H - 5
ELECTRICAL SySTEMS
H - 6
H
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.
Display Panel
The Display Panel is located in the curbside rear roof locker.
Service
The “Select” button allows the service type to be set to either 30 Amps or
20 Amps, to match the incoming service. When power is first applied, the
system will always be in the 30 amp mode. The 30A LED will be ON when
the system is in the 30 amp mode. Momentarily pressing the button again
will switch the system to the 20 amp mode. Momentarily pressing the button
again will switch the system back to the 30 amp mode.
Status
GEN
Service
30A
20A
SELECT
W/H
A/C
MICRO
Power Control System
AC Amps
Precision Circuits Inc