Re: 10 amp booster Re: DCC Wiring - Can it cause a fire?

Mark Gurries
 

V = I * R

Ohms law re-writen to solve for ohms

R = V / I

The equation is setup like this:

Ohms(Wiring) = V(track) / I(booster)

For the 10Amp booster, I(booster) = 10A and Vtrack = 16V (Factory setting)

Ohms = 16V / 10A = 1.6 Ohms per advertised specifications.

However in practice the 10Amp booster puts out close to 12Amps  (Production design margin to guarantee 10amps) which mean the actual real value is closer to 1.3 Ohms.

This is the maximum resistance value one can tolerated from one track terminal on the booster out and around the layout all the back to the other terminal of the same booster.  Your layout wiring should make sure it is less than this value.  Hence the quarter test does just that.  If a short circuit between the rails does not shutdown the booster, you have a wiring problem with to much resistance which in this case means you have more than 1.3 Ohms.




On Jan 22, 2014, at 7:00 AM, madog wrote:



 
What would the ohms be on a 10 amp booster?
I’m in 2 rail O Scale
Bill Kozel
 
From: Steve Haas
Sent: Tuesday, January 21, 2014 11:52 PM
Subject: RE: [WiringForDCC] Re: DCC Wiring - Can it cause a fire?
 

<<If there is a highly resistive connection somewhere in the wiring that is more than about 2.8 ohms when using a 5Amp booster and there is a short circuit on the track,  that resistive point is where all the heat will be because the booster will not have shutdown but instead deliver full power.>>

A local layout has hand laid track and turnouts with powered frogs.  The original track layers and electricians were not too careful about where they cut the gaps beyond turnouts.  We’ve lost the side frames of two different engines to excessive heat when the front wheel set of the engines spanned the gap that isolated the frog from the yard track. 

Good construction minimizes a host of errors – keep those gaps inside the fouling point of your turnouts and equipment and it will reduce the number of problems due to shorts by reducing the possibility of shorts.

Best regards,

Steve Haas

Snoqualmie, WA


Madogbill><>



Best Regards,

Mark Gurries
Electrical Engineer
DCC Website & NMRA DCC Clinics: www.markgurries.com



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