JOHNSON CONTROLS
69
SECTION 3 - HANDLING, STORAGE, AND INSTALLATION
FORM 102.20-N1
ISSUE DATE: 7/06/2016
3
2. Seal the electrical conduits that penetrate the
AHU's exterior (walls, pipe chase or oors) 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
result in condensation that will fail components
prematurely.
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
varying signal and varying output between
stages.
• Increases power to a stage by modulation un-
til another stage is needed.
• Energizes another stage and modulates pow-
er 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 control-
ler like a VFD for electric heat with 0 to 10 VDC
or 4 to 20 mA. The controller modulates a sepa-
rate SCR for each stage.
Installing Electrical Heat Option
Rotating parts and electrical shock haz-
ards exist. Lockout and tagout the fan
motor(s) and heat power disconnects be-
fore servicing, using the latest procedure.
Failure to follow proper safety precau-
tions 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 connected to a pressure probe positioned in the
airstream as shown in Figure 108 on page 70. This
probe has an arrow stamped on it that is viewable from
inside of the control panel. When the heater is located
upstream 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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