Steffes 7140 - Manual (Page 11)

Model
Primary
Voltage
Secondary
Voltage
KVA Hevi Duty Item #
Steffes
Item #
277/480V 480 240 2 HS1F1BS or equal 1017082
347/600V 600 240 2 HS10F2AS or equal 1017080
CONTROL CIRCUIT STEP-DOWN TRANSFORMER
The internal controls and motors of all Comfort Plus Commercial Hydronic systems operate at 240 volts (two
wire). In systems with 277/480 or 347/600 volt element circuits, a transformer must be installed per the installa-
tion instructions to supply this voltage to the system’s controls. This transformer can be purchased as an optional
device from Steffes Corporation or sourced from your local electrical supply outlet. See the matrix below for
proper sizing.
SCR CONTROLLER
The Steffes SCR (Solid State Relay Panel) is an optional control device used with
the Steffes ThermElect (8100 and 9100 Series) and Comfort Plus Commercial
(6100 and 7100 Series) Heating Systems. It utilizes SCR technology to enable
more precise balancing of a building’s overall electric load by varying the amount
of total element input that can be energized in a Steffes furnace at any given time
in relation to the maximum allowable building load. The Steffes SCR optimizes a
building’s power quality and control.
The SCR Controller can only accept input signals from the Steffes furnace but it
can respond to all types of control inputs to include 4 – 20 Milliamp, 1 – 5 Volt
DC, electric meter pulsing, Bacnet or any building energy management system.
With the 4 – 20mA or 1 – 5 volt DC signals, the SCR will provide an output
directly proportional to the input signal. 4mA signal produces 0% output while 20mA signal products 100%
output. With the utility pulse meter input, the SCR output percentage will automatically adjust to maintain a total
maximum system load as dictated by the furnace’s set-up. With a Bacnet, the furnace can be commanded to
varying input levels remotely.
EXTERNAL DUCT SENSOR
The optional external duct sensor (Order Item #1041536) provides the ability to monitor the duct temperature at
an area beyond fresh air makeup and/or beyond other devices and regulate the discharge air temperature
accordingly.
The duct sensor feature is enabled if the 4 bit is set in Location 53 (L053). Once enabled, the Comfort Plus
Commercial Hydronic system monitors temperature at both the duct sensor and the output sensor during Y, W,
or E calls from the thermostat.
If there is a Y and a G call from the thermostat, the system operates the core blowers at the required speed to
maintain the minimum output temperature as set in Location 48 (L048) at the duct sensor. If there is only one
call from Y, W, or E, then the system will operate the core blowers at the required speed to maintain the
maximum output temperature as set in Location 49 (L049) at the duct sensor. The system is set to turn off the
core blowers if the output temperature at the output sensor exceeds 150 degrees Fahrenheit.
Accessories
Comfort Plus Commercial Hydronic Optional Accessories
n
2.04
SCR CONTROLLER
Order Item #1301016