Filter
Top Products
506920−01 09/12
Page 34
Gas Heat Control Mode
NO
NO
YES
YES YES
NONO
YES
YES
NO
NO
YES
YES
NO
YES
NO
Continue at
starting firing rate
T’stat
demand
satisfied
?
Starting firing rate
as determined by
variable capacity
algorithm (35 to
100%)
Differential
less than 2nd stage
differential
?
T’stat
demand
satisfied
?
T’stat
demand
satisfied
?
Firing rate
increased by
5% every 5
minutes up to
100% firing rate
Firing rate
increased by
5% every 5
minutes up to
100% firing rate
T’stat
demand sat−
isfied in less than
5 minutes
?
T’stat
demand sat−
isfied in less than
5 minutes
?
Increase firing rate
to calculated 2nd
stage firing rate
Increase firing rate
to calculated 3rd
stage firing rate
Increase firing
rate to 100%
until thermostat
demand is
satisfied
THERMOSTAT
DEMAND
SYSTEM
IDLE
YES
NO
Differential
less than 3rd stage
differential
?
YES
NO
Differential
less than 4th stage
differential
?
YES
NO
Differential
less than 2nd stage
differential
?
Differential
less than 3rd stage
differential
?
Differential
less than 4th stage
differential
?
Figure 36. Variable Capacity Operation Flow Chart