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Designs, materials, weights and performance ratings are approximate and subject to change without notice. Visit
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6. When the post-purge is complete, the control enters an idle state while continuing to monitor temperature and the state of
other system devices. If a call-for-heat is received, the control will automatically return to Step 2 in sequence and repeat the
entire operating cycle.
7. Built in freeze protection: all models will automatically turn the pump on if the heat exchanger reaches 41°F (5°C) and the
burner if it reaches 37°F (2.8°C), it will turn off at 50°F (10°C).
NOTE: Power must be left on for this protection to function.
During the idle state and heat state, if the control detects an improper operating state from external devices, such as the high-limit
switch, the control will illuminate an error code in the display.
Start-Up Procedures - continued
0–10V Direct Control
Direct Control
In the situation where direct control of the appliance is desired (such as from a Building Management System), the appliance can be
programmed to receive a 0–10 volt DC signal to control operation.
N
ote: This operation is only possible in individually-controlled units (i.e.: not Cascaded) and when each is
individually vented.
There are two variations of this kind of external control: Load Control and Set Point Control. In Load Control, the voltage signal
controls the burner firing rate. In Set Point Control, the voltage signal controls the temperature set point of the appliance. (This is
similar to how the appliance is controlled when operating without an outside signal.)
Setting up Direct Control
There are three steps required to set up this mode of operation. First, connect the incoming voltage signal to pins 5 and 6 on the
control board (see page 11.)
Next, remove the jumper from the remote thermostat terminals (pins 11 and 12, see page 11). If this is not done, the appliance will
fire based on its internal set point when the voltage drops below 1.0VDC. If the appliance is set up with any other external signal here,
this should be removed as well, or that external signal will take over when the 0-10VDC control signal drops below 1.0VDC
Next, go to Parameter S18 (PS18) in the Parameter menu and choose the appropriate control setting. (include picture of menu or
HMI page)
The PS18 settings are:
• 0=Off (default setting--no external control, any external voltage signal ignored)
• 1=Load Control
• 2=Set Point Control
Load Control mode (PS18=1)
When a 0-10VDC input is used for load control, the range of 0-10VDC corresponds directly to a modulation percentage (burner
firing rate). An input of 10.0VDC results in the maximum default fan speed (modulation) for that appliance, and 1.0VDC results in
the minimum default fan speed. The fan speed displayed on the appliance will depend on the range of the fan for that particular
appliance.
Type
Minimum Fan Setting
(1.0VDC)
Maximum Fan Setting
(10.0VDC)
Voltage increment
299
25%
100%
8.33% fan speed
399
25%
100%
8.33% fan speed
599
27%
100%
8.11% fan speed