AERCO BMK 3.0 LN Nat. Gas Jan 2011 - Manual (Page 22)

INSTALLATION
2-10
22 AWG, s uch as Bel den 9 841 ( see
Figure 2-11). Polarity must be m aintained. T he
shield must be connected only at the source end
and m ust be left floating ( not connected) at the
Boiler’s I/O Box.
Regardless of whether voltage or current is used
for the dr ive signal, they are linearly mapped to
a 40°F to 240°F setpoint or a 0% to 100% f iring
rate. No scaling for these signals is provided
2.10.4 B.M.S. (PWM) IN
NOTE
Only BMS Mod el 1 68 c an uti lize P ulse
Width Modulation (PWM), not the BMS II
(Model 5R5-384).
These ter minals ar e used t o c onnect t he
AERCO Boi ler Ma nagement S ystem ( BMS)
Model 16 8 to the un it. T he BMS Mod el 1 68
utilizes a 12 m illisecond, ON/OFF dut y c ycle.
This duty cycle is Pulse Width Modulated (PWM)
to control firing rate. A 0% firing rate = a 5% ON
pulse and a 100% firing rate = a 95% ON pulse.
2.10.5 SHIELD
The SHIELD terminals are used to terminate any
shields us ed on s ensor wires c onnected to t he
unit. O nly s hields m ust be c onnected t o th ese
terminals.
IMPORTANT
DO NO T USE the m A OUT output to
remotely monitor Setpoint, Outlet Temp or
Fire Rate Out.
2.10.6 mA OUT
These terminals provide a 4 to 20 m A output to
the VFD (if so equipped) to control the rotational
speed of the blower. This function is enabled in
the Configuration Menu (Chapter 3, Table 3-4).
2.10.7 0 – 10V OUT
These ter minals pr ovide a 0 to 10V o utput to
control t he r otational s peed of the b lower. T his
function is e nabled i n t he Conf iguration Me nu
(Chapter 3, Table 3-4).
2.10.8 RS-485 COMM
These terminals are used for RS-485 MODBUS
serial c ommunication be tween the u nit a nd an
external “Master” such as a Boiler Management
System ( BMS), En ergy Management S ystem
(EMS), Building Automation S ystem ( BAS) or
other suitable device.
2.10.9 EXHAUST SWITCH IN
These ter minals per mit an ex ternal ex haust
switch to be c onnected to the exhaust m anifold
of the bo iler. T he ex haust s witch s hould be a
normally open type switch (such as AERCO Part
No. 123463) that closes (trips) at 500°F.
2.10.10 INTERLOCKS
The unit offers tw o i nterlock c ircuits f or
interfacing with En ergy M anagement Systems
and a uxiliary eq uipment s uch as pum ps or
louvers. These interlocks are called the Remote
Interlock and Dela yed I nterlock ( Figure 2- 11).
The w iring ter minals f or these int erlocks ar e
located i nside th e I/O Box on t he u nit f ront
panel. T he I/O Box c over c ontains a wiring
diagram which shows the terminal strip locations
for thes e inter locks ( REMOTE IN TL’K IN and
DELAYED INT L’K IN). Both interlocks,
described below, are factory wired in the c losed
position.
IMPORTANT
Both th e Rem ote In terlock and Del ayed
Interlock MUST be in the c losed pos ition
to allow the unit to fire.
2.10.10.1 REMOTE INTERLOCK IN
The r emote inter lock c ircuit is pr ovided to
remotely s tart ( enable) an d s top ( disable) th e
Boiler, if des ired. T he c ircuit is labe led
REMOTE INTL’K IN and is located inside the I/O
Box on t he f ront pan el. T he c ircuit is 24 V AC
and is factory pre-wired in the closed (jumpered)
position.
2.10.10.2 DELAYED INTERLOCK IN
The del ayed interlock is t ypically used i n
conjunction with t he aux iliary r elay described in
paragraph 2. 10. T his inter lock c ircuit is loc ated
in the purge section of the start string. It c an be
connected to t he proving dev ice ( end s witch,
flow s witch etc .) of an aux iliary p iece of
equipment started by the Boiler’s auxiliary relay.
The dela yed i nterlock must be c losed f or the
boiler to fire.
If the delayed interlock is connected to a proving
device that requires time to close (make), a time
delay ( Aux Start O n D ly) that ho lds t he s tart
sequence of the boiler long enough for a proving
switch to make can be programmed. Should the
proving switch not prove within the programmed
time fr ame, the bo iler wi ll shut do wn. T he Aux
Start On Dly can be programmed from 0 to 120
seconds. T his option is l ocate i n t he
Configuration Menu (Chapter 3, Table 3-4).