Grain Dryer Service
Frequently Asked Questions
- I am installing a VFD for the unloading system, is there anything I should know?
- When running hard conduit from the high voltage to the remote cabinet, why do I have to run two separate conduits?
- Why would the blower coupling be damaged after very little time running?
- What type of electrical wiring issues could I run across?
Performance and Operation
- Why is the dryer operating at a lower than expected capacity?
- Why is dryer capacity lower during colder temperatures?
- What is the proper method for cleaning my dryer?
- Why is the dryer not filling with wet grain properly?
- Why am I not generating enough heat in the plenum chamber?
- Why does my LP gas line frost up and what can I do?
- Why does the moisture sensor not read proper grain moisture content?
- Why won't my burner light?
- Why can I light a burner but not keep it running?
- Why does my burner run for only a little while before going out?
- Why can't I get metering rolls to turn?
- I cannot get the safety circuit to energize or any lights or relays to pull in, why?
- Motor will not start, (blower or auger) what should I do?
- The moisture control board is not outputting good voltage to control metering system, why?
- I cannot get the air pressure switch to make and hold the air pressure light on, what steps should I take?
- Leak in plumbing train, what do I do?
- What can I do about small buckling in screens in 10ft tower dryers?
1. I am installing a VFD for the unload system. Is there anything I should know?
The VFD (variable frequency drive) is a good method of protecting the motor and changing speeds of a motor. The VFD changes hertz from 5-72 or anywhere in-between. The more hertz applied the faster the motor runs in rpm’s. The VFD down side is that it emits noise and signal wiring can pick up noise and vary signals.
- Make sure all signal cables are grounded well on one end.
- Make sure wires for the low voltage and signal are not anywhere close to the VFD.
- The VFD motor output wires should not be close to the 120 VAC control wires.
2. When running hard conduit from the high voltage cabinet to the remote cabinet, why do I have to run two separate conduits?
- The signal , Ethernet, communication and thermocouple cables are all vulnerable to noise, induction and signal loss. The best way to protect this wiring from issues is to separate it from any voltage above 24 volt. The 120 volt AC control wiring should run in separate conduit from signal wiring for best results.
- Make certain the cables are all grounded on one end to reduce potential interference.
- The standard remote length is 20' because it represents the maximum run before the noise, induction and signal loss become a problem.
3. Why would the blower coupling be damaged after very little time running?
- If motor coupling (sure-flex sleeve) has gone bad or been damaged while running for a short time frame, then the motor shaft and fan shaft are not properly aligned. The alignment is what the flex sleeve will help with, but when alignment is to far out of tolerance then the coupling will become damaged.
- This could also be because flanges that hold coupling are too tight or too loose. The coupling needs to fit snuggly in place between 2 flanges.
- Incorrect size coupling and flanges were used for the application.
Once a coupling has become damaged, it cannot be re-used.
4. What type of electrical wiring issues could I run across?
Issue: If values on a device do not seem steady?
- Check spring block terminals to make sure wire is engaged in terminal block securely.
- Check to make sure that shielded ground is landed properly to ground.
Issue: If wire does not have proper continuity?
- Check to see if wire is landed in terminal block properly and not clipped onto insulation instead of wire.
- Check to make sure wire is in properly marked terminal for wire number. Wire number and terminal block number should always match.
Performance and Operation
1.Why is the dryer operating at a lower than expected capacity?
- Make sure dryer is completely full of grain.
- Make sure that dryer screens are clean both inside and outside.
- Make sure that heat is at proper values and gauges are reading correctly.
- Make sure that if you have internal floors they are all placed properly.
- Make sure that all columns are moving as the discharge is operating.
2. Why is dryer capacity lower during colder temperatures?
As temperatures reach freezing, dryer capacity is reduced because frozen grain must thaw before it is dried. This can take some time before the kernel is in a state to start to dry. This added time prolongs the process and as a result, reduces capacity.
3. What is the proper method for cleaning my dryer?
- The first method is by brushing the dryer clean. This works well if dryer surface area is not too large or if debris on dryer is fairly light to remove.
- The second method is high pressure water line. The pressure washer can be used to cover a fairly large surface area and will clean off heavier debris. The heavier debris would normally develop on the screens when drying high moisture corn.
- Both methods of cleaning can be done with the dryer full or empty. If dryers are full it is easier to clean with the fans running.
4. Why is the Dryer not filling with wet grain properly?
- The dryer fill switch, rotary or diaphragm type, will not close circuit and start the filling process.
- Check terminal 24 for 120 volts, this feeds switch power to operate.
- Check terminal 45 for 120 volts, this is output from switch to turn fill auger or leg ON.
