probably a lot of ways to do this but that was my thinking.

I am sure that SuberAvid has a system that works - he has been flying his for a while. I like the twin red Cessna Master switches, however, two heavy, 60 amp toggle or rocker switches will do the same job, and can be seperated, but may cost more than the $27, or so, nice Cessna switches.

However, I feel that a couple of technical terms need to be corrected here.

The battery master is connected to a POSITIVE wire,(but I can see that a negative connection would work if that is the only connection to ground), to the CONTINUOUS USE solonoid which is in the POSITIVE main wire close to the battery.

The alternator Master should be on the OUTPUT side of the alternator between it and POSITIVE power bus, bercause the alternator is self-energizing and will continue to be in runaway condition even if the signal power is disconnected.

You should have some heavy (40 to 60 amp) breakers on the alternator output circuit, and on the main battery circuit.

The seperate ignition and fuel pump wire should be on seperate smaller circuit breakers and switches.

I am not an expert on this, so if there are builders who can add to this, or correct my writing, please feel free to do so.

I may have some books on this other than the standard twin-mag wirings you mostly see.

Sorry I couldnt write to Marshawk last night when you were on, but my puter was acting up.

ED in MO

ED in MO ADD: I can see where wiring to the positive side of the BAT SOL would require extra wiring.

Edited 2 Jul 2012 by Ed In Missouri

[EDMO 1078]

I am sure that SuberAvid has a system that works - he has been flying his for a while. I like the twin red Cessna Master switches, however, two heavy, 60 amp toggle or rocker switches will do the same job, and can be seperated, but may cost more than the $27, or so, nice Cessna switches.

However, I feel that a couple of technical terms need to be corrected here.

The battery master is connected to a POSITIVE wire,(but I can see that a negative connection would work if that is the only connection to ground), to the CONTINUOUS USE solonoid which is in the POSITIVE main wire close to the battery.

The alternator Master should be on the OUTPUT side of the alternator between it and POSITIVE power bus, bercause the alternator is self-energizing and will continue to be in runaway condition even if the signal power is disconnected.

You should have some heavy (40 to 60 amp) breakers on the alternator output circuit, and on the main battery circuit.

The seperate ignition and fuel pump wire should be on seperate smaller circuit breakers and switches.

I am not an expert on this, so if there are builders who can add to this, or correct my writing, please feel free to do so.

I may have some books on this other than the standard twin-mag wirings you mostly see.

Sorry I couldnt write to Marshawk last night when you were on, but my puter was acting up.

ED in MO

ED in MO ADD: I can see where wiring to the positive side of the BAT SOL would require extra wiring.

Correction to the above: You will NOT need the 60 amp switch for the BAT Solinoid switch, and you could also use a light-duty switch for the alternator INPUT circuit in case of a short in that circuit. The Cessna switches are made for this use.

I would still go with the 60 amp switch, as well as the Heavy circuit breaker as an addition to the OUTPUT side of the alternator to prevent a runaway from burning up everything connected to the power circuit.

There was a "crowbar" protection article in the "Aero-electronics" section of Kitplanes magazine, which is supposed to be better, but too electronicly complicated for me to want to make.

ED in MO

Edited 3 Jul 2012 by Ed In Missouri

[EDMO 1078]

Just getting ready to wire the panel on my avid with the ea81 and looking for some help. Luckly my brother is a mechanic but what we want to know is the master switch better to be mechanical or electrical and do you switch the positive or the negative, so we can still run hot to ignition and fuel, is this correct?

Thanks for any input

What ea81 are you using? If it is not a Stratus, and you have a Holly or Webber carb, I need info on fuel pumps.

100% of your negative is grounded to the airframe, including the battery. But not the Bat Solinoid with the double connections, and even that eventually goes to ground on the airframe, on one side of the master switch. Your protection is always on the positive side, with that one exception.

If all of my garble confused you, then just go with what SuberAvid wrote. He has a working system.

