Just wrapped up a project I'm really proud of. Large hospital complex here in Savannah with Georgia Power service under Schedule TOU-GSD-8. They had eight rooftop units totaling 400 tons that would all fire up simultaneously during morning startup and after power outages. Peak demand was hitting 285kW every single day at 6 AM, setting the monthly billing demand. Installed a Johnson Controls demand staging system with soft starters on the largest units. First month results - peak demand down to 145kW, saving $1,500 per month in demand charges alone.
Major Win - $18K Annual Savings with HVAC Staging
Eleanor, that's fantastic! What was the total project cost if you don't mind sharing? I've got a similar hospital project coming up in Atlanta and the CFO is asking for comparable case studies. The demand staging makes perfect sense for hospitals since they can't afford any comfort issues - the staged startup shouldn't impact patient areas at all.
Derek, total project cost was $35,000 including the demand controller, soft starters, and installation. The payback is under 2 years at $18K annual savings. The key was getting buy-in from facilities management - they were worried about comfort complaints but we haven't had a single issue. The staging brings units online over a 10-minute window instead of all at once.
Great work Eleanor! We're seeing similar demand issues here in Boise with Idaho Power. Question - did you have to modify any of the existing BAS programming or did the Johnson Controls system integrate directly? I've got a potential project where the existing Siemens system might conflict with add-on demand control.
Warren, the Johnson Controls unit has both standalone and BAS integration modes. We ran it standalone initially to prove the concept, then integrated it with their existing Trane system after the first month. The integration was pretty seamless - just had to map a few contact points and adjust some staging timers in the Trane software.
Eleanor, did you run into any issues with the soft starters? I've had mixed results with them on older HVAC equipment here in Pennsylvania. Some of the 15+ year old units don't seem to play well with the reduced voltage startup. Also curious about maintenance requirements - are the hospital techs able to service the demand controller or do you need specialized support?
Sylvia, we only put soft starters on the four largest units (50-ton and above). The older 25-ton units just got the staging delays without soft starters. The Johnson Controls system has a web interface that the hospital techs can monitor, but any programming changes need to go through their service contract. It's been pretty bulletproof so far - no service calls in the first 8 months.
This is exactly the kind of project data I need for my clients. Eleanor, what's the demand charge rate on that Georgia Power schedule? I'm trying to build a business case for a similar project here in Cincinnati with Duke Energy. Our GS-3 rate has demand charges at $8.95/kW which makes these projects really attractive.
Cecilia, Georgia Power's TOU-GSD-8 has demand charges at $10.34/kW on-peak and $7.89/kW off-peak. The morning startup was hitting during on-peak hours which made the savings even better. With Duke Energy at $8.95/kW you should see similar paybacks. The key is documenting the current demand profile - we used a Fluke power logger for two months to really nail down the patterns.
Eleanor, excellent case study! I'm bookmarking this thread for future reference. Question about the power quality monitoring - did you see any voltage sag issues during the original simultaneous startups? We've had problems here in Wisconsin where large HVAC startup creates voltage drops that affect other equipment. The staged approach should help with that too.
Karen raises a good point about power quality. We see that frequently with Cincinnati Gas & Electric - large motor starts causing voltage dips that trip other equipment. Eleanor's staged approach would definitely help minimize those issues. It's an added benefit beyond just the demand charge savings.