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relay wiring question

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gfr56(at)comcast.net
Guest

Posted: Thu Aug 07, 2008 5:11 am Post subject: relay wiring question

I am looking for the proper way to wire my battery  and starter contactor.

  

 I have a Spruce bought battery contactor, which is  a White-Rodgers Type 70 DC power contactor. I expected to see two large posts  and two small posts on the unit but it has only one small post. The manufactures  web site refers to this as a "Terminal Type 3B – Coil Common to Load" . I want to confirm  how to properly wire this to my DPDT master switch, the manufacturers diagram  shows a pig tail to the small post from large post that is connected to battery  positive. I assume I wire from that large post to the master switch and the back  to small post on the contactor. There is no connection from the master switch to  ground in this case?

  

 Part 2

 I have B&C starter relay, it also has  only one small post. 

 I assume that it is grounded through it's  own case and I should bring positive line through the starter switch and back to  the small post and then pig tail a ground wire from the case mounting bolt   to the firewall ground?

  

 Thanks in advance for your  help.

  Jerry

   [quote][b]

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rlborger(at)mac.com
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Posted: Thu Aug 07, 2008 6:03 am Post subject: relay wiring question

Jerry,



The 12 volt cable from the battery to the battery contactor also provides the power to the contactor.  You run a wire from the single small terminal to your master switch and another wire from the master switch to ground.  The master switch then provides ground to complete the circuit and activate the contactor.



The starter relay requires that 12 volts be supplied to the small terminal for the relay to activate.  Yes, ground is through the case.  If your aircraft is composite or tube and fabric construction then you should run a ground wire from the case mount bolt to the firewall ground block.  If your aircraft is aluminum ground should be available directly from the airframe.  



I hope this helps,

Bob Borger

Europa XS, Rotax 914, Airmaster C/S prop

http://www.europaowners.org/N914XL



On Thursday, August 07, 2008, at 08:27AM, "Jerry Ricciotti" <gfr56(at)comcast.net> wrote:

 	  Quote: 	
		  I am looking for the proper way to wire my battery and starter contactor.



I have a Spruce bought battery contactor, which is a White-Rodgers Type 70 DC power contactor. I expected to see two large posts and two small posts on the unit but it has only one small post. The manufactures web site refers to this as a "Terminal Type 3B - Coil Common to Load" . I want to confirm how to properly wire this to my DPDT master switch, the manufacturers diagram shows a pig tail to the small post from large post that is connected to battery positive. I assume I wire from that large post to the master switch and the back to small post on the contactor. There is no connection from the master switch to ground in this case?



Part 2

I have B&C starter relay, it also has only one small post. 

I assume that it is grounded through it's own case and I should bring positive line through the starter switch and back to the small post and then pig tail a ground wire from the case mounting bolt  to the firewall ground?



Thanks in advance for your help.

 Jerry

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gfr56(at)comcast.net
Guest

Posted: Thu Aug 07, 2008 1:30 pm Post subject: relay wiring question

Thanks for the reply



A  comment and an additional question.

I noticed the battery contactor only works with the large post opposite the 

small post connected to positive and does not work with the other large post 

connected to positive (i.e.. flip flopping the positive)

This does not seem to be the case for the starter contactor, it seems to 

work with either post connected to positive.



Is there a reason for this?

---

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bob(at)bob-white.com
Guest

Posted: Thu Aug 07, 2008 5:35 pm Post subject: relay wiring question

Hi Jerry,



The reason is on the starter relay, the coil is activated by a positive

voltage to the small terminal and the case is grounded.  It has nothing

to do with the large terminals.  On the contactor, one side of the

coil is connected to one of the large terminals (BAT).  The other side

is connected to ground through the master switch.  If you connect the

large terminals backwards, then one side of the coil is NOT connected

to the battery and you can't activate the coil.



You have to get 12V across the coil to activate the contacts on both

devices.  Look at the attached drawing and it should be easy to see why

you can't switch the large terminals on the contactor.



Bob W.





On Thu, 7 Aug 2008 17:27:51 -0400

"Jerry Ricciotti" <gfr56(at)comcast.net> wrote:



[quote] 

 

 Thanks for the reply

 

 A  comment and an additional question.

 I noticed the battery contactor only works with the large post opposite the 

 small post connected to positive and does not work with the other large post 

 connected to positive (i.e.. flip flopping the positive)

 This does not seem to be the case for the starter contactor, it seems to 

 work with either post connected to positive.

 

 Is there a reason for this?

