Kiln Build

[DWyatt]

What a week it's been. Over the last 8 or 9 days my wife, myself, 3 yr old, and 8 month old all caught the covids. Let me tell you, an 8 month old cutting teeth and having covid was like living in hell. We are all on the mend and I still managed to get quite a bit done on the kiln. All the plywood is hung inside and it's time for the floor. I am not sure how well it will come through in the pictured, but please take a moment to appreciate my perfectly chalked lines on the doors for my screw pattern. I put all of the 1/2" plywood on the ceiling by myself. Wow is that stuff heavy when you're 4 steps up a ladder, but I only dropped 2 sheets.



 



 



 

[DWyatt]

Stone is in and compacted. I decided that it wasn't worth going to get the tractor from my parents and that I was just going to wheelbarrow it. 2 hours later I was regretting that choice  :D Last thing to do is screed off the sand, then I'll start getting the foam and plywood down.



 

[DWyatt]

Got the sand all knocked down around 10:30PM Friday night. Used my 8' level and laser to screed off the sand. Now if this 40 MPH wind ever lets up, I'll get the foam down. 



 

[DWyatt]

The floor is in and about half the seals are installed. Unfortunately my small door was about 1/8" too big, it's so hard to predict the hinge swing on a door that 5" thick. And the more unfortunate part is that I have it all made and trimmed out with metal and the only way to fix it is to completely disassemble it and cut an 1/8" off then put it all together    hopefully work is less hectic this week and I can get more done. 

[DWyatt]

Back to square 1 with the small door. Had to take it 100% apart to cut 1/4" off of the width, then put all the trim back on. It'll get hung this weekend.

[DWyatt]

I got the electric pulled and hooked up to the kiln. I ended up just jumping a 50 amp subpanel to the kiln and stuck another ground rod in. Cheap insurance, I suppose. The baffle is installed and the inside park of the l53 is installed. My exterior rated box should be in next week, then I can get everything hooked up. If I could get a weekend that wasn't 40 mph winds and raining, I could actually get this thing finished.

[barbender]

 I do believe the electrical code specifies a 4 wire service (if you are running 220 volt out there) in any case a dedicated ground is supposed to be run back to the main panel, and also tie in to a ground rod like you have. Kind of "double grounded" in a sense. When I was building, the electrical inspector told me that the line of thought is to have a ground running back to source so that power doesn't end up grounding through a propane line or something.

[YellowHammer]

Or through the building, I've seen a guy get knocked to the ground when he grabbed the doorknob on a metal building. 

Yes, if you are going to wire to code for insurance reasons, the NEC requires 4 wires run from a service panel to a sub panel, two hots, a neutral, and a ground wire.  The neutral wire, ground wire and ground rod wire are all bonded to the service panel through the ground bar, and the ground rod must be within 6 feet of the service panel. So 3 wires bonded to earth ground at the service panel all tied together.

The sub panel should have separate neutrals and grounds, and not have bonded ground to neutral and no ground rod at the sub panel.  However, the kiln unit itself, (end machine) can be tied to a ground rod directly to its frame for lightning protection.

You may also consider a lighting protection or surge suppressor panel breaker mounted in your service panel, they take a 220V breaker slot.

Anyway, I'm not the Electrical Code police, just agreeing with Barbender. 

 

[DWyatt]

You are both correct. The electrical supplier I use helps me through my limited knowledge of the electric code. Anytime you are running electric after the first means of disconnect, you carry the ground. My first means of disconnect is at my 400 amp meter base. There are 2 EA 200 amp breakers. One feeds the house and one feeds the shop. The ground is carried to both, then carried to a couple of sub panels. The sub panel I purchased did not have separate neutral and ground bars so I have installed a separate ground bar to the panel. 

I appreciate the insight and while I am not in a inspected county, I try to do things correctly. Luckily a good friend of mine is an electrician and owns his own residential/light commercial electric company so he helps me work through any questions I have. 

