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Vollrath convection oven not heating after power surge. Model COA 8005. Any suggestions?
The 2 Elements have 240v to them. Fans are running. Timer and thermostat status lights on.
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13 Replies
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Are you measuring the voltage at the element or on the contractor?
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Not sure of exact ohm reading but they check ok for continuity.
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Both
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If both elements ohm as 0 or near 0 up to about 10 ohms, and you have 240 volts at the elements, you have heat. Amp them and you should see current flow. The only way there could be no heat is a open element or no voltage. You wouldn’t have voltage at the elements if the contactor wasn’t working.
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I agree. Is it possible to have voltage but no current flow to the elements? I believe it is an electrical issue coming to the power outlet caused by the power surge.
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burtonmac wrote:
Is it possible to have voltage but no current flow to the elements?
Your question should more properly be written as “Is it possible to have voltage but no current flow THROUGH the elements?”
Answer: YES. If the elements are open or there’s an open wire or wire terminal connection meant to supply power to them.
So…as fixbear had said earlier.
There’s something amiss here. Since I’m not standing there looking over your shoulder to see exactly what you’re doing, could you please tell me where EXACTLY you’re placing each of the two meter leads to read voltage getting to the elements?
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From one leg of the element to ground 120v and other leg of the element to ground 120v.
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burtonmac wrote:
From one leg of the element to ground 120v and other leg of the element to ground 120v.
GROUND?
Ground is not part of the circuit which energizes those elements. Therefore, DON’T include it in your tests.
120?
In your original question you said you read 240v. Did you derive that 240v by adding the two 120s together from the readings you described above? If you did, then that’s an entirely incorrect method. For that matter, the two 120v readings you took (while IMPROPERLY referencing GROUND) is probably the same 120v line in both readings – and you have lost connection to the OTHER line somewhere – therefore, no heat.
To make proper voltage readings in a 240v circuit, connect your test leads between L1 and L2.
I’m outta time this morning to elaborate further. Sound like you need someone with more electrical experience to assist you in troubleshooting. This evening, I’ll share something with you to help you understand.
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That explains the confusion with having a element continuity and yet no heat. You should measure across the element legs, not to ground. The ground is just there for stay electrical protection, not anything to do with the operation of a machine. Measure across the element ends with a AC voltmeter set to a 0 to 300 volt scale for a true picture of the potential available. Now when you have zero volts, you can go back to the contactor and re-measure both the output of the contactor and the input. Phase to phase, not to ground or neutral ever. Your heat circuit does not use neutral. If you were troubleshooting a 120 volt control circuit, then you would use the neutral, but never ground.. IF you have good elements, You are going to find either a bad pole in the contactor or a open feed from the contactor to the element. Providing the contactor is working, which should be as you had voltage at the elements.
Please realize that the element is no more that a wire.and if you are testing to neutral or ground both ends will read the same voltage unless there is current flow if there is any open on one leg.
Grounds are on all machines for one reason. That is for life protection from stray currents and voltage. This includes Static, Induction, and shorts from wiring. They are never to be used as a current carrying device. One checks ground only to determine if it is safe to touch or work on something. Never for circuit testing. Today they are also used for elector-magnetic shielding for sensitive parts (radio,radar, micro waves).
Hope this helps you.
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