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Pullable 80A Circuit Breaker

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Speedy11(at)aol.com
Guest

Posted: Mon Aug 21, 2006 8:40 pm Post subject: Pullable 80A Circuit Breaker

Does anybody know a source for a pullable 80A CB to use for the alternator?  I've checked several sources and have found 80A CBs that cannot be pulled - they can only be reset, but none that are pullable.

 I bought one at Sun n Fun only to discover later that it is 28v.

 Stan Sutterfield

  [quote][b]

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khorton01(at)rogers.com
Guest

Posted: Tue Aug 22, 2006 1:53 am Post subject: Pullable 80A Circuit Breaker

On 22 Aug 2006, at 24:37, Speedy11(at)aol.com (Speedy11(at)aol.com) wrote:

 	  Quote: 	
		   Does anybody know a source for a pullable 80A CB to use for the alternator?  I've checked several sources and have found 80A CBs that cannot be pulled - they can only be reset, but none that are pullable.

 I bought one at Sun n Fun only to discover later that it is 28v.

	


I would have thought that the rating meant the maximum voltage that the CB could be used with.  Any lower voltage should be OK.  It is measuring amperage, not voltage, and 80A is 80A, no matter what the system voltage is.

 Kevin Horton

Ottawa, Canada



 



 [quote][b]

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aerobubba(at)earthlink.ne
Guest

Posted: Tue Aug 22, 2006 6:08 am Post subject: Pullable 80A Circuit Breaker

Hi Stan-



 	  Quote: 	
		  I bought one at Sun n Fun only to discover later that it is 28v.


	


28V is the maximum system voltage for that CB.  The CB you bought should be

fine for your 14V installation.



glen matejcek

aerobubba(at)earthlink.net

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denis.walsh(at)comcast.ne
Guest

Posted: Tue Aug 22, 2006 7:01 am Post subject: Pullable 80A Circuit Breaker

While I am waiting for the real experts to weigh in, I offer the  

following unsubstantiated feeling:



I don't think a cb "senses"   either volts or amps.  Rather it reacts  

to heat, whose generation  is better measured in watts which is a  

function of both.



I would therefore surmise that the cb in question would be well  

within its rated range; however would probably not trip a 14 volt  

load until 160 amps.



well, where are the electro-experts now that we need them??

Denis Walsh



On Aug 22, 2006, at 07:06 292080008, glen matejcek wrote:



 	  Quote: 	
		   

 <aerobubba(at)earthlink.net>

  Hi Stan-



> I bought one at Sun n Fun only to discover later that it is 28v.



 28V is the maximum system voltage for that CB.  The CB you bought  

 should be

 fine for your 14V installation.



 glen matejcek

 aerobubba(at)earthlink.net

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nuckollsr(at)cox.net
Guest

Posted: Tue Aug 22, 2006 7:38 am Post subject: Pullable 80A Circuit Breaker

At 10:06 AM 8/22/2006 -0400, you wrote:



 	  Quote: 	
		  

<aerobubba(at)earthlink.net>

  Hi Stan-



 >I bought one at Sun n Fun only to discover later that it is 28v.



28V is the maximum system voltage for that CB.  The CB you bought should be

fine for your 14V installation.


	




   Glen is correct. I'll amplify his words with the notion

   that voltage ratings on switches and breakers are MAXIMUM

   level for operating voltage at the cited current level.

   There is no practical minimum voltage. See:



http://aeroelectric.com/articles/swtchrat.pdf



   While this article speaks specifically to switches,

   the same ratings philosophies apply to breakers

   that are simply automated switches designed to

   sense current.



   Bob . . .

