Bill Kielb

First before tweaking your sitter get a few firings under your belt especially with a kiln that’s filled. It sounds like it might be fairly close. If not and it’s just too far away, Sue McCleod has a decent how to on her website I believe. Orton cone photo below, notice the very small difference especially if the cone is not fully touching. At four o’clock we are only speaking of a degree or two. You may be just fine calibration wise.

Looks like the J230 was spec'd as GrayB indicated*.
The voltage, aren't most homes supplied with 240v?
Be sure that matches up.
fwiw, our home is 240v (the kiln's display indicates ~252v).
Our run is very near fifty feet. The (e23T-3) kiln's plate indicates 48 amps.
I'd considered going with the number four wire, but went with the #6
The cable we bought is rated higher ...75 amps.
The vendor, WireandCableYourWay, had a good price** on #6-3C THHN-PVC TRAY CABLE WITH GROUND
We also went with a fuse/disconnect box and replaced the supplied cord and plug with a waterproof conduit and #6 wires.
*Not sure about the new models, just got several hits for J230 and 43.98 Amps
Ah, GrayB uploaded an image.
**The per foot price hasn't changed. With shipping, still less expensive than local vendors and better specs.
I went with three conductor cable, for down the line someone might need (or want) 120v ...the third conductor is not being used in our setup.
My understanding is the kiln (our kiln, the e23T) requires two conductors only, and the ground.

@Mudfish Fantastic post! Go at this logically, not rocket surgery for sure. You should be able to read your meter size , something like : AC250, 5 PSI, 1/2 PSI differential @ 250 cfh flow. So read it or post it if in question. A 250 Cfh meter can supply more, just the pressure drop across it will be 1/2” at that flow. The regulator on the meter will be key. It drops meter pressure to home system pressure of 7”, so its rated capacity will be very important. Again it should be on the tag for the regulator. For a house your street pressure is likely 2 psi or 55.44” wc. We won’t know this, so an assumption likely can be made your regulator has 2 psi input minus meter losses of 1/2 psi at 250 (or rated) cfh flow …….. etc. In other words the gas company really has to determine the total service capacity. It’s just stuff we will never know.
To operate on your existing service 
Your house pressure - very likely 7-8” wc and most of your appliances have 3-1/2” regulators on them. So important to use the right sizing chart for your line sizing and pick a reasonable starting pressure and ending pressure under full flow to get the btuh needed.. We would like to leave your system pressure as is, all your other appliances depend on it. Stove, water heater, boiler, furnace …. All of them regulate your current pressure form prox. 7” down to 3-1/2” (typ)
Start with what does the current kiln require or what will you expand into in the future
How much = orifices @ desired pressure X no of burners - let’s pick a pressure less than max (7”) leaving some room for pressure drop in the pipe run, fittings and valves… let’s use 5” wc
Sizing existing
Pick from your favorite orifice table: https://www.gordonpiatt.com/wp-content/uploads/2021/07/Natural-Gas-Orifice-Chart-7.E.80.5-Rev-3-05.01.pdf. 1/8” Dia. Orifice @ 5” wc = 48,200 btuh per burner X 5 = 242,000 btuh total. Is that enough? Not sure but let’s finish.
pick piping from chart knowing you likely can drop from 7” to 5” if need be. Most charts limit to 0.3” wc drop so 2” buffer is somewhat conservative here.
Table pg 4-3 http://ecodes.biz/ecodes_support/free_resources/Virginia/fuelgas/pdfs/Chapter 4_Gas Piping Installations.pdf
This manual will let you add equivalent lengths for fittings etc… but by now you get the idea of leaving yourself room by way of pressure drop, orifice sizing etc…. To make the situation best work for what you have available. As long as you can move the desired btuh at a realistic dependable pressure your design should be good. There are lots of ways to get there. Solid knowledge of the basics, likely gives you many options for best solution.
Only other last thought, work in inches of water column. All low pressure stuff is measured that way. 1 psi = 27.72”. Low pressure stuff = Water Column. Medium pressure stuff, 2 PSI. While folks will refer to ounces or 1/4 - 1/2 psi it tends to lead to mistakes. Stick with water column unless venturing toward medium pressure stuff.
Other than that, it looks like you are on the right path to figure out just how many btuh you need or will need in the future to run this for and now should have a way to reasonably size it.
 

