Service manual

A DJM3.2 MANUAL
25ºF the reset is at maximum. The high point of the slope is represented by (***), while (###)
represents the low end.
The second slope, the modified one, shows the results if a 120-ohm resistor is placed in series with
the ambient sensor. When this is done the outside ambient must be colder before the reset begins to
reset the discharge temperature higher. (**) Represents the high end of the slope while (##)
represents the low end.
As the slope rises above the dial set-point line, the discharge temperature increases until it reaches
the non-adjustable reset value allowed. Two factors determine how much reset is given, the set-point
of the control and how far above the set-point the slope is due to the temperature at the ambient
sensor. The resistor being added does not change the slope, only where it crosses the set-point line.
Following, is some numerical data showing how much reset is available without and with the 120-ohm
resistor added.
Pot Reset Ratio
Setting
Reset Amount ºF
(no resistor)
Reset Amount ºF (with a 120 ohm resistor in series)
1
10 18
2
11 20
3
13 24
4
16 30
5
21 37
Make/Break Resets and Overrides
1. "OR" and "V" Override
DAY OPERATION ONLY (dipswitch 3 should be off).
NOTE: This will not operate with intermittent night blower, terminal “K” energized.
• With the contact closed, discharge temperature is at 120ºF.
• With thermostat open, discharge temperature is as per the set-point
dial plus any other reset options values that are activated.
The simpler version of the make/break override options is the one that closes a contact between
the DJM3.2 terminals "OR" and "V". This is designed to operate as an override for day operation
and will drive the discharge temperature up to 120º when the contacts for the thermostat are
closed. When the thermostat is not calling, the discharge temperature value is that shown on the
temperature set-point dial (either the DJM3 mounted dial or the optional remote dial).
This set up is designed for a daytime override where you have the fan operating continuously. It
does not respond to terminal “K” for night heat operation. If you attempt to operate this as a night
time override, the heat cannot start because the supply fan is not operating. Additional steps must
be taken for night operation.
If you want to take additional steps to operate the control as a night heat package, note the
following. The "OR" and "V" operation looks for the fan to be running before it can start the heat. It
has no internal method of starting the fan. If it is the intent to use this option as a night heat
function, you must have the room thermostat operate a relay that will close DJM3 contacts "OR"
and "V"; as well as have a second set of contacts that will re-establish power to the "FS" terminal.
When the "FS" terminal is powered, the DJM3 will see that the fan is operating and it will bring on
the heat to operate at 120ºF-discharge temperature until the room thermostat is satisfied.
Page 17 Revised: 3/11/99
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