Lennox KHA SERIES User Manual

Page 49
Sequence of Operation −T1EH 7.5, 10, 15, 22.5kW − P Voltage
HEATING ELEMENTS:
1 − Terminal Strip TB2 is energized when the unit discon-
nect closes. TB2 supplies line voltage to electric heat
elements HE1 and TB3. TB3 supplies line voltage to
HE2 through HE6. Elements are protected by fuses F3
and F42.
FIRST STAGE HEAT:
2 − Heating demand initiates at W1 in thermostat.
3 − 24VAC is routed from the indoor thermostat through
N.C. primary limit S15. Electric heat contactor K15 and
heat relay K9 are energized. K9 energizes blower con-
tactor K3 and economizer.
4 − 7.5kW units − N.O. contacts K15−1 close energizing
HE1.
10kW 15kW units − K15−1 and K15−2 close energizing
HE2 and HE3.
22.5kW units − K15−1, K16−1 and K16−2 close energiz-
ing HE4, HE5 and HE6.
END OF FIRST STAGE HEAT:
5 − Heating demand is satisfied. Terminal W1 in the ther-
mostat is de−energized.
6 − Electric heat contactor K15 is de−energized.
7 − 7.5kW units − N.O. contacts K15−1 open de−energizing
HE1.
15kW units − K15−1 and K15−2 open de−energizing HE2
and HE3.
22.5kW units − K15−1, K16−1 and K16−2 open de−ener-
gizing HE4, HE5 and HE6.
Sequence of Operation −T1EH 7.5, 15, 22.5kW − Y, G, J Voltage
HEATING ELEMENTS:
1 − Terminal Strip TB2 is energized when the unit discon-
nect closes. TB2 supplies line voltage to electric heat
elements HE1 and TB3. TB3 supplies line voltage to
HE2 and HE3. Elements are protected by fuses F3 and
or F42.
FIRST STAGE HEAT:
2 − Heating demand initiates at W1 in thermostat.
3 − 24VAC is routed from the indoor thermostat through
N.C. primary limit S15. Electric heat contactor K15 and
heat relay K9 are energized. Heat relay K9 energizes
blower contactor K3 and economizer.
4 − 7.5kW and 15kW units − N.O. contacts K15−1 close en-
ergizing HE1.
22.5kW units − N.O. contacts K15−1 close energizing
HE2 and HE3.
END OF FIRST STAGE HEAT:
5 − Heating demand is satisfied. Terminal W1 in the ther-
mostat is de−energized.
6 − Electric heat contactor K15 is de−energized.
7 − 7.5kW and 15kW units − N.O. contacts K15−1 open de−
energizing HE1.
22.5kW units − N.O. contacts K15−1 open de−energiz-
ing HE2 and HE3.

Lennox KHA SERIES Specifications

General

Brand	Lennox
Model	KHA SERIES
Category	Heat Pump
Language	English