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III−OPTIONAL ECB26 ELECTRIC HEAT
A−Matchups and Ratings
Tables 2 through 4 show all approved CB26UH and
CBX26UH to ECB26 matchups and electrical ratings.
B−Electric Heat Components
ECB26 parts arrangement is shown in figure 4. All electric heat
sections consist of components mounted to the electric heat
vestibule panel and electric heating elements exposed directly
to the airstream. 208/230V electric heat sections may be
equipped with circuit breakers. The circuit breakers are des-
ignated by CB in the model number.
1−Electric Heat Sequencer Relays 1 and 2
Relays are N.O. sequencer relays with a resistive
element for a coil and a bi-metal disk which actuates
the contacts. The relays are located on the electric heat
vestibule panel and are energized by a 24V heating de-
mand (W1 and W2) via jack/plug 2. When energized, the
internal resistance heats the bi-metal disk causing the con-
tacts to close. When the relay is de-energized, the disk
cools and the contacts open. The relays energize
different stages of heat, as well as the blower. The
blower is always first on and last off.
2−Primary Limits 1, 2, 3 & 4
The primary limits are located on the electric heat vestibule
panel and exposed directly to the airstream through an
opening in the panel. They are SPST N.C. auto −reset lim-
its. The limits are factory set and not adjustable.
208/230 Volt Electric Heat Sections
Each stage of the 208/230 electric heat is protected
by a primary high temperature limit. Each stage uses the
same style of limit. The primary limit is wired in series with
a heat element. When either limit opens, the corre-
sponding heat element is de-energized. All other
heating elements remain energized. The primary high
temperature limit opens at 150
_
F + 5
_
F (65.5
_
C + 2.8
_
C)
on a temperature rise and automatically resets at
110
_
F + 9
_
F (43.3
_
C + 5.0
_
C) on a temperature fall.
3−Circuit Breaker
Line voltage connections are made to circuit breakers in
the electric heat sections with circuit breakers (designated
by CB in the model numbers). Table 1 shows the amp rat-
ing for each circuit breaker used. Single phase electric
heat uses two pole circuit breakers.
TABLE 1
ECB29 CIRCUIT BREAKERS
UNIT
CB1
AMPS
CB2
AMPS
CB3
AMPS
ECB26-5CB-1 (P)
30 AMP
−−−
−−−
ECB26-7CB-1 (P)
45 AMP
−−−
−−−
ECB2610CB-1 (P)
60 AMP
−−−
−−−
ECB26-15CB-1 (P)
60 AMP
30 AMP
−−−
ECB26-20CB-1 (P)
60 AMP
60 AMP
−−−
4−Heating Elements
Heating elements are composed of helix wound bare
nichrome wire exposed directly to the airstream. The ele-
ments are supported by insulators mounted to the wire
frame. For single phase applications, one element is
used per stage. Each stage is energized indepen-
dently by the corresponding relay located on the
electric heat vestibule panel. Once energized, heat
transfer is instantaneous. High temperature protec-
tion is provided by primary high temperature limits.
FIGURE 4
ECB26−7, -7CB, -10, -10CB 208/230
VESTIBULE PARTS ARRANGEMENT
HEATING ELEMENTS
CIRCUIT BREAKER
PRIMARY LIMITS
1, 2, 3 & 4
ELECTRIC HEAT
SEQUENCER
1 & 2