Fredrick Paget on thu 8 jan 04
>Hi all;
>
>In my studio there's a large kiln [single phase, KW rating 12] that I want
to disconnect it and connect my kiln [single phase, KW rating 5.5] .......
>...... I just
>want to check with the good people on clayart and see if the electrician is
>trying to exaggerate the job and charge me more .
May
The smaller kiln will work on the higher capacity line but you loose
some protection from a short circuit. The wiring in the smaller kiln
won't be as well protected and could possibly start a fire if this
happened. The difference here is not too great so maybe nothing bad
would happen. It could just trip the breaker of blow the fuse. Talk
it over with the electrician. There may be an electrical code issue
here but I don't know since you are in England and I am in the US.
Fred
--
From Fred Paget, Marin County, California, USA
fredrick@well.com
May Luk on thu 8 jan 04
Hi all;
In my studio there's a large kiln [single phase, KW rating 12] that I want
to disconnect it and connect my kiln [single phase, KW rating 5.5] The
electrician told me the switch fuse unit is too strong for my kiln. Instead
of plug and play, he told me that I should wire it separately- new cable
from the main and new switch box. I check "The Electric Kiln" book, the onl=
y
thing I found about fuse is page 52; "...cable and fuse be of the correct
rating.."
There's a TV show a few days ago on Builders and Plumbers from hell. I just
want to check with the good people on clayart and see if the electrician is
trying to exaggerate the job and charge me more =A3=A3=A3.
Many thanks in advance
May
London, UK
John Rodgers on fri 9 jan 04
May,
If you are not going to use the large kiln any more, that is, it is to
be disconnected and not used, then it is not a problem. The existing
wiring - provided it was sized properly for the big kiln - is more than
adequate for the smaller kiln which will draw a lower amperage load. The
circuit breaker for the bigger kiln will not be safe to use on the
smaller kiln however. Breakers are sized just above the rating of the
equipment to be on the circuit. It a short occurs, current greater that
the circuit is designed for will be drawn through the wires. This will
cause the breaker ot get hot and it will pop open, shutting off the
elctricity to your kiln. If the breaker is to big, it will allow far too
much current to be pulled during a fault, and a fire could result
anywhere down stream of the breaker before the breaker ever gets hot
enough to open. This could result in a fire inside a wall where it is
not seen until it is to late. Hense, you can use the existing wiring on
a lower load kiln, but you MUST change the breaker to more closely match
the load of the smaller kiln.. I don't know the specific code, but the
breaker capacity must be something like 10-15% greater than the maximum
current rating of the appliance or kiln. Your electrician will know. DO
NOT attempt to operate the kiln until the breaker is changed.
Now, if you plan to use both kilns, you should have a second circuit
installed for the smaller one, and simply leave the other one alone. It
seems adquate for the bigger kiln as-is. With a new circuit for the
smaller kiln, smaller wire can be used, as can a smaller breaker.
However, you will not be able to replace the smaller kiln with a larger
one because of the smaller wire. If yo go with wire that matches the
bigger kiln, at some later day you can upgrade to a bigger breaker
without haveing to change the wiring because your wiring will be
adequate from the get-go!!
Good luck.
John Rodgers
Chelsea, AL
May Luk wrote:
>Hi all;
>
>In my studio there's a large kiln [single phase, KW rating 12] that I want
>to disconnect it and connect my kiln [single phase, KW rating 5.5] The
>electrician told me the switch fuse unit is too strong for my kiln. Instead
>of plug and play, he told me that I should wire it separately- new cable
>from the main and new switch box. I check "The Electric Kiln" book, the only
>thing I found about fuse is page 52; "...cable and fuse be of the correct
>rating.."
>
>There's a TV show a few days ago on Builders and Plumbers from hell. I just
>want to check with the good people on clayart and see if the electrician is
>trying to exaggerate the job and charge me more £££.
