Operating Instructions
Introduction and
Overview of Demand
Control
Congratulations on your decision to purchase the
Energy Sentry Model 9212
Series 3
Electric Demand
Controller. As the owner of an all-electric home metered
under the Demand Billing rate, you are now one of a
growing number of consumers who can lower their
monthly electric bills by reducing energy demand peaks.
The Energy Sentry 9212 Demand Controller enables
you to reduce these peaks while maintaining efficient
use of energy. Your decision to purchase a 9212 repre-
sents a sound and intelligent investment which will
repay you for years to come in reduced electric bills,
added convenience and peace of mind. The 9212 is
without question the finest, most versatile electric
demand controller on the market today
.
The Demand Billing Rate
Not all electricity costs the same. The reason for this
is the billing rates which your utility makes available to
you. The most common are the Energy and Block Rates.
Under the Energy Rate, you are billed for total energy
used per month (total Kwh use) regardless of how you
use this energy. Owner A in Figure 1 illustrates a typical
daily energy use pattern. Notice the demand peaks in
the morning and evening. Under the Energy Rate, these
peaks do not affect Owner A’s bill since he pays for the
total Kwh use only.
Utility companies are concerned about these demand
peaks since they increase the costs of supplying elec-
tricity to their customers. As a result, some utilities offer
a Demand Billing Rate which is a preferred rate to reward
customers who control their peak usage of electricity.
Billing under the demand rate works like this: Suppose
you are heating or cooling your home, washing dishes,
drying clothes and cooking the family dinner all at the
same time. Chances are your home is at peak energy
usage or drawing electricity from the electric company
at a maximum rate. This peak energy usage is illustrated
by Owner A of Figure 1. Under the Demand Rate you
pay for both total energy use (in Kwh like the Energy
Rate) and for your highest average peak energy usage
during the billing period (highest average KW demand).
When compared to the Energy Rate, the Demand Rate
offers a much lower charge for total Kwh use. But, since
there is also a demand charge for the highest average
peak energy usage during the billing period, the savings
could be offset if this demand peak is high.
Now refer to Owner B in Figure 1. In this case, Owner B
is billed under the Demand Rate but has controlled his
peak demand and has correspondingly reduced his
demand charge. The result will be a lower electric bill for
using the same amount of electricity as Owner A. The
key to his savings is in controlling his peak demand and
leveling out his energy usage.
2
Figure 1. The graph shows identical energy consumption over a one day period, but at two
different peak demand levels.
19
15
10
5
12am
1
2
3
4
5
6
7
8
9
10
11 12pm
1
2
3
4
5
6
7
8
9
10
11
12
kW
DE
MA
ND
TIME
OWNER A
ENERGY USE-UNCONTROLLED
OWNER B
ENERGY USE-CONTROLLED
DEMAND RATE