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EngA ENGINEERED AIR DJM2.4, Installation, Operation And Maintenance Manual, Page: 30 / 37

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EngA ENGINEERED AIR DJM2.4 Installation, Operation And Maintenance Manual Download Page 30

 

 

 

 

DJM2.4 MANUAL 

 

30 

Oct 00 R2

 

Regulator Gas Pressure Responses 

On some indoor units the vent orifice fitting on the RV appliance regulator is to be vented to 
atmosphere. The field installed vent line should be sized adequately, especially on longer runs. If 
there is more than one regulator connected to a common run, which includes the main regulator 
and the line, is not adequately sized, changes in pressure on the RV diaphragms are applied to all 
regulators. This includes the main regulator so an erratic inlet pressure will result and cause 
improper combustion and also burner pulsating problems. 

 

Some DJ unit manifolds have RV appliance regulators with a vent-limiting orifice, usually a brass 
orifice marked ‘12A06’. Ensure that this tiny orifice is free of dirt or debris. A plugged orifice will 
impede regulators opening flow and cause improper air/fuel mixtures. 

Rumble During Light Off 

The low fire combustion air quantity being too great usually creates this condition, or the low fire 
gas-firing rate is set too low. Always check the main gas inlet pressure first before making any 
adjustments. At high fire it should be a minimum of 6½ inches on units designed for 7-inch 
natural gas inlet pressure. 

(Minimum 12 inches on 14-inch natural gas design and 11½ inches on 

propane units.)

 

Rumble is usually not a problem with the rectangular shaped high turndown burner. On the 
standard burner it is possible to get small amount of rumble whenever a burner is lit after being 
cold for an extended period of time. After the first light it settles down. This is because the warm 
burner has a greater back pressure than the cold one; thus a lower air velocity occurs when the 
burner plate is warm. 

One of the more common causes on the regular burners 

(round burners)

 is if the combustion 

blower light off speed is set too high. Check if the light off speed is too high with an accurate 
tachometer or by using a meter that measures hertz connected to the “YS and GS” terminals of 
the speed sensor. Light off speed is 2700 RPM 

(45 Hz)

. 

Another item that can create rumble on the standard 

(round)

 burner is if the turndown is 

adjusted too low. At low fire the standard 

(round)

 burner can only modulate to 40% of the high 

fire rate. This leaves too much air at low fire for the quantity of fuel. To correct increase the low 
fire manifold pressure to the proper firing rate. A rough rule of thumb for low fire manifold 
pressure is: 

DJ40  

0.6" 

DJ60 

0.6" 

DJ100 

0.8" 

Ensure that these pressures are set with the modulating gas valve at low fire 

(1.8 VDC on its 

terminals)

 and the combustion fan running at 1800-1850 RPM.

 

Burner Staying On 

The DJM2.4 is designed to maintain a stable discharge temperature. Depending upon pot 3 CONT 

(PI)

 setting, the DJM2.4 may not respond instantaneously to a sudden decrease in the discharge 

set point. After the burner has been steadily firing for an extended period of time, if the set point 

Summary of Contents for ENGINEERED AIR DJM2.4

Page 1: ...ND FACTORY CANADIAN EASTERN FACTORY 1401 HASTINGS CRES SE CALGARY ALBERTA T2G 4C8 Ph 403 287 4774 Fx 888 364 2727 32050 W 83 rd STREET DESOTO KANSAS 66018 Ph 913 583 3181 Fx 913 583 1406 1175 TWINNEY DRIVE NEWMARKET ONTARIO L3Y 5V7 Ph 905 898 1114 Fx 905 898 7244 SALES OFFICES ACROSS CANADA AND USA Retain instructions with unit and maintain in a legible condition Please give model number and seria...

Page 2: ...from the unit There are two copies provided with the unit One is in an envelope for copying then return it to the unit or store in a safe place The other is attached to the control panel door and should never be removed If a copy of the function for a particular unit is needed contact Engineered Air with the unit serial number and DJM2 model number ex model DJM 2 4 Warning m c This unit is connect...

Page 3: ...DJM2 4 MANUAL 3 Oct 00 R2 ...

