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Innovation - Edge [i] Installation, Operation, Maintenance Manual
CHAPTER 8
– WATER HEATER MANAGEMENT
OMM-0143_A
• GF
-216
•
9/6/2019
Technical Support
•
(800) 526-0288
•
Mon-Fri, 8 am - 5 pm EST Page 112 of 170
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
“Manager” / “Client” scenario where only one device, the Manager, can initiate a
communication sequence. All other
Edge
Controller equipped units on the network are called
Clients. However, since the WHM software code resides in each
Edge
Controller that is part of
the system, any one of the
Edge
Controllers can be selected to control the system.
The WHM Manager monitors the Air/Fuel Valve position (VP) of all enabled units. When this
valve position (% open) exceeds a user-selectable limit (
Next On Valve Pos
), 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 (
Next Off
Valve Pos
) threshold, the WHM Manager 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 Manager 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
The following sections describe new Water heater Management 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
Edge
Controller.
The Valve Feedback signal from the Neptronic Valve is connected to the
Edge
Controller via
the I/O box. When the
Edge
Controller 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.