[PRCo] Re: Heaters

[TEP]

Nothing changes. I am still working in traction and this includes 
specifying subway, LRT and streetcars. How much heat to provide is 
always an issue. Some authorities want toaster ovens, but the reality is 
that in cold weather passengers dress for it -- as should the operator. 
Too much heat is a common complaint.

Modern IGBT propulsion wastes little so it is no longer economic to 
extract heat from the resistors. The usual compromise is to keep the 
heat level to what can be handled by convection heaters under seats or 
on the sidewall -- plus some ceiling heat if there is air conditioning. 
This avoids the maintenance issue of fans with the heaters. The result 
is an installed capacity of 15- 30 kW, depending on car size and city. 
The car takes a while to warm up and could be on the chilly side between 
pulling out of the yard and getting warmed up by rush hour passengers, 
it will be fine thereafter.

Some subway systems have no interior heat at all, relying on tunnel 
warmth and passengers (300 Btu each). Even with surface sections some 
properties rely on retained heat -- until the train gets back into the 
tunnel. I was working on Beijing Line 1 last year. A long surface 
extension had just opened. The old subway cars got so cold that they put 
velour cloth covers over the horizontal stainless steel stanchions -- 
until new rolling stock with heaters took over for this last winter.

Even in temperate climates more and more systems are specifying air 
conditioning. I always push for opening windows -- even if fitted with 
crew locks. There is nothing worse than being stuck in a sealed car with 
failed air conditioning, shades of the 1700s that I frequently rode in 
the Pittsburgh summers of the 1960s.

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Tom Parkinson Vancouver BC
604 733-5430  fax 733-5437
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