Airpax Snapac Breaker - install on each hot terminal or just one on common terminal

JD2035RROGR Forum Member DIGITAL SUBSCRIBER

I am wanting to use a postwar transformer (likely LW) to power a small layout. This includes a lionchief loco, an accessory or two, fastrack switches, and UCS section.

I plan to add TVS and Airpax Snapac breaker(s). My question is, can I use 1 breaker on the common wire or should each separate voltage get it's own breaker? My assumption is that having it on the common side is fine, you just lose power to everything if there is a short on any one of the "hot" terminals. I appreciate your expertise in advance.

11/19/242:30 PM

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DougklinkOGR Forum Member DIGITAL SUBSCRIBER

Generally a breaker is on each red output so you can size the breaker to protect the current from that particular output. You're not just protecting the items on the layout but you're trying to keep the current of each output within it's design limits. Mine are all on the red output terminals.

11/20/246:07 AM

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Rod StewartOGR Forum Member SUPPORTING MEMBERDIGITAL SUBSCRIBER

As said above. Also if you have only one CB in the common return, when it opens all lines go dead. Best to have several on the individual hots. 10 amp CB’s are usually good for our purposes.

Rod

11/20/249:16 AM

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SteveHOGR Forum Member SUPPORTING MEMBERDIGITAL SUBSCRIBER

The LW is rated at 125 Watts input power. When it warms up, it's output Wattage is expected to be roughly 75% of this, which is about 94 Watts.

With it's track output set to 16-18V for a Lionchief loco, the LW would only deliver 5 to 6 Amps. There's a good chance 10 Amp breakers would not trip during a derailment.

Generally speaking, I agree with the earlier replies that's it's usually better to install a breaker on the Hot side of every transformer output, especially when there is more than one transformer with interconnected Commons.

However,

If only using one transformer on your layout and you don't mind having all power interrupted during a derailment or track overload, IMO it should be okay to use only one breaker in series with the Common. On an LW, Common is the A post.

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