Installations Instructions

40
Call for 2nd-Stage Heat - Thermostat contacts close R to W1
and W2.
Af t er a successf ul Light Of f Sequence and expi r at ion of
t he Igni t ion St abil izat i on Per iod:
• The furnace control board adjusts to the low firing
rate of 35%.
• After 2 minutes, the furnace control board
increases the firing rate to 80%.
• Thereafter, the IFC will increase the firing rate
by 10%, at a rate of 1% per second, every 10
minutes for the remainder of the call for heat.
• The circulator fan is adjusted to the appropriate
CFM, corresponding to the current firing rate.
Call for 2nd-Stage Heat with 1st-Stage call for heat call in
progress, with conventional 2-Stage Thermostat.
• The furnace control board increases the firing rate
to 100% at a rate of 1% per second for the
remainder of the W2 call.
• The circulator is adjusted to the appropriate CFM,
corresponding to the current firing rate.
MIN.
50%
78%
(80%)
100%
IGNITION
2 MINS.
CALL FOR
2ND STAGE HEAT
UNIT CALL FOR HEAT ENDS
Figure 48
Call for 2nd-Stage Heat satisfied; Call for 1st-Stage Heat
remains.
• The furnace control board remains at the current
firing rate until the 1st-Stage call for heat is
satisfied.
HEATING OPERATION WITH CTK01 THERMOSTAT (COMMU-
NICATING)
• When the Thermostat Heat Setup DIP switch is
set to 2-Stage heat, the furnace control board
operation will be compatible with a CTK01
communicating thermostat.
• When a call for heat is sent, the furnace will go
through the Light Off Sequence, at which time
the Heat Current Demand Status will still show
0%. After the successful Light Off Sequence and
expiration of the Ignition Stabilization Period:
• The furnace control board adjusts to the low firing
rate.
• After 2 minutes, the furnace control board accepts
the specific heat requested demand.
• If the differential is equal to or less than 2 degrees,
the furnace control board will follow the
conventional 2-Stage algorithm, equivalent to a
W1 request and be reflected in the heat current
demand status %.
• If the heat differential is greater than 2 degrees,
the furnace control board will follow the
conventional 2-Stage algorithm, equivalent to a
W2 request and be reflected in the heat current
demand status %.
• The circulator will operate per the heat airflow
profile.
HEATING OPERATION WITH CTK02**, CTK03** &
CTK04** THERMOSTAT (MODULATING COMMUNICATING)
• When the Thermostat Heat Setup DIP switch is
set to 1-Stage heat, the furnace control board
operation will be compatible with a modulating
communicating thermostat (CTK02**, CTK03 or
CTK04).
• When a call for heat is sent, the furnace will go
through the Light Off Sequence, at which time
the Heat Current Demand Status will still show
0%. After the successful Light Off Sequence and
expiration of the Ignition Stabilization Period:
• The furnace control board adjusts to the low firing
rate.
• After 2 minutes, the furnace control board accepts
the specific Heat Requested Demand.
• If the differential is 2 degrees or less, the heat
current demand status will show 50%.
• If the specific heat requested demand is above 2
degrees, the heat current demand status will
track the specific heat requested demand.
• The circulator fan will operate per the heat airflow
profile.
CONDENSATE DRAIN TRAP PRIMING
The drain trap
MUST be primed prior to furnace startup. To
prime, fill the drain trap with water. This ensures proper
furnace drainage upon startup and eliminates the possibility
of flue gases escaping through the drain system. Please see
requirements in Condensat e Dr ai n Lines & Dr ai n Tr ap sec-
tion.
FURNACE OPERATION
Purge gas lines of air prior to startup. Be sure not to purge
lines into an enclosed burner compartment. Follow NFPA 54,
National Fuel gas Code 8.3 for proper purging methods. In
Canada, follow approved purging methods in B149.1-15.
Check for leaks using an approved chloride-free soap and wa-
ter solution, an electronic combustible gas detector, or other