Hello All, I am looking at using an HP Server power supply (DPS-460EB) to provide 12v track power. The issue I have is that it can put out 38.3Amps Max. can I put a fuse in between it and the main bus line, if so what amp Fuse should I use? Bruce
Well, that's a good question. The answer is YES, you need a fuse or circuit breaker. But the value of the fuse(s)/CBs depends. Assuming the PS has over-current protection, you do not need a fuse to protect the power supply itself. But you need to protect wiring, and other items you that could be damaged from passing too much current (e.g. auto-reversers, current/occupancy detectors, locomotives, track, etc. And 38 amps can do a LOT of damage. Since you are going to use 12V, I assume you are using N scale? If so, I would not power any track with more than 5 amps. If you have a large layout and will run more than 5 amps worth of equipment or accessories from the track bus, I would break up your layout into multiple zones or blocks with 5 amps or less each. It is also a good idea to power accessory decoders from a separate zone from any track zones, so that they don't suffer outages during a track short that could be cleared by throwing a switch under DCC decoder control (if their DCC zone is not shorted out by the same event). BTW, in the case of multiple power zones or blocks, I would strongly suggest a circuit breaker module made for DCC, instead of a fuse. Some modules can protect/supply multiple blocks/zones. Your command station likely has output over-current protection itself as well. The main risk is that a locomotive that shorts a high current track bus can get very hot before you realize what's going on, and become irreparably damaged (melted), so you want something that will automatically shut off the power to the short before the damage becomes excessive. Rails can get hot enough to burn or damage the track/ties/base as well. Worst case, a small gauge wire carrying 38 amps can start a fire it if is in contact with wood, or other combustible materials long enough. But with a 38 amp supply, I would still use a fuse at ~1.5x to 2x the maximum current your command station/booster(s) can supply, between the CS and power supply. Better to blow a fuse than destroy a CS/B. If you are HO or larger, I doubt a 12VDC supply is enough voltage for your command station/booster to supply the sufficient power to your locomotives.
