Digger said:Mike,
Its a switching power supply so it will just fold back if overloaded. Then once the overload is removed it will come back. What you would see if you put a volt meter on the output is that if you place a short circuit on the output it will probably hiccup (it will fold back and then come back and see the short and fold back and rinse and repeat until the short is gone). I say probably as I have seen a few switching supplies that just fold back and don't hiccup and they stay off until their input power is cycled.
Switch mode designs are very efficient, light weight (usually compared to a linear) and cost effective.
Contrary to DEL's statement that the AL400U is fused on the main board it is NOT fused on the output. Their installation instructions even verify that fact so I have no idea where he is getting his information. While their is a "primary" protective device that is NOT protecting the output. It is a switch mode and inherently limited in itself and does not need a PTC to make the output "Power Limited" nor does it need a fuse to protect it on its output.
Altronix makes good quality products and you cant go wrong with them in my opinion. Year ago I tested several of their designs for safety compliance and I would have no hesitation to buy any of their products for my own use. Same goes for Elk Products and other mfg's.
The distribution board that Altronix makes for the al400ul comes in two versions, one with fuses and one with PTC breakers. It breakes the 4 amp power supply out into four individually fused 1 amp outputs.
Mike.