Yes, I think parallel is the way to go.
 
You didn't answer all my questions about whether you have a single thermostat for your apartment, one for the floor (shared between apartments), or one for the whole building (don't feel bad, we have a 39,000 sqft dormitory/classroom/dining hall building up in the Adirondacks that until recently only had a single stat in it!).  I gather from you answer that you share the control with other people. It is possible in a building as big as yours that in cold weather your central boiler is always making steam and individual radiators have some sort of thremostatically controlled valve...
 
I think there are thermostatic radiator valves (they can also be used for on/off control if you wish to dumn-down the operation) that might work okay.  The only problem is if they are not calling for heat until after the boiler is done firing then it could be a little cool until the boiler fires again (assuming that's the way your building operates).  Of course if it hung on a radiator right under a window (the usual location for radiators) it would probably always be calling for heat due to the cold draft from the window.
 
Bear in mind that running steam pipes is a bit tricky in that they like to pitch down to the trap to allow the condensate that forms in the pipe to get there without filling the pipe and causing water hammer. Wherever a rise takes place (as to go over a doorway, for instance) they like to put a trap at the bottom to remove any condensate that has formed up to that point. The trap then has to have an outlet piped downhill to the condensate tank. Piping vertically (called "risers") from below is the most common method (especially where windows repeat vertically) with "laterals" tapped off.  Having a steam supply riser on one side of the window with a condensate return riser on the other side makes for efficient piping in large buildings (where windows are close together you can share a supply or return riser between two windows).
 
More Steam Heat 101
 
BruceVac (I like it) letting off steam...
 
-----Original Message-----
From: This isn`t an orifice, it`s help with fluorescent lighting. [mailto:[log in to unmask]]On Behalf Of Met History
Sent: Sunday, January 25, 2004 5:44 PM
To: [log in to unmask]
Subject: [BP] OK, BruceVac, so a "series" connection in a two pipe steam system...



...won't work.   But what about a "parallel" connection, that is, two separate branches leading to two separate valves leading to two separate radiators leading to two separate traps leading back to a single return line?   
 
Why would I want this?  Because, with steam radiators, it seems to be either all or none - off or on.  So that if its a one dog night you could just use one radiator and if its a two dog night ... etc.    With the new slimline "baseboard" cast iron radiators such "twinning" becomes realistic.  
 
Best,  Christopher