Demand charges can be accidentally set higher than normal
when the lead chiller fails, since lead chillers tend to be backed up by
less efficient and less reliable machines. The worst case is where a lead
chiller fails followed quickly by the failure of one or more of the less
efficient machines. Once the chillers are finally put back on line they all
tend to "load up" to maximum tonnage levels to recover the building and
thereby set an unusually high electrical demand. Where the electric rate
schedule has a demand ratchet, this can be quite costly. There are several
potential solutions including:
- Better preventative maintenance (so that chiller failure is less
likely in the first place),
- Chiller replacement coupled with load reduction (e.g., through
improved lighting or better HVAC control).
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