# 600 volt DC trolley line traction power service in a home.



## hornetd (Oct 30, 2014)

I was called in to investigate a branch circuit outage in a large home that had been converted to an office with guest rooms located on S ST NW in the District of Columbia. The building was once a large family home which had been donated to a church lobbying organization. I put a circuit tracer on one of the deenergized receptacle outlets and went to find the breaker. I could only isolate the tracing signal to a 30 ampere double pole fused switch supplied from the Service Conductor trough. Needless to say I was puzzled. I traced the branch circuit wiring inside the interior walls with no difficulty at all. I had never had such an easy time tracing a concealed circuit before then. The circuit fetched up into a wooden cabinet enclosing a field assembled panel built from individual parts. It was located above the top landing of the basement stairs. When I opened the wooden door of the cabinet I found out why it was so easy to trace that branch circuit. The wiring was knob and tube. The wooden cabinet was lined with *asbestos* sheeting. Since the asbestos sheeting was cement coated I wasn't too concerned about harming the occupants of the building because unless the asbestos sheeting is broken it will not cause asbestos fibers to become airborne so that they could be inhaled.

The panel consisted of porcelain based fuse sockets with lay in wire terminals on one end through which the original 10AWG feeder conductors ran to energize every other fuse holder and connect the neutral to the alternate fuse sockets. There were 2 fuse sockets on each porcelain base. Those supplied the two poles of a double pole single throw switch. The pivot point of the switch armatures were connected to the fuse holders' screw shells. The use of the screw shells of the fuse holders for the load connections of the circuit was the only aspect of the assembly that made sense. The actual branch circuit conductors were connected to the stationary jaws of the switches. That meant that the fuse holders' center contact was always energized unless the 30 ampere enclosed fused switch supplying the feeder from the service was opened. The armatures of the double poled switches are always energized if the feeder switch is closed and an intact fuse was located in the socket. Take note that the double poled switches served no purpose except to open the branch circuit supply for reasons unknown to me. In case the biggest problem is not obvious the neutrals were fused along with the energized conductors. 

At the next meeting of the local's retired member group I asked if anyone could tell me more about the panel. A couple of them explained that the panel would have been a 600 volt DC trolley traction power service. They were only used for lighting. 5 120 volt bulbs would be supplied in series in each branch circuit to make up a suitable load for the 600 volts DC. They advised that I could confirm that by checking the switches for each room light for the T stamped into the support strap that indicated they could close on a tungsten filament load supplied from DC power without being damaged. Sure enough I found 2 of what may have been the original switches with the T marking. 

Tom Horne


----------



## wcord (Jan 23, 2011)

Looks kinda like this?









Pretty standard for a K&T fuse 'panel' in houses.
I did find 1 like this in an old hospital. Must of had 40 ccts in it.
Commercial 'panels' were wired the same but usually on a slate backboard and a copper busses


----------

