Lexxy on fri 30 nov 01
I really don't know where else to turn and the folks at Skutt say there is
nothing more they can do.
Is there anyone at all out there on this list with any ideas please help
me...here are the facts:
Kiln is 8 yr old KM1018 with the control box and no more than 60 firings.
[I've had it since new...just got rolling again a few months ago].
Replaced thermocouple [it crumbled], no problem, had 3 good firings.
Then when the kiln would not complete a firing I called Skutt and per their
recommendation I tested the elements with a ramp/hold cycle to 2000º and
they all looked fine and got there in about 2 hours. Skutt said it sounded
like the elements were fine.
Then it would cut off, first at 80% to complete ^6 firing, then at about
1200º, then at about 500+º it tripped the circuit breaker. I turned the CB
back to try again and the control box exploded...a short and big black mark
between #3 and #4 wire connections to the bar.
It's a 50 amp breaker and 6ga wire was used, CB box is only 6' from the kiln
receptacle and it's a 200 amp box .[this is the 3rd house I have done my own
wiring for kiln].
Skutt send new set of wires and new bar...so I replaced damaged wires
carefully where the are secured to elements and the ones that go from the
bar to the relays, etc. Then I found that the short had blown both relays
and the whole control box.
Ordered and replaced [$300 worth] including both relays and whole new
controler with keypad. Got 2 good firings but they took 14 hours at slow
speed where they used to take about 12.
NOW... today... it trips the breaker again at about 1200º + ...there is no
error message when the circuit is tripped...I guess. [It was fired in open
garage with fan on a cool night, with few other circuits drawing ...heat
wasn't even on. And there was no wind or branches on the service line to
cause a brown out].
There is nobody where I live who repairs kilns. I'd have to take it 150
miles away.
[Husband offered to buy me a new kiln but that's ridiculous...guess he is
real tired of the whole episode.]
I was going to check the elements again before writing to the list, but I'm
SOOO afraid to turn it on and have it blow away all that new expensive stuff
again. This is what happened just before all the fire and smoke happened
before.
I am tormented... wondering what it could be. I thought that surely there
is someone here on the list who has years of experience with electric kilns
and has, at least, some ideas for me to check into. I would appreciate any
help at all.
Lynn/Lexxey[on internet]/Alexis [pick one!]
Please check out my website at: http://www.flummoxed.org/lexxey/index.htm
Imzadi D. on fri 30 nov 01
have an electrician check the circuit box and all the wiring GOING to the
kiln. If you keep changing all the kiln wiring, then the problem may have
developed at the other end of the wiring. Have they done roadwork on your
block recently? The problem may be coming from the street.
Imzadi
scott lykens on sat 1 dec 01
It sounds like a lot more juice is coming into that kiln than we think. Kiln
componenets burning up wouldnt be a lack of power, rather too much, Have you
measured your juice comming into and out of the breakers. Maybe your not
running a constant 240. Ive heard of folks getting 260 -280 by accident into
there 240 box. If its a good unit, it will hold up nicely for a spell, but
the breaker itself will end up kicking at maximum amp draw and the kiln
components toast.
I had access to a kiln 240V@48A 1Ph. Started with a 50A breaker, which blew
when the system was under a low load, actually it would trip if no other
kilns were on. With one other kiln on, it would only trip after a few hrs
on high, with 2 other kilns on it wouldnt trip.
tried a 60A, problem continued, a70 A , problem continued, starting lookin
around with a volt meter, juice was accelerating through the main system
breaker, One of the two 100A breakers was fairly new, but ill crafted, it
has been slightly damaged but frozen open, and the thing was creating an
increase in the variance of voltage, in addition to the variance from the
company, turned out that after 9pm the company was pushing out extra
voltage into our area that was ordinarilly in use the rest of the day, and
since we never had decided to work on kilns at 10pm at night, we never had
noticed, we had checked during other times of the day, but always got very
decent voltage from the electric company. until we checked at bedtime
just a hunch, but im thinkin its either the electric company or your 200 amp
service that is to blame. It sounds like you may have ruled out your
service, Maybe you should 3 wire with your 50 amp breaker. might slow down
the firing but it also might prevent components from blowing up.
>It's a 50 amp breaker and 6ga wire was used, CB box is only 6' from the
>kiln
>receptacle and it's a 200 amp box .[this is the 3rd house I have done my
>own
>wiring for kiln].
>
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william schran on sat 1 dec 01
>If the circuit breaker trips, then 9 times out of 10, you have a
>short somewhere. Might have a connection that shorts only when
>things heat up and there is expansion - just a guess.
Bill
>
>______________________________________________________________________________
>Send postings to clayart@lsv.ceramics.org
>
>You may look at the archives for the list or change your subscription
>settings from http://www.ceramics.org/clayart/
>
>Moderator of the list is Mel Jacobson who may be reached at
>melpots@pclink.com.
