In today market where large single input hot water boilers for multistory buildings are being replaced with multiple residential hot water boilers (to heat individual units), the installation and servicing of these units are not typical.
With the baseboard sometime installed 6 – 8 floors above the boilers, you have to make sure the boiler’s *COLD water fill pressure is high enough to reach the top floors of the building.
Using the following procedure you can calculate what the fill pressure should be for a given building:
Given: Baseboard on top floor of a 6-story building with boiler located in the basement. Each floor is 10 FT. high; therefore the total height to baseboard is 50 FT plus 8 FT for basement = 58 FT.

Given: Every 2.3 Ft of water equal 1 PSI.

 

FORMULA:

Height to baseboard   58 FT
Ft of water = 1PSI
2.3 = 25.22  minimum fill pressure to get water to the top floor baseboard

To eliminate flow noise and assure that the system is completely filled, add 4 PSI to the fill.

Final *cold fill = 25 + 4 or 29 PSI

 

*Note: System water temperature will effect system pressure, all ways check system fill pressure with water temperature below 100 F.

Note: The operating pressure of the boiler cannot exceed the maximum operating pressure of the boiler casting.

Under standing how to adjust and check system fill pressures can aid in trouble shooting noisy operation, no heat and inadequate heat on top floors of unusually high buildings using residential hot water boilers.