Can someone give me an idea of HEP requirements for a typical air-conditioned commuter coach? Many years ago, I saw an LIRR genset in Morris Park; it had a 3-71 and I recall the nameplate saying something in the neighborhhood of 18 kW.

I have been using this as a guideline, but wonder if it is accurate any more. IIRC, some of the Amtrak units have 800 kW HEP alternators. At 20 kW per car, this equates to a 40 car train, not too likely to be seen on Amtrak! (Yes, I know about the AutoTrain, but the car carriers don't use that much juice for lights.) Or is the extra capacity for diners, hot water for showers in sleepers, etc.?

A typical modern commuter coach (single level) will have a 10-12 ton air conditioner, but it will typically also have a "re-heat" circuit, to help with dehumidification. Once the car has stabilized, you can typically get by with 25-30 Kw of power, but if you are in reheat season, you will need 50 Kw.

The old LIRR car with the Delco plant you are referring to only has 6 ton of air conditioing and no dehumidification.

Modern double decker cars have a pair of 10-12 ton air conditioners; MARC Train Service in Washington-Baltimore has found out that its old 425 Kw HEP plants run into trouble bringing up a seven car train from dead cold/hot (depending upon season) without phasing in the cars. The new Wabtec/Boise locomotives presently on order to replace all of their diesels will have 800 Kw HEP plants to meet the demand.

I am familiar with a former Amtrak Capitoliner converted into a geometry car, but with its original HVAC. It cannot run 100 % of its heat (floor and overhead) on its 55 Kw diesel generator without overloading it.

Steve Zuiderveen

Steve,

Thanks for all the information. I thought my 20kW number might have been a bit low.

My day job is in a plant where we have to control humidity, so our steel stock doesn't rust, and we have similar "re-heat" equipment. Sometimes we have dehum, hot gas and heat on all at the same time to control humidity, and our energy bills are huge for a plant our size.

I never got to ride in those LIRR cars during the summer, but 6 tons doesn't sound like a lot of AC capacity. I do remember they had a lot of complaints, though, back in those days-

If that's one of the 11 extra cars for Harrisburg service added to the Metroliner oder, it was intended to be supplied from overhead wire with comparatively unlimited capacity.