We are in a commercial building and are being billed per-ton hour for the chilled water usage on our 20-ton, chilled water fed Liebert upflow A/C unit. We are trying to figure out how much we are paying for how much tonnage we are actually using in a month. Our last bill said we used 2,904 ton hours, and the amt was just shy of $500. This 20-ton unit runs 24/7 and maintains a temp of around 70 degrees, and the chilled water valve is open 100% of the time to maintain that temp. So, we are trying to figure out how the ton hours are being calculated on the meter -- with 720 hours in a month, we expected something like:
720 * 20 = 14,400 ton hours
At 2,904, that comes out to around 4 tons, which we know we are using more than that.
Where are we going wrong here?