Control Options; Installing Electrical Heat Option - Pace PAI Installation And Assembly Manual

SECTION 3 - HANDLING, STORAGE, AND INSTALLATION
2. Seal the electrical conduits that penetrate the
AHU's exterior (walls, pipe chase or floors) ex-
ternally and internally so that the unconditioned
air will not be drawn into the AHU through and
around the conduit. The unconditioned air will re-
sult in condensation that will fail components pre-
maturely.
3. Check all accessible electrical connections for
tightness prior to the actual startup. Many connec-
tions contain several strands of wire, and while
they were tightened at the time of assembly, they
should be checked and retightened if needed. The
dangers from a poor connection are overheating
and component failure.
DO NOT PENETRATE any main or aux-
iliary drain pan.

Control Options

The available control options are:
• Staging - Has no controller, but contactors are
energized by providing control power to each
contactor from the external BMS source.
• Step Controller - A mechanical/electrical device
that receives a 0 to 10 VDC or 4 to 20 mA signal,
and step-on heat stages.
• Vernier Silicone Controlled Rectifier (SCR)
• Completely electronically controlled by vary-
ing signal and varying output between stag-
es.
• Increases power to a stage by modulation
until another stage is needed.
• Energizes another stage and modulates
power until another stage is needed. 0 to 10
VDC or 4 to 20 mA.
• Less expensive than a full SCR. This system
utilizes a step controller and one SCR that
modulates and resets for each stage.
• Full SCR - Completely electronically controlled by
varying signal and varying output of a controller
like a VFD for electric heat with 0 to 10 VDC or
4 to 20 mA. The controller modulates a separate
SCR for each stage.
Form PA102.20-N1

Installing Electrical Heat Option

Rotating parts and electrical shock haz-
ards exist. Lockout and tagout the fan
motor(s) and heat power disconnects
before servicing, using the latest pro-
cedure. Failure to follow proper safety
precautions may result in serious injury
or death.
Application Information
Follow the procedure given in these instructions to find
the minimum air velocity for safe operation. The mini-
mum velocity must be provided at all points over the
heater face area.
Failure to meet this requirement may
result in serious damage or nuisance
thermal cutout tripping.
The maximum air inlet temperature for open coil heat-
ers is 100°F, and for finned tubular heaters is 80°F.
Sufficient working space must be provided per para-
graph 110-26 of the NEC.
This electric heater is not designed for or intended to
be used for temporary heat prior to system startup/bal-
ancing.
Mechanical Installation
All heaters will contain an adjustable airflow switch in
the heater control panel. This switch will be preset to
close at a differential pressure of approximately 0.3 in.
water column (WC). In all cases, the switch will be con-
nected to a pressure probe positioned in the airstream
as shown in Figure 137 on page 82. This probe has
an arrow stamped on it that is viewable from inside
of the control panel. When the heater is located up-
stream of the fan, this arrow will point away from the
fan. When the heater is located on the downstream
side of the fan, the arrow will point away from the fan
or with the airflow.
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Installation & Assembly Manual │ PACE
Issue Date: 07/03/2018
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