First firing of used kiln

Ok, first question....how long should it ordinarily take an electric kiln to
fire to cone 06? I think I was close when it cut off. It was so late that I
just thought it was finished and went on to bed. This morning I realized it had
thrown the breaker! CAN YOU HEAR ME CUSSING? This kiln says it's 45 amps, my
wiring is for 50 amps and it wasn't even turned up all the way. What
happened???
Gaye, furstrated in San Antonio

On 17 Aug 2003 15:02:11 GMT, (GaSeku) wrote:

Ok, first question....how long should it ordinarily take an electric kiln to
fire to cone 06? I think I was close when it cut off. It was so late that I
just thought it was finished and went on to bed. This morning I realized it had
thrown the breaker! CAN YOU HEAR ME CUSSING? This kiln says it's 45 amps, my
wiring is for 50 amps and it wasn't even turned up all the way. What
happened???
Gaye, furstrated in San Antonio

How long it should take to get to cone 06 depends on how high you turn
up the kiln. If you immediately turned it to high, you should
probably hit cone 06 within two hours. Of course, you might well blow
up your ware doing this.

A 50 amp circuit likely won't take a continuous 45 amp load for
several hours. You probably need a higher rated circuit. It's
possible that you have a weak circuit breaker and replacing it would
help, but I wouldn't count on it. Best to check the owner manual for
the kiln and use the recommended amp circuit. Also, use copper wire
only. No matter what your electrician may say, aluminum wiring and
kilns are a bad combination and can lead to fires.

deg

Sorry I wasn't clear. My question should have been, "how long, if you follow
all the kiln directions, shouldit take to fire to cone 06"?
I think it fired long enough to be ok, but it's still to hot to open. I'm
keeping my fingers crossed!

We're going to go to a 60 amp breaker.

Thanks for the tip on aluminum wiring.

On 17 Aug 2003 17:09:37 GMT, (GaSeku) wrote:

Sorry I wasn't clear. My question should have been, "how long, if you follow
all the kiln directions, shouldit take to fire to cone 06"?
I think it fired long enough to be ok, but it's still to hot to open. I'm
keeping my fingers crossed!

There are just too many variables to answer that question. Hopefully,
you used witness cones or, at least, there is a cone in the sitter.
If the cones aren't at least starting to bend, you are woefully
underfired.


We're going to go to a 60 amp breaker.

I received email from Tom Buck saying that "breakers are designed to
handle 80% rated load continuously". For a 60 amp breaker, 80% is 42
amps. And just to make sure you know, you should not increase the
breaker rating without making sure the wiring can handle the higher
current load. A fire would just ruin your day. :-)

deg


Thanks for the tip on aluminum wiring.

almost the exact scenario happened to me, twice, with my brand new skutt kiln a
few years back. had a 60 amp breaker, which was sufficient. anyway, it turned
out that the breaker was defective; we tried replacing it and it works fine
now.

i've heard the opposite about aluminum vs copper wire for hi-temp applications,
but i'm not an expert on that stuff at all. i'd still check a few sources
because it's such a critical safety issue.

the other issue to be wary of, regardless of the type of wiring you use, is to
make sure that the whole circuit is engineered to be robust enough to carry the
current without frying. the fatter (larger "guage") wire, the more current it
will carry. if you install a 60 amp breaker but your circuitry can't safely
handle 60 amps, then you've defeated the purpose of the breaker, i.e., to shut
off the circuit at a certain point (but not below it) for safety reasons.

anyway, good luck and great firings to you with your new kiln. just know that
once these bugs are worked out -- but it's worth dealing with them right --
they'll be a distant memory!

eric
SpunMud

Ah, "one day they'll be a distant memory".....I can't wait for THAT day!

The wire we are using is a 6, so we should be ok. I think it had to have been
the breaker in this case.

Gaye

Well, if it turns out that that I'm underfired, I can just start all over once
we replace the breaker, right? I could probably also fire a bit faster now that
everything is dried for sure?

On 17 Aug 2003 17:45:15 GMT, (SpunMud) wrote:


i've heard the opposite about aluminum vs copper wire for hi-temp applications,
but i'm not an expert on that stuff at all. i'd still check a few sources
because it's such a critical safety issue.


I believe all the kiln manufacturers specify copper wiring. Here's a
link to a Clayart discussion on the issue -
http://www.potters.org/subject16764.htm

Aluminum wiring was used in houses at one time, but building codes now
ban it. There's just too much danger from oxidized connections
causing fires. As noted in the link above, aluminum can be used
safely, but it requires special connectors and specially trained
electricians. The extra cost of copper is a small price to pay for
added safety.

deg

Another tip on the use of fuses or circuit breakers....... after a couple of
firings re-tighten the terminals of the electrical connections. the heat
cycling makes electrical connections loose, this causes a slightly higher
resistance joint which rapidly overheats causing the cable insulation and
surrounding parts to burn. If anyone is interested in seeing what happens to
a circuit breaker with loose terminals email me and I'll send an image of
what happened to mine!

I would always recommend using copper cable because the resistance is lower
than aluminium (more amps for the same size cable) and copper does not have
the associated corrosion problems that aluminium has. In the UK we rarely
use aluminium and certainly not in domestic wiring.

regards

Kevin


"SpunMud" wrote in message
...
almost the exact scenario happened to me, twice, with my brand new skutt
kiln a
few years back. had a 60 amp breaker, which was sufficient. anyway, it
turned
out that the breaker was defective; we tried replacing it and it works
fine
now.

i've heard the opposite about aluminum vs copper wire for hi-temp
applications,
but i'm not an expert on that stuff at all. i'd still check a few sources
because it's such a critical safety issue.

the other issue to be wary of, regardless of the type of wiring you use,
is to
make sure that the whole circuit is engineered to be robust enough to
carry the
current without frying. the fatter (larger "guage") wire, the more
current it
will carry. if you install a 60 amp breaker but your circuitry can't
safely
handle 60 amps, then you've defeated the purpose of the breaker, i.e., to
shut
off the circuit at a certain point (but not below it) for safety reasons.

anyway, good luck and great firings to you with your new kiln. just know
that
once these bugs are worked out -- but it's worth dealing with them
right --
they'll be a distant memory!

eric
SpunMud

snip

Point of information:

Kilns, and all other electrical devices are rated at their top amperage, or
"amp draw"
depending on its use. Motors in electrical devices can draw up to 125%
of the rated draw when starting, and are rated separately for that.

When planning wiring, or trying to size a circuit breaker, one should always
use a figure of the amp draw being a maximum of 80% of what the circuit
needs to be.

Therefore, a device such as a kiln that draws 50 amps should be on a circuit
of

50= 80%, therefore 50=4/5, or about 62.5 amps.

A 60 amp breaker will NOT do. You would need to go to 70 amps or better to
accomodate your "load" or amp draw.

Higher is always better. Don't forget that you also have voltage loss
through the wire.
The longer the wire has to be, the greater the voltage loss. This also
leads to
higher amperage draw as well.

That's what the National Electrical Code in the US says, anyway.

If your wire is of sufficient size, it is a simple matter of replacing the
circuit breaker.
If it is NOT, then you will (yes, WILL) end up overheating the wire and
cause a fire
(and not in the kiln).

Be safe, spend the money and do it right.

Best,
Wayne in Key West