Bus connection wire size help?

[Ragsf15e]

I’ve been spending more quality time with my electrical system and keep finding minor issues and weird changes that have accrued over 50 years.  Most recently I realized that  my main bus was at 14.1V and solid (good alternator), but my JPI reads a bit less.  I traced good voltage back until I found a connection on the main bus to power bus that was a little corroded.  I cleaned it but that only half fixed the problem.  Nothing is easy with a 50+ year old airplane.  Now to my question... the connection wire between the power bus and the aux bus in the manual is “part #800214-009”.  This wire connects the two buses that have the battery input and the alternator input and the 50a aux bus.  Seems like it should be pretty substantial.  My airplane appears to have about a 14g wire there (not original) where the parts manual says “-009”.  I’ve closely read the parts manual and can’t for the life of me find that part number or the appropriate wire size.  I circled the part in the manual below...  help?

Edited December 18, 2020 by Ragsf15e

[PT20J]

Here are a couple of ideas:

1) Any MSC has access to dealer information (I think they call it the parts portal or some such) about Mooney part numbers that sometimes has this level of detail. Maybe @M20Doc can help out.

2) Stacey Ellis at the factory usually turns around answers pretty quickly technicalsupport@mooney.com. He'd have access to all the manufacturing specs and drawings.

Skip

[Ragsf15e]

7 minutes ago, PT20J said:

Here are a couple of ideas:

1) Any MSC has access to dealer information (I think they call it the parts portal or some such) about Mooney part numbers that sometimes has this level of detail. Maybe @M20Doc can help out.

2) Stacey Ellis at the factory usually turns around answers pretty quickly technicalsupport@mooney.com. He'd have access to all the manufacturing specs and drawings.

Skip

Thanks.  Yeah those are probably the best way to go.  I try to get help here or figure it out for myself before bugging Lasar or DMax or Stacey but sometimes they are the experts.

The manual for later years is much more clear on laying out wire sizes, so I was also just thinking of using their “flexible bus bar braid” or 6awg wire spelled out in those.

[Immelman]

Have you had a look at AC 43-13, in the electrical section? It is... a bit time consuming to understand all the graphs, but I think worthwhile to select the correct conductor.

Factors include...

...current

...maximum altitude

...length

...# of wires in the bundle

[Aerodon]

The drawing for a 28V M20K shows the avionics bus wire to be 10Ga.  I think I looked at the allowable table and found 14Ga to be acceptable on a 14V airplane.  

Aerodon

[PT20J]

2 hours ago, Aerodon said:

The drawing for a 28V M20K shows the avionics bus wire to be 10Ga.  I think I looked at the allowable table and found 14Ga to be acceptable on a 14V airplane.  

Aerodon

Power = voltage X current. So, the current is higher for a 14 V system than a 28 V for the same power. Wire size is based on current carrying capacity, so the wire for a 14 V system should be larger than for a 28 V system, not smaller.

Skip

[N201MKTurbo]

That jumper in my plane is a piece of braided wire with terminals on both ends. That’s probably why it has a Mooney number. A piece of 10 Ga would probably be ok, but I would check with 43.13 1B

[Aerodon]

1 hour ago, PT20J said:

Power = voltage X current. So, the current is higher for a 14 V system than a 28 V for the same power. Wire size is based on current carrying capacity, so the wire for a 14 V system should be larger than for a 28 V system, not smaller.

Skip

Yes, I wasn't trying to say the 28 and 14V planes I was looking at were equivalent.  The 14V plane I was worked it out for had a 35A breaker switch for the avionics master.  The 28V Mooney has a 100A avionics relay, no circuit breaker or fuse. 

Have you noticed how some manufacturers require the same CB for 14/28V, others show say 5/3A for 14/28V.   

I'm working through a new CB list for a 28V M20K.  New avionics installations shift some devices over to the main bus (displays, GI275, engine monitor etc.).  Then in general, there's a major reduction in required power.  (more integration and fewer devices).

