nsmheralds@netzero.net on fri 30 dec 05
Greetings and...er...reductions to y'all! Having solved a couple of the=
problems with my friend's kiln, I now have another.
Today, I attempted a bisque fire. I could only get one of the four sets=
of elements to activate no matter what I did. After noting that the te=
mp. climbed to 1000 F and remained there for 3 hours, I shut it off, unp=
lugged it and reopened the control box to follow a hunch. Sure enough, =
I had two of the leads to the bottom banks of elements crossed (I had re=
moved them to take the switch apart when I was troubleshooting last week=
.). After switching them, I put it all back together.
Then I plugged it back in and turned the temp control knobs to High. Al=
l the elements seemed to be humming normally...for about ten seconds. T=
hen all but the one that had been previously functioning just stopped. =
This was accompanied by some short, intermittent buzzing sounds coming f=
rom the wall socket. I have a couple of ideas (niether of which I'm qua=
lified or knowledgible enough to explore myself with any degree of accur=
acy or competency), but I'd like to know if anyone on the list has encou=
ntered this. I realize there are some on the list who advocate hiring p=
rofessiona electricians, but that does not appear to be an option at thi=
s time.
Here are a few details regarding what I understand about the wiring:
The kiln is designed to be hooked to a 4-wire circuit with optional equi=
pment ground. Her husband has it wired to a 3-wire 30-Amp circuit.
The UL plate says the kiln should run on 20 Amps, with 208 or 230 volts =
(Note that the manual says 30 Amps and 208 or 240 volts.).
It's a Skutt model 181, about 30 years old according to the guy to whom =
I talked on the phone last week, and doesn't have a timer (I omitted thi=
s detail in my previous post regarding this kiln.).
If y'all have any ideas or any more questions, please feel free to ask (=
or maybe to clobber me for being silly about something about which I've =
been blaringly silly).
Nathan Miller
Thistillium Pottery
Newberg, OR
=
William & Susan Schran User on fri 30 dec 05
On 12/30/05 1:10 AM, "nsmheralds@netzero.net"
wrote:
> Here are a few details regarding what I understand about the wiring:
> The kiln is designed to be hooked to a 4-wire circuit with optional equipment
> ground. Her husband has it wired to a 3-wire 30-Amp circuit.
> The UL plate says the kiln should run on 20 Amps, with 208 or 230 volts (Note
> that the manual says 30 Amps and 208 or 240 volts.).
I would suggest you first contact a tech at Skutt while sitting in front of
the kiln with the panel cover off and explain exactly where all the wiring
goes and what changes have been done.
I'm not an electrician, but the idea of changing a 4 wire to a 3 wire
without some additional internal wiring changes, does seem to invite
problems.
-- William "Bill" Schran
Fredericksburg, Virginia
wschran@cox.net
wschran@nvcc.edu
Carl Finch on fri 30 dec 05
At 10:10 PM 12/29/2005, nsmheralds@netzero.net wrote:
>Greetings and...er...reductions to y'all! Having solved a couple of the
>problems with my friend's kiln, I now have another.
>Today, I attempted a bisque fire. I could only get one of the four sets
>of elements to activate no matter what I did. After noting that the temp.
>climbed to 1000 F and remained there for 3 hours, I shut it off, unplugged
>it and reopened the control box to follow a hunch. Sure enough, I had two
>of the leads to the bottom banks of elements crossed (I had removed them
>to take the switch apart when I was troubleshooting last week.). After
>switching them, I put it all back together.
>Then I plugged it back in and turned the temp control knobs to High. All
>the elements seemed to be humming normally...for about ten seconds. Then
>all but the one that had been previously functioning just stopped. This
>was accompanied by some short, intermittent buzzing sounds coming from the
>wall socket. I have a couple of ideas (niether of which I'm qualified or
>knowledgible enough to explore myself with any degree of accuracy or
>competency), but I'd like to know if anyone on the list has encountered
>this. I realize there are some on the list who advocate hiring
>professiona electricians, but that does not appear to be an option at this
>time.
>Here are a few details regarding what I understand about the wiring:
>The kiln is designed to be hooked to a 4-wire circuit with optional
>equipment ground. Her husband has it wired to a 3-wire 30-Amp circuit.
>The UL plate says the kiln should run on 20 Amps, with 208 or 230 volts
>(Note that the manual says 30 Amps and 208 or 240 volts.).
>It's a Skutt model 181, about 30 years old according to the guy to whom I
>talked on the phone last week, and doesn't have a timer (I omitted this
>detail in my previous post regarding this kiln.).
Buzzing in the receptacle sounds like a bad connection. I would check for
discoloration or pitting in the plug, and loose wires on the back of the
receptacle (perhaps not easy to do because the wires are thick and
stiff). My 50-amp receptacle has embossed in it instructions to torque the
clamping screws to 28 inch-pounds--if I recall.
That Skutt model 181 does seem to be listed on their web site
, but you ought to get some advice from them over the
phone.
I'm not sure why (or how) hubby decided to use 3-wire rather than 4-wire,
but that sure sounds suspicious to me. 3-wire (generally referred to as
2-wire plus ground) is for straight 240v (sometimes referred to as
220v). 4-wire (again, 3-wire plus ground) is for supplying both 240v and
120v. In either case, the ground (bare or covered in green) is not a
conductor in the sense that the other wires are. Its only purpose is to
carry away the bad stuff in case of a malfunction--it is referred to as a
"safety ground."
Color code for "4-wire" is: red and black for hot, white for neutral, and
green or bare for ground. Between red and black there will be
240v. Between either red or black and white there will be 120v.
Color code for "3-wire" is: black for hot, white for neutral and
green/bare for ground. Between black and white there will be 120v.
Since your kiln is a "4-wire," that means that it expects BOTH 240v and
120v--probably for the reason described below by Clayart's kiln-electrics
paragon, Arnold Howard, a couple years ago:
=============from Clayart, 6/25/03=====================
From: Arnold Howard
Subject: Re: L&L J2927 wiring (3 and 4-wire systems)
To: CLAYART@LSV.CERAMICS.ORG
The 4-wire system was required in the earlier Paragon A-series kilns
because they used 4-way rotary switches. Around 1987, we converted to
infinite control switches. That type requires a 3-wire system.
The 4-way rotary switch that we used had 2 elements wired to each
switch. On LOW, both elements fired on 120 volts. On MEDIUM, only 1
element fired on 120 volts. On HIGH, both elements fired on 240 volts.
Since the kiln was actually 120/240 volt, it required the neutral
current-carrying wire. The 4th grounding wire was for safety.
Technically, our 4-wire kiln will operate on 3 wires. That is why
Francis Darby and the others working here at the time fought
electricians so often. It will operate, but it's not considered safe.
Our UL Listing requires a 4-wire circuit.
Electric kilns that use infinite switches need only 2 current-carrying
wires. The third is a grounding wire.
I hope this helps those who have older 4-wire kilns.
Sincerely,
Arnold Howard
Paragon Industries, L.P.
www.paragonweb.com
==================end======================
I would guess (!) that Arnold's "technically" statement (operating a 4-wire
kiln on 3) comes from the fact that neutral and ground are tied together at
some point, and thus the ground could be used as a neutral. For myself, I
wouldn't try it!
--Carl
in Medford, Oregon
| |
|
