Tom from Memphis. Client did a major LED lighting retrofit and HVAC upgrade 18 months ago. They expected demand charges to drop significantly. Demand charges dropped modestly in the first 6 months but have been creeping back up. The client is frustrated and questioning whether the retrofit was worthwhile. What should I look at?
Demand charges after a major equipment retrofit
Lisa from Portland. The LED and HVAC improvements reduce base load and average demand but the billing demand is still set by the peak 15-minute reading. If anything else on the circuit spikes during that peak window the demand reading can be high even after a retrofit.
Tom again. The client added a commercial dishwasher to their cafeteria about 8 months ago. That timing matches when the demand started creeping back up.
Lisa again. There it is. A large commercial dishwasher with a booster heater can draw 15 to 20 kW. If it is running during the lunch peak when other loads are also high it would be contributing to the demand reading.
Sandra from San Diego. Also check whether the HVAC retrofit changed the staging or startup sequence. New control systems sometimes inadvertently change when equipment starts up, which can create new coincident demand peaks that did not exist with the old system.
Tom here. The facilities manager mentioned the new HVAC control system changed the morning startup sequence. That is something I had not connected to the demand issue.
Sandra again. New controls that start all HVAC zones simultaneously rather than sequentially is a very common source of unexpected demand increases after retrofits. The individual units use less power but their simultaneous startup creates a new coincident peak.