Service manual

A DJM3.2 MANUAL
MODEL DJM3.2 and 3.3
If you note errors or omissions, please contact Wade Pascoe at [phone] or Fax [phone] or
(243-5059).
To ensure warranty is honoured, only a qualified HVAC service person, which has received training on
the DJM3, should be employed for service and troubleshooting. If further information is required please
contact the nearest Engineered Air office.
NOTE: The DJM3.2 is similar to the rest of the DJM3 control family, the addition being
the DJM3.2's improved operation as a DOOR HEATER (with dipswitches 7 and
8) and therefore a revised nighttime operation. Please note that the terms DJM
and DJM3 mean DJM3.2 in this manual.
I. APPLICATION
There are two DJM controls - the DJM Model 2 and the DJM model 3. Use the DJM3.2 except:
• Where wired to CTRAC, METASYS or MEGATRAC;
• As replacement for the original DJM (instead use the DJM-2).
The DJM3.2 can switch the low limit off and can also have constant maintain purge. These features allow
application of this control to “stairwell pressurization” or as “air doors”.
II. SERVICE
Before servicing this product, the service technician should be familiar with the following points in this
guide:
• The control has a fuse that should be checked if the control is dead and there is 24 VAC to "T1 and
T2".
• System Timings
• Basic Operation
• Status Lights
• Temperature Readout
• Calculated Set-Point
• Auto Bypass Low Limit
Read the "Special Service Information" if combustion fan runs at full speed only and does not slow
down to light pilot.
Some DJM3's have resets that reset discharge air temperature. Refer to the wiring diagram to determine
if room thermostats, return thermostats, remote set points, ambient resets, building management resets
(BMS), etc., are in use. If used, refer to reset information in this guide after familiarizing with above
.
Do not adjust pots or dipswitches unless you are familiar with operation, effect, and how to return to
correct setting. This needs special equipment in some cases. Noting settings will not allow return to the
correct point on some sensitive pots.
Refer to the "Manual Service Switch", "Manual Firing Set Up Pot", and the "Combustion
Set Up"
section to adjust combustion.
III. GENERAL DESCRIPTION
The DJM3.2 is a programmed logic control designed for use on the Engineered Air series of "DJ"
heaters. The DJM3.2 modulates a variable speed combustion blower in conjunction with an electro-
magnetic modulating gas valve (usually MAXITROL). The combustion blower speed and the gas valve's
flow rate will be modulated to satisfy the discharge temperature requirements.
Page 1 Revised: 03/11/99