Inputs To Mcb; Dipswitches - A.O. Smith VB/VW 1500, 2000 Instruction Manual

INPUTS TO MCB

TEMPERATURE SENSORS:
Temperature probes (MCB - outlet and either inlet or tank are
required): The MCB accepts analog temperature inputs from
up to three sensors (inlet, outlet, and tank).
Manual Reset High Limit (MCB - required): The MRHL or manual
reset high limit is a hi-limit switch located inside the outlet probe.
It is a normally closed switch that opens if the probe is exposed to
a temperature higher than the trip point. Once tripped, the control
system needs to be manually reset.
Thermostat input or Enable/Disable (MCB - optional): This input is
set up to work with an externally connected thermostat that provides
a contact closure. If this input is closed and everything else is in
the proper state, a "call for heat" condition will be initiated. These
leads should be shorted together when a thermostat is not being
used. If it is desired that the thermostat control the temperature of
the boiler, the operating setpoint of the system should be set higher
than the temperature that the thermostat is controlling. This will allow
the thermostat to control the boiler. When the thermostat closes, a
call for heat will be generated until the thermostat determines that the
required temperature has been reached.
AIR PRESSURE SENSORS (OPEN CONDITION INDICATES FAULT):
Blocked Flue (MCB - required): Normally closed switch that opens
if the flue becomes blocked during operation.
Blower Prover (MCB - required): Normally open switch that closes
when the air pressure produced by the blower is above the set point.
GAS PRESSURE SENSORS (OPEN CONDITION INDICATES FAULT):
Low Gas (MCB - required): Normally open switch that closes when the
gas pressure rises above the trip level. This input is enabled/disabled
by a dip switch on the MCB
Hi Gas (MCB - optional): Normally closed switch that opens if the gas
pressure exceeds a set value. This input is enabled/disabled by a dip
switch on the MCB.
WATER LEVEL SENSOR (OPEN CONDITION INDICATES FAULT):
Low Water Cut Off (MCB - optional): Normally closed switch that
opens when water drops below a preset level. This input is enabled/
disabled by a dip switch on the MCB.
WATER FLOW SENSOR:
Flow (MCB - required): Normally open switch that closes when
flow meets a set value.
MCB - Ten Position Dipswitch SW1:
Dipswitch configurations are READ ONLY ON POWER UP. These switches are only to be set at the factory or by authorized trained
personnel! Once set the boiler will operate according to the chosen options. If a switch is changed, power must be cycled before the
change will take effect. The status of all dipswitches can be observed on the system status screen on the UIM.
Dipswitch Function
SW1 P1: Selection of the type of boiler application:
SW1 P2: Trials for ignition:
SW1 P3: IRI Gas Valve Not Available:
SW1 P4: Controlling Probe:
SW1 P5: Powered Venter:
SW1 P6: Low Water Cut Off: (LWCO)
SW1 P7: Low Gas Pressure
SW1 P8: Modulation:
SW1 P9:
SW1 P10:
NOTE: If the unit powers up with the number of stages selected by dip switches exceeding the number of FCBs, the MCB will detect this
condition and go into a hard lockout. After changing the dipswitches, the power must be cycled off and back on to accept any changes.
FLAME SENSOR:
Flame (MCB - required): Returns a signal to the microprocessor
when flame is detected on the burner. If the flame rod is missing
or shorted, the flame will not be detected.
OUTPUTS FROM MCB
RELAY CONTACT OUTPUT:
Alarm (MCB - 24VAC - optional): Provides electrical power to
operate an external alarm. This can be an audio device (i.e.,
Sonalert), a visual device (lamp), or any other device that will
operate with the voltage and current level provided.
Pump (MCB - 120VAC - required on systems that do not have
an external pump): Provides electrical power to directly operate a
pump or the coil of an externally connected contactor.
Blower (MCB - 120VAC - required): Variable speed blowers utilize
the high blower output only.
Igniter (MCB - 120VAC - required): Provides power to operate
the HSI igniters.
Gas Valve (MCB - 24VAC - required): Provides power to activate
the gas valve. The gas valve cannot be activated when the MRHL
contacts are open.
Low Water Cut Off (MCB - 24VAC - optional): Directly connected to the
24VAC line to provide power to operate an external LWCO device.
MCB AND PDB INDICATOR LAMPS AND FUSES
A green LED is mounted on the PDB to indicate when line voltage
is applied (the PDB also contains a yellow and red LED, and a test/
run jumper that are used during installation to verify proper power
connections). A red LED on the MCB is used to indicate when the
24VAC input fuse has blown.
Yellow LEDs are located near the microcontrollers on the MCB.
These LEDs are "heartbeat indicators," and blink approximately
twice per second to indicate that the microcontrollers
are running.
MCB JUMPERS
The MCB has two jumpers. JP1 on the MCB is used to terminate
the external communications line. It is normally left off and installed
when the external cable is very long.
IGNITERS
The EMC 5000 modulation system operates with a Hot
surface Igniter.
MCB/FCB Dipswitches:
Hot Water Boilers
On = VW
On = 3
NOT USED
On = Tank (Remote)
On = Yes
On = Yes
On = Yes
NOT USED
NOT USED
NOT USED
Example of Dipswitch configuration:
VB model, 1ignition trial, not used, tank / remote probe, no power vent, No LWCO,
no low gas pressure, modulation, not used, not used.
38
Switch Position
Hydronic Heating Boiler
Off = VB
Off = 1
NOT USED
Off = Inlet
Off = No
Off = No
Off = No
NOT USED
NOT USED
NOT USED