Security system with HVAC fault reporting

Claim 1

Apparatus for controlling and monitoring temperature in a space over time so as to determine therefrom indications of whether faults in an HVAC system may have occurred and report those faults, wherein the HVAC conditions in the space are affected by the HVAC system, comprising: an alarm system for receiving an indication of HVAC fault conditions related to the space and reporting said HVAC fault conditions to a monitoring station through a communications medium; a thermostat in communicating connection to said alarm system, said thermostat for controlling the temperature in the space; error detector connected to said alarm system and said thermostat for detecting a presumed HVAC fault condition in the HVAC system by monitoring temperature from said thermostat, said error detector connected to trigger said alarm system reporting to said monitoring station said HVAC fault condition upon its detection wherein said error detector maintains an accumulated error value over time, said accumulated error value being equal to a past accumulated error value plus a current error value representative of a difference between a control limit set by the alarm system and an actual space temperature measured by the thermostat, said error detector indicating the HVAC fault condition to said alarm system when said accumulated error value attains a first predetermined relationship with an error value suggestive of a fault condition within said predetermined time.