@YellowHammer I do have a question about one of your comments that I should not have a ground rod at the subpanel that I believe differs from my understanding. My understanding that since it is a subpanel, the ground is carried to the panel and the ground and neutral shall not be bonded at the panel. As long as these conditions are met, a ground can be added at the subpanel. Youtube video below from Electrician U that I believe explains what I understood.

[doc henderson]

our pool has everything bonded to ground.  that include the lights grounded to the wire mesh under the concrete, and back to the panel with a wire to earth ground.  you want that breaker to snap if any current goes to the wrong place.  all the grounds and neutral/common wires go to the same bar in my main panels. you can have current feedback via a ground and thus to the metal part of a tool.  In a tornado you could have a pole go down and in theory lose neutral but not the 120-volt legs.  Do it right.  the question sometimes "what is the right way".

[NCWoodsGuy]

Nice kiln build!

Not sure about swimming pools but my experience is only the first (main) panel where power comes from the utility is to have the ground and neutral bonded. All sub panels that feed from that main shall have the ground and neutral separate, as someone posted above. Local codes may vary of course.

Odd local variation here in my part of NC is the service entrance main requires two ground rods spaced 6 feet apart. I thought that was weird.

[doc henderson]

I know some soil types offer better ground, and moisture plays a role.  maybe a safeguard in case a wire breaks or comes disconnected.  I think it ends up the same if the main is bonded together, it all acts the same.

[Larry]

When I worked for the phone company I learned lots about earth grounds. Most equipment installations at minimum, required three ground rods in a specific pattern for protection from voltage surges. Once the ground rods were in place we used something called a megger (ohm meter on steroids) to measure ground resistance. It was interesting to see the results as some failed.

When I moved to Arkansas I learned of a grounding system far far better than a rod. Its called a Ufer which is a ground wire tied to the building rebar. I made this discovery because our soil has a rock or three which tend to make driving ground rods difficult.

More than ya ever wanted to know about ground rods.
 

[YellowHammer]

The video is pretty good, and he may be 100% right, but believe there is some ambiguity of the NEC that causes confusion, and I may be wrong, the inspectors may be wrong or who knows, and although the NEC can be considered minimums, apparently my inspection department takes them as absolutes.

I failed an inspection several years ago because my Licensed electrician had grounded my service panel, my sub panel but not my equipment (planer).  The 4 wire branch is called an equipment ground for a reason, I was told by the inspector, and so we removed the sub panel ground rod wire, and grounded the planer with it's own ground rod and we passed.  I was told the equipment had to have a ground rod, but not the branch panel, and not both.  Either way, when we removed the branch panel earth ground rod wire, we passed. 

We just wired up a mobile home, and when the installers set the home, the only ground rod was to the main service disconnect at the pole.  I questioned the inspection department about this, and they sent me an inspection packet, which included this cute little drawing of a 4 wire in conduit, with no ground at the mobile home interior branch panel.  The document had several pages and the diagrams of the service panel were quite detailed about grounding. 

Reading from NEC code  250.32(A)Exception:  A grounding electrode shall not be required where only a single branch circuit, including a multiwire branch circuit, supplies the building or structure and the branch circuit includes an equipment grounding conductor for grounding the normally non current-carrying metal parts of equipment.

So in this case it's not a requirement, and in my case, my inspectors read this as if it's not specially spelled out as a requirement, then doing anything different violates the NEC requirement.

So anyway, if you Google it there is lots of confusion, but seems to me the more ground rods the better, until I failed my inspection...

I do know that in the equipment testing world, putting too many ground rods in is a definite "do not do" golden rule, as it causes tremendous ground loop errors that is easily picked up by our test equipment.  Basically, the golden rule in the testing world is "ground once, and ground at the source."

So, I guess the answer from me is if I had my old job, I could just call up the head of the Director of the NEC and ask him, but now all I can do if read the codes and get failed by the inspectors for putting in too many grounds, wrongly or rightly. 