Page 4: ...E OVERRIDE 8 VIII STATUS LIGHTS 8 IX BASIC BURNER OPERATION 10 X TEMPERATURE CONTROL GENERAL OVERVIEW 11 XI BMS CONTROL 13 XII BMS CALIBRATION AND SET UP 13 XIII DISCHARGE SENSOR READOUTS CALIBRATION ETC 14 XIV BURNER SET UP 16 XV SPECIAL SERVICE NOTES 24 XVI SET UP WHEN INSTALLING A DJM2 4 IN FIELD 33 XVIII MISCELLANEOUS NOTES 34 XIX MAXITROL GAS VALVE DRAWINGS 37 ...

Page 5: ... BMS The DJM2 has no built in low limit therefore it can be applied as stairwell pressurisation in case of fire The DJM2 is designed to replace the original DJM and has additional features to assist in troubleshooting II SERVICE To ensure warranty coverage and safe operation this equipment should only be serviced by qualified HVAC Technicians Gas Fitter and other properly trained trades people Bef...

Page 6: ...t is not recommended but if a second control is connected to the DJM2 4 it will respond to the control with the greatest signal If direct reset control is required the DJM3 controller should be used Basic Features The basic features of the DJM2 4 include the following 1 Proportional and Integral PI temperature control 2 Can be used with the Johnson TE 6000 sensor and internal DJM2 set point pot It...

Page 7: ...ture sensors flame rod etc This is to avoid voltage crosstalk stray induced high voltage signals that can adversely affect electronic controls V SYSTEM TIMINGS Pre purge 50 seconds combustion blower must run 50 seconds before flame can be lit on initial heat call if no combustion fan is in operation immediately before heat call Maintained Purge 4 minutes combustion blower runs after flame is turne...

Page 8: ...fferent applications slightly different settings may be required Tests have indicated the best settings for various applications are For use with Maxitrol TS114 or Johnson TE 6000 960 sensors this pot should be left in the centre position 9 o clock or less position For use with a building management control system the pot should be set in the full CCW proportional position This includes METASYS an...

Page 9: ...e AC volts present on terminals YS to GS When the combustion blower is running there should be 4 to 6 VAC present If the AC voltage is not present check the tachometer sensor to magnet gap It should be 1 16 to 1 8 inch If the gap is okay replace the speed sensor Further information found in section Checking Speed Sensor located on page 24 If the voltage is constantly 10 VDC and the sensor is locat...

Page 10: ...ower is started 3 After the combustion blower is started the DJM waits until the blower reaches the correct pre purge speed Approximately 3450 RPM 4 When the correct speed is obtained the pre purge time delay is started While the combustion fan is operating in the pre purge mode the heat exchanger is purged of any unwanted gases that may be present 5 After the pre purge cycle is complete the combu...

Page 11: ...s while the DJM2 4 is operating in its maintain purge mode the control logic goes to step 6 and the burner will re light 12 If there is no heat call within the 4 minute maintain purge mode the combustion blower is shut off If another call for heat is initiated at this time the control logic returns to step 1 Service Mode When DJM2 4 terminals SV and SR are jumpered the DJM2 4 is placed into servic...

Page 12: ... etc The C TRAC pots are set as per the normal factory recommended settings To set the DJM2 4 controlled by a C TRAC See Section XVIII DJM2 Slaving From C TRAC for more information The C TRAC pots are to be set as per the following assuming it is sitting horizontal the label DJM2 4 is horizontal then CONT Pot 3 would normally be set at about the 9 o clock position or midway on its stroke If you wi...

Page 13: ...If desired the wiring may be changed such that the BMS or control voltage is wired to terminals and These terminals are optically isolated and will eliminate the requirements for a separate ungrounded isolating transformer The control providing the signal to the and terminals needs to be a 0 10 VDC signal that has capability of a 20 ma or stronger drive For new installations we recommend using ter...

Page 14: ... have an input impedance of 500 ohms on the and terminals At 10 VDC input the current would be 20 mA If the host BMS system cannot source 20 mA the input impedance can be increased to 1500 ohms by removing cutting resistor R19 680 ohms This resistor is located next to terminals and To gain access to R19 to cut it the DJM2 4 must be turned over BMS Calibration Refer to instructions in above section...

