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The safety of your dryer is in the hands of the safety circuit. These are a series of components that are tied together. If one fails, the system will shutdown insuring the safety of your grain dryer.
The contacts for incoming hot and neutral are found in the High Voltage cabinet.
The 120 volt input power to the dryer circuit for dryer controls comes from the bottom side of the transformer and runs to the top of the 8 amp mini-breaker. This breaker should be turned off and the voltage should be checked before turning the mini-breaker on. If the voltage reads anything outside of 125-volts, the supply voltage needs to be checked before powering on the mini-breaker.
Next to the mini breaker is a neutral block, which feeds all neutrals throughout the entire dryer. This neutral is connected to the neutral from the secondary side of the transformer that is standard equipment.
The incoming neutral line is connected to TB5 (white wire) and the hot line is on TB33 (after circuit breaker). The incoming 120-volt supply is an 8 amp mini-breaker.
The Safety Circuit can be viewed on page 4 and 5 of the electrical schematics. Page 4 is the Dryer Control or Fault Control portion of the Safety Circuit while page 5 of the electrical schematics contains the Dryer Safety, or Human Safety portion of the Safety Circuit. Components associated with the Dryer Control, or Fault Control portion of the Safety Circuit include the Fan Motor Overloads, High Limit Switches Linear Limits (if equipped) and Gas Pressure Switches for export model dryers. The components associated with the Dryer Safety, or Human Safety portion of the Safety Circuit are the E-Stops, Safety Relay and Plenum Door Switches for export dryers.
There are two ways to troubleshoot the Safety Circuit. One is through the Safety Circuit page of the Pinnacle 20|20 control while the other involves use of a voltmeter.
The first part of the safety circuit is the Dryer Control or Fault Control portion of the Safety Circuit. Refer to page 4 of the electrical schematics to see this portion of the safety circuit that matches exactly to your particular dryer.
The second part of the safety circuit will help diagnose a dryer shut down. This is the Dryer Safety or Human Safety portion of the Safety Circuit. See page 5 of the electrical schematics to see this portion of the safety circuit that matches exactly to your particular dryer.
This section will help with diagnosing in cases of a shut down. Common situations are explained with resolution(s) to get the dryer back to operation.
The safety circuit can be diagnosed by using a voltmeter to determine which component(s) is keeping the safety circuit from closing. Below will guide you in checking the following components, if equipped: Fan protectors, high limits, linear limits, high gas pressure switches, and plenum door switches.
The Safety Circuit can also be diagnosed by using a DC voltmeter and the dryer schematic. Using the schematic as a guide, use the voltmeter to look for 24 vdc at terminals in the Low Voltage Cabinet. Be sure the Voltmeter is first set to read DC Voltage which is depicted with a straight line next to the V as opposed to a wavy line which depicts AC voltage. Take the black lead of the Voltmeter and place it in Terminal 320 (TB320). Next, move the red lead of the voltmeter to the first terminal of the Safety Circuit (TB341), followed in order by TB401 as shown below until 24 Volts no longer appears and 0 Volts measures on the Voltmeter instead.
TB341 Beginning of the safety circuit after circuit breaker #341
TB401 Fan protector #1
TB402 Fan protector #2 (if equipped)
TB403 Fan protector #3 (if equipped)
TB404 Fan protector #4 (if equipped)
TB405 Fan protector #5 (if equipped)
TB406 Fan protector #6 (if equipped)
TB407 Fan protector #7 (if equipped)
TB408Fan protector #8 (if equipped)
The dryer will only have the number of fan protector terminals as the dryer has fans
TB421 High limit #1
TB422 High limit #2 (if equipped)
TB423 High limit #3 (if equipped)
TB424 High limit #4 (if equipped)
TB425 High limit #5 (if equipped)
TB426 High limit #6 (if equipped)
TB427 High limit #7 (if equipped)
TB428 High limit #8 (if equipped)
The dryer will only have the number of high limits as the dryer has burners.
TB431 Linear Limit #1 (if equipped)
TB432 Linear Limit #2 (if equipped)
TB433 Linear Limit #3 (if equipped)
TB434 Linear Limit #4 (if equipped)
TB435 Linear Limit #5 (if equipped)
TB436 Linear Limit #6 (if equipped)
If the dryer is an export model dryer, the following items will be included in the Safety Circuit.
TB451 High gas pressure switch #1
TB452 High gas pressure switch #2
TB453 High gas pressure switch #3
TB454 High gas pressure switch #4
TB455 High gas pressure switch #5
TB456 High gas pressure switch #6
TB457 High gas pressure switch #7
TB458 High gas pressure switch #8
The dryer will only have the number of high gas pressure switches as they dryer has burners. If there is 24 vdc at terminal #460, the safety circuit is complete.
