'heating and cooling apparatus such as a heat pump. A
ENERGY MANAGEMENT CONTROL station reports to the controller an eight bit message
APPARATUS notifying the controller of the temperature at that station and the controller instructs the station to actuate its
BACKGROUND OF THE INVENTION 5 heating and cooling apparatus to achieve a desired tem
1. Field of the Invention perature at that station. The controller instruction may This invention is in the field of energy management take the form of actual heat pump commands or a desystems and more particularly a system for managing a sired station "set point" temperature. In the latter case, large number of separate heating and cooling devices at each station has a microprocessor that measures the separate locations. 10 temperature "float" between controller instructions and
2. Description of the Prior Art if the temperature direction is up and the desired ternEnergy management systems are commonly used in perature is outside a predetermined "dead band" from
those applications where a relatively large number of the actual station temperature, the station microprocesstations at separate locations which have individual sor actuates the heat pump cooling mode until the deenergy requirements are managed by a central control- 15 sired temperature is reached. And if the temperature ler. In such systems each station reports to the control- direction is down and the aforementioned "dead band" ler the current conditions at the station and the control- exists, the heat pump heating mode is actuated until the ler determines the energy requirements for that station desired temperature is reached.
and transmits information to that station to control a Each station can forward other information to the
local energy system at that station to bring the current 20 controller such as whether the zone controlled by the
condition to a desired condition. station is occupied by a person. Thus when each station
For example, where the energy management system controls the temperature of a hotel or motel room, the
is for heating and cooling of each station the controller controller can make desired adjustments to the transmit
can receive the current temperature at each station and ted temperature to the station taking into account room
then transmit signals to control the station heating and 25 occupancy for energy conservation purposes.
cooling system to obtain a desired temperature at that The dock rate of the controller varies in order t0
station. The communication between the controller and accomodate the time r ired by the controlier to per
each station is performed repetitively at frequent inter- form jts functions xhe fastest clock bit rate js limited b
vals to increase control quality. It is often necessary for ^ ^ ifed for ^ ... ... tQ form itg
one controller to communicate with a relatively large 30 "> r
, c . .. ... , ,, , , J ,l temperature conversion and other functions. Each sta
number of stations, in the order of hundreds, and there- * , , ,. „ ., iri ... . . .
r •* • i.- ui J ■ J ♦ • • 4.u \ 4.u e ti. tlon control adjusts itself to a controller clock pulse rate
fore it is highly desired to minimize the length of the . , . it_ J , , „ , .... r- i_ .
?■ . , , .■ period in the order of 0.1 sec and higher. Each station
communication message to each station, the communi- f , , , ,, ...
„„t; „„,,,,„, ,-_„:,„„ „„♦„ „„j tut, „ has a fail safe mode so that when no clock transition is
cation power requirements and the communication , . . , ,
hardware 35 recelve° 'or a period such as ten seconds all counters
and the heat pump command register are reset to zero
SUMMARY OF INVENTION awaiting restart of the clock bits. Thus if the controller
An energy management controller that has a pro- senses an alarm condition it can stop transmitting the
grammable computer processor communicates with a c,ock blts and each statl0n wl11 S°,nto the fal1 safe mode
plurality of remote stations on three line pairs. The first 40 before the heat PumP interlocks trip and have to be
line pair carries serial clock bits; the second line pair manually reset.
carries serial "data out" bits; the third line pair carries Because of the economy in communication message
serial "data in" bits. Each station has a microprocessor length and the use of a station microprocessor a large
or microcontroller that has a counter which counts the number of stations may be controlled from a single
clock bits and each station compiles an address count. 45 controller and the very low line current requirements
The address count is incremented by one after each reduce the wire size of the line pairs and provide large
predetermined number of clock bit transitions, or bit system capacity.
edges, and as will become apparent, the predetermined It is therefore an object of this invention to provide
number of clock transitions corresponds to the number an energy management control system having econo
of "data out" and "data in" bits desired for a communi- 50 mies of communication message length and line power
cation message between the controller and each station. requirements and that has a large system control capac
Each station can be manually set to a particular re- ity.
spective address count for that station. Once the num- Another object is to provide a controller transmitting
ber of clock transitions reaches that address count for a serial clock bits to a plurality of stations each station
particular station, that station is automatically enabled 55 having a microprocessor for digitizing information
to communicate with the controller for an address gathered at the station and for counting clock bits and
count period which is until the next address count incre- each station can be set to enable itself for data communi
ment. After the address count period, that particular cation for a period after a predetermined number of
station data communication with the controller is dis- clock transitions are counted and to synchronize with a
abled and another station is enabled to communicate 60 periodic controller communication,
data with the controller. Each station continually re- A further object is to provide a system of the previ
ceives clock transitions from the controller, however. ous objects wherein each station provides operating
In this manner the stations are sequentially enabled for inputs to energy using equipment such as a heating and
data communication with the controller without the cooling system and has a microprocessor for sensing the
need for address bits from the controller. 65 direction of temperature float at the station between
The interchange of information between the control- communications from the controller to actuate the heat
ler and each station may take many forms. In the dis- mode or cool mode of the system depending on such
closed preferred embodiment each station has its own direction.