User Guide

MODE 7 (External Target Temperature Input and Setpoint
w
ith Primary/Secondary Piping)
Mode 7 is designed for an external input signal and
s
etpoint with primary/secondary piping. The external input
signal can be provided from a BMS, an EMS, or a tekmar
tN4 System Control for space heating. The setpoint can be
used to heat an indirect domestic hot water tank.
T
he external input signal creates an internal demand and
changes the boiler target according to a linear scale. The
control stages the boiler to maintain the boiler target at the
boiler outlet sensor. Refer to section E for a description of
external target temperature operation.
Once a setpoint demand is present, the control stages the
boiler to maintain the boiler target at the boiler supply
sensor. If both an external input signal and a setpoint
demand are present at the same time, the control targets
the higher of the two requirements. Refer to section B for a
descr
iption of setpoint operation.
MODE 8 (External Direct Drive Operation)
Mode 8 is designed for an external input signal to directly
control the staging rate of the boiler with either parallel
or primary / secondary piping. The heat demand and
setpoint demand inputs are disabled. Refer to section F for
a description of external target temperature operation.
STAGING MODE (STGMODE)
The control can operate up to four stages in order to
supply the required target temperature. The method of
staging used by the control is either P (proportional) or
P
ID (Proportional & Integral & Derivative), and is selected
using the STGMODE item in the Adjust menu.
Proportional & Integral & Derivative (PID)
PID staging allo
ws the control to deter
mine when the next
stage is required to turn on. After a stage is turned on in
the firing sequence, the control waits a minimum amount of
time (Stage Delay) before turning on the next stage. After
the minimum time delay between stages has expired, the
control examines the control error to determine when the
next stage is to fire. The control error is determined using
PID logic.
Proportional logic compares the actual operating sensor
temper
ature to the boiler target temper
ature.The colder the
temperature, the sooner the next stage is turned on.
Integral logic compares the actual operating sensor
temper
ature to the boiler target temper
ature over a period
of time.
Derivative logic determines how fast or slow the operating
sensor temper
ature is changing.
If the temperature is
increasing slowly, the next stage is turned on sooner. If
the temperature is increasing quickly, the next stage is
turned on later, if at all.
6
EM-40-SM Service Manual
BTC
Mode 7
0-10 V (dc)
tN4 System
Control
Boiler
Outlet
Sensor
Boiler
Supply
Sensor
Boiler Inlet Sensor
Relay
BTC
Mode 8
External
Control
BTC
0-10 V (dc)
Direct Drive
Boiler
Outlet
Sensor
Boiler
Outlet
Sensor
Boiler Inlet Sensor
Boiler Inlet Sensor
Boiler
Supply
Sensor
175 °F
170°F
180°F Setpoint
Proportional Staging
185°F
190°F
155°F
150°F
145°F
140°F
160°F
165°F
water
temperature
droop
water
temperature
droop
water
temperature
droop
Boiler
Outlet
Sensor
Boiler
Outlet
Sensor
Boiler Inlet Sensor
Boiler Inlet Sensor
Boiler
Supply
Sensor
175 °F
170°F
180°F Setpoint
Proportional Staging
185°F
190°F
155°F
150°F
145°F
140°F
160°F
165°F
Stage 4
Stage 3
Stage 2
Stage 1
water
temperature
droop
water
temperature
droop
water
temperature
droop
175 °F
170°F
180°F Setpoint
P.I.D. Staging
very little
temperature
droop
185°F
165°F
Stage 4
Stage 3
Stage 2
Stage 1
P.I.D. = Proportional + Integral + Derivative
BTC
Mode 7
0-10 V (dc)
tN4 System
Control
Boiler
Outlet
Sensor
Boiler
Supply
Sensor
Boiler Inlet Sensor
Relay
BTC
Mode 8
External
Control
BTC
0-10 V (dc)
Direct Drive
Boiler
Outlet
Sensor
Boiler
Outlet
Sensor
Boiler Inlet Sensor
Boiler Inlet Sensor
Boiler
Supply
Sensor
175 °F
1
180°F Setpoint
Proportional Staging
185°F
190°F
1