RCCD Solves the Most Common Problem
in the HVAC Industry – Overcapacity


The only means of regulation in most AC units is On/Off cycling – 100%, or nothing. This leads to:

  • Too-short run times, which doesn’t allow condensate to truly leave the building (It takes 12 minutes of ‘On’ time to start draining water out of the condensate drain)
  • Discomfort due to elevated humidity levels during mid-season
  • Reduced compressor life due to frequent starts
  • Wear and tear on the contactor and fan motors
  • Potential freezing of the evaporator coil in low load conditions


The traditional air conditioner works at its design capacity only 3% of the time; the rest of the time it has excess capacity. This causes short run times, excessive compressor starts, and reduces the ability of the unit to control humidity.


The RCCD solves these problems by matching the system capacity to your current needs over a wide range of operating conditions.


A continuous capacity modulation range of from 0 – 60% is typical with the RCCD. This is like having a 2-to-5 Ton AC unit, instead of a 5 Ton only system.  The best part is that this capacity modulation is completely automatic – nothing else is required – no fancy thermostats or proportional controllers.


RCCD simply keeps the evaporator temperature constant; as the room temperature approaches the set-point, the heat flow will decrease. As you get closer to the desired temperature there is less load to the system. Systems with RCCD will continue running (and dehumidifying), but at reduced power usage.

Refigeration Capacity Control Device - RCCD


The RCCD is of benefit in all traditional HVACR systems that use fixed displacement / fixed speed compressors.

RCCD greatly improves performance in applications like:

  • Spaces with large variability of loads like schools, libraries, office spaces, conference rooms etc. If these units are sized to handle full occupancy, they will be grossly oversized during unoccupied periods and will tend to short cycle and develop humidity issues.
  • Technology shelters with varying load. Units sized to handle the full load in a technology shelter will tend to short cycle under most operating conditions. This leads to compressor burn-out due to issues with oil return.
  • Units with zoning controls benefit greatly by being able to adapt to the current load conditions.
  • Chillers benefit from stable evaporator pressure (temperature), and they can more easily respond to varying load with greatly reduced risk of freezing the heat exchanger.
  • Multi-stage systems that use the RCCD on the first circuit (first in, last out) can double or even triple the modulation range.
  • Any home air conditioner where people complain about increased humidity during mid-season. In humid environments (coastal, Midwest) the typical air conditioner will satisfy the thermostat quickly on all but the hottest days, and then it will switch off for an extended period of time. The water condensed on the evaporator coil and in the drain pan will then evaporate back into the conditioned space. Remember, the only humidity that is truly removed from the space is the water that flows out of the drain pan! Extended run times with reduced power consumption address this issue.