24
MCP15-500.9
d. Save the setting by simultaneously holding Buttons
#1 and #2 until the LED turns OFF. If this is not
performed within 5 minutes, the control will default
to the previously saved settings and return to normal
operating mode.
9. For furnace models with Digit 11=6 or 8, if no errors or
alerts were recorded by the board (these will be on the
3 LED displays as an “A” or “E” followed by a number),
proceed to the next step. If any alerts or errors were logged
by the board, refer to the “Clearing Furnace Control Board
Error Codes” section on the next page to clear the errors.
10. For furnace models with Digit 11=6 or 8, verify the furnace
control board and modulating valve is communicating
properly by adjusting the Fire Rate Input on the control
board from 10.0 to 2.0 with the up and down buttons.
• The high fire manifold pressure may be in the range of
3.3" W.C to 3.5" W.C. for Natural Gas (9.5 to 10.0" W.C.
for Propane) at the 10.0 Fire Rate Input setting.
• The low fire manifold pressure must not go below the
minimum manifold pressure specified on the serial plate
at the 2.0 Fire Rate Input setting. If the manifold pressure
drops below the minimum specified or flame is lost, repeat
the "Check/Adjust Pressure at Combination Gas Valve"
section on the previous page and then repeat the “Low
Fire Setting” sequence described above.
11. Once the setting of the modulating valve has been
completed, replace the valve cover that was removed
earlier.
12. Move the field installed manual shut-off valve to the “OFF”
position, remove the manometer, and replace the 1/8" pipe
plug.
13. After the plug is in place, move the field installed manual
shut-off valve to the “ON” position and recheck the pipe
plug for gas leaks with soap solution.
14. For units with furnace model Digit 11=4, repeat the entire
process for the 2nd furnace.
Place Primary Furnace Control Into “Checkout Test Mode”
(Applies to furnace models with Digit 11=6 or 8)
The primary furnace control board (Figure 25.1) has
functionality to be put it in a manual operation “Checkout Test
Mode” for testing purposes as noted in the previous sections
for checking and setting gas pressure. To enter that mode,
perform the following steps:
1. The Checkout Test mode is only available when the
furnace control board detects an “E09” error condition
(No Firing Rate Input). To accomplish this, temporarily
disconnect wire #804 from the furnace control board and
create a call for heat from the main Carel controller. Be
sure to insulate the end of the signal wire so it cannot
cause a short.
2. Press the MODE button for at least 4 seconds until the
LED display changes to display “Lo9”.
3. Press the DOWN button briefly to change the display to
“tSt”, and then briefly press the MODE button to enter the
Checkout Test mode.
4. When the Checkout Test mode is entered, the control
board will initiate a normal ignition sequence with the Firing
Rate Input set to a simulated 10.0 VDC. The simulated
Firing Rate Input can be set to different 1.0 VDC step
values from 10V to 2V. A 10V signal will give maximum fire
rate while a 2V signal will give the minimum fire rate. Once
burner ignition has been achieved and the control enters
the RUN mode, the normal runtime data parameters,
including the Firing Rate, will be continuously displayed on
the furnace control board LED indicators.
START-UP PROCEDURE - CONTINUED
8. Adjust the Low Fire Setting as follows:
a. For units with furnace model Digit 11=6 or 8, place
the furnace control into the “Checkout Test Mode” as
instructed in the next section and set the Fire Rate
Input to 2.0.
b. Press and hold Button #2 on the modulating valve
until the LED light blinks red, then release.
c. With the valve now in the low fire setting mode,
confirm or adjust the low fire manifold pressure to be
no less than the minimum shown on the furnace serial
plate in the box called “Min. Manifold Pressure”. If the
pressure needs to be adjusted:
Press or hold Button #1 to increase gas flow and
press Button #2 to decrease gas flow. It is best
to push and release button #2 to single step the
valve to the minimum manifold pressure. Pressing
and holding the button is likely to cause the valve
to close too far and lose flame.
Figure 24.1 - Maxitrol EXA Modulating Valve
O
N
1
2
3
1
2
3
4
BUTTON #1
BUTTON #2
CONTROL SIGNAL
WIRING TERMINALS
SUPPLY POWER
WIRING TERMINALS
POSITION FEEDBACK
WIRING TERMINALS
(ONLY ON UNITS
WITH FURNACE MODEL
DIGIT 10=6 OR 8)
DIP SWITCHES
(SEE TABLE
FOR SETTINGS)
LED INDICATOR
Furnace Model
Digit 11
(Capacity Control)
DIP Switch
Settings
4
SW #1
OFF
SW #2
OFF
SW #3
OFF
6 or 8
SW #1
OFF
SW #2
ON
SW #3
OFF
c. Press and hold Button #1 on the modulating valve
until the LED lights solid red, then release.
d. With the valve now in the high fire setting mode,
confirm or adjust the high fire manifold pressure to be
3.5" W.C. for Natural Gas (10.0" W.C. for Propane).
If the pressure needs to be adjusted, press or hold
Button #1 to increase gas flow and press or hold
Button #2 to decrease gas flow.
e. If 3.5" W.C. for Natural Gas (10.0" W.C. for Propane)
cannot be attained, recheck the inlet gas pressure as
described previously. After addressing any issues, if
the pressure still cannot be attained, step the valve
closed using button #2 to the point where manifold
pressure begins to be impacted. If the pressure at
that point is less than 3.3" W.C. for Natural Gas
(9.5 to 10.0" W.C. for Propane), corrective action is
required.
f. Save the setting by simultaneously holding Buttons
#1 and #2 until the LED turns OFF. If this is not
performed within 5 minutes, the control will default
to the previously saved settings and return to normal
operating mode.
