York DM036 Installation Manual

Also see for DM 036: Technical guide

Contents

York DM036 Installation Manual Manual pdf 38 page image

5011492-XIM-B-081538 Johnson Controls Unitary Productsthermostat is calling for cooling, the UCB will operate in the lowambient mode.Low ambient mode operates the compressors in this manner:10 minutes on, 5 minutes off. The indoor blower is operatedthroughout the cycle. The 5-minute off period is necessary todefrost the indoor coil.Low ambient mode always begins with compressor operation.Compressor minimum run time may extend the minutes ofcompressor operation. The off cycle will begin immediatelyfollowing the elapse of the minimum run time.When operating in low ambient mode, an evaporatortemperature below 26ºF will de-energize the compressor. If thecall for cooling is still present at the end of the ASCD and theevaporator temperature is above 26ºF, the unit will resumeoperation.Safety ControlsThe unit control board monitors the following inputs for eachcooling system:1. A suction line freezestat to protect against low evaporatortemperatures due to a low airflow or a low return airtemperature, (opens at 26 ± 5 °F and resets at 38 ± 5°F) oran evaporator low limit sensor to protect against lowevaporator temperatures due to a low airflow or a lowreturn air temperature, set at 26°F.2. A high-pressure switch to protect against excessivedischarge pressures due to a blocked condenser coil or acondenser motor failure, (opens at 625 ± 25 psig).3. A low-pressure switch to protect against loss of refrigerantcharge, (opens at 50 ± 5 psig).The above pressure switches are hard-soldered to the unit. Therefrigeration systems are independently monitored andcontrolled. On any fault, only the associated system will beaffected by any safety/preventive action.The unit control board monitors the temperature limit switch ofelectric heat units and the temperature limit switch and the gasvalve of gas furnace units.Compressor ProtectionIn addition to the external pressure switches, the compressoralso has inherent (internal) protection. If there is an abnormaltemperature rise in a compressor, the protector will open to shutdown the compressor. The UCB incorporates features tominimize compressor wear and damage. An Anti-Short CycleDelay (ASCD) is utilized to prevent operation of a compressortoo soon after its previous run. Additionally, a minimum run timeis imposed any time a compressor is energized.The ASCD is initiated on unit start-up and on any compressorreset or lock-out.Flash Codes or Error MessagesThe UCB will initiate flash a code on the Simplicity Lite Control(see Table 28) or sent error message to the LCD Simplicity SEControl associated with errors within the system.ResetRemove the call for cooling, by raising thermostat setting higherthan the conditioned space temperature. This resets anypressure or freezestat lockouts.Electric Heating Sequence Of OperationsThe following sequence describes the operation of the electricheat section.Single-stage heating (7, 10, & 15 kW 460V heaters. All otherheaters MUST use a two-stage thermostat):a. Upon a call for heat by the thermostat, the heatersequencer (1S) will be energized. After completing thespecified fan on delay for heating, the UCB will energizethe blower motor.b. The thermostat will cycle the electric heat to satisfy theheating requirements of the conditioned space.Two-stage heating (applies only to 20 and 30 kW heater 460Vheaters.):a. Upon a call for first-stage heat by the thermostat, theheater sequencer (1S) and contactor (2M) (20, 30 kW460 volt) will be energized. After completing the specifiedfan on delay for heating, the UCB will energize theblower motor.If the second stage of heat is required, heater sequencer(2S) or contactor (3M) (20, 30 kW 460 volt) will beenergized. After completing the specified fan on delay forheating, the UCB will energize the blower motor.b. The thermostat will cycle the electric heat to satisfy theheating requirements of the conditioned space.Safety ControlsThe control circuit includes the following safety controls:1. Temperature Limit Switch (TLS) - This control is locatedinside the heater compartment and is set to open at thetemperature indicated in the Limit Control Setting Table 23.It resets automatically. The limit switch operates when ahigh temperature condition, caused by inadequate supplyair flow occurs, thus shutting down the heater andenergizing the blower.