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Checked all limit switches, t-stats, moisture sensor and element. All check out fine.
what am I missing?
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Did you check power to the unit.
The heating coil requires the full 240 volts while the control and motor run off half the line (120 volts).
Try flipping the breaker off/on slowly a couple times.
Sometimes you can loose half the line without actually tripping the breaker.
If this does nothing, check the voltage at the plug
L1 to L2 should be 240 volts
L1 to Neutral and L2 to Neutral, both should be 120 volts.
If OK
Unplug the unit and check the wires at the terminal strip in the machine to make sure none are loose or burned out
If OK
Check the power at the terminal strip.
Do this with the heater off and on.
[COLOR="Red"]Be careful as 240 volts is lethal !!![/COLOR] |
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i had done all what you advised except with the element unhooked.
Initially when i checked at terminal strip i had only one leg hot even though i had 240 with cord disconected. As soon as i hooked cord back up to strip one leg would disapear. After trying it a second time I had 240 across terminal strip but still only 120 at each side of element. Reading from one side of element to another with volt meter i had 0 volts. Reading each side to ground I had 120v.
I am an HVAC tech and this one is getting to me even.:confused:
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Rank: Member
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Originally Posted by: denman  Did you check power to the unit.
The heating coil requires the full 240 volts while the control and motor run off half the line (120 volts).
Try flipping the breaker off/on slowly a couple times.
Sometimes you can loose half the line without actually tripping the breaker.
If this does nothing, check the voltage at the plug
L1 to L2 should be 240 volts
L1 to Neutral and L2 to Neutral, both should be 120 volts.
If OK
Unplug the unit and check the wires at the terminal strip in the machine to make sure none are loose or burned out
If OK
Check the power at the terminal strip.
Do this with the heater off and on.
Be careful as 240 volts is lethal !!! would a defective coil that ohms out ok cause this condition?
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[COLOR="DarkRed"]would a defective coil that ohms out ok cause this condition?[/COLOR]
No.
The reason you saw 120 on both sides of the element when referenced to ground is that the element is not drawing any current so there is no voltage drop across it. It then acts the same as a normal piece of wire.
[COLOR="DarkRed"]
Reading from one side of element to another with volt meter i had 0 volts.[/COLOR]
Yes you would because you are reading the same 120 volt leg on both sides of the element.
What is the model number?
Did you do the measurements with the motor running or was it off but the timer was in a heat cycle position?
The reason I ask the above that on many units L2 goes through a set of timer contacts then through a thermal-cutoff, a hi-limit thermostat and the operating thermostat contacts to the heating coil. So even when the unit is off as long as you have the timer in a dry mode there is 120 when referenced to ground all along this circuit path.
When the motor starts it has a centrifugal switch that closes when the motor gets close to operating speed and it switches in L1 to the heating coil so you get 240 volts (L1 to L2) across the coil.
One thing to note is that Neutral/ground has nothing to do with the heat coil circuit.
That you did not have 240 and all of a sudden did would lead me towards a bad connection in the line cord, the terminal strip or the wall receptacle. May even be a bad breaker.
I have seen where you get a voltage but as soon as you put a load on it, it disappears. |
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