AERCO RECON 1000 - Manual (Page 116)

RECON Water Heaters Installation, Operation & Maintenance Manual
CHAPTER 8 – WATER HEATER MANAGEMENT
Page 116 of 178 AERCO International, Inc.  100 Oritani Dr.  Blauvelt, NY 10913 OMM-0103_0A
PRI: 10/28/2014 Phone: 800-526-0288 GF-147
8.2 WHM PRINCIPLES OF OPERATION
The WHM system communicates with the plant water heaters via a RS485 network utilizing
Modbus RTU protocol (8 bit, 9600 baud, no parity). All Modbus networks are implemented using
a Master/Slave scenario where only one device, the Master, can initiate a communication
sequence. All other C-More equipped units on the network are called Slaves. However, since
the WHM software code resides in each C-More that is part of the system, any one of the C-
Mores can be selected to control the system.
The controlling Master monitors the Air/Fuel Valve position (VP) of all enabled units. When this
valve position (% open) exceeds a user-selectable limit (WHM Nxt On VP), the WHM will open
the sequencing valve of another water heater in the system. Conversely, when the valve
positions of all enabled units have dropped below a different user-selectable limit (WHM Nxt Off
VP) threshold, the WHM will close the sequencing valve on a unit. The philosophy behind this
approach is to maintain the fire rates (Air/Fuel Valve % open) at a level that maximizes heater
efficiency.
In addition to collecting Air/Fuel Valve position data, the controlling Master also monitors the
total accumulated operating time for each unit on the system and attempts to balance the
system so that all units operate for approximately the same number of hours.
8.3 NEW AERCO WHM FEATURES
8.3.1 Valve feedback
The Valve Feedback feature is designed to confirm that the Neptronic Valve has successfully executed
either a Valve-Open or Valve-Close command from the C-More.
The Valve Feedback signal from the Neptronic Valve is connected to the C-More via the I/O box. When
the C-More issues either a Valve-Open or Valve-Close command to the valve, the Valve Feedback signal
is monitored to confirm that the Neptronic Valve has successfully opened or closed. If there is a mismatch
between the Valve Feedback signal and the Valve-Open or Valve-Close command for a period of time
exceeding the value entered in “Valve Fdbk timer” a fault is invoked.
This feature can be enabled or disabled in the “Valve Feedback” menu item .
8.3.2 Valve Supervisor
This feature periodically monitors the Neptronic valve status (On or Off) and compares it to the
Valve command. If there is a mismatch, a fault is displayed and the unit will react as follows:
1. If the Valve is Stuck Open, it displays the “Valve Stuck Open” fault message but continue
with the unit operation (do not shut the unit down).
2. If the Valve is Stuck Closed, it shuts down the unit and displays the “Valve Stuck Closed”
fault message.
8.3.3 Valve Control
The Valve Control logic has been redesigned to assure proper valve operation. Critical valve
positioning (On or Off) is assured by the development of two independent valve control
functions, with one function monitoring the results of the other.