Wrong.

Those plastic boxes are new. They haven't always been there, even though the trains have had operating electric headlights for quite some time now.

The low water alarm system was installed six or seven years ago now as part of a plan to add redundant safety appliances to the DLRR locomotive boilers. In reading the various posts discussing the little black box on the rear end beam of #4's tender I find that most of the information is correct to a degree, but expressed in loose context.

Here is what I know about the low water alarm system: The train's electrical system, including the solenoid valve for the air compressor, is a positive ground system. That means that the + poles on the storage batteries are attached to the frame of the locomotives and coaches and the - poles are attached to the switches and ultimately the devices they energize. I am not sure why a positive ground system was used on the railroad, it was common in the early days of automobile electrical systems, but by the 50's when the trains were designed were no longer in favor. The low water system uses a control relay that requires a negetive ground electrical system which is half the reason it gets its own battery. The other half is, occaisionally it is necessary to change out the large train system batteries in the middle of operations for various reasons so one of the design parameters was that the low water system be completely independant of the train's electrical system. This is why you see 2 boxes in the photo of #4. The large box painted the color of the tender is the train's batteries and the smaller black box is for the low water system.

There is a probe in the boiler that detects conductivity when it is emersed in water. As long as the probe is covered, no signal is sent to the control. When a low water condition occurs, an alarm and light come on alerting the crew that the water level is low in the boiler. The crew has a certain amount of time to correct the condition or the system will shut off the fuel to the burner.

The solar panels are low wattage battery chargers and are there to keep the battery for the low water system charged and exercised.

Maybe they don't fire folks for spreading inaccurate information, eh?

Well you wouldn't believe how some of our leads from the Roundhouse check out our posts and they know who works for the DRR and who doesn't and when we provide the wrong info, we will hear about it!
But Robert is a Train Wreck, and your right, we have two battery boxes, the big one contains a large marine battery to power the lights and accessories for the entire train! The small battery is for the low water sensor and if it does go off because of low water and you can't fix the situation in time, the fuel is shut off, you have to call the roundhouse to come out and unlock the system and your are officially fired!!
And while the electrical system has worked for 52 years, its really having a time now keeping up. I have seen prototypes for using steam generators on our locomotives as an alternative but to date nothing has been decided.
Dog