Thread Number: 68545  /  Tag: Ranges, Stoves, Ovens
Hot plate woes, Pt. II
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Post# 912950   12/28/2016 at 22:37 (325 days old) by LordKenmore (The Laundry Room)        

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I posted about a hot plate I took out of service a while back after getting an electric shock.

 

Last week, someone dumped a box of mixed kitchen things upon me, including a Presto hot plate. Today, I thought I'd test it. I know, based on comments on my earlier thread that voltage checks may not be accurate with a typical multi tester, but I decided to check, anyway. Just to find that this one also has a voltage reading of up to 80 volts between metal burner frame and ground...

 

I am not amused. I might test this on a GFCI (as suggested before), but I'll have to find someone who has that newfangled technology. But it's a bit frustrating having this hotplate, upon which I'd pinned so many hopes, raise safety questions.

 

Interestingly, perhaps, I did the voltage check on my West Bend slow cooker hot plate, and found a reading of zero. Too bad that doesn't get hot enough to boil water...





Post# 913030 , Reply# 1   12/29/2016 at 15:25 (324 days old) by Artcurus (Odessa)        

Lordkenmore,

Post pics. As many as you can. Especially if you can get it apart.


Post# 913092 , Reply# 2   12/30/2016 at 02:25 (324 days old) by LordKenmore (The Laundry Room)        
Post pics.

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One photo for now...

 

The hotplate hasn't been cleaned up any. I guess with something like this there is that feeling "make sure it works before investing time!" I might see if I have the tools to open it up this weekend. It might give me something to do during the New Year's Parties I'm not invited to. [Sound of background sobbing.]


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Post# 913260 , Reply# 3   12/31/2016 at 04:11 (323 days old) by tolivac (greenville nc)        

If the hotplate is that bad---THROW IT OUT.At how cheap these are-just easier and cheaper to buy a new one.If you really want to do leakage tests from the cord prongs to the appliance case-a "Megger" is a good investment.Smeo are as low as $400.You might be able to find used Biddle Crank ones for less.The megger works much like a regular ohmmeter-it generates a higher voltage and reads in megaohms.Use them a lot at the transmitter site.Other appliance repairmen often have these.A regular ohmmeter isn't so good for this because the output voltage is too low to test the breakdown voltage of insulation.Folks that work with HV equipment have a megger as standard equipment.For higher voltage tests-you use a hipot tester.This is a calibrated,current limited variable HV power supply that can read leakage currents.You typically use it to read from a motor or transformer lead to the units case.We also use the hipot to test new tubes and vacuum capacitors.The hipot tester can also "cook" gas out of unused power tubes and vac caps.Just cook the device until the leakage current goes to its min values.

Post# 913637 , Reply# 4   1/2/2017 at 13:51 (320 days old) by kb0nes (Burnsville, MN)        

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I'd not be overly concerned with your measurement, all electrical devices leak to a degree and the high input impedance of the meter probably makes it look worse then it is.

If you want to try a different measurement that may tell you more try measuring the resistance from a metal part of the chassis to both terminals of the plug. As long as the resistance reading to the chassis is 120,000 ohms or higher then the maximum leakage current is only 1 milliamp. A GFI is generally set to trip at ~6 times that amount of leakage. I'd bet the resistance you measure will be well higher then 120k ohms.

Please report back with the resistance you measure if you take a second to do the test. Also are you using a digital or analog meter? Digital meters have much higher input impedance which means they load the circuit being measured less then an analog meter (generally this makes them superior) but in this case it makes the reading more likely to be spurious.


Post# 913669 , Reply# 5   1/2/2017 at 17:24 (320 days old) by LordKenmore (The Laundry Room)        

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I'll have to try that resistance check, Phil.

 

The meter is digital, and, if makes a difference, probably rock bottom. (It was given to me by someone who had an addiction to Harbor Freight, and i think he was giving these meters out right and left for a while...)

 

As I mentioned before, too, one limitation is the user (or more accurately, knowledge of...) I know enough to be dangerous. LOL 





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