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Hopperdhh(at)aol.com
Guest

Posted: Tue Aug 22, 2006 7:58 am Post subject: Pullable 80A Circuit Breaker

Glen,

  

 CB's are rated in volts only to show what kind of circuit they should be  used in.  In other words don't use a breaker rated for 28 volts in a  120 volt circuit.  A 28 volt breaker would IMHO be fine for use in a 12-14  volt circuit.  It is in series with the load, so it can only know the  current.  It has no way of knowing the voltage or therefore the wattage of  the load.  It is heat activated by having a small amount of  resistance, and the heating power is I*I*R.  (I is current, and R is  resistance.)  This causes it to waste a little power (and voltage) in order  to do its job.

  

 Dan Hopper

 RV-7A

  

 Playing with electricity since age 2 when I plugged a key into a wall  outlet.  Nothing happened so I plugged in another key.  I'm told it  sent me across the room.  I've been hooked on the stuff ever since!

  

  

 In a message dated 8/22/2006 11:03:30 A.M. Eastern Daylight Time,  denis.walsh(at)comcast.net writes:

  	  Quote: 	
		  -->    AeroElectric-List message posted by: Denis Walsh    <denis.walsh(at)comcast.net>



While I am waiting for the real experts    to weigh in, I offer the  

following unsubstantiated feeling:



I    don't think a cb "senses"   either volts or amps.  Rather it    reacts  

to heat, whose generation  is better measured in watts    which is a  

function of both.



I would therefore surmise that    the cb in question would be well  

within its rated range; however    would probably not trip a 14 volt  

load until 160 amps.



well,    where are the electro-experts now that we need them??

Denis Walsh



On    Aug 22, 2006, at 07:06 292080008, glen matejcek wrote:



 	  Quote: 	
		   -->    AeroElectric-List message posted by: "glen matejcek"  

    <aerobubba(at)earthlink.net>

  Hi    Stan-



> I bought one at Sun n Fun only to discover later    that it is 28v.



 28V is the maximum system voltage for that    CB.  The CB you bought  

 should be

 fine for your 14V    installation.



 glen matejcek

    aerobubba(at)earthlink.net



bsp;    -->  nbsp;                - NEW MATRONICS LIST WIKI -

_-=  ;  p;               - List Contribution Web Site  ;                             =========================
	




	


 

  

  [quote][b]

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Hopperdhh(at)aol.com
Guest

Posted: Tue Aug 22, 2006 8:06 am Post subject: Pullable 80A Circuit Breaker

Glen,

  

 Sorry, I should have said Stan at the top.  I agree with you  completely.  Bob's post came in after I hit send, so I think we are all in  agreement.

  

 Dan

  

 In a message dated 8/22/2006 12:02:38 P.M. Eastern Daylight Time,  Hopperdhh(at)aol.com writes:

  	  Quote: 	
		        Glen,

    

   CB's are rated in volts only to show what kind of circuit they should be    used in.  In other words don't use a breaker rated for 28 volts in a    120 volt circuit.  A 28 volt breaker would IMHO be fine for use in a    12-14 volt circuit.  It is in series with the load, so it can only know    the current.  It has no way of knowing the voltage or therefore the    wattage of the load.  It is heat activated by having a small amount    of resistance, and the heating power is I*I*R.  (I is current, and R    is resistance.)  This causes it to waste a little power (and voltage) in    order to do its job.

    

   Dan Hopper

   RV-7A

    

   Playing with electricity since age 2 when I plugged a key into a wall    outlet.  Nothing happened so I plugged in another key.  I'm told it    sent me across the room.  I've been hooked on the stuff ever since!

    

    

   In a message dated 8/22/2006 11:03:30 A.M. Eastern Daylight Time,    denis.walsh(at)comcast.net writes:

    	  Quote: 	
		  -->      AeroElectric-List message posted by: Denis Walsh      <denis.walsh(at)comcast.net>



While I am waiting for the real      experts to weigh in, I offer the  

following unsubstantiated      feeling:



I don't think a cb "senses"   either volts or      amps.  Rather it reacts  

to heat, whose generation  is      better measured in watts which is a  

function of both.



