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Details compatible electronic thermostats and cautions against power-stealing models for proper system function.
Specifies requirements for motorized dampers, including type, voltage, and current ratings for reliable operation.
Outlines compatibility with standard residential gas/electric HVAC systems and lists supported heating/cooling stages.
Explains the patented feature designed to reduce heat stratification in multi-story homes by balancing air distribution.
Describes the built-in 5-minute delay to prevent compressor damage from rapid on/off cycling.
Details the LED flash patterns indicating normal operation, equalizer cycle, and short cycle protection status.
Details thermostat/damper wiring, controller power sourcing, and fuse specifications.
Illustrates connecting zone thermostats to control unit terminals, including power and signal connections.
Provides a diagram showing how the ZC2S control units connect to standard HVAC mechanical systems.
Explains the dipswitch settings for test mode, fan mode selection, and Thermal Equalizer timing.
Details how to set the heat run time thresholds that activate the Thermal Equalizer cycle for optimal comfort.
Presents a comprehensive visual guide for wiring thermostats, control unit, HVAC system, and dampers.
Summarizes the LED flash codes for monitoring system status, including normal operation and protection modes.
Reiterates the compressor protection delay and its indication via the status LED.
Consolidates dipswitch configurations for test mode, fan selection, equalizer mode, and heat run time settings.
The RCS Model ZC2S is a 2-zone HVAC control unit designed to manage temperature in residential forced-air systems. It allows two standard electronic thermostats to connect to a single heating and cooling HVAC mechanical system, providing independent temperature control for two distinct zones. This unit is compatible with standard gas or electric heating HVAC systems up to 5 tons, supporting one stage of heating and one stage of cooling.
The ZC2S operates automatically and is transparent to the user, with each zone's thermostat providing complete and independent control. The unit supports auto-changeover between heating and cooling modes, prioritizing heating calls. It is designed to work with most electronic thermostats that are either battery-operated or use both sides of the 24VAC power (R and C terminals) from the HVAC system. It is crucial not to use "power stealing" thermostats, as these will not function properly with the ZC2S. Older mechanical thermostats with "anticipator" circuits are also not recommended. Thermostats connect to the zone control unit terminals in the same way they would connect directly to the HVAC system.
For independent temperature control, the ZC2S regulates the flow of conditioned air to each zone using motorized dampers. It employs a two-position, on/off control system and is designed for use with normally open, two-position, spring-return, 24VAC, 2-wire motorized dampers, such as the RCS RD Series. Normally open dampers ensure fail-safe operation, meaning conditioned air will still be available even if a damper motor fails. When one zone calls for heating or cooling, the damper for the other zone closes. The maximum rated current for all dampers is 1 Amp, typically supporting two dampers.
A key feature of the ZC2S, particularly useful in two-story homes, is the patented Thermal Equalizer feature. This addresses heat stratification, where heat naturally rises, causing upstairs zones to overheat during heating cycles while downstairs zones remain cooler and continue to call for heat. The Thermal Equalizer monitors the duration of heat calls from the downstairs zone (Zone 1). After a selectable time period, it temporarily stops the heat call and recycles the overheated upstairs air back down to the downstairs zone. This "equalizer cycle" reduces heat buildup upstairs and returns excess heat to where it's needed downstairs, resulting in more comfortable temperatures upstairs and energy savings. During an equalizer cycle, the Zone 2 damper (upstairs zone) closes, and the high-speed fan turns on.
The ZC2S also incorporates a Short Cycle Protection Delay to prevent potential damage to the compressor from rapid on-off cycling. This feature introduces a 5-minute delay between successive compressor operations. This delay is normal during troubleshooting, and for testing purposes, the 5-minute delay can be reset by removing power from the controller.
For monitoring the unit's status, a Status LED is provided. In normal operation, the LED flashes once per second. Different flash patterns indicate specific modes: two flashes signify an Equalizer Cycle is active, and three flashes indicate that the Short Cycle Protection Delay is active (compressor output inhibited).
Installation of the ZC2S involves mounting the controller near the HVAC mechanical system or in a convenient indoor service location like a garage, basement, closet, or utility room. Mounting directly onto the HVAC unit is generally not recommended due to potential vibration and heat. Standard 18-gauge thermostat wiring should be used for connecting thermostats to the controller and the controller to the mechanical system. For dampers, the zone damper outputs provide 24VAC at a maximum of 1 Amp, and 18-gauge thermostat wire is also suitable. The ZC2S Control Units are powered by the HVAC system's 24VAC R and C (common) terminals, eliminating the need for an external transformer. The total damper draw must not exceed 1 Amp per zone. The controller is protected by a 2AG style 2 Amp fuse.
Configuration of the ZC2S is done via a configuration dipswitch, SW1. SW1 Position 1 (Test Mode): This is for service technicians only. Setting it to OFF enables normal operation with all delays active. Setting it to ON activates Test mode, reducing delays to 10 seconds and shortening run times to one minute, which aids in system checkout and troubleshooting. This mode should not be used for normal operation. SW1 Position 2 (Fan Mode Select): This position determines fan operation during heating calls. Setting it to OFF is for standard gas systems (no fan with heat calls), while setting it to ON is for electric heating systems (fan with heat calls). SW1 Positions 3 & 4 (Thermal Equalizer Mode Select): These two dipswitches determine the duration of the equalizer cycle after it has been triggered by a Heat Run Time timeout.
General| Manufacturer | RCS |
|---|---|
| Model | ZC2S |
| Category | Control Unit |
| Current Rating | 2A |
| Input Voltage | 24 VDC |
| Output Voltage | 24 VDC |
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