 

 

 ---

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nuckolls.bob(at)cox.net
Guest

Posted: Fri Aug 08, 2008 10:11 am Post subject: relay wiring question

At 05:27 PM 8/7/2008 -0400, you wrote:




Thanks for the reply



A  comment and an additional question.

I noticed the battery contactor only works with the large post opposite the 

small post connected to positive and does not work with the other large 

post connected to positive (i.e.. flip flopping the positive)

This does not seem to be the case for the starter contactor, it seems to 

work with either post connected to positive.



Is there a reason for this?



  Nothing special . . . it's the factory's way of accommodating a variety

  of design goals for incorporating the device into an electrical system.



  I'll refer you to the 3rd and 4th pages of the .pdf catalog for

  the 70 series contactors from Stancor:



http://aeroelectric.com/Mfgr_Data/Contactors/Stancor-WhiteRogers/Stancor_70-Series.pdf



  Note that the 4-terminal device features no internal

  coil connections. This is the style contactor I used to

  offer (B&C still does) as "universal" to the task of battery

  contactor, cross-feed contactor, hydraulic pump contactor,

  alternator b-lead contactor, etc. In all these instances,

  the little terminals and fat terminals are interchangeable.



  In cases where you want to purchase a bunch of contactors

  for use as a battery contactor only, then they'll be pleased

  to sell you a version wherein one coil connection is tied to

  a fat terminal. Obviously, one of the fat terminals needs to

  be designated "BATTERY" and if you look at the contactor

  shell, this terminal will be labeled "BAT" or "BATTERY".



  This leaves you but one wire to hook up to the battery

  master that pulls the free end of the coil to ground to

  energize the contactor.



  This feature can be used in a variety of applications

  where "pull to ground" control is desired. Just connect

  the BAT terminal to power source and the other terminal to

  supply the load.



  If you want to use the contactor in a "pull to bus"

  situation, you can also purchase a version where one

  end of the coil is internally connected to contactor

  case. Now, the fat terminals are still interchangeable

  but attention must be paid to the small terminal(s)

  where one will be internally connected to case. This

  wiring convention is quite common in intermittent

  duty, starter contactors.



----------------------

On Thursday, August 07, 2008, at 08:27AM, "Jerry Ricciotti" 

<gfr56(at)comcast.net> wrote:



I am looking for the proper way to wire my battery and starter contactor.



I have a Spruce bought battery contactor, which is a White-Rodgers Type 70 

DC power contactor. I expected to see two large posts and two small posts 

on the unit but it has only one small post. The manufactures web site 

refers to this as a "Terminal Type 3B - Coil Common to Load" .



   The term "3B" comes from the schematic description of

   functionality from the 4th page of the above catalog

   excerpt. In this case, your coil suppression device would

   go between the small terminal and the one marked "BAT" as

   opposed to the externally jumpered wiring depicted

   in:



http://www.aeroelectric.com/Pictures/Contactors/s701-1.jpg

  I want to confirm how to properly wire this to my DPDT master switch, the 

manufacturers diagram shows a pig tail to the small post from large post 

that is connected to battery positive. I assume I wire from that large post 

to the master switch and the back to small post on the contactor.



   No, you wire the battery to the BAT terminal of the contactor

   and take a single wire from the small terminal through your battery

   master switch to ship's ground. This is illustrated in all of the

   z-figures.



There is no connection from the master switch to ground in this case?



   Yes there IS a master switch ground connection . . .

   as shown in the z-figures.

Part 2



I have B&C starter relay, it also has only one small post.



I assume that it is grounded through it's own case and I should bring 

positive line through the starter switch and back to the small post and 

then pig tail a ground wire from the case mounting bolt to the firewall ground?



   Yes, except if you have a metal firewall, there's no need

   for an extra ground between the mounting flange and

   the firewall ground.



        Bob . . .



        ----------------------------------------)

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

        ----------------------------------------

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nuckolls.bob(at)cox.net
Guest

Posted: Fri Aug 08, 2008 10:42 am Post subject: relay wiring question

I discovered a diagram I'd published a few years ago at:



http://aeroelectric.com/Pictures/Schematics/Contactors_PU_and_PD.pdf



In this drawing, you see the control paths for the

classic "pull down" to ground control of battery contactor

(shown in red) and the "pull up" to bus control typical

of starter contactors (shown in green). I've also published

a one-pager on the three common contactor wiring conventions

at:



http://aeroelectric.com/Pictures/Schematics/Contactor_Wiring_Conventions.pdf



Bob . . .

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