Technical FAQ's

Diedrich Manufacturing, Inc. IR/VR Series Troubleshooting Guide

ROASTER
IGNITION CONTROL/GAS REGULATOR

QUESTION #1:   Thermostat on, no spark, and no pilot gas?

Possible Causes:
a.   No main power
b.   Faulty transformer
c.   Faulty thermostat
d.   Faulty limit
e.   Faulty ignition control unit

SOLUTION:
With power on and thermostat set high, set your test meter to the 24-volt scale.   Probe terminals TH and TR. If you do not read 24 volts, the problem is not the ignition system. Perform normal system checks of main power, transformer, thermostat and the limit control. If you do read 24 volts at terminals TH and TR the problem is in the ignition system. Check for loose or defective wiring.   If the wiring is good then the ignition controller requires replacing.

QUESTION #2:   Have spark, no pilot gas flow?

Possible Causes:

SOLUTION:

  1. Set test meter to 24 volt scale.
  2. Be sure main gas valve (gas cock or selector arm) is turned on.
  3. With gas on and system sparking, probe terminals PV and TR. With 24 volts at these terminals and pilot gas does not flow, replace the gas valve.
  4. If you do not read 24 volts at terminals PV and MV/PV replace the ignition control unit.

QUESTION #3:   Have pilot gas, no spark?

Possible Causes
a.   Defective ignitor/sensor and/or its wiring
b .   Faulty ignition control unit

SOLUTION:

  1. Set test meter to ohm scale.
  2. Disconnect the wire from the IGN terminal on the ignition control unit.
  3. Touch one meter probe to the tip of the ignitor/sensor rod in the pilot. Touch the other probe to the quick-connect at the other end of the ignitor/sensor wire.
  4. If you have continuity from the tip of the ignitor/sensor rod to the connector and no spark, replace the ignition control unit.
  5. If you do not have continuity through the wire and the ignitor/sensor, check for loose wire connection in the wire. Repair as needed.
  6. Check to see if spark shorts to furnace through a cut in the ignitor wire.

QUESTION #4:   Have pilot flame; main burner will not turn on?

Possible Causes
a.   Faulty main valve coil in the gas valve.
b.   Faulty ignitor/sensor and/or its wiring.
c.   Ground wire not attached to furnace chassis.
d.   Flame rectification signal from pilot to ignition control unit weak.
e.   Faulty ignition control unit.

SOLUTION:

  1. Set test meter to 24 volt scale.
  2. With pilot flame on ignitor/sensor - probe terminals MV and MV/PV on the ignition control unit. If you read 24 volts here, but not at the gas valve, there is a loose wiring connection. Repair or replace as needed.
  3. If you read 24 volts at MV and MV/PV and the pilot flame is impinging on the ignitor/sensor rod, the problem may be:
           a.   Faulty ignitor/sensor and/or its wiring.
           b.   Faulty ignition control unit.
           c.   No flame rectification signal to ignition control.
  4. Set test meter to the ohm scale. Set thermostat low - system off.
  5. Check continuity through the green ground wire between the pilot mounting bracket and the ignition control unit. Repair or replace as needed.
  6. Check continuity through the green ground wire between the gas valve and the ignition control unit. Repair or replace as needed.
  7. Check ignitor/sensor for continuity, through the spark/sensor rod. Also, check ignitor/sensor ceramic for cracks. Repair or replace as needed.
  8. Reconnect all wires that were disconnected, including the ignitor/sensor wire and the ground wire.
  9. Set thermostat high. With the pilot burning and the flame on the ignitor/sensor rod, if the main burner does not turn on - replace the ignition control unit.

QUESTION #5:   Short cycling of main burner. Main burner turns off before the thermostat is satisfied?

Possible causes
a.   Draft condition pulls pilot flame away from ignitor/sensor rod.
b.   Incorrect thermostat anticipator setting.
c.   Pilot flame gets smaller when main burner comes on.
d.   Faulty limit control.

SOLUTION:

  1. Check the thermostat anticipator setting.   Set to .7 amp.   A lower setting will cause short-cycling.
  2. Set thermostat high, with main burner on, observe the pilot flame impingement on the ignitor/sensor rod. If the pilot flame is small and a draft condition pulls the flame away from the ignitor/sensor rod the burner will turn off then on again.
    • Adjust pilot flame higher or clean pilot oriface.
    • Bend the ignitor slightly
  3. If the flame impingement on the ignitor/sensor is stable and the system short-cycles, the the limit switch requires checking.
    • Set test meter to 110 volt scale.
    • When the system cycles off, probe the switch terminals of the limit switch.
    • If you read 110V or 24V across the switch terminals, then the limit switch is open and the limit switch requires replacing.
  4. A pilot flame that is set too high will also cause burner to short cycle.   Pilot flame lifts over ignitor/sensor.   Adjust the pilot flame to a lower setting.

QUESTION #6:   Gas Supply Conversion - Natural   to L.P. or vice-versus.

SOLUTION

  1. Turn off gas to roaster.
  2. Remove orifices from the rear of burners and replace with L.P. orifices.
  3. Remove the jet (bell shaped cap) from the gas tube connected to the pilot.
  4. Remove slotted cap located on the ignition module just above the on/off switch (pilot adj.)
  5. Remove adjusting screw and spring.
  6. Install new L.P. spring and adjust screw.
  7. Replace slotted cap.
  8. Note:   It is recommended only a certified gas technician perform the conversion.

ELECTRICAL VACUUM SENSOR

QUESTION #1:   Flame out during roast?