Page 15: ...set point to match the measured discharge temperature Adjust pot 1 until the meter reading is 1 8 volts DC Note information below A second calibration method for the TE6000 without a meter is Ensure there is no signal such as voltage on that would call for a higher discharge than the temperature at the set point Next measure the temperature immediately next to the discharge air sensor Adjust the s...

Page 16: ...rner plate and High Turndown rectangular Burners Cutting a jumper wire located next to terminal PV1 makes the selection For high turndown burner operation the jumper wire must be cut There are two pots located close to terminal SP which affect the burner set up These pots are to be adjusted only by a qualified service technician using proper combustion analysis equipment Pot 7 second pot from the ...

Page 17: ...f the air and fuel may have a great affect on the set up you select If both the combustion air and the fuel are at a constant temperature throughout the heating season once combustion is set it should remain similar through the season However this usually only occurs on indoor units Setting up an outdoor unit is not the same as setting up a unit or a boiler inside a building When a unit is located...

Page 18: ...sure is set up at the appliance regulator ES345D L This valve has a built in high fire regulator Used on DJ140 models The above valves differ from each other in size configuration BTU capacity physical layout and low fire set up Check the unit you are working on to verify what type of modulating gas valve you have to ensure the correct combustion set up method is used Top Loading Ensure that there...

Page 19: ...in from less than 1 5 VDC until 2 25 VDC is reached 7 Check the O2 reading again at this point If the O2 has increased adjust the spring activated low fire adjustment on top of the valve until the O2 reading is same as the low fire reading at 0 VDC you are correcting for valve hysteresis with this adjustment 8 CURVE MATCHING PROCEDURE Switch to high fire setting approximately 3450 RPM or 57 5 Hz f...

Page 20: ...ng the DJM2 Service pot 4 SER fully CCW Turn the ES345 low fire adjustment screw found under the valve cover near the wire terminals fully CCW Adjust DJM2 pot 8 MINSP until the combustion fan is turning 1250 RPM 10 RPM 20 8 Hz for 10 1 turndown 1195 RPM 5 RPM for 15 1 turndown 19 91 Hz Voltage to the ES valve should be 0 volts DC The low fire bypass adjustment on this valve is under the top cover ...

Page 21: ... These valves do not have high fire regulators High fire pressure is set up at the appliance regulator This series of valve has been replaced with the M520 620 series ES345D L This valve has a built in high fire regulator High Fire Set Up 1 Place a jumper across the DJM2 4 terminals SV and SR to force the control into a manual firing mode 2 Set manual firing pot 4 labelled SER located near the mid...

Page 22: ...d burners set pilot as per the following procedure Install a 10 000 ohm resistor in series with the flame rod circuit Connect a DC voltmeter across the resistor The reading will be in millivolts if your meter does not auto scale Connect a manometer to the pilot line Run the burner on main flame for a few minutes to have the burner plate warm Leave the pilot on but turn the main gas off You will ha...

Page 23: ...up for propane fuels for either the high turndown or the standard burner are similar to the above The only modification suggested is it may be desirable to increase the oxygen settings by 1 to 1 5 above those for natural gas High turndown burners operating on propane fuel will generally exhibit the following High Fire 3 5 O2 will appear yellow from behind the burner However if you could view it fr...

Page 24: ...ls GS and OS to the Hall Effect speed sensor if the DJM2 4 is powered The speed sensor allows a return signal to be measured on the YS and GS terminals If the fan is rotating above 500 RPM the signal can be read as either an AC or DC voltage and it will be about 5 volts This is because the fan is turning at a high rate of speed and your meter is averaging the reading If the DJM2 4 has 24 volt powe...

Page 25: ...refer to LED 1 for more information If the test is done only for voltage and it proves to be correct there could still be a problem as the DJM 42 has a refined sensing circuit This circuit is looking for the magnet to be split fairly evenly The duty cycle test gives a reasonable view of the magnets split between north and south poles Speed Sensor Values With the speed sensor disconnected from the ...

Page 26: ...next item Cold Discharge Temperature in Cold Weather At the time of installation and air balancing the air balancer in warmer weather often adjusts the unit s airflow If the unit is designed for Make up Air outside air being drawn into the building and heated as it passes through the unit then the quantity of air being delivered into the space will vary considerably as the outside air temperature ...

