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equipment / electric kiln installation

updated sun 23 sep 01


Cindy Strnad on thu 20 sep 01

Wow, John!

What a great post. You explained many things I hadn't fully understood. I'm
saving your post so I can refer to it if I need to, later. I had a complete
new electrical service installed to handle my kilns. It was good, because
what I had was ancient, inadequate, and probably dangerous. It was good, but
of course it wasn't cheap. One more suggestion, which I didn't notice in
your post:

Keep the kiln as close as possible to the electrical service. Longer wires
increase resistance and decrease the power that gets to the kiln. If you
have quite a ways to go, you may need larger gauge wire.

Cindy Strnad
Earthen Vessels Pottery
RR 1, Box 51
Custer, SD 57730

John Baymore on thu 20 sep 01


Saw your post and thought I'd comment.......

I have recently been given a small electric kiln, and I would like to
utilize the receptacle for my clothes dryer as power to it.

Problem is; my dryer receptacle is a three prong "y" shaped receptacle.
The kiln's plug is four prongs, two parallel, one round and one "L"
shaped. I was told that I just needed to buy a dryer cord/plug for it, bu=
I am concerned that it might not be sufficient for the amount of
electrical current that it draws.

Your concerns are likely very well justified, and it is good that you jus=
didin't go ahead and do this without "asking around" a bit. Here's some
hopefully useful background........ add it into all the other stuff you a=
"told" , and weigh it all, ....... and then go forth.

Electricity has pressure....... called Voltage (Volts), and flow
volume...... called Amperage (Amps) which is sometimes also refered to as=

Current. There is also a factor that is called Resistance (measured in
Ohms)........ which will come up a bit too. With electrical appliances
you need to address both Volts and Amps, and have a least a tiny
understanding of the impact of Resistance on things.

The various shaped plugs that are available for electrical appliances are=

intended to make sure that you don't plug the wrong device into an outlet=
. =

110 V and 220 V are different......... the amperage rating of 220 V
circuits have differnt plugs/sockets, and so on. For a gross example,
plugging a device that draws 100 Amps of current into a circuit that was
designed for 50 Amps of current can cause problems. At the very least...=
the breaker or fuse will constantly blow . At the most...... the adde=
draw (Amps) will cause a fire in the interior of the wall.

One big issue is the wire, usually located in the wall, between the mains=

service and the plug. Wire is not a perfect conductor of electricity. I=
has resistance to the flow of electrons. This Resistance causes heat to =
generated. This is very much like the coils in the kiln. If the wire
going to the outlet is too thin for the amount of flow (current), the wir=
gets hotter than it is desigend to be. If it gets hot melts=

the electrical insulation and/or catches the wood framing near it on fire=
. =

Bad. =

Kiln wiring thickness is usually toward the BIG side........ and is
dependant on the length of the run and the amperage and voltage needed at=

the kiln end of things. It is also usually recommended that it be COPPER=
not aluminum wiring. Picking the correct wiring for the job is VERY
important., and every installation has to be looked at carefully to get t=
right stuff.

The "electrical circuit" for a device consists of a combination of the
fuse or breaker, the wire between the main supply and the appliance, all
the connectors, and the device itself. Like the old proverbial
chain........ the curcuit is only as robust as the weakest link. (The
intent is that the weakest link is the fuse or breaker .) If any part=

of the circuit is inadequate to handle the voltage or current.... that wi=
be the place it "fails". So it is not enough that the breaker or fuse is=

"high enough" for the rating on the kiln. You have to look at the whole

All but very small kilns running on so-called "220" VAC (Volts, Alternati=
Current) draw more Amperage than a home dryer will. I am not a "dryer
guy".....but I think most are rated for use on a 20 to 30 Amp breaker. =

This does not cover a lot of "220 V" electric kilns except the smallest. =

Remember..... the circuit that was installed for a home dryer was desigen=
to handle....... you got it........... a home dryer . Electricians
install home dryers all the time..... they know what to do and what they
can "get away with" and what Code is. (Most DON'T know diddly about
electric kilns.) The wiring and connectors were put in suitable
(hopefully) for an electric kiln.