The vacuum sensor is the reason that the flame is turning itself off from the cooling bin position. The purpose of the vacuum sensor is to insure a sufficient airflow through the roasting drum for proper combustion characteristics of the gas burner.
     The vacuum sensor measures the airflow through the roasting drum and is the most sensitive vacuum area in the machine. When you move the air control from roasting position to the 50/50 position, you are reducing the airflow through the roasting drum, and by moving the air control from the 50/50 position to the cooling bin position, you are reducing the airflow even further.
     The vacuum sensor is intended to shut the gas off when airflows are physically being restricted by residue build-ups in the ducting, and even further reduced by moving the air control handle to the cooling bin position.
     The cap on the roof may also be a restrictive type cap which could also cause this problem.

SOLUTION
1. Adjust vacuum sensor using instructions below.

VACUUM SENSOR ADJUSTMENT FOR IR-SERIES ROASTERS

To adjust the vacuum sensor, remove the panel directly behind the cooling bin on the right hand side of the machine. You will find the vacuum sensor, a gold-colored disc with a small rectangular box with the name "Dwyer" on it. To remove the cover, loosen the screw facing in towards the center of the machine. You may need a mirror or feel along the backside of the vacuum sensor. Only loosen the screw and remove the cover.
     With the cover removed, you will be looking directly at a small gold adjustment screw that you will turn counter clockwise to decrease the sensitivity of the unit. Once the cover is removed, start the roaster and let the burners ignite. With the burners lit, go back to the vacuum sensor and turn the screw two (2) full rotations counter clockwise.
     Go back to the air control handle, place it in the cooling bin position. If the flame goes out, place the air control back in the 50/50 position and let the burners ignite. Go back to the vacuum sensor, turn the vacuum sensor two (2) more full rotations counter clockwise.
     Go back to the air control handle, place it in the cooling bin position. If the flame stays lit, you have completed the adjustment. Replace the cover by placing the tabs over the lid screw and snap the outside portion of the cover in place.
     If the burners fail to stay lit in the cooling bin position, repeat the above procedure until the burners stay lit in the cooling bin position. Always count the rotations of the screws so that you are always aware of your starting point. If more than eight (8) full turn are required, please call Diedrich Coffee Roasters at (208) 263-1276.
     Vacuum Sensor Adjustment Screw - turning clockwise decreases sensitivity. Turning counter clockwise increases sensitivity.

MECHANICAL

QUESTION #1:   Abnormal roaster vibration.

Possible causes
   a.   Sprocket and/or chain out of alignment.
   b.   Excess build up on impeller wheel.
   c.   Bad bearing in motor.
   d.   Loose motor mounts.

SOLUTION:
   1.   With a level, make sure both sprockets are in line vertically.
   2.   Remove and clean impeller and housing.
   3.   Repair or replace damaged motor.
   4.   Check all motor mounts and tighten if needed.

QUESTION #2:   Squeaky or grinding bearings.

Possible Causes
   a.   Bearings require lubricating
   b.   Bearings require replacing

SOLUTION:
   1.   Lubricate the bearings with food grade grease
   2.   Replace the bearings.

QUESTION #3:   DRUM ADJUSTMENT PROCEDURES (Prior to 1996)

SOLUTION:

    1. To adjust end gaps for the roasting drum, start off by removing the brass front cover from the machine. Begin by removing the six (6) screws on the stainless steel cover, and remove the cover. This is most easily accomplished by slightly twisting the upper tabs on either side of the hopper, both in the clockwise or the counter clockwise rotation to create more clearance between the stainless cover and the loading hopper.
    2. Next, remove the three (3) screws that hold the stainless steel chute in place and then remove the four (4) brass bolts holding the brass in place.
    3. When re-assembling the front cover, the brass bolts only need to be finger-tight, as the insulation below the mantle in compressible and tightening the bolts with a wrench and torqueing them will crush the insulation.
    4. Now you are ready to adjust the roasting drum end gaps.
    5. Start by loosening the two (2) set screws on the front bearing as well as the two (2) set screws on the rear bearing. Establish a 1/8" to 3/32" gap between the back plate and the roasting drum by slightly tapping on the drum shaft with a hammer and a wooden block to prevent marring the drum shaft.
    6. Loosen the two (2) bolts holding the front plate to the roaster frame. This requires a 7/16" wrench.
    7. Using two (2) - ¾" wrenches, loosen the inner jam nut on the four (4) spreader bars, them either turn in the outer bolts to decrease the front gap so it is also 3/32" or loosen turning counter clockwise the four (4) outer bolts to increase the front gap. Always turn the adjustment bolts evenly to keep the front plate parallel with the roasting drum surface. Now, tighten the jam nuts and re-measure the gaps. The drum may have to be re-set either forward or backward to even out the end gaps. Check all measurements, and if they are all consistent and accurate, tighten down the jam nuts thoroughly, tighten down the setscrews on the front and rear bearings and reverse removal procedures to install front cover.

QUESTION:   DRUM ADJUSTMENT PROCEDURES (1996 to Present)

SOLUTION

CLEANING

See your operational manual or contact Diedrich Tech Support   

AFTERBURNER

ELECTRICAL

QUESTION:   (S.Err) Error message on A/B temperature control.

Possible causes:
•  Bad thermal couple connection.
•  Bad thermal couple wire.
•  Bad thermal couple probe.

SOLUTION:

QUESTION:   Temperature on A/B does not change.

Possible causes
   •  Bad temperature controller.
   •  Bad thermal couple-probe.
   •  Bad thermal couple wire.

SOLUTION:  

GAS

QUESTION:   Afterburner will not get up to temp.

Possible causes:

SOLUTION: