Price offers three types of control over
electric coils Binary (staged), SCR, or EMC
Staged or Binary Control Staged heat is the most economical and
simplest type of heat available. The binary
(on/off) signal is used to close contactors
to energize each stage individually. Binary
heat is not the most energy efficient or
comfortable way to control reheat as it can
cause swings in room temperature.
The SCR (Silicon Controlled Rectifier) option
provides proportional modulation at the
heater over its full operating range. Solid
state electronics ensure reliable efficient,
and silent operation.
Benefits of SCR
- Time proportional control of the duct
heater maintains room set-points
more accurately than on/off or staged
systems, providing maximum comfort
in the space.
- Energy Efficient – Because room setpoints
are accurately maintained,
undershoot and overshoot is avoided,
reducing operating costs.
- Mechanical contactors are eliminated.
Zero cross switching of the thyristor
prevents electrical noise.
- Silent Operation – Solid state switching
of the coil elements eliminates noisy
contactors or the requirement for more
costly mercury contactors.
- SCR accepts a variety of industry
standard inputs - 0-10 VDC, 4-20mA, 24
VAC (steady or pulse).
SCR with Discharge Air Temperature
All Price SCR's have the option of adding a
discharge air temperature (DAT) probe. This
DAT probe provides the SCR with feedback
on the air temperature being providing to the
space. In order to prevent stratification of
warm air its important to limit the maximum
When the optional DAT probe is provided
with the SCR, it must be field mounted in
the duct work downstream from the heater.
Price recommends mounting the probe at
least 2 feet downstream from the heater.
Using the on board dial of the SCR allows
the installer to select anywhere in the range
of 65F - 130F. ASHRAE recommends the
heating air temperature does not exceed
15F above the room temperature. Therefore
a DAT setting of approximately 90F is
recommended for typical applications.
On a call for heat (with the DAT probe
connected) the SCR will cycle on and
continue increasing the heat output every few seconds until the dial set point
is reached. Note that any input signal
(above 2 VDC for BAS, above 4mA or 24
VAC - pulse mode) will cause the SCR with
DAT to target its dial set point. If the DAT
probe is disconnected the SCR will revert
to normal operating mode (Non DAT mode)
and modulate proportionally based on input
The Electronic Modulating Control (EMC)
option is a Price exclusive feature which
provides all of the advantages and benefits
of SCR control plus an electronic flow
Benefits of Electronic
Air Flow Sensor
The air flow sensor responds to radiant
heat of the heating element which, in turn,
is influenced by the air flowing through the
heater to dissipate the heat. The patented
air flow sensor and associated electronic
controller modulate the power to the heater,
adjusting the heater’s capacity to match
the air flow available. This unique concept
allows the heater to respond exactly to the
quantity of air flowing through it as well
as safely shut down in case of a total loss
of air flow..