AERCO Boiler Valve Controller (BVC) PRIOR to Serial-12-840-1 - Manual (Page 13)

INSTALLATION
13
For a Benchmark Series Boiler the I/O Box is located on the lower portion of the boiler front
panel as shown in Figure 4. For a KC1000 Series Boiler, the I/O Box is located on the left side
of the boiler as shown in Figure 5.
Internally, each I/O Box (see Figure 6) contains several board-mounted relays and terminal
strips. Refer to the wiring diagram on the cover of the I/O Box when making all wiring
connections.
The basic purpose of the electrical interfacing between the BVC, the MOV, and the Boiler I/O
Box is to insure that the water supply valves are open before the boiler is allowed to fire. The
electrical interface must facilitate the sequence of events described as follows:
1. When the boiler is about to be fired, an electrical signal is sent from the Boiler I/O Box to the
BVC unit requesting that the boiler’s MOV be opened.
2. The BVC then attempts to open the MOV for that particular boiler subject to whatever time
delay is set in the C-More Control Unit (see AERCO Manual GF -112). This “Start on Delay”
feature is intended to prevent “over temperature” conditions. The customer should always
check the MOV manufacturer’s specifications as to the MOV’s “Time-to-Open” value. This
value should always be verified by customer testing. Once the “Time-to-Open” is
established, the C-More should be set to have a “Start on Delay” value that exceeds the
MOV “Time-to-Open” value by typically 5 seconds or so. Note that the C-More “Start on
Delay may be set anywhere between 0 and 120 seconds.
3. In addition, the MOV must be opened within the set AUX Interlock boiler firing delay time
interval. This delay may be set from 0 to 120 seconds. If the MOV fails to open within the
prescribed AUX Interlock time delay interval, a “Proof of Open” confirmation will not be sent
to the Boiler I/O Box. It should then be determined why the MOV did not open as expected.
4. If the MOV is opened successfully within the expected 120 second time interval, The BVC
sends a “Proof of Open” confirmation to the boiler, allowing it to fire. This is accomplished by
closing the connection between the “close” and “common” terminals on the MOV. The Boiler
I/O Box now knows it is okay to fire the boiler, since it has been provided proof that the
boiler’s supply flow valve is open.