- The safety circuit must be good for fill system to run, ready or power light ON.
- If fill light comes on and safety circuit drops out immediately, check switch for wire to ground, this is a dead short 120 volts to ground.
5. Why am I not generating enough heat in the plenum chamber?
- The LP or Natural gas fuel supply does not have enough supply to increase temperatures past a given point, contact the utility company.
- Modulating valves will not adjust temperature to give proper increase in chamber temperature. Remove bulb from heat and put into ice or a cool place and restart the burner. The burner should go to maximum output and trip off high limits if you do not control temperature with hand valve. If temperature does not go to maximum and stays where it was before exposing bulb to cold temperatures, then power element is bad and must be replaced.
- Proportional valve may not be opening to allow more fuel to burner. Proportional valve has a clear cover and slot cut into shaft. Actuator is orange Belimo valve and will rotate slot from shut position, slot is 90-degrees from pipe train. In the open position, slot is in line with pipe train. This is controlled by 0-10 DCV signal and 24 DCV to run motor, check Belimo for voltage. 1 to 2 is 24 DCV and 1 to 3 is 0-10 DCV at the Belimo actuator.
- Check gas pressure gauges for pressure while running burner, loss in pressure can result in a loss in chamber temperature. If gauges are not properly working they need to be replaced.
- If no pressure is shown on gauges, check solenoids for opening. 120 volts to a solenoid should open coil and diaphragm.
- If solenoids are opening and no pressure is indicated on the gages, check hand valves for open position and check LP strain filter to see if it is plugged.
- If burner is operating and flame looks small, check air inlets and/or burner orifice for obstructions. Maxon burner holes could be corroded and need to be opened up with drill bit.
6. Why does my LP gas line frost up and what can I do?
LP gas lines normally frost up because the liquid is filling the pipe and expanded to become vapor. This causes the pipe to become very cold and atmospheric vapor to condensate on pipes as frost.
- The most common problem is that the line has a restriction. This is where the frost will begin. The obstruction must be cleaned out of pipe to reduce frost.
- Strain filter being plugged will be a restriction, clean out filter in strainer.
- If a solenoid is only opening part way, take the valve apart and look for brown tar like substance that can be cleaned off with alcohol.
- Water in feed line will freeze line, add bottle of heat to line at tank valve connection
- Vaporizer might need to be pushed further into the flame as the vaporizer is not heating the LP to proper level and pipes are cold leaving vaporizer. Note: if the pipes are too hot leaving vaporizer (over 180 degrees) this can also damage the regulators.
7. Why does the moisture sensor not read proper grain moisture content?
- Wiring cable from moisture sensor to PLC unit may not have the shield grounded properly.
- VFD noise is creating a variable signal and wires from sensor need to be pulled out of wiring harness and run separately from voltage wires.
- Build-up on moisture sensor, clean off sensor.
- Sensor does not read proper temperature and cannot be adjusted to read proper temperature. The thermistor or thermocouple is damaged and sensor needs to be replaced.
1. Why won't my burner light?
- Air pressure was never achieved, adjust air pressure switch once fan is running.
- Check 120 volts with volt meter at terminal L1 on ignition board.
- Check spark plug or igniter for proper 3/16” to ¼” gap and porcelain is intact.
- Check that wire is in good shape with no breaks or insulation missing.
- Check 120 volts with volt meter at terminal V1 on ignition board, with wires pulled off of V1. Power is only on V1 for trial for ignition 7 to 10 seconds, identical time that gas valve light is ON.
- Check 120 volts with volt meter at terminal V1 on ignition board, with wires re- attached to V1. If no voltage is present then solenoid coil or gas valve light is bad and needs replacing.
- If power is at L1 to board and is never at V1 power leaving board, then board is bad and needs replacing.
- Power at L1 and V1, gas controls are all operating, and then check gas pressure gauge is working and changes with trial for ignition.
Why can I light a burner but not keep it running?
If you can light a burner and flame extinguishes after 7 to 10 seconds, then we are not sensing the flame is present.
- Make sure dryer is properly grounded to chassis of dryer.
- Check the flame sense probe & wire, to make sure it is not damaged.
- Check wire from S1 on ignition board to flame sense probe, replace it and do not try to repair wire.
- If a lot of moisture is present around flame sense probe, a rubber boot might need to be added to protect terminal ends.
- Re-adjust flame sense probe to ensure flame emersion.
3. Why does my burner run for only a little while before going out?
If you can light and maintain flame for longer period of time than 7 to 10 seconds, then the ignition board is sensing flame is present but then dropping out flame after a little time of running.
- Burner is not adjusted properly and must be adjusted until flame is mostly blue with small portion of orange.