 

Aerodon

[Ragsf15e]

1 hour ago, N201MKTurbo said:

That jumper in my plane is a piece of braided wire with terminals on both ends. That’s probably why it has a Mooney number. A piece of 10 Ga would probably be ok, but I would check with 43.13 1B

Yes, I found mention of the “flexible bus” or braided connection in the maintenance manual for later years.  It has a Mooney part number.  I read through 43.13 and come to the same conclusion as @PT20J ... it’s bigger than 14gage.  I really analyzed my electrical diagram and the wire could potentially carry 50amps to the aux bus (includes pitot heat, gear actuator, avionics, lights, fuel pump, etc), 5 amps to the voltage regulator, and whatever charging amps the battery needs.  Basically that adds up to the entire output of the alternator.  Now I know it doesn’t normally carry that much, but I think I’m gonna try to find the right braided flex bus or at least go big.  The 43.13 charts seem to indicate 6 or 8 for that load.

[RLCarter]

2 hours ago, N201MKTurbo said:

That jumper in my plane is a piece of braided wire with terminals on both ends. That’s probably why it has a Mooney number. A piece of 10 Ga would probably be ok, but I would check with 43.13 1B

So is the braided wire insulated? My 65’ E has probably a #6 going between bus bars

[N201MKTurbo]

8 minutes ago, RLCarter said:

So is the braided wire insulated? My 65’ E has probably a #6 going between bus bars

Yes, it has some spaghetti tube over it. 

[carusoam]

Cool drawing...

Looks like one wire is number 009, the next one over is 010... numerically in order... find the chart with all the data on it to see what wire 009 is...(?)

The busses probably aren’t that far from each other... if you accidentally over size it... it won’t cost much more... or have more resistance...

A multi strand braided cable has less chance of failing without giving notice first...

I see the Shunt is pretty close in the layout...  they have a chance of frying something when a bare wire lands on it... (sparks fly as does molten metal...)

A reminder to use insulation, or put a roof over things that can have gravity drop things on them...

Kind of planning for the next 50 years... 

PP thoughts only, not a mechanic or electrician...

Best regards,

-a-

[Ragsf15e]

10 hours ago, carusoam said:

Cool drawing...

Looks like one wire is number 009, the next one over is 010... numerically in order... find the chart with all the data on it to see what wire 009 is...(?)

The busses probably aren’t that far from each other... if you accidentally over size it... it won’t cost much more... or have more resistance...

A multi strand braided cable has less chance of failing without giving notice first...

I see the Shunt is pretty close in the layout...  they have a chance of frying something when a bare wire lands on it... (sparks fly as does molten metal...)

A reminder to use insulation, or put a roof over things that can have gravity drop things on them...

Kind of planning for the next 50 years... 

PP thoughts only, not a mechanic or electrician...

Best regards,

-a-

Yes, the diagram is pretty good, but the part list of wire numbers is not included.  At the beginning, it does say all the wires are part “#800214-xxx” with xxx being the -009 part.  Unfortunately that part number isn’t found anywhere else.  The braid or a short section of large gage wire seem to be the best idea for the jumper.

 I do see the shunt in the diagram, but The drawings aren’t to scale and I have no idea where mine was installed when my jpi930 went in.  Could be anywhere!  So far, I haven’t let out any smoke!

[TCUDustoff]

@Ragsf15e  Did you ever figure this out?  I am going to have to probably replace my cable due to a stupid mistake yesterday.  Looking at AC 41.13, I think an 8 AWG or 6AWG wire will work for 50A at an estimated 8 feet length (I need to replace -147 as well). 

I really wish we had some more detail in the older parts manuals!

[1964-M20E]

What Dustoff said.  As an EE I would use #8 or #6 AWG wire depending on what size breaker you have on you alternator.  50A breaker #8 would be fine for a 60A chose the #6.  A little larger wire will not hurt other than installation.

[TCUDustoff]

@1964-M20E  Thanks for the confirmation.  I am going to measure the OD of the stock wire and, as long as its similar, I will probably go with the #6.  I still have a generator, and the breaker is 50A, but it doesn't hurt other than the pocketbook if it will fit in the existing adle clamps.

