# Car Heat Questions



## /6 matt (Jul 7, 2015)

Why is it on passenger cars, railroads installed boilers in their diesel locomotives and retained steam as a heat method? With the lower efficiency of steam heat coupled with the added expense of providing a source of steam, it would have been smarter to convert the fleet to utilize electric heat and take advantage of that nice big 3 phase alternator inside the locomotive. Can anybody tell me what part of the picture I am missing? :dunno:


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## Lehigh74 (Sep 25, 2015)

I'm guessing it was less expensive in the short run to add a boiler to a diesel or electric loco than it was to convert or replace the passenger fleet.


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## tkruger (Jan 18, 2009)

I wonder if there is a safety concern running high voltage lines from car to car along the train. Steam may leak but only cause a small area to be affected. Electric going to a metal chassis could be far more dangerous.


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## Lehigh74 (Sep 25, 2015)

I don't think it was a safety thing. Eventually, they did switch to electric heat with power from either the locomotive or a head end power car


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## MRLdave (Nov 1, 2011)

To a degree. it was a carry-over. Steam locomotives don't make much electricity, but make lots of steam. During the transition era there were both steam and diesel locos pulling the trains.......if you chose electricity for new cars, you couldn't pull them with the steam power, and there were thousands of existing steam cars that you could no longer mix in to a consist with electric cars. Many cars from the 30's on (steam era) ran into the AMTRAK era. The cost of converting existing cars would have been high........much higher than installing a steam generator in a loco. And depending on location and time of year, you didn't need every loco to be steam equipped. And electric heat isn't that much more efficient than steam......ask anyone that has lived with electric baseboard heaters.

And you can't use power directly off the loco.......even when the railroads did switch over, they removed the boilers and added electric generators in the empty spot in the locos (head end power, HEP), to power the cars.


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## Old_Hobo (Feb 20, 2014)

Looks like MRLdave hit it on the head! Canadian railways (CN) also made steam generator cars to help produce steam:


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## cv_acr (Oct 28, 2011)

You'll also note that in NO CASE is electrical power for passenger cars EVER supplied directly from the main generator on any normal diesel locomotive.

Passenger units have an additional, separate generator for the "Head-end power" (HEP) supply.

Or an EGU (Electrical Generator Unit) car is used.


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## Hot Water (Oct 24, 2015)

CV_acr,

Your statement "also note that in NO CASE is electrical power for passenger cars EVER supplied directly from the main generator on any normal diesel locomotive." is not totally accurate. Since the original poster was inquiring about passenger operations, I would consider that the EMD F40PH series of passenger units fairly "normal".

The EMD F40PH models have the capability to switch from "normal HEP" mode (power supplied by the crankshaft driven HEP generator) to "stand-by" mode, where the prime mover diesel engine is reduced in speed and 480 volt, three phase HEP power for the passenger cars, is taken directly from the main generator/traction alternator.


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## cv_acr (Oct 28, 2011)

I did not realize that "stand by" detail. I had assumed power was ALWAYS directly from the HEP generator provided for that purpose. Certainly engines without a HEP generator are not used to power passenger cars in operation; then an EGU is required.

Which I guess from a trackside, outsider perspective is pretty similar to "you always need a dedicated HEP generator", even if technically you can provide that stand-by power in station.


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