Questions about L&L kiln: front loader EFL2626

[Helmsalee]

I'm making plans to build a pottery studio on my (very rural and remote) property, and am planning to buy an L&L front-loading kiln: L&L EFL2636.

Three questions, before I place my order:

Re: Vent. I've read on this forum that venting a kiln is not absolutely necessary if the kiln room won't have people in it while firing. But the (excellent, clear, and detailed) documentation on the L&L website says that all kilns should be vented because of the corrosive nature of the fumes inside the kiln, which shorten its life — quite a different concern than the concern for human health. My studio will have a separate kiln room, divided from the rest of the studio by a wall with a door that will be closed during firing. It will have a window that will be open in nice weather, and a gable fan that will always run during firing no matter the weather. The studio building itself is on a different part of the property from my house. What do you think? Should I buy the vent kit or not?

Re: Wiring. The kiln I've chosen has two wiring options. One is to hard-wire the kiln to the fuse panel. The other is a 6-foot cord that plugs into a receptacle wired to the fuse panel. I thought I'd prefer the plug-in option so that I could buy the optional casters and move the kiln if necessary (though I don't imagine it would be moved often, or even ever). Do you see any downside to the plug-in cord option?

Re: Fuse. The L&L documentation for this kiln says that a certain kind of fuse should be installed instead of a breaker because breakers are more apt to trip and ruin the firing due to the nature of the energy demands. Sounds reasonable to me, though I imagine my electrician will press to install the usual breakers and I'll have to insist. Any opinion about this?

Thanks in advance for any advice.

Helmsalee

[Fred Sweet]

Helmsalee-

Did you mean the eFL 2635 or the eFL2626? The reason I ask is because the eFL 2635 only is offered as a hard-wired version, where the eFL2626 has both.

Personally I prefer to hard-wire larger kilns, as I have found that with fewer wire connection points there is less chance for loose connections, causing hot wires and a decrease in performance. The hard-wired pigtail can be the same 6’ length as the plugin variety, thereby giving you the option of the casters, though at 600 lbs for the eFL2635, I’m not sure you would be doing much moving of it.

I didn’t see any mention of using fuses instead of breakers in the literature that I read on the L&L website. I did see where they list “fuse sizes” for all of the eFL kilns, but I just assumed that they used that term because it was shorter and would take up less room in their column heading.  I’ve always used breakers, and have rarely had them trip, assuming that they are correctly sized; and never had a tripped breaker “ruin” the work.

I suspect that Neil Estrick will chime in on this subject, as he is more familiar with electric kiln set up and repairs.

Regards,

Fred

[Helmsalee]

Thanks for your input, Fred.

Yes, I'm looking at the EFL2626. Sorry about the typo. I've edited the title of the post to correct it.

The shipping weight of the EFL2626 is only 575 lbs (only! hah!). I figure on casters and with a little extra volunteer muscle, I could push the kiln around if it were on casters and I were motivated enough. But I see your point about fewer wire connection points. I've rewired a sailboat, and know well the virtues of continuous, and short, wire runs. I don't have much experience with AC, and frankly it scares me. So I want to do it right.

About the fuse versus breaker, I've cut and pasted the entire text of the relevant pdf file I found on the L&L website. Here it is:

-----------------------------------------------------------------------------------------