Out of curiosity, the original wiring has an odd braiding on it and is not the typically, modern sheathing; is generic MIL-W-22759/16 from any of our friendly aircraft supply stores the modern day equivalent?  Just want to make sure I get the right stuff. Sure the OP will be in the same boat if he still needs to replace. 

 

[1964-M20E]

Just now, TCUDustoff said:

@1964-M20E  Thanks for the confirmation.  I am going to measure the OD of the stock wire and, as long as its similar, I will probably go with the #6.  I still have a generator, and the breaker is 50A, but it doesn't hurt other than the pocketbook if it will fit in the existing adle clamps.

Out of curiosity, the original wiring has an odd braiding on it and is not the typically, modern sheathing; is generic MIL-W-22759/16 from any of our friendly aircraft supply stores the modern day equivalent?  Just want to make sure I get the right stuff. Sure the OP will be in the same boat if he still needs to replace. 

 

That's what I have used for any wire replacements under the guidance of my A&P.  I think there are some outfits that will cover the UNSHIELDED WIRE MIL-W-22759/16 with a braid if you are really a stickler for an original look but I would not want to pay for it.

[Ragsf15e]

6 hours ago, TCUDustoff said:

@Ragsf15e  Did you ever figure this out?  I am going to have to probably replace my cable due to a stupid mistake yesterday.  Looking at AC 41.13, I think an 8 AWG or 6AWG wire will work for 50A at an estimated 8 feet length (I need to replace -147 as well). 

I really wish we had some more detail in the older parts manuals!

I eventually found the jumper within the tangle of CB wires.  It had been moved at some point and left me with my 50amp aux bus cb powered through about a 18g wire.  Moved the original jumper to its proper location and cleaned all the contacts.  All is well.  I would have to guess that it’s 8g wire.

[Oscar Avalle]

On 6/7/2021 at 8:30 AM, 1964-M20E said:

That's what I have used for any wire replacements under the guidance of my A&P.  I think there are some outfits that will cover the UNSHIELDED WIRE MIL-W-22759/16 with a braid if you are really a stickler for an original look but I would not want to pay for it.

Where can I purchase 9 feet of M5086/2-4. The only places I found want to sell me 100 feet for 724... Any suggestions?

[chriscalandro]

Ok. 
I do t care what the part number or the manual says. It’s been 50 years and I’m sure things in your electrical system have changed. The wire should be rated for the breaker.
 

If you have a 50amp breaker you need a wire capable of 50 amps. If you have a 70amp breaker, you need a wire capable of carrying 70 amps. 
 

if you have a 25 amp breaker you only need a wire capable of carrying 25amps. 
 

this is for the breaker from the main bus to the aux bus. 
 

don’t look at the manual, or go to a Mooney service center, or order Mooney specific parts, get the wire that is required for the electrical system that is in YOUR airplane. 
 

It’s an easily googleable thing to figure it out. 

[1964-M20E]

3 hours ago, Oscar Avalle said:

Where can I purchase 9 feet of M5086/2-4. The only places I found want to sell me 100 feet for 724... Any suggestions?

1' Foot, 4 AWG Gauge Tinned Copper Wire, Stranded Marine Boat Battery Cable USA | eBay

 

try this

[EricJ]

On 6/7/2021 at 5:16 AM, TCUDustoff said:

@Ragsf15e  Did you ever figure this out?  I am going to have to probably replace my cable due to a stupid mistake yesterday.  Looking at AC 41.13, I think an 8 AWG or 6AWG wire will work for 50A at an estimated 8 feet length (I need to replace -147 as well). 

I really wish we had some more detail in the older parts manuals!

As you mentioned, Ch 11 in AC 43.13 is your friend, and Fig 11-2 suggests that 8 AWG would be fine with margin.

[corvar01]

I don't know if you figured this out yet, but my 74 M20F has a 6 gauge wire running from the 50 amp c/b to the aux bus. 

[TCUDustoff]

@corvar01  I've been busy with work and should have followed up, but yeah we figured it out.  Thanks for the confirmation, however!