44
SYSTEM OPERATION
O
PERATION
U
SING
A
S
INGLE
S
TAGE
H
EATING
T
HERMOSTAT
Using a single stage thermostat, the options for high fire
delay are: 10 minutes; 20 minutes; or auto
•
The automatic second stage logic is a method of en-
ergizing the second stage valve based on the recent
average of the heating duty cycle. During a typical
heating day there will be at least one call for heat
within a 3 hour period, and usually much more often.
During this mode the low to high stage delay is deter-
mined by using the average calculated duty cycle from
the table below. Once the specified delay time has
expired the second stage valve will be energized
• On the heating cycle following a period of 3 hours (or
greater) in which there is no call for heat, the second
stage valve will energize based on the average calcu-
lated duty cycle prior to the three hour no call for heat.
If the average calculated duty cycle is less than 50%,
then the low to high stage delay will be determined
from the table below. In this case, an assumption is
made that the outside temperature is fairly mild and
the long time between calls for heat was due to a low
thermal loss in the building. Going quickly to second
stage heat is not required in this instance.
•
If the average calculated duty cycle is 50% or greater,
then the heating cycle will be treated as if high stage
is needed and the transition from low to high stage
delay will happen quickly. In this case an assumption
is made that the outside temperature is cold and that
the thermostat is likely coming out of setback. Since
assumptions are being made during this heating cycle
the duty cycle for this heat cycle will not be used in
the average calculated duty cycle formula for future
heating cycles.
•
The duty cycle is calculated every cycle and used
during the next cycle. The equation for the duty cycle
is calculated as follows: Duty Cycle = (Time the ap-
propriate stage is ON) / (Time of the complete cycle).
•
The average calculated duty cycle is determined by
averaging the previous average calculated duty cycle
with the duty cycle from the previous cycle. This places
a large emphasis on the previous cycle but allows a
large variation in any one duty cycle to be averaged
out after just a few complete heating cycles.
•
If there is no load activity for 24 hours or more then
set the Duty Cycle = 100%
•
The initial default average calculated duty cycle = 50%
Duty Cycle %
Valve Output
Demand
0-38
1
st
Stage, 12 minute 2
nd
Stage
Light
38-50
1
st
Stage, 10 minute 2
nd
Stage
Light to Average
50-62
1
st
Stage, 7 minute 2
nd
Stage
Average
62-75
1
st
Stage, 5 minute 2
nd
Stage
Average to Heavy
75-88
1
st
Stage, 3 minute 2
nd
Stage
Heavy
88-100
1
st
Stage, 1 minute 2
nd
Stage
Heavy
1
2
3
4
90
OFF
OFF
120
OFF
ON
150
ON*
OFF*
180
ON
ON
1
2
3
4
90
OFF
OFF
120
OFF
ON
150
ON*
OFF*
180
ON
ON
*Factory Setting
Blower Off Delay Dip Switches PCBBF139
Heating Fan Off
Delay
S3
Dip Switch
Purpose
Switch Group
Function
Blower Off Delay Dip Switches PCBBF137
Purpose
Switch Group
Function
Dip Switch
Heating Fan Off
Delay
S1
Heat Mode Blower Off Delay Timing
C
OOLING
M
ODE
:
L
OW
S
TAGE
C
OOLING
M
ODE
S
EQUENCE
:
•
On a call for lo cool, the Ylo and G thermostat con-
tacts close signaling the control module.
•
The LED will display a “GREEN”1 flash
•
The compressor and condenser fan are energized. The
compressor is connected to the Ylo terminal of the
control module.
•
The circulator fan is energized at lo cool speed after a
cool on delay. The electronic air cleaner will also be
energized.
•
After the thermostat is satisfied, the compressor is
de-energized
•
Following the 60 second Cool Mode Fan Off Delay
period, the cool circulator and air cleaner relay are
de-energized.
•
When the call for “Ylo”and “G”are presented simulta-
neously, the control will honor the Cool On delay and
keep the circulator de-energized. After the Cool On
delay, the circulator fan and air cleaner relays are
energized. The circulator fan is energized at the cool
speed. If a call for “G”is present prior to a call for “Ylo”,
the circulator will remain at the FAN circulator speed
during the Cool On delay.
S
INGLE
COOLING
STAGE
THERMOSTAT
OR
2
ND
STAGE
COOLING
M
ODE
SEQUENCE
.
•
On a call for cool, the Y and G thermostat contacts
close signaling the control module.
•
The LED will display a “GREEN”2 flash
