HomeRoast Digest


Topic: Voltage Question - IR2 (19 msgs / 454 lines)
1) From: Larry Williams
While roasting with the IR2 this morning on a outside GFI circuit 
outlet, I noticed the power cord close to the plug getting very warm - 
almost too hot to hold.  On my second batch during roasting I measured 
the outlet voltage with a digital meter.  It indicated 113.2 volts.  
After roasting the outlet measured 122.5 volts.  Can someone interpret 
what I am seeing.  OR is this the way IR2 prevents the roaster from 
incinerating the beans with too much heat?  Kind of like a built in 
extension cord.  I am planning to change the outlet, because the wires 
are connected using the "push-in" connector instead of the screws.  The 
outlets are 25 years old. 
Larry Williams
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2) From: Ira
At 09:36 AM 7/25/2008, you wrote:
<Snip>
After you change the outlet measure it again. If the cord stays cool 
and the voltage goes up, you found the problem.
Ira
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3) From: Bob Hazen
Yep.  I agree with Ira.  You're dissipating a fair amount of power in the 
outlet.  Could be the socket doesn't grip the plug very well or the inside 
connections are bad.
Regardless, get that outlet changed!  Don't use it again until it is 
replaced.  It is unsafe.
I'm inclined to re-write that in all caps, but I hope you get my point.
Bob

4) From: Rich
If the cord is getting hot its the cord, not the outlet.  Use a larger 
gauge cord.  That will be a LOWER gauge number.
Bob Hazen wrote:
<Snip>
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5) From: Ira
At 12:12 PM 7/25/2008, you wrote:
<Snip>
Copper is a great conductor of heat, if the outlet gets hot, the cord 
plugged into it gets hot also. Change the outlet to a good one and 
test again, if it still gets hot we'll talk about what else it might be.
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6) From: Bob Hazen
Larry originally said his cord is getting hot near the plug.  It's likely 
the outlet.
You're right, if it were getting hot the full length of the cord, it's 
probably undersized.
Bob

7) From: Allon Stern
On Jul 25, 2008, at 4:02 PM, Bob Hazen wrote:
<Snip>
On the other hand, if it gets hot right where the plug is attached to  
the cord, it could be that the copper strands in the cord are broken  
and frayed from years of (ab)use; that spot gets flexed a lot, and is  
a common failure point in cords. If this is the case, replace the cord.
-
allon
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8) From: raymanowen
This is where you can make use of your thermocouple meter. Tape the probe to
the wires entering the push connectors, one at a time. Try to orient the
thermocouple bead right against the wires, if possible, but make the same
contact with both the black or colored wire and the white wire.
Test the outlet for the GFCI function. If it works, there's no reason not to
just replace the wires under the screw terminals if the push in connectors
aren't welded to the wires. Could be, because 15% of the power is being lost
somewhere.
If you install a new GFCI outlet, also pull some new 12ga or preferably,
10ga wire. Bigger wires are always better, and 14ga wire is better used for
doorbells and night lights.
Cheers, Mabuhay -RayO, aka Opa!
On Fri, Jul 25, 2008 at 10:36 AM, Larry Williams
wrote:
<Snip>
-- 
"When the theme hits the bass, I dance the Jig!" - -Virgil Fox at the Mighty
Wichita (ex- NYC Paramount) WurliTzer- 1976
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9) From: Rich
The cord will always start to heat up next to the outlet.  Has to do 
with the available voltage per inch of cord.  It is the cord.  After you 
fix the cord problem you can check the outlet.
Bob Hazen wrote:
<Snip>
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10) From: Rich
If the gauge of the cord is less than the gauge of the conductors 
supplying the outlet then the cord will heat at that transition point. 
As the length of cable increases the voltage available decreases and the 
incremental power dissipation decreases.    Or, if the supply cable is 
14 ga. and you plug in a 16 ga. cord it will get hot at the plug, every 
time, new - used - or abused.  If the outlet is defective it will be 
very hot.  Unplug cord and place palm of hand flat on cover plate, you 
will know if it has a problem.
Allon Stern wrote:
<Snip>
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11) From: Dave Bush
Heat is generated when electric current encounters resistance, so look for the source of the resistance--not enough conductor. The outlet should be fine unless 1) it's connected with pushed-in wires (which tend to get loose and heat up) instead of screw terminals or 2) it's worn out and making poor contact with the plug. Either can cause an outlet to get hot. Assuming the cord is of sufficient wire gauge and is not getting warm except at the plug, then it could be the plug. It's possible the connection between the wires and the prongs in the plug is poor with inadequate copper and is heating up.
To isolate the problem, plug in another high wattage appliance directly into the outlet and see if the outlet gets hot. If the outlet gets hot then it's either worn out or the connections on the backside need to be improved. If nothing gets hot, then it's probably the plug on the original cord assuming the original cord doesn't get hot--just the plug. In that case, replace or repair the plug or cord.
It's also possible that there's more than one source of the heat (of the possibilities above) so keep that in mind if one improvement doesn't solve the problem.
Dave
On Friday, July 25, 2008, at 04:46PM, "Rich"  wrote:
<Snip>
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12) From: Bob Hazen
Where do you get this stuff?  You are wrong.  This is Ohms Law 101.  If the 
gauge of two series conductors are different, the heating >will not< be 
localized at the transition point.  Kirchoff's laws indicate the current is 
the same in both sections.  The smaller wire will have greater resistance. 
Dissipation is I^2*R.  The smaller wire along its full length will be warmer 
than the bigger wire.  I really don't think you're leaking electrons along 
the way.
If the connection to the socket is bad (read high resistance) it will get 
warm at that point.  Kirchoff's laws still apply.  You have the same current 
going through the high resistance and I^2*R is bigger, therefore the 
connection is hotter.
It could be, as you say, a bad connection to the plug or a loose connection 
between the plug and socket.  It's not unheard of to have fractures 
somewhere along the cord and heating at that point.
It's all about the increased resistance - somewhere.  Not the transition.
Bob

