R
Features and Benefits
ZN510 & ZN524 Controls
More ZN524 Controller Functions: When the building owners choice is Trane Tracer controls, the ZN524 con- troller is required when any of the fol- lowing applications are selected on a single and dual circuited equipment.
•Waterside Economizer
•Hot Gas Reheat (Dehumidification)
•Boilerless Control for Electric Heat
•Water Isolation Valve Control (for Variable Speed Pumping)
Entering Water Temperature Sampling
The ZN524 controller will sample the entering water temperature to deter- mine proper control action for units equipped with boilerless electric heat or waterside economizer.
Waterside Economizer
Entering water temperature (EWT) sam- pling will automatically occur at power up when the unit is equipped with a waterside economizer (WSE). The EWT is used to determine if economizing is feasible. When the conditions are met, the isolation valve(s) are driven open for three minutes and the EWT reading is taken. The determination as to whether or not the economizer can be enabled will be made and the controller will take appropriate action. The isola- tion valve will remain open regardless if the WSE or the DX cooling is enabled.
The unit’s waterside economizer will contain a
Low leaving air protection will be fur- nished to protect the unit against deliv- ering air that is cold enough to sweat discharge air grilles. Coil icing protec- tion will also be provided.
Waterside economizer cooling will be active during occupied, unoccupied and standby cooling modes.
Boilerless Control Electric Heat and Supplemental Electric Heat: The ZN524 supports a single stage of boilerless electric heat operation or concurrent heating.
When the unit is configured for boiler- less control, the EWT will be used to determine whether DX heating should be disabled and the electric heater enabled. When these conditions are met, the isolation valve(s) are driven open for three minutes and the enter- ing water temperature reading is taken. The determination as to whether or not to utilize electric heat will be made and the controller will take appropriate action. If boilerless electric heat is enabled, then the isolation valve will be closed, shutting down the water flow to the unit.
When the unit is configured for concur- rent operation of DX heating (compres- sor in heat pump mode) and electric heat, the electric heat will act as a sec- ond stage of heat for single compressor units, and a third stage of heat for dual compressor units. Note: With concur- rent (or supplemental) electric heat, the electric heater is field provided.
Water Isolation Valves
Variable speed pumping systems are supported by the ZN524 controller when water isolation valves are pres- ent. Up to two isolation valves are sup- ported by the controller (one for each compressor circuit).
The valves are normally closed unless DX heating, DX cooling, waterside economizer or dehumidification is requested. When the isolation valves
are driven open for operation, the out- puts will be driven for 20 seconds to ensure adequate water flow before the compressor outputs are energized. Once an isolation valve has been opened, it will remain open for a 10 minute minimum to reduce excessive cycling of the valve.
Dehumidification Dehumidification for the single and dual circuited
Dehumidification can only occur when the controller is in the cooling mode. A humidity transmitter is used to meas- ure the zone’s relative humidity (RH), then compares the zone relative humid- ity to the relative humidity enable/dis- able setpoint parameters. The default values for dehumidification enable is 60% RH with the disable point at 52% RH. These values are configurable.
23 |
