INSTALLATION INSTRUCTIONS
66-1142-1
® U.S. Registered Trademark
Copyright © 2004 Honeywell International Inc.
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MCBA14C
Commercial Boiler Control System
APPLICATION
The MCBA14C Commercial Boiler Control System provides heat
control, flame supervision, circulation pump control, fan control
and boiler control. It has electric ignition. It will also provide boiler
status and error reporting.
FEATURES
• NTC resistors for measuring and guarding temperatures.
• PWM-driven revolution controlled dc-fan for optimal
modulation control.
• 24 Vac gas valve.
• 24 Vac is fused (Fuse F3) with a 4AT fuse.
• PWM-driven circulation pump for optimal energy
consumption.
•DHW-pump.
• Various function-inputs.
• Connections for external comfort control.
• Connections for extra inputs/outputs.
• Easy modification of the parameters on three levels:
— End user.
— Installer/service mechanic.
— Manufacturer (OEM).
SPECIFICATIONS
Electrical Ratings
Line voltage requirement: 120 Vac (+10%/-15%).
Power Consumption: 8 W.
Gas Valve: 1.72A ac.
External load: 0.1A ac.
Fan: <35W dc.
Total 24 Vac: <75 VA.
Fan: <20W dc.
Total 24 Vac: <50 VA.
Electrical Connections:
Line Voltage: 120 Vac, 60 Hz.
Fuse (F1): 5A, fast acting.
Main Voltage Connection: X1, pins 1 and 2.
MCBA Earth Ground Connection: X1, pin 6.
Power Connection, Central Heating (CH) Pump: 120 Vac, 60Hz.;
5A maximum current; X1, pins 3 and 4.
Power Connection, Domestic Hot Water (DHW) pump; 120 Vac,
60 Hz; 1A maximum current; X1, pins 3 and 5.
Heat Request (CH), parallel shift input, X2, pins 8 and 9. Current:
2 mA, dc.
Air Pressure Switch; X2, pins 7 and 9. Requirements:
Current: 2 mA, dc.
Minimal Gas Pressure Switch: X2, pins 6 and 9. Requirements:
Current: 2 mA, dc.
Overheat Thermostat (optional): X2, pins 9 and 10.
Negative Temperature Coefficient (NTC) Inputs: X3, X4, X5.
Flow Temperature (NTC1): X3, pins 1 and 5.
Return Temperature (NTC2): X3, pins 2 and 5.
DHW Temperature (NTC3): X3, pins 3 and 5.
Outside Temperature (NTC4): X3, pins 4 and 5.
Flue Gas Temperature (NTC5): X4, pins 1 and 2.
Outside Temperature (NTC4): X5, pins 3 and 4.
Analog Input: X4, pins 2 and 3.
Used to connect a 0 to 10 volt analog input, a water pressure
sensor, or an extra NTC-6.
Switch Inputs:
DHW-Thermostat: X3, pins 3 and 5.
On/Off Switch: X3, pins 4 and 5.
Flame Sensor:
Flame Current: Minimum 3 microampere dc (typical 2 micro-
ampere).
Isolation Resistance: Minimum 50 megohms.
DC Fan: X2, pins 1, 2, 3, 4.
+ Connection (X2-3): Vopen maximum 45V.
PWM Control Output (X2-1):
Ri: 12 kilohms.
Fmin: 941 Hz.
Fmax: 3.3 kHz.
Tacho Input (X2-4).
Gas Valve Output: X2, pins 11 and 12:
Contact Voltage: 24 Vac, 60 Hz.
Current: 1.7A ac, maximum.
PWM-driven CH Pump (X3, pins 5 and 6):
Output VL: 0.5V maximum.
Output VH: 14V maximum (open).
High Voltage Connection (used for the ignition spark. High voltage
connection must have a good connection with the earth
ground contact of the MCBA.
Voltage: 15 kV.
Spark Gap: 1/8 in. (3 mm); maximum 3/16 in. (5 mm).
Communications (X5, pins 1 and 2):
Environmental Ratings:
Temperature Range:
Operating: 32°F to 150°F (0°C to 60°C).
Storage: -13°F to +167°F (-25°C to +75°C).
Humidity:
At 77°F (25°C): 85% RH.
At 150°F (60°C): 50% RH.
Approvals:
CSA
Component Approval, ANSI Z21.20 Automatic Ignition Systems.
INSTALLATION
When Installing This Product…
1. Read these instructions carefully. Failure to follow them
could damage the product or cause a hazardous condition.
2. Refer to the wiring diagram provided as part of the
appliance or refer to Product Data sheet, form 65-0279.
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