ED in MO

Edited 3 Jul 2012 by Ed In Missouri

[marshawk 82]

Thanks Randy and Ed for the help , I just ask the questions and my brother kinda figures out the technical stuff.Ed my engine was built by a fellow named Karlo Khunner ,its a gear reduction drive and I am using a TBI-40 throttle body injection from rotec,the fuel pump is a facet ,wish I could tell you more but my D.C. wirng skills really suck, can handle any A.C probs but not much ac stuff on planes :hammerhead:

[EDMO 1078]

Thanks Randy and Ed for the help , I just ask the questions and my brother kinda figures out the technical stuff.Ed my engine was built by a fellow named Karlo Khunner ,its a gear reduction drive and I am using a TBI-40 throttle body injection from rotec,the fuel pump is a facet ,wish I could tell you more but my D.C. wirng skills really suck, can handle any A.C probs but not much ac stuff on planes :hammerhead:

Funny how lives are different - AC and newfangeled puter-type stuff was too much for me. Did fine with DC in school. Hated the supercycle stuff on commercial planes - got really shaken physicly by it once.

Whenever you have a question, there are usually answers on this site, and even some opposing opinions. Just sort out what you need.

Good Flying

ED in MO

[EDMO 1078]

Thanks Randy and Ed for the help , I just ask the questions and my brother kinda figures out the technical stuff.Ed my engine was built by a fellow named Karlo Khunner ,its a gear reduction drive and I am using a TBI-40 throttle body injection from rotec,the fuel pump is a facet ,wish I could tell you more but my D.C. wirng skills really suck, can handle any A.C probs but not much ac stuff on planes :hammerhead:

Failed to mention that the BAT Solinoid should be located close as possible to the battery, on the box is a good place.

Let me know how the TBI works out - might trade my Holly carb for one someday.

ED in MO

[SuberAvid 617]

I am sure that SuberAvid has a system that works - he has been flying his for a while. I like the twin red Cessna Master switches, however, two heavy, 60 amp toggle or rocker switches will do the same job, and can be seperated, but may cost more than the $27, or so, nice Cessna switches.

However, I feel that a couple of technical terms need to be corrected here.

The battery master is connected to a POSITIVE wire,(but I can see that a negative connection would work if that is the only connection to ground), to the CONTINUOUS USE solonoid which is in the POSITIVE main wire close to the battery.

The alternator Master should be on the OUTPUT side of the alternator between it and POSITIVE power bus, bercause the alternator is self-energizing and will continue to be in runaway condition even if the signal power is disconnected.

You should have some heavy (40 to 60 amp) breakers on the alternator output circuit, and on the main battery circuit.

The seperate ignition and fuel pump wire should be on seperate smaller circuit breakers and switches.

I am not an expert on this, so if there are builders who can add to this, or correct my writing, please feel free to do so.

I may have some books on this other than the standard twin-mag wirings you mostly see.

Sorry I couldnt write to Marshawk last night when you were on, but my puter was acting up.

ED in MO

ED in MO ADD: I can see where wiring to the positive side of the BAT SOL would require extra wiring.

Thanks Ed, I didn't look at my wiring schedule and was trying to do this from memory; and maybe I was not very clear so I will have to relook at the solonoid wiring. The solonoid main lugs connect the battery positive main wire but I thought it was tripped on by a switch to the negative. I will have to check this again. Also will figure out how to install the 60 amp breaker on my alternator output.

[EDMO 1078]

Thanks Ed, I didn't look at my wiring schedule and was trying to do this from memory; and maybe I was not very clear so I will have to relook at the solonoid wiring. The solonoid main lugs connect the battery positive main wire but I thought it was tripped on by a switch to the negative. I will have to check this again. Also will figure out how to install the 60 amp breaker on my alternator output.

Randy, If you read my corrections, you are probably right on the negative switching. Otherwise, you have to run another hot from the bat to the switch and another wire back to the solinoid. I'm fairly sure that you only ran hot from bat to solinoid, and the negative up to the switch. Makes sense to me so you dont have an extra hot wire going a long ways.

However, if you ran the extra hot from bat to ignition and pumps, you could use that and back to sol from switch, then a short one from sol to ground near bat. I like the negative switching better - one less hot wire to cause trouble.

At least yours is real - mine is still in my head.

Thanks.

ED in MO

Edited 5 Jul 2012 by Ed In Missouri

[EDMO 1078]

Thanks Ed, I didn't look at my wiring schedule and was trying to do this from memory; and maybe I was not very clear so I will have to relook at the solonoid wiring. The solonoid main lugs connect the battery positive main wire but I thought it was tripped on by a switch to the negative. I will have to check this again. Also will figure out how to install the 60 amp breaker on my alternator output.

Randy,

I forget where I saw the schematic, but in addition to the breaker on the output, they also showed a big, bright, flashing RED LED light assembly hooked up to the breaker and put in a very visable place, to warn you that when the breaker trips that you are only running on battery power. Believe this light assembly can be bought at Radio Shack, or an eletronics supply.