NOTES CONCERNING CIRCUIT PROTECTION FOR ELECTRIC KILNS
         Electric kilns are resistance heating devices. The electrical circuit that provides power to the kiln must be wired in
accordance with the National Electrical Code (NFPA 70, last edition is 1996) as interpreted by the local authority having
jurisdiction where the kiln is located, e.g., a township building inspector. The circuit can be defined as the device (kiln)
itself plus the wires (conductors) supplying power to it.
         There are two common methods of protecting electrical circuits: fuses and circuit breakers. Fuses self-destruct when they
sense an overload in the circuit. Circuit breakers are commonly used in new construction; they trip (turn off power) when
they sense an overload, and can be reset (turned back on) when the circuit is returned to normal.
         Circuit breakers are more convenient because of this feature. However, they can cause nuisance tripping and ruin kiln
firings when they trip part way through a firing. This is because most circuit breakers are activated thermally; if the circuit
breaker temperature rises above a preset level, a bimetallic element inside the circuit breaker opens, and the power is
turned off. This works well most of the time; however, over time the bimetallic element becomes weaker because
resistance heating circuits are at their rated load longer than other types of electrical loads such as motors. Eventually the
circuit breaker becomes too weak to hold itself closed over a long enough time to finish a kiln firing, unless the circuit is
drastically oversized to compensate for this gradual aging process.
         There are many different types of fuses, including dual-element time delay, one-time, sub-cycle, etc. Most of these
designations relate to how quickly a fuse will “blow” in response to an overload, and these types of fuses have been
developed to protect not only the circuits, but also varying types of equipment. For instance, SCR’s (silicon controlled
rectifiers) need to be protected from voltage spikes which can occur within 1/60 of a second and destroy the device - these
are usually protected by ‘semiconductor’ fuses which are very fast acting, current limiting, and have no time delay.
         Another consideration in selecting fuses is the interrupting capacity in amperes - in other words, how big a short circuit can
be opened by the fuse. In large industrial plants this can be an important factor, because if enough power is available it
would be possible that a short circuit would allow too many amperes to flow into a circuit for a general purpose type fuse
to interrupt - which could potentially cause an electrical fire. Most residences and small commercial shops do not have
enough power available before the main circuit protector (usually a 200 amp circuit breaker) would open, and a small
interrupting rating (10,000 Amps or 50,000 Amps) is enough.
         For protecting kiln circuits, ‘one-time’ general purpose type fuses should be used. These are inexpensive, have no
appreciable time delay, and are available in a large variety of sizes. They are also widely and easily available, and are made
by several large fuse manufacturers. Different manufacturers have different designations for their ‘one-time’ fuses; some of
the more common ones are:
MANUFACTURER       MAX RATED VOLTS       INTERRUPT RATING       FUSE DESIGNATION
LITTELFUSE                    250 VOLTS                           50,000 AMPS                        NLN
BUSSMAN                        250 VOLTS                           50,000 AMPS                       NON
GOULD SHAWMUT   250 VOLTS                          50,000 AMPS                       OT

LITTELFUSE                    600 VOLTS                           50,000 AMPS                       NLS
BUSSMAN                       600 VOLTS                            50,000 AMPS                      NOS
GOULD SHAWMUT  600 VOLTS                           50,000 AMPS                       OTS

-----------------------------------------------------------------------------------------

I look forward to Neil's input, and anyone else's who has more experience than I do (and that means nearly everyone in this forum).

Helmsalee

[Roberta12]

Helmsalee, Neil will have the absolute best information for you when he sees your post.  I bought a smaller L&L 5.5 years ago.  Because we were putting it in new construction, because we had to upgrade our electrical and because the electrical inspector didn't really know much about kilns, he insisted we hardwire the kiln. So we did.  Pro....when the insurance person came out to inspect the new structure and the kiln he said "Oh, great!  It's hardwired.  That is much safer!"  and I had no problem getting insurance coverage on my business equipment.  Con....because it is hardwired, it is a bit more challenging to drop that front panel down to access the internal workings.  However, your kiln is a front loader and maybe your control panel is on the side or something?? Anyway, Thought I would share.  I really do like my L&L.  Great customer service.

 

Roberta

[Mark C.]

Send a Pm to (neilestrick) on this site-he will see that right away and respond.

He is the moderator on this equipment area so just click on his name on home page to send that message.

He is the absolute guy to have every L& L answer for you .

[Helmsalee]

Thanks, Roberta12. I hadn't thought of the insurance angle, though of course I intend to advise our insurer once the building is complete and fitted out. I think that, on the front loader, the cover of the panel swings away, so shouldn't be a problem. I look forward to hearing what Neil has to say.

Mark C., thanks for the advice to PM Neil. I've done that, and am eager to hear what advice he offers.

Helmsalee

[neilestrick]

@Helmsalee Sorry I didn't get to this yesterday. My son had a track meet out of town.

Definitely get the vent. It will extend the life of the elements, reduce corrosion to the rest of the kiln, make your glazes look better, and keep your lungs healthy.

I don't have a problem with plugs, as long as they're inspected a couple times a year to make sure there's no corrosion. I have seen outlets fry out, but I've also seen power connections on hard wired kilns fry out. Anything can corrode. The majority of kilns I sell and repair have plugs, and I haven't seen a fried outlet in a couple of years. If you hard wire it, make sure there's enough cord to be able to easily open and close the kiln control box for maintenance and repair. See if your insurance company has a preference, and also make sure they're good with the kiln in general.

Have your electrician install a fused disconnect. It's a fuse box with a lever to disconnect the power. It's super handy because it's an easy way to shut down the kiln for repairs or if there's an emergency. You don't want to have to run to find the breaker box if you need to shut down the kiln. In many studios, the kiln is only used every few weeks, so the disconnect is a good way to shut down power to the kiln when it's not in use. Breakers are not meant to be used as on/off switches on a regular basis. The fuses also add another layer of protection, and do a better job than the breaker.

[Helmsalee]

Neil, thank you for the information. This is very helpful. Especially thanks for the explanation of the fused disconnect. Makes perfect sense.

Helmsalee