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A-Matchups and Ratings
Tables 4 thru 11 show all possible CHA16 to ECH16
matchups and electrical ratings.
B-Electric Heat Components
ECH16 parts arrangement is shown in figures 32 and 33.
All ECH16 units consist of electric heating elements ex
posed directly to the airstream. Multiplestage elements
are sequenced on and off by time delays in response to
thermostat demand.
1-Contactor K15
Contactor K15 is a threepole doublebreak contactor
located in the control box. All ECH16 electric heat sec
tions are equipped with K15. K15 is equipped with a
24VAC coil which is energized when pilot relay K9
closes. When K15 is energized, the heating elements
(first stage heating elements if equipped with multi
stage heater) are energized.
2-Contactor K16
Contactor K16 is also a threepole doublebreak con
tactor located in the control box. All multiple stage
ECH16 electric heat sections are equipped with K16.
K16 is equipped with a 24VAC coil which is energized
after time delay DL2 closes. When K16 is energized,
the second stage heating elements are energized.
3-Contactor K17
Contactor K17 is also a threepole doublebreak con
tactor located in the control box. All three stage
ECH16 electric heat sections are equipped with K17.
K17 has a 24VAC coil which is energized after time de
lays DL2 and DL4 close in sequence. When K17 is en
ergized, the thirdstage heating elements are ener
gized.
4-Contactor K18
Contactor K18 is also a threepole doublebreak contac
tor located in the control box. ECH16185-60 208/230V
electric heat unit (which is equipped with four stages of
heat) and 208/230V ECH16275/30075 (which is
equipped with two stages of heat) are equipped with K18.
K18 has a 24VAC coil which is energized after time de
lays DL2, DL4 and DL5 close in sequence. When K18 is
energized, fourthstage heating elements are energized
(ECH16185-60) or heating element 4 is energized
(ECH16275/30075).
5-Contactor K75
Contactor K75 is also a threepole doublebreak contac
tor located in the control box. Only 208/230V
ECH16275/30075 (which is equipped with two stages
of heat is equipped with K18. K18 has a 24VAC coil
which is energized after time delays DL2, DL4, DL5
and DL18 close in sequence. When K18 is energized,
second stage heating elements are energized.
6-Relay K9
Relay K9 is a threepole doublethrow pilot relay in
tended to electrically isolate the CHA16 and ECH16
24V circuits. The coil of relay K9 is connected to first
stage heating demand from the CHA16. When K9 is
energized, three sets of contacts switch. When K91
switches, the indoor blower is energized. When K92
closes, second stage electric heat is enabled (but not
energized until second stage demand is received from
the thermostat). When K93 closes, contactor K15 is
energized.
7-Relay K19
Relay K19 is a singlepole doublethrow pilot relay also
intended to electrically isolate the CHA16 24VAC cir
cuits from the ECH16 24V circuits. The coil of relay K19
is connected to secondstage heating demand from the
CHA16. When K19 is energized, a single set of con
tacts switch. When K191 closes, secondstage elec
tric heat is energized.
8-Time Delay DL2
Time delay DL2 is factory installed in all multiplestage
electric heat units. DL2 allows staging by providing a
timed interval between the first and second heating ele
ments. The delay control is a singlepole singlethrow
24VAC relay with normally open contacts. When the
relay coil is energized, the contacts are delayed 30 sec
onds (+
20%) before closing. When the relay coil is de
energized, the contacts are delayed 1 second (+20%)
before opening.
DL2 is energized with first stage thermostat demand in
50kW 208/230V electric heat units. In all other multiple
stage electric heat units, DL2 is energized only after re
ceiving a second stage thermostat demand.
9-Time Delay DL4
Time delay DL4 is identical to DL2. It is factory
installed in all multiplestage electric heat units with at
least three stages of electric heat. DL4 allows staging
by providing a timed interval between the second and
third heating elements. The delay is identical to DL2.
DL4 is energized with second stage thermostat demand
in 50kW 208/230V electric heat units. In all other multiple
stage electric heat units, DL4 is energized only after time
delay DL2 closes.
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