User Guide

9
EM-40-SM Service Manual
A setpoint is a fixed water temperature target that the
boiler is to maintain at the operation sensor once a demand
is present. The boiler maintains the boiler target by
o
perating the stages using proportional or PID logic
together with the boiler differential.
Mode 1 or 2 and Heat Demand (Dem 1)
A heat demand is required whene
ver heat is required for the
primary heating load. A heat demand is generated when a
voltage between 24 and 120 V (ac) is applied across the CD
(common demand) and the Ht D (heat demand). Once volt-
age is applied, the control turns on the Dem 1 segment in the
display and control operates the boiler stages to maintain the
BOIL TARGET 1 at the boiler outlet sensor (Mode 1) or the
boiler supply sensor (Mode 2).
Mode 1 or 2 and Setpoint Demand (Dem 2)
A
setpoint demand is required whenever heat is required
for the secondary heating load such as an indirect
domestic hot water tank. A setpoint demand is generated
when a voltage between 24 and 120 V (ac) is applied across
t
he CD (common demand) and the Set D (setpoint demand)
(pins 1 and 3). Once voltage is applied, the control turns on
the Dem 2 segment in the display and control operates the
boiler stages to maintain the BOIL TARGET 2 at the boiler
outlet sensor (Mode 1) or the boiler supply sensor (Mode 2).
Modes 4 to 7 and Setpoint Demand (Dem 2)
A setpoint demand is required whenever heat is required
for the secondary heating load such as an indirect domestic
hot water tank. A setpoint demand is generated when a
voltage between 24 and 120 V (ac) is applied across the
CD (common demand) and the Set D (setpoint demand).
Once voltage is applied, the control turns on the Dem 2
segment in the display and control operates the boiler stages
to maintain the BOIL TARGET at the boiler outlet sensor
(Mode 4, 6) or the boiler supply sensor (Mode 5, 7).
Section B: Setpoint Operation
Section C: Dedicated Domestic Hot Water (DHW) Operation
When mode 3 is selected, the BTC provides dedicated
DHW operation.
A DHW tank temperature sensor is required to be
connected on the Com and the Sup/D terminals (4 and 6).
The DHW tank sensor must be installed in an immersion well
to measure the tank temperature.
The TANK TARGET setting is used to set the desired DHW
tank temperature. The TANK DIFF setting is the differential
below the target.
An internal heat demand for DHW is generated when
the measured DHW tank temperature falls below the
TANK TARGET – TANK DIFF. The internal heat demand
is removed once the measured DHW tank temperature
exceeds the TANK TARGET.
Once an internal demand is generated, the Dem 1 segment
turns on in the LCD. The control then closes the Pump
contact, which starts the boiler pump and the control turns
on the boiler pump segment in the display. The control then
operates the boiler stages to maintain the programmed tank
target temperature.
Note: A v
oltage does not need to be applied to the heat
demand or the setpoint demand in this mode of operation.
Setpoint Operation
+ 1/2 Differential
Setpoint Target
-
1
/2 Differential
Dedicated DHW Operation
Tank Target
Tank Target
-
Tank Differential
Reset Ratio
Decreasing Outdoor Air Temperature
Increasing Water Temperature
OUTDR DS GNOUTDR DSGN
B oil
DS GNBoil DSGN
B oil STAR TBoil START
OUTDR
S TAR TOUTDR START
Proportional Staging
A Minimum On Time
B Minimum Off Time
C Interstage On Delay
D Interstage Off Delay
A B C D
Fixed Differential
Differential
Des ired Temperature
Desired Temperature
Increasing
Temperature
Increasing Time
ON ON
OFF
OFF
Automatic Differential
Differential
Low
Heat
Load
ON
ON
OFF
OFF
Differential
High
Heat
Load
ON
ON
FFOFFO
Setpoint Operation
+ 1/2 Differential
Setpoint Target
-
1/2 Differential
Dedicated DHW Operation
Tank Target
Tank Target
-
Tank Differential
Reset Ratio
creasing Water Temperature
OUTDR DS GNOUTDR DSGN
B oil DS GNBoil DSGN
B oil STAR TBoil START
OUTDR S TAR TOUTDR START