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| Question: |
| What?s the best way to test a heater before installing it? |
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| Answer: |
A disconnected heater can be expected to work properly when installed if its resistance measures within ten percent of an easily calculated optimum level.
To calculate the heater?s resistance value, first solve for R using the formula R=VxV/(Wx1.065), where R equals ohms, V equals voltage and W equals wattage. Volts and watts should be stamped on the heater. The 1.065 factor accounts for the fact that the resistance of the nichrome element wire increases resistance by about 6.5 percent from room temperature to hot temperature.
Next, test the heater using an ohmmeter. Make sure at least one of the two lead wires is not connected to anything. Measure the resistance from one lead wire to the other lead wire.
If the resistance you measure is within 10 percent of the calculated value of R, the heater should be good, though it is possible to measure some resistance if part of the heater is good and part is bad. |
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| Question: |
| How can I test a heater without stopping production? |
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| Answer: |
During operation, a heater that?s working properly will draw current in amperes within ten percent of an easily calculated optimum level.
To check a heater on a running machine, you first need to figure the optimum level of current your heater should draw. Use the formula I=W/E, where I is the current in amperes, W is the wattage and E is the voltage.
You should find the watts and volts stamped on the heater. To find I, the current in amperes, use a clamp-on ammeter. For the meter to read correctly, you must measure the current in only one of the lead wires going to the heater. You must also make the measurement while the controller is calling for heat, because the temperature controller turns the heater off some of the time.
If the current you measure is within ten percent of the optimum performance value of I that you calculated, the heater is most likely good.
A bad heater may still draw current. For example, the inside of the heater may be made up of two parallel heaters. If one of the parallel heaters is bad, the current will be half the calculated amount. Depending on how the inside of the heater is constructed, it is possible to measure several different current values, indicating that part of the heater is bad and part is still working. |
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