Balancing vs. zoning in Apts

arg

I need opinions.

I have 3-story apartment buildings that are too hot on first floor, not bad on second floor, and too cold on 3rd floor. System designs vary somewhat but all have unevenness problems.

1960s era buildings have hot water boilers running generally at 20-45 psi, 120-170 F. Boilers vary from new twinned units installed Oct 2007, to other single units as old as early 1990s. Pumps are Bell & Gossett. All the boilers and pumps were started and checked by the pros in the fall. They have done some band-aiding but long term solutions will have to wait until summer.

Basement distribution piping is black steel in the basements with gate or globe manual shutoffs on each supply and return. Copper risers. In unit piping is copper with fin-tube baseboard. Most buildings have the zone valves in the units, with common risers usually serving the three stacked units. One bldg. has all zone valves in the basement with individual risers and returns for each unit.

Previous owners installed Fluidmaster Pro-Temp controls with outside air temp sensors, return and supply water sensors only. No zone sensors. Previous owners disconnected and removed unit stats and zone valve servos. Their approach seemed to be to run everything wide open.

Also there are no bleeder valves on the 3rd floor. Previous owners used icemaker saddle taps as needed.

1. What is the problem causing the unevenness? Bleeding seems to help short-term only.

2. What is the best approach to balancing these systems? (Won't break the bank, will work reliably)

3. What should I do about the bleeder situation?

Thanks.