>
>Many thanks in advance
>
>May
>London, UK
>
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Bruce Girrell on fri 9 jan 04
> In my studio there's a large kiln [single phase, KW rating 12] that I want
> to disconnect it and connect my kiln [single phase, KW rating 5.5] The
> electrician told me the switch fuse unit is too strong for my
> kiln. Instead of plug and play, he told me that I should wire it
> separately- new cable from the main and new switch box.
I would certainly ask him to justify the new run. As long as you downgrade
the fuse/breaker to the appropriate size the rest should be fine. You need
new wire only if the KW goes up.
Most people, in fact, wouldn't even bother downgrading the fuse/breaker (do
you install a 1 amp breaker just because you have only one light plugged
into a lighting circuit?). But for a heavy duty dedicated circuit like this
you should. Consider the case where the kiln develops an electrical leak to
ground. The leak may not be sufficient to trip the 60 amp breaker now in
place. Even though the wiring can handle the current and won't start a fire,
you still have a dangerous situation. A 30 amp breaker stands a much better
chance of tripping and alerting you to the problem.
Bruce "only familiar with the US electrical code, though" Girrell
piedpotterhamelin@COMCAST.NET on fri 9 jan 04
Hi Mary
If your electrical power supply is 240 volts, your large kiln is computed at 50 amps and requires a 60 amp breaker and a larger gauge wire. Your smaller kiln is rated at 23 amps and requires a 30 amp breaker with a smaller gauge wire. It depends on the distance of your main box from the kiln as "voltage drop" is affected by the length of the wire.
The smaller diameter or gauge wire could fit into the 60 amp circuit breaker and the wire connection at your kiln sitter. But you are dangerously risking frying the circuits in your kiln.
The larger diameter or gauge wire wouldn't fit into the wiring connection on your kiln sitter. Too heavy of a wire; you would have to jam it in and leave some wire hanging. Very dangerous.
I am not an electrician. These are the parameters that you should consider.
The costs of the damage done to the kiln is probably greater than the costs to have the electrician do the job correctly and safely. Kiln relays cost $125, sitters are $250, switches are $25. Coils are $20 plus.
The costs for a new 30 amp breaker is about $35, the wire depending on the distance. I would install an second circuit breaker above the kiln as well. If you need to quickly shut off the kiln due to an emergency or someone else is watching it, they could have a hard time finding the proper switch in the main box with so many to chose from. This intermediate box is $35 or so. Insurance companies also love it when you install them. And it is a second protection for your kiln.
If you retain the 60 amp circuit, you will have it for a larger kiln, when you need it. Have the new 30 amp circuit installed separately if possible. Later, you can be a two kiln studio.
Good luck
Rick
--
"Many a wiser men than I hath
gone to pot." 1649
Michael Wendt on sun 11 jan 04
The cheapest solution is to install a
sub panel with an appropriately rated
breaker at the end of the large wire
and use it as the "kill switch" near the
kiln. It is actually REQUIRED by the
national electrical code in the US that
for duration loads like kilns, the breaker
and wiring be sized so that the load never
exceeds 80% of the circuit capacity.
It is always allowed to run any lighter
loads than the circuit capacity.
As someone pointed out, a 100 watt lamp
on a 20 amp circuit will never pose a heating
problem to the 20 amp circuit. The breaker
is sized to prevent a wiring fire even in the
face of a dead short anywhere in the circuit.
Code reference :
422-28 Overcurrent Protection
( for branch circuit appliances)
(1993) so probably
still in force.
Regards,
Michael Wendt
Wendt Pottery
2729 Clearwater Ave
Lewiston, ID 83501
wendtpot@lewiston.com
www.wendtpottery.com
John wrote:
This could result in a fire inside a wall where it is
not seen until it is to late. Hense, you can use the existing wiring on
a lower load kiln, but you MUST change the breaker to more closely match
the load of the smaller kiln.. I don't know the specific code, but the
breaker capacity must be something like 10-15% greater than the maximum
current rating of the appliance or kiln. Your electrician will know. DO
NOT attempt to operate the kiln until the breaker is changed.
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