This may have been in Kitplanes "Aero Electrics" section, and that may have also been on the "crowbar" circuit. I think I have seen it other places, but dont remember where right now.

Anyway, sounds like a good plan.

If you need help on this, NORTHERN LIGHTS ELECTRONICS in Anchorage is the place to ask. JIM WEIR, The guy who owned it does the Kitplanes articles. If you get the scoop for this, please send a copy to me.

ED in MO

Edited 7 Jul 2012 by Ed In Missouri

[marshawk 82]

Hi Ed,is the red light for a tripped breaker in addition to a voltmeter gauge,I don't have a volt meter gauge in my panel but was told I should put one in but probably should have both?We are going with the cessana type mmaster switch you recommended ,thanks for all the info

[EDMO 1078]

Hi Ed,is the red light for a tripped breaker in addition to a voltmeter gauge,I don't have a volt meter gauge in my panel but was told I should put one in but probably should have both?We are going with the cessana type mmaster switch you recommended ,thanks for all the info

The red light will let you know that you are only running on battery power and that the alternator is not on line.

The voltmeter will not get your attention like the flashing red light.

Personaly, I depend more on the ampmeter than the voltmeter, but think you need both.

Thanks to Randy for getting my attention to the negative switch for the battery solinoid, and running a hot bypass line to the breakers/switches to ignition and fuel pumps.

ED in MO

Afterthought: I had a generator trash itsself in a 182 during my commercial pilot training when I was almost to the threshhold on a night flight to a short runway - lost all lights and electric flaps, that got my attention about as much as a flashing red light would have ! Not to mention that I had my instructor, the airport manager, and the President of Ozark Airlines on board. I finished the landing OK.

Edited 7 Jul 2012 by Ed In Missouri

[SuberAvid 617]

The light and meter is a good idea. I have MGL gages in mine including a 2 1/8 battery gage that gives volts, amps and says if it is charging or discharging. Most of the newer MGL gages also already have a red LED built in that you can set for any point you want it to alarm at beyond the limits you set plus an alarm light wire if you want to add another. I happen to have bought one of my MGL gages befor they built in the light and I added a red alarm light of my own (the gage still had the alarm wire for a light) and it is about 1/2" so you see it a little faster. The battery gage saved my butt just the other day; I took off to go fishing and was a mile or so from the RW when I noticed I was discharging rather than charging; everything else was in the green but my CHT and water temps were a little higher than normal. I cranked it around and landed and found that my alternator mount had cracked at a weld so the belt was slipping and that belt also drives the water pump. I rewelded it and made sure I had full penetration this time. Sure glad I had the battery gage that was the first indictor something was wrong.

[EDMO 1078]

The light and meter is a good idea. I have MGL gages in mine including a 2 1/8 battery gage that gives volts, amps and says if it is charging or discharging. Most of the newer MGL gages also already have a red LED built in that you can set for any point you want it to alarm at beyond the limits you set plus an alarm light wire if you want to add another. I happen to have bought one of my MGL gages befor they built in the light and I added a red alarm light of my own (the gage still had the alarm wire for a light) and it is about 1/2" so you see it a little faster. The battery gage saved my butt just the other day; I took off to go fishing and was a mile or so from the RW when I noticed I was discharging rather than charging; everything else was in the green but my CHT and water temps were a little higher than normal. I cranked it around and landed and found that my alternator mount had cracked at a weld so the belt was slipping and that belt also drives the water pump. I rewelded it and made sure I had full penetration this time. Sure glad I had the battery gage that was the first indictor something was wrong.

Yes, good judgement. Jim Weir says a flashing red light will get your attention faster than a solid one. Believe there is a flashing one that is also about 1/2 inch and self-contained.

ED in 107F MO (think MO stands for Mizery right now!) no AC in hanger, so no building getting done)

[EDMO 1078]

OK - Here is a copy from "Sportplane Construction" that will settle the question about the negative to switch for the battery solinoid wiring. The other best place to find wire, breaker and switch sizes is AC 43-13. If you want to read electronic articles written by Jim Weir for Kitplanes mag, go to www.rst-engr.com/kitplanes. I cant seem to get it working, but the October 2001 mag has the overvoltage relay article and schematic in it.

BUT NOTE: This is not the same as the 60 amp breaker on alternater output that other circuits say you need.

ED in MOSolinoid.pdf

Edited 8 Jul 2012 by Ed In Missouri