I'm looking at utility data for a building on a college campus that has a central utility plant. They list cooling energy in ton-hrs and It seems really high for all buildings across the board.
However - if you assume that ton-hrs is the metered chilled water usage and not the chiller energy, its not that bad. For example if the chilled water usage is 1 ton-hrs, that's 12,000 BTU's of cooling energy delivered. However, if whats being measured is chilled water usage (and not chiller energy), then 1 ton-hr is not the energy consumed by the chiller - that should be 12,000BTU/COP of the chiller. So if the chiller COP is 4 - then that's only 3,000 BTU's of energy consumed to deliver that ton-hr.
So - to get to the point - does anyone know if campuses monitor their chilled water usage (in ton-hrs) as chiller energy or cooling delivered?
(I hope this makes snese)
Vikram Sami, LEED AP
I've usually seen this metric as chilled water usage at the building vs.
chiller energy. This goes in line with installing a Btu meeting for a
campus chilled water system, so you can define the chilled water energy
used at the building, similar to district steam.
Mark Nieman, PE, CEM
Dear Vikram,
I think that the definition of ton-hours is inherently an "cooling energy
delivered" or "useful energy", metric.
James V. Dirkes II, P.E., LEED AP
Vikram:
?
I agree with James. Chiller energy would be measured in electric or gas units
(energy input)..
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Ton-hours is a load (useful energy) function.
?
John R. Aulbach, PE, CEM