Although the following items are not in series with the previously mentioned items, tripping any of these items will disengage the safety circuit and produce a red warning screen.
If the dryer is an export model, the following items, if tripped will disengage the safety circuit.
TB491 Plenum door #1 safety switch
TB492 Plenum door #2 safety switch
TB493 Plenum door #3 safety switch
TB494 Plenum door #4 safety switch
TB495 Plenum door #5 safety switch
TB496 Plenum door #6 safety switch
TB497 Plenum door #7 safety switch
TB498 Plenum door #8 safety switch
Before diagnosing the Safety Circuit, it is recommended to have a good understanding of the Pinnacle 20|20 Control.
The Pinnacle 20|20 Control features a tab on the home page titled Troubleshooting. Pressing this tab populates different options. One of these options is the Safety Circuit tab. Pressing the Safety Circuit tab will bring up a page that visually illustrates the Safety Circuit and all associated components. To troubleshoot the disruption of the Safety Circuit, look for the component on the page that has a grayed out globe next to it as opposed to a green globe. Green globes indicate that the component and that particular part of the Safety Circuit is good. A grayed out globe indicates that the break in the Safety Circuit is associated with that particular component.
One thing to note is that the High Limits and Motor Overloads are wired in series respectively. Meaning, if one of the High Limits or Motor Overloads are tripped, all the High Limits or Motor Overloads proceeding the tripped one will appear on the Safety Circuit screen tripped as well. So the first High Limit or Motor Overload that appears with the grayed out globe should be addressed first as it is very likely that once addressed, all that follow may be good as well.
For more information on diagnosing the Safety Circuit via the HMI, refer to the documentation on the Pinnacle 20|20 control system.
Emergency Stops, also known as "E-Stops" come installed throughout the dryer. There may also be “Customer E-Stop”, installed by other equipped that is tied into the dryer, that if tripped, will disengage the safety circuit. To check, visually inspect if any of these red E-Stop buttons are depressed:
Remote cabinet
Low voltage cabinet
High voltage cabinet
Customer E-Stop (Optional, provided by customer)
Customer connections are for remote equipment and are used to interface the grain dryer with fill and takeaway equipment. The grain dryer does not supply power for these interfaces. An auxiliary power source should be used to power customer equipment.
F1-F2 = Fill equipment status
F3-F4 = Fill 2 dry contacts
F5-F6 = Fill 1 dry contacts
F1 and F2 is a signal to the PLC confirming that customer fill equipment is not in a fault condition and can be started.
F3 and F4 are a dry set of normally open contacts that close when the dryer fill cycle begins. When this closes (when the call for grain happens), the dryer will start all the customer’s equipment that is associated with Fill 2. It is the last of the fill equipment to stop.
F5 and F6 are a dry set of normally open contacts that close when the dryer fill cycle begins. When this closes (after the delay following the call for grain expires), the dryer will start all the customer’s equipment that is associated with Fill 1. Fill 1 equipment will stop after the call for grain but before fill 2 equipment stops.
T1-T2 = Takeaway equipment status
T3-T4 = Takeaway 2 dry contacts
T5-T6 = Takeaway 1 dry contacts
T1 and T2 is a signal to the PLC confirming that customer takeaway equipment is not in a fault condition and can be started.
T3 and T4 are a dry set of normally open contacts that close when the dryer Takeaway START button is pressed. This starts all customer’s equipment associated with Takeaway 2 immediately after the button is pressed. Equipment tied to this signal will stop after the Takeaway STOP button is pressed and the Takeaway 2 Stop Delay has elapsed.
T5 and T6 are a dry set of normally open contacts that close when the dryer Takeaway START button is pressed and the Takeaway 1 Start Delay has elapsed. This starts all customer’s equipment associated with Takeaway 1. Equipment tied to this signal will stop immediately after the Takeaway STOP button is pressed.
E1-E2 = Customer E-Stop status
E3-E4 = Safety Relay Circuit 1
E5-E6 = Safety Relay Circuit 2
E1 and E2 is a signal to the PLC confirming that all customer equipment included in the safety circuit are satisfied
E3 and E4 breaks the 24V signal and initiates an emergency shutdown of the dryer.
E5 and E6 breaks the 24V signal and initiates an emergency shutdown of the dryer.
Breaking either E3/E4 or E5/E6 will result in the same emergency shutdown of the dryer
Listed below are common issues that may occur while operating your Mathews Company grain dryer along with suggestions on what to do.