Electrical Systems - House
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DIPLOMAT 8•219
energizing all of the controlled loads. The control Module sends a signal to the
display panel causing the load meter to display actual load current, the generator
service indicator to light and all power status indicators to light.
If 120 Volt AC is present at the distribution panel L1 and L2 inputs the sys-
tem will assume that 120 Volt AC, 30 Amp shore power is available and the
energy management feature will be enabled. If only 20 Amp service is avail-
able the user must select the 20 Amp service mode by momentarily press-
ing the 20/30 Amp select switch on the Control Panel. Initially, all relay
contacts are closed and the total current is monitored. If the total current
should exceed the service limit the system will turn off the first load in the
shedding table. As it turns the loads off it calculates the amount of current that
was removed, which is the value for that load. This value is placed in memory.
If the current remains above the service limit the system will turn off the next
load in the shedding table. Again, it calculates the amount of current that was
removed and places this value,which is the value of that load, in memory. The
system continues to turn off loads until the total current falls below the serv-
ice limit or all of the six controlled loads have been shed. Through this
process the system has “learned” the amount of current that each particular
load draws. This feature compensates for the differences in current draw over a
range of line voltage and ambient temperature, by re-learning the load each
time it is turned off or “shed.”
The 50 Amp Smart EMS now waits until the total current is lower than the
service limit and enough current is available (as compared with the amount in
memory for the last load shed) before it will turn that load back on. This
assures that there is sufficient current to operate the load.
NOTE: There is a two minute minimum delay period after a
load is shed before the load will be turned on again to pre-
vent air conditioners from turning on with a head pressure.
Three Hour Averaging:
The RVIA (Recreational Vehicle Industry Association) in conjunction with
the NEC (National Electrical Council) have established rules regarding the
rating of electrical systems and the use of energy management systems.
One of these rules requires that if any energy management system is used,
the average total load current for the system over a three hour period be
limited to 80% of the service rating. For that reason the 50 Amp EMS
calculates the average running current for the system and, if it exceeds
80% of the service rating, the EMS sheds loads to reduce the average
current below that limit.
For example: If a system operating under 120 Volt AC, 30 Amp service has
been running at the 30 Amp limit for three hours, the EMS will change its
shedding threshold to 24 Amps and turn off loads until the 24 Amp limit is
attained. If the user selects the 20 Amp service mode this limit will translate to
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