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Steam pressures with Vari-Vac
Looking a several larger buildings in NYC...
Typical building is around 400,000 sq ft and has ~400 units. Two 300 HP Cleaver Brooks feeding steam to a Vari-Vac controlled distribution system with one or two main valves, communicating with the Vari-Fac, supplying the building. Apartment terminal units are PTACs with variable speed blowers. Operating pressures at the boilers are higher than I typically see for a 2 pipe steam system...around 7 PSI is typical. Vari-Vac DCC1000 control panel.
Two questions floating around my head:
1. Can the boiler pressure be dialed down on this type of system? 7 PSI seems really high, but I'm not quite grasping the relationship between the varying load at the PTACs (due to variable speed blowers), the Vari-Vac valve/vacuum modulation requirements, and probably 3 other things I don't know I'm not grasping.
2. Can I nix the vacuum system and install orifice plates?
The goal here is to recommend effective energy conservation opportunities. Thanks a ton!