Was on a service call today and I need a little input from the smart people here. Situation:Electric range was giving lady a shock when she touched the pot on the stovetop. Measured 40 VAC from the burner surface to the frame. This is a 3 wire setup, with the ground and neutral bonded at the stove. The feed is from 120Y/208.
Could there be any current coming back on the neutral from the elements? I checked the elements, nothing rang out to ground. And it only did it on the 2 larger burners. It also had a digital clock/timer in it. Could it somehow have cuased current to flow on the nuetral and thus through the frame?
The root cause is probably a bad element but that should be caught by the grounding. I had a problem in my house with this that traced back to a bad ground clamp on the grounding electrode. The whole house was "hot to ground" and the place it showed up was standing on the terazzo floor barefooted, touching the stove. A real morning "waker upper". The fact that the burner is hot to the stove frame seems to indicate this is a more localized failure. The real answer might be as simple as throwing away the bad element. Those burner pans sitting on the enamaled stove surface are not really a grounding path.
[This message has been edited by gfretwell (edited 11-01-2006).]
#71573 - 11/01/0610:22 PMRe: electric range question
If it were a 3w set up where the neutral and EGC share the same conductor I would confirm the integrity of that wire back to the panel. If any the connections this conductor are compromised and 120v loads that are L-N can provided the opportunity for current to pass through a person who is touching the appliance and a grounded item at the same time instead to that current returning by way of that neutral/EGC conductor. If this is the failure then it substantiates why a separate neutral and EGC are superior.
#71574 - 11/02/0603:42 AMRe: electric range question
My 2c worth, I am assuming that you are talking about electric elements not gas burners?. To my way of thinking, the outside of the elements should be at ground potential, hence there should be no shock hazard. What is going on if there is 40V with respect to ground?. What did you test this with?.
#71575 - 11/02/0605:27 AMRe: electric range question
Are these plug in elements ? If so the scraping earth may be corroded and not making a low resistance contact to keep the outer element casing at earth potential. If an element is on the way out, the internal resistance wire may be touching somewhere to the outer casing. Sometimes that is very visible as a hotspot which is a lot brighter light yellow orange than the rest of the elements while on full power. When the earth is high resistance there may be a certain amount of leakage which may cause part of the power to leak through the casing to earth and a higher current will be drawn from the supply untill the element burns out, and will cause a rise in potential of the actual element casing.
edited for typo's RF.
[This message has been edited by RODALCO (edited 11-02-2006).]
The product of rotation, excitation and flux produces electricty.
#71576 - 11/02/0612:46 PMRe: electric range question
Burners in electric ranges and ovens run at 208 or 240 volts. The only need for a neutral at all is for the 120 volt accessories, such as clocks, lights and timers. My guess would be that the neutral is open or has a fault so the neutral isn't able to provide a return path from one or all of the 120 volt accessories. Does the clock and light work properly?
I am concerned that you mentioned 120/208 since this would indicate a three-phase service. Is this in a multi-tenant building? If so, the panel in this unit would effectively be a sub panel. In this case, there should be a fourth wire for the ground connection to the range.
"But the guy at Home Depot said it would work."
#71577 - 11/02/0602:52 PMRe: electric range question
Uh, I guess I should have paid closer attention to the original post "from the BURNER to the top". I was in the mindset the the top was energized and the measurement was being taken from it to perhaps the sink plumbing. That makes a big difference.
No doubt, the burner(s) has failed. Most appliances only switch one leg of the 208/240 feeding them, so a fault would certainly be capable of energizing the coil itself even if turned off.