Drying it sandwiched between two pieces of drywall sheetrock wallboard whatever you call it in your area works fairly well. Make sure its pretty dry before unsandwiching it because if its only partially dry it may still warp. When firing lay it flat on a shelf with fine silica sand under your slab.  ...works fairly well but some of the other fine folks here might have other ideas they can send your way.

+1 drying between wall-board.
In my limited tile-making efforts I also turned the slab+boards over from time.
Re the use of silica sand, I found this a powerful analogy.
PS I was taught that non-optimum rolling can make the slab more likely to warp: frequent turning & unsticking from the rolling surface, gradual reduction in thickness, rolling in multiple directions, don't let any thickness guides constrain the slab's edges, ....

@PeterH Looks like masking and looks like the shadowing may have been airbrushed underglaze. That’s what strikes me

You guys are the best!!! The search for a kiln for my dad continues.
Thank you so very very much

Bein' curious, and settled down for a late afternoon snooze*, taking a minute to look for that...
...found a scanned version of Hopper's book. The piece is "Trifoot Plate - Southwest Series."
Searching that string, found on Hopper's blog the same/similar image, captioned thus:
"RH - TRIFOOT PLATE - SOUTHWEST SERIES.
THIS EXAMPLE SHOWS CONTROLLED LOCALIZED FUMING OF CHROMIUM RED GLAZE ON TOP OF TIN-OPACIFIED TERRA SIGILLATA"
Here: PHOENIX: BRUSHSTUFF #1 (rhrising.blogspot.com)
Sorry about the all caps, that's a direct copy/past (quotes added, of quote!).
 
*Had appointment this a.m. (6:30 !!) with the specialist for a root canal.
Yep, time for a nap!

@PeterH Looks like masking and looks like the shadowing may have been airbrushed underglaze. That’s what strikes me

Looks like the image Bill posted correlates "o'clock position" to degree angle.
I'm not finding many graphics that depict correlation between degree angle and degree temperature.
This one is a large cone 10 cone; the rate* is indicated (in °C)

The temperature degrees per angle degree is greatest at the beginning of the fall/bend, least at the end.
More fun here: Untitled (thermaltechnologies.com.au)
How closely we have to hit the target for heat work for optimal results may certainly vary.
In my (limited) experience, within a half cone to a full cone is plenty close enough for bisque, given that it's not a full cone on the cold side, for then I have to rush a bit to keep the glaze layer from being too thick. I don't mind having to slow down a bit for bisque that's not as absorbent...
For glaze fire, some clays are much more sensitive to overfiring than others (per that same limited experience).
 
*Temperature difference between clock/angle positions depends on the rate - how fast/slow the temperature is rising.
 

I think it likely works, but I really want pictures to unveil if it has a regulator downstream, what is the regulator model #? 1/8” is ok - sort of, but I would rather have the number stamped on the orifice. If not, burner model, measure the orifice with a number drill instead of guessing.
Piping is easy to figure out, but knowing the actual required capacity is most useful. The piping chart below is for low pressure with 0.3” drop and probably at 3.5”. Operating pressure. Just looking at 1” 60 feet without fittings at the above referenced pressures, maybe 200000 btuh max ……….. Is that enough - no way to know - updraft, or down draft, again who knows? Pictures, a few measurements you can very easily get there but it will take some effort.
Will 1” pipe at house pressure work? It will do something that’s for sure. Will it fire well - maybe, maybe not, impossible to tell. I really need pictures to develop questions or estimate supply line sizing for real. Absent that - maybe it will work great.
 

