Johnson Controls YORK SOLUTION LD09624 Installation And Start-Up Instructions Manual Download

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2-40

ForM 102.20-N1 (1109)

installation

Available Control Options

• Staging - No controller, but contactors are

energized by providing control power to each
contactor from external BMS source.

• Step Controller - device to receive a 0- to 10 VDC

or 4 to 20 mA signal and step on heat stages.

• Vernier SCR - completely electronically con

trolled  by  varying  signal  and  varying  output
between stages.  Increases power to a stage by
modulation until another stage is needed.  Ener-
gizes  another  stage  and  modulates  power  until

another stage is needed. 0 to 10 VDC or 4 TO

20 mA. Less expensive than 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. 0 to 10 VDC or

4 to 20 mA. The controller modulates a separate

SCR for each stage.

Installation

Rotating parts and electrical shock

hazards exist. Lock out and tag out

the  fan  motor(s)  and  heat  power
disconnects  before  servicing.    FOl-
lOW  THE  lATEST  “lOCKOUT
TAGOUT” PROCEDURE.  Failure to
follow proper safety precautions may
result in serious injury or death

APPliCAtiOn inFORMAtiOn

1. Follow the procedure given in this instruction to

find the minimum air velocity for safe operation

(see Fig. 3-25).

At least this minimum 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 trip-
ping.

2. The maximum air inlet temperature for open coil

heaters is 100°F, and for finned tubular heaters,

80°F.

3. Sufficient working space must be provided per

paragraph 110-26 of the NEC.

4. This electric heater is not designed for or intended

to be used for temporary heat prior to system
startup / balancing.

MEChAniCAl inStAllAtiOn

1. 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" W.C.

In all cases the switch will be connected to a pres-

sure probe positioned in the airstream. 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 again

point away from the fan or with airflow.

If it is incorrectly installed, remove the (2) screws

holding the pressure probe in place and rotate 180°

and reinstall. The airflow switch pressure port that

is not connected to this pressure probe will be run
to the exterior of the air handling unit to source a
reference differential pressure. In some situations

it may be necessary to adjust this airflow switch

setting to allow for proper operation. Precautions

must be made at this time to make sure that the

airflow switch does not provide a false indication

of airflow. Failure to meet this requirement may

result in serious damage or nuisance thermal cutout
tripping

(see Fig. 2-60 and 2-61).

2. A visual inspection of the heater elements should

be made prior to use of the heater. If physical
damage is evident, a Megohm test should be used
to validate the heater elements are safe for use. If
a minimum value of 10 megohms is not achieved
then any damaged elements or ceramic insulators
must be replaced prior to operation.