[Sod saw]

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Glad to hear that you are ready to finish up, hope that you get good weather.  I am still messing with door seals even after a few years of use.  What did you find best for gasket material, weather seal?

Yellowhammer, When I build electrical systems I need to know what the "system" is going to be used for.  In the case of radio/Tv station or recording studio or large computer systems or equivalent, then your observation about having only one ground source is absolutely correct.  Ground loops will  drive you nuts.

Doc.  Your pool observation is also correct as far as the code goes.  Everything metal must be bonded together.  There are different engineering (physics) reasons than for an electrical service entrance.

Now let's look at the National Electrical Code itself.  When an installation is prohibited the language in that section of the code will reflect that.  When an installation is required, the language in that section of the code will reflect that also.  

Now the gray area:    When an installation is not specifically prohibited (such as an extra ground rod someplace), then you can do it if you wish but you can not ignore other required sections of the code.  

Perhaps as an example (let's use our imagination for a moment) Yellowhammer has a 3 phase planer that has new wires from a sub panel to feed their new planner.  Let's assume that the electrician ran only 4 conductors to the planner control box.  3 hot wires and a neutral.  In this example the inspector is correct in saying that the planer steel frame needs grounding.  A ground rod is ok and/or another 5th ground wire run back to the sub panel is ok.  Yes you can install a rod and the 5th ground wire at the same time. The gentleman on the video is correct, the code does not prohibit a ground rod along with a separate ground wire to the panel (sub panel).

I disagree with Yellowhammer's inspector where he had the ground rod removed from the sub panel.  UNLESS it was for ease and convenience of connecting to the planner with the minimal of work and expense.  I was not there but have run into inspectors who require something because they misunderstand the intentions of the language of the code as pointed out above.   And sometimes I misunderstand too and need help with clearing up code intentions.

Let's look at sub panels- - - - If a sub panel is within the same building as the main service entrance panel, then that sub panel must have: neutral wire, the hot wires (2 or 3 depending on phases) and a separate ground wire in the same runway connected to the ground in the main service entrance panel but connected to its own ground buss within the sub panel.  Within that sub panel the white neutral (not always needed) will be connected to its own buss insulated from the ground buss.

Oh, by the way, one question on our electrical license tests;  What color is the green ground wire?

Now on to an exception to the grounding of sub panels. I hope that this does not confuse folks.  If you have a main service entrance panel in a building (house as an example) and you have an out  building that you wish to run wires to,  You can treat that out building as though it has its own main service entrance.  In other words the code does not require that a separate ground wire be run to that building.  But as stated above, the code does not prohibit a separate ground wire to bond that panel in the out building to the main panel in the house.  Without that separate ground wire from house to out building panel, you will need two ground rods in the out building, just like you need two points of ground with the main service entrance.  And yes, if you believe that the earth will not conduct electricity well, you are correct that you can always add more rods further and further apart.

Having explained that exception, I always run a separate ground wire from panel to all sub panels, regardless of whether it is in an out building or not.  Ground rods can be extra if you wish.

When dealing with audio, video, computers etc.  All equipment should be bonded to only one common ground location, and not the lightning system.

Larry's grounding to rebar is great if you have it.  Not many pole barns or houses have access to it.  The National Electrical Code requires only two rods for Electrical Service Entrance in most cases.  More can be added if poor grounds are noted in that area.

A note here about storms and the loss of the neutral connection from the service entrance at the building to a pole.  I have been asked to repair many major ice storm damaged homes because the ice brought down only the neutral wire from the pole to the house.

Without proper ground rods (or bonded copper water pipe from street to house). Those houses had 240 volts flowing throughout the whole electrical system.  Any appliances that were "on" got fried. Except for appliances that were designed to operate on 240 volts.   Light bulbs blew, kitchen  appliances died, refrigerators died, cloths washers, stereo, GFI outlets, you can fill in the blanks here.  My point is that even new services can have corroded ground connections or weak conducting ground paths to the dirt.  And don't overlook the utilities outdoor connectors from pole to building.  They have the pleasure of being out there in all kinds of weather and temperature changes.

