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

Reply to
GaSeku
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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

Reply to
Dewitt

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.

Reply to
GaSeku

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.

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

Reply to
Dewitt

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

Reply to
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

Reply to
GaSeku

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?

Reply to
GaSeku

I believe all the kiln manufacturers specify copper wiring. Here's a link to a Clayart discussion on the issue -

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wiring was used in houses at one time, but building codes nowban it. There's just too much danger from oxidized connectionscausing fires. As noted in the link above, aluminum can be usedsafely, but it requires special connectors and specially trainedelectricians. The extra cost of copper is a small price to pay foradded safety.

deg

Reply to
Dewitt

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

Reply to
Kevin Baldwin

Is the *real* issue the fact that you ask about a *used* kiln?

I recently bought a small said-to-be 1300decC top-loader kiln (equipped only with a controller) from a sweet old lady who used it only for glass work. It bisqued OK (albeit a little over fired - the controller is unreliable - what a surprise) but crapped out way before 1260degC on the glost firing. In fact it sat at around 1180/1200 for so long that everything was *over* fired.

So I concluded the elements were knackered and/or that the 1/4" gap all around the lid/body interface that made a nice orange stripe all around the garage was/were to blame!

The heat output of a kiln will not only be a function of amps x volts but kiln size/volume, insulation efficiency and depth, efficiency (age) of elements, heat loss through gaps (vents/spyholes) etc etc.

A small* kiln at UK 230/240V with a 13A plug-in supply *can* do cone 10. A larger (18" cube) kiln will require* a 40A supply for example. Having looked at a lot of kiln specs, only 'very large' kilns need anything more than a standard domestic supply (using a dedicated spur, of course) can provide. my understanding is that one can assume 100A from the normal supply - which must, of course, supply all simultaneous demand (cookers, power showers (of up to 10kW) etc etc). Don't worry about aluminium cable: I don't think anyone but a complete cowboy would use it in a domestic setting. Well, not in the UK anyway.

*check the manufacturers' specs. It all depends.

So really there is no answer to your question except to say that your kiln is knackered for one of any reasons: probably not the power supply.

Of course, if you are in North America (and you probably are, since you didn't bother to say where you are) all bets are off: I have no idea about weird (and apparently even locally variable) American electricity regulations and 110v supply which North Americans seem to have inflicted upon themselves in an effort to emulate the best the 3rd world can offer).

Reply to
no spam here, thanks

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

Reply to
psci_kw

Hi Wayne, My kiln says it draws 45 amp, so I think we're ok with a 60 amp breaker. The wire is a 6, I believe, and should be ok. I'm still nerbous over it though! Thanks for your advice. Gaye

Reply to
GaSeku

Actually, the standard in the USA is 220V feed to the main panel. It's a 2-phase system, in that each line is 110V from a common earth ground. So the wiring that is distributed around most of the house for lights and standard receptacles is taken from one line or the other to ground, for 110V. These circuits are usually rated at only 20 or 30 amps.

But major appliances like ovens, ranges, electric clothes dryers, and of course kilns usually use the full 220V (except for small "test" kilns, etc.).

Bob Masta dqatechATdaqartaDOTcom D A Q A R T A Data AcQuisition And Real-Time Analysis Shareware from Interstellar Research

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Reply to
Bob Masta

You may also have a problem because it isn't wired on it's own dedicated line. My new skutt kept going off if the house dryer was on, even though I told the electrician to hard wire the kiln into it's own dedicated line. It took me a while to figure out that it was the dryer doing it since I didn't realize that my husband who was in the house, turned on the dryer. After several outages, he told me about the dryer. We turned off the dryer and the kiln went up to cone 6 with no problem; but somehow it is connected to a house wire which services the dryer. We are now waiting to get an electrician to rewire the kiln on it's own, true, dedicated line.

Reply to
ShambhalaPottery

We're in the process of building a studio and have decided to run the kiln on its own. It's going to be a hassle and an extra expense, but I think we'd realy regret not doing it in the long run. Thanks for your advice!

Reply to
GaSeku

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