Do you know this piping system?

chuckadoo

What it is:

3 story older apartment building 163ft x 35ft
Steel piping
no zones, one thermostat in hallway.
tenants have no control whatsoever, not even shutoffs in unit/radiators.
radiators are those that look like a cover to a cast iron radiator, but just has a short section of large finned “baseboard” across bottom (sorry I don’t know proper name).
Seems to be very well balanced, no “too hot/too cold” complaints.
no piping exposed, except for supply leaving boiler room and return coming back.
all radiators are in the same spot in each apartment.
each apartment has 3 radiators

Could the piping be “reverse return” vertically for all floors, and also “reverse return” horizontally on each floor?

Could there be one main loop in basement and each radiator “stack” (eg. 1st floor, 2nd floor, 3rd floor living room radiators) share their own supply and return risers, with some kind of steel monoflo fitting in basement?

or????

the problem:
random radiators are stone cold.
8 apartments are affected.
6 top floor, 2 second floor 
Only one radiator per apartment are cold.
(I could not enter all apartments, and could not verify if the cold 2nd floor radiators are directly beneath cold third floor radiators.)
No air capture/elimination devices, except for manual bleeds at radiators.
I would bleed and bleed only water at cold radiators until I was dumb in the face😁

any advice/ piping layout knowledge/ etc. would be much appreciated!

chuckadoo

Maybe 1950’s building 

mattmia2

Those emitters are called convectors. Pictures of the element far enough back to get the whole element and the piping would help. Probably have a valve for balancing and control and a bleeder at each connector. Probably air somewhere but not where It can find it's way to a convector or at least the ones you tried.

Pictures of the boiler might give us a clue. Any exposed piping in the basement would help a lot more.

Zman

My guess would be mono flow. Some pictures would sure help. Do the radiators have coin vents? What does the near boiler piping look like?

Big Ed_4

Say there were no changes in the pipe work . If a convector does not heat , the normal problem is air , dirty fins or valve is off ...