System Type
APR Control for Heat Pumps
Heat pumps have a sizing problem that makes modulation especially valuable: in colder climates they are sized for the heating load, which leaves them oversized for cooling and short cycling all summer. APR Control adds continuous capacity modulation so the unit runs at part load instead of cycling.
New or existing equipment
On heat pumps, APR Control fits both ways: retrofit onto the equipment you already run, or built into new equipment by OEMs, contractors, and third-party modifiers, with no design-day capacity penalty.
Why heat pumps end up oversized for cooling
A heat pump's heating capacity falls as the outdoor temperature drops, so in a cold climate it has to be sized to still deliver heat on a cold design day. In colder regions the heating demand can be several times the cooling demand (U.S. DOE Building America), so right-sizing for heating usually leaves the same unit oversized for cooling.
That mismatch is the root of the summer problem. An oversized-for-cooling heat pump satisfies the space quickly on a mild day, shuts off, and starts again: short cycling that wears the compressor and gives up humidity control.
The takeaway: variable capacity lets a heat pump be right-sized for heating and still behave well in cooling. APR Control adds that variable capacity to a standard heat pump, so it modulates through the mild-weather cooling hours instead of cycling on and off.
How APR Control fixes it
APR Control is a suction pressure-activated mechanical valve, sized to the lead compressor, that modulates refrigerant flow to match real-time load. On a heat pump running in cooling, it turns the oversized capacity into continuous part-load operation: the compressor runs instead of cycling, with no impact on the unit's rated capacity during design day conditions. In heating mode, APR Control is inactive when the system is piped per our instructions, so it modulates cooling without affecting heat-pump heating operation.
Runs Instead of Cycling
Continuous modulation through the mild-weather cooling hours the unit is most oversized for.
Humidity + Reliability
Longer runtimes hold humidity; fewer compressor starts extend equipment life.
A2L and Refrigerant Compatibility
APR Control applies to heat pumps across new and old refrigerants (R-410A, R-454B, R-32, plus legacy R-22), with A2L heat-pump guidance from Rawal Devices Engineering. See the Refrigerants Hub for the transition picture.