Hulk gives good advice, however, there is nothing that says you have to fire on a kiln shelf. You run the risk of the glaze running onto the kiln floor, but if that's a problem you can live with, firing on the floor is no problem. Does your glaze run?
A kiln shelf helps to distribute weight if your piece is heavy. (If your piece is heavy it might stress the bricks if fired without a shelf.)
You might also check to see how much your kiln lid sags.  (If at all?) This too affects how tall you can fire.
Its been my experience that most clays shrink about 5% from wet to bone dry. (At least my cone 6 slip cast porcelain does.) Doing a little test will help you determine the amount of shrinkage of your clay.
As Hulk suggests leaving 1/4" space between the top of the piece and the kiln lid is good. I might make it 1/2" if I'm unsure?

With a base shelf and half inch risers underneath it, you'd be down to 25.5" to start (given 1" shelf).
My experience* says leave a smidge of room for expansion.
Although everything gets hot and therefore expands, perhaps not all at the same rate, so leave a quarter inch, at least?
Mainly to avoid touching and therefore melting together, also 
   a) extra space between wares and the elements to reduce any spitting of bits/droplets onto the elements, and
   b) extra space between wares where reducing fuming** is a concern.
Use a tape measure or ruler to get the available space.
If you're throwing/making to the available vertical, the subsequent clay shrinkage should leave plenty of wiggle room...
Check back later for more input from other Forum members!
 
*I'm typically firing three to five levels in my 27" kiln. Sometimes I leave just a quarter inch from top of the ware to the next shelf (or the lid); so far, a-ok.
**I like how my red glaze picks up some blue/cobalt. The chrome seems to get around as well.

Do the holes go all the way to the clay?
...looks like they do (also not scientific!). If so, perhaps there are some larger "off gassing" particles in the new clay?
They appear (also not scientific) to be random - all over the surface. If you're dipping, the glaze layer near the foot should be thinner.
Are the problem forms thicker than your test tiles? If so, that could be another indication of problem particles, for the thinner wares "burn out" more and faster in the bisque.
And so, if the new clay has more/bigger bits of stuff to burn out, a longer more thorough bisque fire - with plenty of oxygen - could help.
See also drop & hold glaze fire: Drop-and-Soak Firing (digitalfire.com)
 

To drop and hold, the next segment has a lower target temp/target.
Here the rate is maxed at 9999, and the hold is long, three hours (crystal formation), and the final segment is a controlled cool, falling two hundred degrees at the rate of 500°/hour, then holding there for a full hour.
 
For a bisque hold (per prior post, to burn out stubborn organics in thick wares, and/or clays with lots of organic!), I don't believe it matters if the hold is on the way up or down. When running my manual kiln, I held at 1500°F on the way up and down! 
The new kiln, I set the 1500°F hold on the way down.
See "Custom Ceramics Program" in the L&L notebook.
Give a shout if any questions come up?
There are regular members (and Mods) here that are very familiar with writing and editing custom programs.
There are Horned Lizards in California!
Grackle, the figures, how charming, and beautiful glazes, thanks for sharing!

It would be interesting to see just how many departed significantly. Lots of old glaze recipes fall into a reasonable range around 0.3:0.7. I would love to see real comparison data on this, anecdotal often has the potential for perception bias.

All very available HVAC ductwork parts, available stuff -
For that fan You should be able to use a 12” flanged take off, 12” hard pipe duct and or 12” flex duct to isolate vibration or as needed. Steel duct attachment would be 3 screws for round rigid, worm drive clamp is easy and goof proof for the flex. Seal all seams with metalic duct tape UL181- P for rigid or UL181-FX for flex connections. Duct sealant (brush applied) is more permanent than tape but taking it apart for maintenance a bit of a pain. Advise adding a decent backdraft damper and well thought out discharge louver. Cheapest flanged take off I could spot below:
The take off from the original OP appears to be a bit adapted for use (might be the photo), connection shown below, typical.