- Pressure is too high and pulling away from burner face or ground rod.
- Chassis ground is not properly bonded and ground is intermittent.
- Modulating valve is not functioning properly and closing down too far. The modulating valve is designed to hold a given temperature or set point that can be adjusted. If the valve cannot hold a temperature then the power element on bottom of valve needs to be replaced.
- Check fuel supply for flow restrictions.
4. Why can't I get metering rolls to turn?
- Make sure auger is turned on and running.
- Check 120 volt power at incoming fuse on SCR Board.
- Check fuse on SCR Board.
- SCR Board output power on ARM+ and ARM- which is from 5-70 dc volts to DC 1/3hp motor.
- Use pipe wrench to move metering rolls if they are stuck or bound. To check metering roll remove chain and check to see if you can rotate metering sprockets by hand.
- Does SCR board have a control signal to wiper and field -, range is 0-12.5 dc volts.
5. I cannot get the safety circuit to energize or any lights or relays to pull in, why?
- Dryer does not have or has lost the neutral leg to control circuit
- Measure voltage from neutral to ground, if voltage is present check transformer to make sure neutral is bonded to ground. This is a floating neutral and we do not want this condition on this equipment.
- Relay or timer is not seated in holder or socket.
- Wire in safety circuit is not properly landed in terminal block.
- Check rear door, high limits and motor control resets
Motor will not start (blower or auger), what should I do?
- Disconnect is not energized.
- Manual motor protector breaker is not turned on.
- No power to stop and start switch.
- Check for proper voltage across lines and line to ground.
- Motor is bad, replace motor. Motor leads can be checked for continuity using voltage meter and trained electrician.
- Motor rotor has seized and motor is in locked rotor condition, this will generate very large amp draw and hold amp draw until breaker trips. Replace motor or have motor re-worked by motor shop.
7. The moisture control board is not outputting good voltage to control metering system, why?
- The board is 120 volt input to operate and dc voltage to control VFD or SCR for metering system. Check 120 volt input voltage to make sure it holds steady.
- Output voltage should remain from 0-12.5 DCV output to control discharge speed to device.
- Disconnect wires from output +/- and check for DC voltage, if input is good than output should be able to measure DC voltage as you adjust potentiometer. If you cannot read any voltage replace board.
- Adjust moisture control potentiometer and switch from plus to minus lights on and off. If you cannot adjust lights check to see if board is powering on each light as you turn pot.
- Can you adjust speed of motor? If you turn potentiometer the resistance should change from 0-5K, if it does not replace potentiometer.
- If lights will both come on at same time, turn potentiometer located on board labeled dead band. Rotate until one of the two lights goes out and other remains on.
- If speed of drive will not control and simply runs all the way open 100% or all the way closed to 0 speed, the potentiometer is most likely lost one lead and can be checked for continuity on each line, replace the potentiometer.
8. Cannot get air pressure switch to make and hold air pressure light on, what steps should I take?
The air pressure switch receives power on one side of terminal once fan contactor is energized and fan is running. The dryer must be full of grain to create required air pressure to satisfy switch.
- If light is not ON and fan is running, check to make sure that adjustment on switch is all that might be needed to energize air pressure light.
- If adjustment is not enough to energize switch, then check air pressure light by jumping terminal at air pressure switch. If light does not come on check wiring to switch and to light. Does light work when energized?
- Disconnect wires from switch and unscrew switch from tube. While fan is running can you feel air from chamber coming out of tube port? If not clean out tube and/or clean off filter inside chamber on opposite end of tube.
- If air is feeding into switch and air pressure switch is not making and one side of terminal is 120 volts, then make sure opening on switch has plug with small orifice to create low pressure side. Make sure nothing is internally wrong with diaphragm. Make sure diaphragm is not frozen solid. Replace air pressure switch.
9. Leak in plumbing train, what do I do?
- If leak is developed in flex hose it cannot be repaired and must be replaced immediately. Do not attempt to run with any leak in hose.
- If gas leak occurs then we need to tighten fitting or replace fittings to seal properly. All the plumbing assembled and installed at MC is done with Teflon tape and non-hardening Teflon paste.
10. What can I do about small buckling in screens in 10ft tower dryers?
- The screen that buckles creates a small gap between the screen and the channel ring. This normally develops because the screen material has shifted and hardware is bound end of hole or slot in screen and channel ring. Grain can leak through opening which makes this a functional and appearance issue.
- The proper tool required is a ratchet wrench, nothing battery or electric powered. Loosen the nuts on the ring channel where the buckle or indentation is. Do not remove nut from bolt. Loosen hardware on both sides of buckle. The hardware once loose will allow screen to shift and take normal shape back, hardware can then be re-tightened.