Page 27: ...any factors including duct layout this location may not represent an average duct temperature Most discharge temperature sensors can be relocated into the duct work to correct problems of temperature stratification etc Last but by no means least is the application of a BMS sensor in the discharge by a control contractor Engineered Air suggests that both our sensor and the BMS sensor should be loca...

Page 28: ...ools and the fan shuts off The DJM during this time has modulated to low fire There is not enough heat produced to remake the auto fan switch the DJM may continue to modulate at low fire depending on temperature conditions at the sensors Suggested resolution When C TRAC terminal K is powered at night the coil of a relay is powered The contacts of the relay are located between the DJM main gas feed...

Page 29: ...the pilot tube 9 Usually changing the pilot assembly will not have much of an affect on the pilot signal if both assemblies are in good condition and installed correctly 10 Ensure the pilot assembly gasket is tightly installed to stop air leakage into the pilot area 11 Standard round burner only If the burner plate is not centered in the hole it may allow too much of a gap over the top of the burn...

Page 30: ... high turndown burner On the standard burner it is possible to get small amount of rumble whenever a burner is lit after being cold for an extended period of time After the first light it settles down This is because the warm burner has a greater back pressure than the cold one thus a lower air velocity occurs when the burner plate is warm One of the more common causes on the regular burners round...

Page 31: ... Not Respond to Signal to Open Items that may contribute to this are Ice in valve in bottom or above diaphragm Burnt out coil Sticky substance or debris in valve Modulating Valve Sticks When Returning to Low Fire If the modulating valve sticks partly open as the combustion fan slows down the combustion process will be very poor The products of combustion may smell badly or in rare instances even f...

Page 32: ...ure failure due to thermal stress or freezing Another source of excess condensation is when a unit designed with capacity to heat 100 outside air is operating with very little outside air therefore operating at a low fire or cycling This allows the cool flue gases from low fire to cool and condense in the chimney Burner Pulsing Backfiring An improper air fuel mixture usually causes this condition ...

Page 33: ...ntly turn off the manual valve on the pilot line Check to see if the fire has gone out If it has then the pilot solenoid is leaking and should be changed If there was no difference gently turn off the firing valve for the main manifold If this stops the fire this would prove the main solenoid blocking valve was leaking Replacement of Combustion Fan Motors Motors being used for combustion fan appli...

Page 34: ...n acceptable temperature control band 4 NOTE If the DJM2 is controlled by a C TRAC2 1 or Metasys then resistor R19 should be cut before installation If the DJM2 4 is being controlled by a BMS signal that cannot put out enough VA to drive the DJM2 4 resistor R19 should be cut If the DJM2 is controlled by a C TRAC Megatrac METASYS or other BMS device that is wired to terminals and then Set combustio...

Page 35: ...ct as described in the DJM2 manual section X Secondly if the above does not resolve the problem adjust the C TRAC COOLING DEADBAND Pot 3 to number value eleven Also access the C TRAC Pot eleven on the back of the C TRAC and set it to number 2 Thirdly if the above steps do not resolve the issue use an open sensor contact the factory for details Fourth if after doing the above and reasonable control...

Page 36: ...ater usage and water quality There are water level controls sensing minimum and maximum water levels in the water heater A buildup of moisture and or dirt on some portions of the sensor ceramics may allow the heat to operate without proper water levels This could result in damage to the heat exchanger SH tank When servicing these water level sensors should be confirmed as operating correctly at le...

Page 37: ...VER W LOCK RING VENT HOLE MUST BE PLUGGED IF VALVE IS TOP LOADED LOCATION BOTTOM SIDE FOR SECOND LOW FIRE ADJUSTMENT BYPASS WHITE PLASTIC DISK COVERING PLUNGER BLACK SIDE UP SPRING ON TOP OF PLUNGER POWER DRAWS PLUNGER UP REVERSE ACTING POWERS CLOSED MR410 MR510 AND MR610 N O VALVE DJ 20 DJ 40 WITH A1010 AMPLIFIER DJ 60 WITH DJT MODULE PACKS XE AND RT WITH MAXITROL A1010 AMPLIFIER SET HIGH FIRE MA...

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