Additionally.... the existing dryer circuit may have been a do-it-yoursel=
job by a homeowner reading a DIY book..... you never know .

If you kiln draws an equal or lower Amperage to the breaker for the
dryer..... then you COULD hook it up there. But even in that case the
actual wiring deserves a good "look-see" anyway to make sure of what you
have. A kiln is on "high" longer than a dryer is on full heat..... letti=
the dryer "get away" with more "leeway" in the circuit. So a 30 A dryer
might be fine on the circuit .... and a 30 A kiln could cause problems
....even though the breaker is technically an "OK" rating at 30 A.

If the dryer outlet has one shape socket and the kiln plug has another...=
it is a good indicator that they are NOT a happy match for each other.

There are also issues such as whether you have 220 V, 208 V, or something=

else on your so-called "220" line. The kiln is designed to operate on a
particular Voltage.... if your Voltage at the kiln's location differs, i=
could fire more slowly, not be able to reach peak temperature, or burn ou=
elements more quickly, and so on.

Also..... a connector that is loose, or of dissimilar metals (copper and
aluminum, for example), can offer greater resistance than it should. So
shoddy workpersonship in the installation, or corrosion from age or
flooding you don't know about, or other factors can make the connection
points subject to generating excess heat (from the resistance to electron=

flow). These points too can cause fires. They need to be done correctly=

and WELL. If it is an existing installation, they should be carefully
inspected. For larger kilns, the general recommendation is that the kiln=

be hardwired to the service. The resistance provided by the plug and
socket can be problematic and subject to corrosion, generating unwanted
heat that can deteriorate the connection point... and that corrosion
creates more resistance ....and that creates even more heat and..........=
you get the idea ..

All in all.... much as you probably don't want to hear this....... IF YOU=

HAVE TO ASK about this kind of stuff...... you probably should employ the=

services of an electrician to check out your electrical service, get the
specs on the kiln, and set you up correctly. First, call the manufacture=
of the kiln you have to get the wiring recommendations from them.... and
then have the electrician follow them EXACTLY. The kiln suppliers know
their equipment. Don't let the electrician "save you money" and substitu=
something like aluminum wire or a slightly thinner guage of wire or
anything. Even an electrician is likely to look at the kiln and see it
only as a "big toaster". Learn enough yourself so that you can reasonabl=
evaluate the competence of the electrician.....but let him/her do the
actual work. =

The little extra you spend now will give you peace of mind. Burning down=

your house or, god forbid, having someone die in a fire........ not the w=
you want to to go.

As I said in another recent post on controllers and kiln sitters.......
electric kilns are NOT just big toasters .

Hope this is of help.



John Baymore
River Bend Pottery
22 Riverbend Way
Wilton, NH 03086 USA

603-654-2752 (s)
800-900-1110 (s)

"Earth, Water, and Fire Noborigama Woodfiring Workshop 2002 Dates TBA"=

John Baymore on sat 22 sep 01


Thanks for the kind words!

One more suggestion, which I didn't notice in
your post:

Keep the kiln as close as possible to the electrical service. Longer wire=
increase resistance and decrease the power that gets to the kiln. If you
have quite a ways to go, you may need larger gauge wire.

This was sort of implied in there.... but not very directly said. Guess =
didn't say it clearly enough. Thanks for clarifying it for everone. =

Yes....... and heavy guage copper wire gets expensive FAST . =

The general idea you mention is pretty similar for gas kilns also..... as=
broad generality, the longer the run of supply line the larger the
diameter, and the more costly it'll likely be .



John Baymore
River Bend Pottery
22 Riverbend Way
Wilton, NH 03086 USA

603-654-2752 (s)
800-900-1110 (s)

"Earth, Water, and Fire Noborigama Woodfiring Workshop 2002 Dates TBA"=