I      would therefore surmise that the cb in question would be well       

within its rated range; however would probably not trip a 14 volt       

load until 160 amps.



well, where are the electro-experts now that      we need them??

Denis Walsh



On Aug 22, 2006, at 07:06 292080008,      glen matejcek wrote:



 	  Quote: 	
		   --> AeroElectric-List message posted by:      "glen matejcek"  

      <aerobubba(at)earthlink.net>

  Hi      Stan-



> I bought one at Sun n Fun only to discover later      that it is 28v.



 28V is the maximum system voltage for that      CB.  The CB you bought  

 should be

 fine for your      14V installation.



 glen matejcek

      aerobubba(at)earthlink.net



bsp; -->      nbsp;             - NEW MATRONICS LIST WIKI  tion      Web Site ;                                 =========================


	


	


   

    

 	  Quote: 	
		  



matronics.com/Navigator?AeroElectric-List

.matronics.com/">http://forums.matronics.com

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://www.matronics.com/contribution">http://www.matronics.com/contribution



	
	


 

  

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mprather(at)spro.net
Guest

Posted: Tue Aug 22, 2006 8:16 am Post subject: Pullable 80A Circuit Breaker

Err..  I am not an expert, but I don't think that is completely correct.

Heat generated is correct, but the heat is generated solely by the current

passing through the CB.  The system voltage has no bearing on how much

heat is generated.  Draw the circuit and you can see why.  The CB goes in

series with the load.  Beit a 2V or 200V system, a particular current

through the CB causes a corresponding voltage drop across the CB while the

CB is closed.

The voltage rating is more related to the ability of the CB to open an

operating (overloaded) circuit.  The higher the system voltage the harder

it is to open the circuit (break the current) for a given current. 

Voltage rating is likely about contact speed and distance (maybe not

both).  A larger system voltage implies the need for faster contacts

and/or larger contact distance.

Regards,

Matt-

 	  Quote: 	

 <denis.walsh(at)comcast.net>

 While I am waiting for the real experts to weigh in, I offer the

 following unsubstantiated feeling:

 I don't think a cb "senses"   either volts or amps.  Rather it reacts

 to heat, whose generation  is better measured in watts which is a

 function of both.

 I would therefore surmise that the cb in question would be well

 within its rated range; however would probably not trip a 14 volt

 load until 160 amps.

 well, where are the electro-experts now that we need them??

 Denis Walsh

 On Aug 22, 2006, at 07:06 292080008, glen matejcek wrote:

> 

> <aerobubba(at)earthlink.net>

>  Hi Stan-

>

>> I bought one at Sun n Fun only to discover later that it is 28v.

>

> 28V is the maximum system voltage for that CB.  The CB you bought

> should be

> fine for your 14V installation.

>

> glen matejcek

> aerobubba(at)earthlink.net

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N1DeltaWhiskey(at)comcast
Guest

Posted: Wed Aug 23, 2006 8:16 am Post subject: Pullable 80A Circuit Breaker

Matt,



I am not an expert either, but I*R is not the only source of heat that might 

affect a CB.  For thermally activated (TA) CB, it is quite possible for 

external heat sources to reduce the load carrying capacity of the TACB by 

providing "pre-heating."



Say a TACB will trip when the sensing element reaches 600F (I have no idea 

what the actual temperature is - it may be much less than that).  At ambient 

temperature of 70F, we have to provide enough heating to elevate the sensor 

temperature by 530F.  However, if a situation arises which causes the 

ambient temp of the unit to rise, say to 300F, the amount of current the 

TACB to elevate the temp of the sensor an additional 300F is decreased 

(i.e., reduced capacity).



I visited a client just this week where they were having nuisance trips of a 

circuit breaker.  Cause: determined to be a bad connection of the CB to the 

bus.  Remedy: the bus was flipped over to get the pitting away from the CB 

contacts and a secure connection was then made.



Regards,



Doug Windhorn

---

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