Fault Detection and Diagnostics for Rooftop Air Conditioners

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3. Elimination of preventative maintenance for a savings of $2000 per RTU over
the life of the unit.
4. On average, the performance of the system was degraded for 40% of its lifetime
with an EER and cooling capacity degradation of 21% and 30%, respectively.
This assumption is based upon limited field results and should be confirmed
through additional analysis.
5. No demand savings. This is a very conservative assumption and should be
considered in more detail in future studies.
6. One coil cleaning service can be saved per year through automated FDD.
7. A 60% probability that a refrigerant charge fault will occur once during the
equipment lifetime.
8. A 60% probability that a filter/drier restriction fault will occur once during the
equipment lifetime.
9. A 6-ton RTU having an initial of cost of $4500.
10. A cost for the FDD system of $300.
Table E-5 gives estimates of total lifetime net savings (total savings minus FDD
system cost) for an individual RTU operating in different buildings and locations. The
estimated savings over the life of the unit range from $4000 to $10,000 per RTU. The
annual net savings range from $400 to $1,000 and the estimated payback period is less
than one year. Greater savings are possible in hotter climates due to larger cooling
requirements. The savings would be greater for heat pumps because they operate
throughout the whole year.