Energy Management with Three Hour Averaging
The current entering the main circuit breaker is routed through a sensor. This
sensor measures the current flowing through the main breaker, which is the
total amount being drawn by all the 110 volt circuits in the RV. When this cur-
rent exceeds 30 Amps, the EMS will turn off the controlled loads in an effort
to bring the total current to the limit of the incoming service.
The ENERGY MANAGEMENT SYSTEM limits the average current entering the
Main service breaker over a three hour period to 80% of the 30 Amp service
rating. Therefore, if the average current entering the main service breaker over
a three hour period exceeds 80% of 30 Amps (24 Amps) the 30A Smart EMS
will automatically change the service limit to 80%. Correspondingly, the 30A
Smart EMS will restore the service limit to the full 30 Amp value when the
average current drops below 80% of the 30 Amp rating. When the lowered
service limits are enabled, the decimal point in the lower right-hand corner of
the Load Meter on the Display module will be lit.
In addition the ENERGY MANAGEMENT SYSTEM feature is used when the
generator is the power source to prevent the generator’s circuit breaker from
tripping due to an overload. The Control Module is configured to enable the
feature using the configuration dip switches.
Controlled Loads
The system offers control of up to four 110 VAC powered loads. Loads that
are controlled are connected to one of the relay circuits of the EMS. There are
five total control relays in the EMS. Only four of these can be used in a given
application.
Operation
In operation, when the 110 VAC and 12 VDC are initially applied, the system
will energize the relays at one second intervals, closing the normally open
contacts on each of the five relays while monitoring the total current. If the
total should exceed the service limit, the system will turn off the last load that
was turned on. As it does this, it calculates the amount of current that was
removed, which is the value for that load. This value is placed in memory. The
system has “learned” the amount of current that particular appliance draws.
This feature compensates for the difference in current draw over a range of
line voltage and ambient temperature, by relearning the load each time it is
turned off.
The system now waits until the total current is lower than the service limit, by
the amount in memory, before it will turn that load back on. This assures that
there is sufficient current to operate the load.
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