FireRight/Warner Instruments on sat 1 dec 01
Lynn ~
Electric circuits really aren't that mysterious. In our experience,
most of the symptoms and damage of the type you mention results from loose
connections.
Loose connections cause voltage drops which, in turn, cause power
dissipation at that point. The terminal therefore heats up, which sets up a
pattern of expansion and contraction, by virtue of which the connection
becomes progressively more loose and troublesome. In the end, the area often
becomes red hot, damaging insulation, terminal components, and so on.
Insulation may melt, permitting wiring to short together, or to ground,
resulting in a catastrophic failure. High current circuits, such as those
used for large kilns, are particularly susceptible to this sort of thing.
In the case of circuit breakers, these devices are in part
temperature sensitive. Loose connections at their terminals, or sometimes
the clip terminals where they clip to the bus bars in the service box,
effectively reduces their current handling capacity. Your 60-amp breaker
therefore turns into a 30-amp breaker, and you're plagued by a bunch of
nuisance trips even thought there really nothing wrong beyond the breaker
itself.
A long time ago, when I was a fledgling "Field Service Engineer" for
test chambers, an old Master Electrician taught me that a good maintenance
practice is to regularly inspect such wiring for signs of problems. Remove
power from the equipment, then using the biggest screwdriver you can find,
make sure all connections are as tight as you can possibly make them. If you
find terminals or wiring that have already been damaged from over-heating
... which usually take on a dull color, or may even have become corroded ...
clean them up, if possible, else replace the damaged section of the wiring
or the damaged parts.
When everything is clean and bright and tight, try again.
-=gw=-
----- Original Message -----
From: "scott lykens"
To:
Sent: Saturday, December 01, 2001 3:56 PM
Subject: Re: Skutt kiln mystery/please help!
> It sounds like a lot more juice is coming into that kiln than we think.
Kiln
> componenets burning up wouldnt be a lack of power, rather too much, Have
you
> measured your juice comming into and out of the breakers. Maybe your not
> running a constant 240. Ive heard of folks getting 260 -280 by accident
into
> there 240 box. If its a good unit, it will hold up nicely for a spell,
but
> the breaker itself will end up kicking at maximum amp draw and the kiln
> components toast.
>
> I had access to a kiln 240V@48A 1Ph. Started with a 50A breaker, which
blew
> when the system was under a low load, actually it would trip if no other
> kilns were on. With one other kiln on, it would only trip after a few hrs
> on high, with 2 other kilns on it wouldnt trip.
>
> tried a 60A, problem continued, a70 A , problem continued, starting
lookin
> around with a volt meter, juice was accelerating through the main system
> breaker, One of the two 100A breakers was fairly new, but ill crafted, it
> has been slightly damaged but frozen open, and the thing was creating an
> increase in the variance of voltage, in addition to the variance from the
> company, turned out that after 9pm the company was pushing out extra
> voltage into our area that was ordinarilly in use the rest of the day,
and
> since we never had decided to work on kilns at 10pm at night, we never had
> noticed, we had checked during other times of the day, but always got very
> decent voltage from the electric company. until we checked at bedtime
>
> just a hunch, but im thinkin its either the electric company or your 200
amp
> service that is to blame. It sounds like you may have ruled out your
> service, Maybe you should 3 wire with your 50 amp breaker. might slow
down
> the firing but it also might prevent components from blowing up.
>
> >It's a 50 amp breaker and 6ga wire was used, CB box is only 6' from the
> >kiln
> >receptacle and it's a 200 amp box .[this is the 3rd house I have done my
> >own
> >wiring for kiln].
> >
>
>
> _________________________________________________________________
> Get your FREE download of MSN Explorer at http://explorer.msn.com/intl.asp
>
>
____________________________________________________________________________
__
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your subscription
> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at
melpots@pclink.com.
>
Ceramic Design Group on sun 2 dec 01
>
> Loose connections cause voltage drops which, in turn, cause power
> dissipation at that point. The terminal therefore heats up, which sets up a
> pattern of expansion and contraction, by virtue of which the connection
> becomes progressively more loose and troublesome. In the end, the area often
> becomes red hot, damaging insulation, terminal components, and so on.
> Insulation may melt, permitting wiring to short together, or to ground,
> resulting in a catastrophic failure. High current circuits, such as those
> used for large kilns, are particularly susceptible to this sort of thing.
To add to this excellent post, one of the real "bad boys" in electrical
connections in kilns are the insulated twist type connectors wherein two
wires are twisted together and further twisted as this insulated cap
tightens.
We have replaced all these types of connections with properly rated split
bolt connectors. These devices hold the wires together firmly and do not
become loose. As these connectors are not insulated, just make sure that
they don't come into contact with anything. We use these connectors between
the elements and the power supply wires.
Jonathan
--
Jonathan Kaplan
CERAMIC DESIGN GROUP
PO Box 775112
Steamboat Springs, CO 80577
(970) 879-9139
info@ceramicdesigngroup.net
www.ceramicdesigngroup.net
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