Slant/Fin EM-10 Service Manual - Manual (Page 7)

7 EM-40-SM Service Manual
STAGE DELAY (STG DLY)
The stage delay is the minimum time between firing first
to second stage, second to third stage, and third to fourth
stage and is determined by the Stage Delay setting. It can
be manually set, or it can be set to automatic in which the
boiler mass determines the stage delay time.
BOILER MASS (BOIL MASS)
The boiler mass setting allows the installer to adjust the
control to the thermal mass of different types of heat sources
used. The boiler mass setting automatically determines the
stage delay on, stage delay off, minimum on time and
minimum off time of the stages. A higher thermal mass
setting provides slower staging, while a lower thermal mass
provides faster staging.
Proportional (P)
Proportional staging, also known as step staging, is based
on manually adjusted settings that determine when the
next stage is required to turn on. These manual settings are
based on temperature and time. The interstage differential
sets the temperature drop at which the next stage turns on.
However, in order for a stage to fire, the interstage delay
on and minimum off times must first elapse.
Interstage Differential (STG DIFF)
The interstage differential is the temperature drop at which
the next stage will turn on. Once a stage turns on, the
next stage cannot turn on until the temperature drops
the interstage differential below the temperature at which
the previous stage turned on. The interstage differential
is adjustable through the STG DIFF setting in the Adjust
menu.
Interstage On Delay (ON DLY)
The interstage on delay is the amount of time that must
elapse before turning on the next stage. Once a stage turns
on, the next stage cannot turn on until the interstage delay
on time elapses. The interstage on delay is adjustable
through the ON DLY setting in the Adjust menu.
Interstage Off Delay (OFF DLY)
The interstage off delay is the amount of time that must
elapse before turning off the next stage. Once a stage turns
off, the next stage cannot turn off until the interstage delay
off time elapses. The interstage off delay is adjustable
through the OFF DLY setting in the Adjust menu.
Minimum On Time (MIN ON)
The minimum on time is the minimum amount of time that
a stage must be on before it is allowed to turn off. Once a
stage turns on, it cannot turn off until a minimum on time
elapses. The minimum on time is adjustable through the
MIN ON setting in the Adjust menu.
Minimum Off Time (MIN OFF)
The minimum off time is the minimum amount of time that
a stage must be off before it is allowed to turn on. Once a
stage turns off, it cannot turn on until a minimum off time
elapses. The minimum off time is adjustable through the
MIN OFF setting in the Adjust menu.
BOILER DIFFERENTIAL (DIFF)
A heat source must be operated with a differential in order to
reduce short cycling. The boiler differential is divided around
the boiler target temperature. The first stage
contact will close once the water temperature at the
operating sensor is 1/2 of the differential setting below the
boiler target temperature, and will open once the water
temperature at the operating sensor is 1/2 of the
differential setting above the boiler target temperature.
Manual Differential
The differential can be manually set using the DIFF setting
in the Adjust menu.
Auto Differential
Auto differential is only available when using PID staging.
If the Auto Differential is selected, the control automatically
determines the best differential as the load changes,
thereby improving efficiency. During light loads, the
differential is increased to allow longer on and off times to
reduce the potential for short cycling. During large loads, the
differential is narrowed thereby improving comfort in heating
spaces by reducing temperature swing.
Proportional Staging
A Minimum On Time
B Minimum Off Time C Interstage On Delay
D Interstage Off Delay
A B C D
B oil MAX
B oil MIN
WWS D
OUTDR DS G N
B oil DS G N
B oil S TAR T
OUTDR S TAR T
Fixed Differential
Dif
ferential
Des ired Temperature Desired Temperature
Increasing
T
e
mperature
Increasing Time
ON ON
OFF OFF
B oil MAX
B oil MIN
WWS D
OUTDR DS G N
B oil DS G N
B oil S TAR T
OUTDR S TAR T
Automatic Differential
Dif
ferential
Low
Heat
Load
ON ON
OFF OFF
Dif
ferential
High
Heat
Load
ON ON
F F O F F O
B oil MAX
B oil MIN
WWS D
OUTDR DS G N
B oil DS G N
B oil S TAR T
OUTDR S TAR T