This control system coupled with a multi-stage thermostat will better dehumidify room air by automatically running the heat pump’s fan at lower speed on the first stage of cooling thereby implementing low sensible heat ratio cooling. On the need for higher cooling performance the system will activate the second stage of cooling and automatically switch the fan to the higher fan speed setting. This system may be further enhanced with a humidistat. Units not having automatic low sensible heat ratio cooling will not be accepted; as an alternate a hot gas reheat coil may be provided with control system for automatic activation.
Control shall have all of the above mentioned features of the CXM control system along with the following expanded features:
a.Removable thermostat connector.
b.Night setback control.
c.Random start on return from night setback.
d.Minimized reversing valve operation (Unit control logic shall only switch the reversing valve when cooling is demanded for the first time. The reversing valve shall be held in this position until the first call for heating, ensuring quiet operation and increased valve life.).
e.Override temperature control with 2-hour timer for room occupant to override setback temperature at the thermostat.
f.Dry contact night setback output for digital night setback thermostats.
g.Ability to work with heat pump or heat/cool (Y, W) type thermostats.
h.Ability to work with heat pump thermostats using O or B reversing valve control.
i.Emergency shutdown contacts.
j.Boilerless system heat control at low loop water temperature.
k.Ability to allow up to 3 units to be controlled by one thermostat.
l.Relay to operate an external damper.
m.Ability to automatically change fan speed from multistage thermostat.
n.Relay to start system pump.
o.75 VA control transformer. Control transformer shall have load side short circuit and overload protection via a built in circuit breaker.
Remote Service Sentinel (CXM/DXM):
Solid state control system shall communicate with thermostat to display (at the thermostat) the unit status, fault status, and specific fault condition, as well as retrieve previously stored fault that caused unit shutdown. The Remote Service Sentinel allows building maintenance personnel or service personnel to diagnose unit from the wall thermostat. The control board shall provide a signal to the thermostat fault light, indicating a lockout. Upon cycling the G (fan) input 3 times within a 60 second time period, the fault light shall display the specific code as indicated by a sequence of flashes. A detailed flashing code shall be provided at the thermostat LED to display unit status and specific fault status such as over/under voltage fault, high pressure fault, low pressure fault, low water temperature fault, condensate overflow fault, etc. Units that do not provide this remote service sentinel shall not be acceptable.