Control System Operation; Emc 5000 Modulation Control; Control System Features - A.O. Smith 100 Series Service Handbook

EMC 5000 MODULATION CONTROL

VF Boilers are equipped with the EMC 5000 Modulating Control System. EMC 5000 is an electronic boiler
Control System developed by A. O. Smith. EMC stands for Energy Management Control. The Control System
modulates the Boiler's firing rate between 25% and 100%; a four-to-one turn down rate.
This section of the Service Manual will cover Control System navigation and operation. The Control System
includes three main electronic components: a UIM (User Interface Module), a MCB (Modulation Control
Board), and a PDB (Power Distribution Board).
See MCB - Modulation Control Board on page 19, PDB - Power Distribution Board on page 28 and UIM - User
Interface Module on page 40.

CONTROL SYSTEM FEATURES:

• EMI / RFI filtering - EMI = Electro Magnetic Interference, RFI = Radio Frequency Interference. These
are two forms of electrical line noise that can cause erratic operation in electronic devices. The electrical
noise filtering built into all Control System circuit boards helps eliminate erratic operation caused by
EMI/RFI.
• Help Screens - text based operational information to help the user understand how to change settings
and navigate Control System menus.
• Self Diagnostics - text based diagnostic information (error and fault messages) on board to help
service technicians quickly and accurately identify and correct operational problems.
• Error History - the Control System retains a 9 event history of error messages with a time stamp.
Helps service technicians diagnose load and/or environmental conditions that may be contributing to
operational problems or Control System lock out conditions.
• Short Cycle Protection - if the Boiler logs more than 30 heating cycles in one hour the control enters
a short cycle prevention mode. The Boiler will continue to operate in this mode. The UIM will display
and log a "Short Cycle Cond" error message with the yellow Standby system status LED flashing. The
Control System will add a 180 second delay before activating subsequent heating cycles during this
operating mode.
The short cycle protection mode can be ended (reset) by touching the Select button on the UIM while the
error message is displayed.
• Temperature Probe Filtering - the Control System filters data from the inlet, outlet, and remote Tank/
Loop temperature probes for 4 seconds before activating a heating cycle. This filtering helps prevent
short cycling caused by momentary fluctuations in temperature.
• Pressure/Flow Switch Filtering - the Control System constantly monitors the state of various switches
such as the blower prover, blocked flue and low gas pressure switches. Input data from these switches
is filtered (de-bounced) for 4 to 6 seconds. This desensitizes the input signal and prevents nuisance
error/fault conditions due to momentary fluctuations caused by wind gusts or blower speed changes.
• iCOMM™ Compatible - VF Boilers are compatible with the A. O. Smith iCOMM™ remote monitoring
system. The iCOMM™ system hardware and monitoring service is purchased separately. The
iCOMM™ remote monitoring system allows users to monitor critical operational, diagnostic and energy
usage data from a secure web site.
The iCOMM™ system can automatically notify selected personnel via email and/or cellular phone text
messages if operational problems or user defined Alert Conditions, such as low system water temperature,
occur.
iCOMM™ system is also compatible with BACnet compliant supervisory controls and building management
systems. For more information call 888 928-3702.

CONTROL SYSTEM OPERATION

Servicing should only be performed by a Qualified Service Agent 39