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III-OPTIONAL ECH16 ELECTRIC HEAT
A-Matchups and Ratings
Tables 4 through 15 show all possible CHP16/20 to ECH16
matchups. Also shown in the tables are ECH16 electrical
ratings.
B-Electric Heat Components
ECH16 parts arrangement is shown in figure 18. All ECH16
units consist of electric heating elements exposed directly to
the airstream. Elements are sequenced on and off by heat
relays or contactors in response to thermostat demand.
1-Relay K15
Relay K15 is a singleĆpole singleĆthrow relay located on
the control panel of all commercial singleĆphase ECH16
units (15, 20 and 25 kW). K15 is equipped with a 24VAC
coil which is energized when pilot relay K43 closes.
When K15 is energized, the first stage heating elements
are energized. (HE1 in ECH16Ć15; HE1 and HE2 in
ECH16Ć20 and ECH16Ć25).
2-Contactor K15
Contactor K15 is a threeĆpole doubleĆbreak contactor
used in all commercial threeĆphase ECH16 units. K15 is
equipped with a 24VAC coil which is energized when piĆ
lot relay K43 closes. When K15 is energized, the first
stage heating elements are energized.
Contactor K15 used in ECH16Ć15Ć1Y and ECH16Ć25Ć1G
units is equipped with a set of auxiliary singleĆpole
doubleĆthrow contacts. The auxiliary contacts are not
used in this application.
3-Relay K16
Relay K16 is a singleĆpole singleĆthrow relay located on
the control panel of all commercial singleĆphase ECH16
units (15, 20 and 25 kW). K16 is equipped with a 24VAC
coil which is energized when pilot relay K43 closes.
When K16 is energized, the second stage heating eleĆ
ments are energized (HE2 in ECH16Ć15; HE3 and HE4
in ECH16Ć20 and ECH16Ć25).
4-Contactor K16
Contactor K16 is a threeĆpole doubleĆbreak contactor
used in commercial 20 and 25 kW threeĆphase ECH16
units. K16 is equipped with a 24VAC coil which is enerĆ
gized when time delay DL2 closes. When K16 is enerĆ
gized, the second stage heating elements are enerĆ
gized.
5-Relay K17
Relay K17 is a singleĆpole singleĆthrow relay located on
the control panel of all commercial singleĆphase ECH16
units (15, 20 and 25 kW). K17 is equipped with a 24VAC
coil which is energized when pilot relay K43 closes.
When K17 is energized, the third stage heating eleĆ
ments are energized (HE3 in ECH16Ć15; HE5 and HE6
in ECH16Ć20 and ECH16Ć25).
6-Resistor R6
A resistor is used in parallel with the coil of heat relay K32
in ECH16RĆ5 electric heaters. The resistor is rated 150
ohm +
10%, 10 watt.
The resistor reduces the effects of inrush current on the
thermostat. Heat relay K32 draws approximately 0.7
amps immediately after being energized. As the relay
coil heats, the current subsides. Within a few seconds
after being energized, the current is reduced to minimum
level (approximately 0.18 amps).
Contactor K16 used in ECH16Ć25Ć1Y unit is equipped
with a set of auxiliary singleĆpole doubleĆthrow contacts.
The auxiliary contacts are not used in this application.
7-Relay K43
Relay K43 is a doubleĆpole doubleĆthrow pilot relay used
in all commercial ECH16 units. The relay uses a 24VAC
coil which is energized by thermostat demand. The coil
is wired in series with the primary high temperature limit
S15. If an overtemperature condition becomes present,
pilot relay K43 is immediately deĆenergized and electric
heat operation immediately stops.
When relay K43 is energized, normally open contacts
K43Ć1 and K43Ć2 close. When K43Ć1 closes, contactor
K15 (and time delay DL2 if so equipped) are energized
to begin electric heat operation. When K43Ć2 closes, the
indoor blower begins operating on heating speed.
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