Hi TahoeBlue, Welcome to the Forum!
LaurenF hasn't been on the Forum since November last.
You might try sending a message (which will be delivered via email); navigate to their profile page, select "message"...
Looks like Lauren had found something - perhaps a sheet metal flange? - that bolts up, per the second image.
...12" fan, 13-1/2 in bolt circle diameter, search string suggestion, "12" round duct flange"
...maybe
duct flanges | McMaster-Carr
or
12" Flowtite Plain Duct Fitting at Menards®
Gotta go to root canal appointment; I'd rather look up more flanges tho'!
 

Just so you know a little of the where and why of all the caution here,  electricians seem to have difficulty sizing breakers and wiring for kilns. The general rule for kilns (known as a continuous resistive load)  is simple in that not less than 125% of the rated load, nor more than 150%. Your kiln is 48 amps so a 60 amp breaker and wiring is recommended by the manufacture and fits this rule.
For everyday stuff, Electricians are usually taught never to load a breaker more than 80%. Brand new from the store, they are rated at 80% of their load. In your case a 50 amp breaker typically would only be used for a 40 amp load following this rule……... So that ……. somehow a 50 amp breaker was used coupled with the initial 120v hookup of a 2 pole breaker raises flags as to how it was all done.

It is #6 copper wire for all three wires, this I know I confirmed with the electrician. 

It's a scam. I get these emails all the time about kiln purchases and they have a specific freight carrier, etc, etc. They'll probably want to use a stolen credit card to pay for it or something like that.

Do not replace the 50 amp breaker with the required 60 amp breaker unless the wire is 6 ga. or better.

I've been tempted to put in the work and see how the ratio holds up. It would make for good content.

Thank everyone, this is a great group!  Just unloaded the kiln with the 5 minute hold, and all looks good.  I was a little worried it might get a bit hot, but seems fine.  I watched the temp right at the end, and it went from 2167F to 2171F, 
I am firing electric to cone 5, but honestly, the witness things would indicate more of a 5.5 or 6.  My first firing with this kiln was a cone 6, and i really felt that it was too hot (colors washed out, etc), so switched to cone 5 with much better results.  I do not see any pitting in this batch.  Tried some different things with stains and clear glaze on white that look good (photo).  Adding a photo of the 4 "horny toads" also known as Texas Horned Lizards.  3 different glazes--slate blue, sage, and  jade.  The jade (most green), is a glaze from my college days, and it has barium carbonate in the mix, so i only use it on non food items.
Giving a good deal of thought to the hold on bisque firing.  I have a black clay that i love, but it is SO messy (turns my hands orange), and tends to blister, but MAYBE if more of the iron or whatever was burned out in the bisque......  I have also experimented with using it as a slip over red clay, and I like some of the results, and will do more with that.
All that said.  I have an L and L kiln with the auto vent system--how do it l Iower the temp for a bisque hold?  I am still learning the menu and I thought I could only HOLD at the final firing temp?

I am not a hold person as to me it simply adds heatwork. In a practical sense there are folks who fire one cone lower but add a hold to get to the next cone heatwork without the peak temperature. In that case firing to cone five with a fifteen to twenty minute hold often gets one to cone six. (Usually verified with cones)
Why do that? Some glazes do not like higher peak temperatures. Some underglazes change color significantly with peak temperature. It is a pretty functional way to fire a cone to two cones max higher without hitting the actual peak temperature. 
Firing higher or for longer has never healed pinholes for me, often made them worse. Drop some temperature and hold however has helped on s some of my pinhole situations.
whatever works for you and your desired glaze results is likely the best answer. Whatever is done, I strongly suggest  always nice to have cones in place so you genuinely know how much heatwork was done. As to suggested time, 15-20 minutes generally gets you to the next cone.