13) From: Morris Nelson
If something is hot, something is wrong. (duh) 
Cost to push the "test" button on the GFI outlet $0.
Cost to plug the cord into another outlet $0.
Cost to run roaster without cord $0. 
Cost to exchange the cord correctly rated $10-$30.
Cost to replace the outlet $200-$300.

14) From: raymanowen
" Cost to replace the outlet $200-$300."
R&R 6 screws, unless you also have to pull a missing ground wire.
Oh, boy- Is somebody taking applications? -ro
On Fri, Jul 25, 2008 at 6:36 PM, Morris Nelson wrote:
<Snip>
-- 
"When the theme hits the bass, I dance the Jig!" - -Virgil Fox at the Mighty
Wichita (ex- NYC Paramount) WurliTzer- 1976
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15) From: Rich
have you called the electrician lately?  You think the plumber is 
expensive....
raymanowen wrote:
<Snip>
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16) From: Larry Williams
Replaced the outlet.  The wires were corroded and had to be cleaned, and 
the GFI was defective, so I replaced it.  Roasted a couple of batches 
and the cord was warm along it's whole length, but not as hot as 
before.  Not enough to worry about in my opinion. 
Thanks all
Larry Williams
Rich wrote:
<Snip>
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17) From: Morris Nelson
You are quite fortunate that you found the corrosion, Larry.  It could have
taken the whole house.  Also, you might consider checking the other outlets
in your house for corrosion/problems.
Morris

18) From: Larry Williams
I have a few more outside outlets to check, and will check a few inside. 
Thanks
Larry
Morris Nelson wrote:
<Snip>
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19) From: raymanowen
"...the cord was warm along it's whole length..."
That's completely normal. A few cent's worth of copper, X (a hopefully large
production run) = Save a Few Bucks. Happens with toasters, too. A bread
toasting cycle is fairly short, so no great heat build up.
Engineers read the books and see that others have loaded that much current
in the small gauge wire- "We can do it too, assuming the cord will never be
coiled up."  Hence, the short lead wires on all the appliances, so they have
to be located a few inches from the outlet.
The ruse goes like this: "The power cord on this appliance is purposely
short, to avoid a trip hazard. [PferdeScheiße]  If you use an extension
cord, it must be large enough to handle the current." [We didn't, but you
must]
European standard uses 220v to save copper power wiring. Rather not risk
getting shocked on 220v ? Ain't nobody been shocked on 110v - it's more like
the 150v + sinusoidal peak Zap!
Cheers, Mabuhay -RayO, aka Opa!
Got Grinder? 208v 3Ø?
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