Gas lines should never be the source of grounding.

have fun but be safe


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[Sod saw]

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Having just studied the drawing shown by Yellowhammer in his post I find that they would violate all of our Electrical Utility requirements as well as the National Electrical Code.

The reason for this note is to illustrate the different requirements in different areas of the country.

Your drawings show 2 inch diameter electrical conduit from the meter area to the mobil home.  At the meter area where that PVC (plastic) conduit connects to the pole box, your conduit connects directly to the box.

Here in NY State, we have been know to have winter freezing the ground to about 4 feet deep.  As we all know, when water freezes it expands causing the surface of the earth to rise up forcing the electrical conduit to jam its way into the box breaking fittings and bending boxes.   When the ground thaws it settles to below the original elevation of last fall causing the electrical conduit to pull out of the box on the pole.  

How to solve tis issue?

We are required to install a slip joint where the conduit joins into the box to allow the ground to move the conduit up and down without stress on the conduit pipe or the wire connections within the box.

Just a detail but important to the area where you live.  

Oh by the way, I have never used those flexible pipe hose things under trailers .  I should think that they work well for you where the trailer might bounce on its springs, or the ground settles.

Question:  Did your electrical company drawing omit the caution tape over the pipe under ground?


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[YellowHammer]

Lots of info to digest for sure!  I love it.  

I reviewed the NEC codes I could find, and they are pretty ambiguous and poorly worded.  For example, as far as I can tell, in 2023 the section 352.44(B) was added which requires expansion fittings to be installed above grade when direct buried PVC conduit emerges from the ground and compensation is needed for earth settling or movement, including frost heave.  So what is meant by compensation for earth settling?  Compaction by a mechanical or man powered tamper?  What else could be done to not require compensation for earth settling?  I could argue that I could fill in the ditch with 100% washed compacted gravel and then I wouldn't be in violation?  I hate ambiguity in technical codes and documents.

Prior to that, the table 352.44 states PVC expands 3.65"/100ft for 90°F temp range, which means any run longer than 6.85' requires an expansion fitting, however, with the drawing by the county, with the 18" bury depth of the conduit, and the placement of the weatherproof disconnect, then the vertical run of the conduit won't exceed that, so would meet code.  However, it would not meet code based on the 2023 update, assuming that I filled with uncompacted dirt, but if I backfilled the ditch and compacted the clay, then I would meet code. 

Also, as far as I could see, the requirement for marking tape is describes in NEC 300.5 (3) where it states "Underground conductors buried 18" below grade shall have making tape" and even though the county didn't require it as far as I could tell, I run it as a routine step whenever I l trench wire or water.  I have a little transmitter/tracer that I can send a signal down conductive marking tape, and find it.

Either way, the inspectors in my county have the final word, and what they say is law and I couldn't get insurance for my two kilns or any of my operation until I passed inspections with the code cops and the yearly Fire Marshall inspections.      

[DWyatt]

I love all this information, mainly because electric is something that I know enough about to be dangerous.  I can however follow directions really well which is why I ALWAYS consult with my electrical supplier (and his son who is licensed) as well as my buddy who is an electrician. I normally leave these interactions with saying that there are specific reasons why my PE is as a civil engineer. I can see everything I work on, which is not the case when working with electric.

I live is an unzoned, no inspection township within my county. I am doing all of this work as an individual for my own use, not as a business. While I thoroughly enjoy that I don't have "the man" to deal with when I want to put up a new building, I would love to have more guidance when it comes to electrical. From the sound of things, the NEC is left widely open to interpretation on many items. Even if I had an inspector, they could say completely different things than Yellowhammer's inspector when it comes to this topic in particular. 

Grey areas, kind of like the spelling of gray are well...grey...or gray. My mind works much better with black and white. 

My goal with not only this build, but any build is to build things in the correct manner. I am not going to cut a corner in an attempt to save a few dollars. Electrical systems, if done incorrectly, can be devastating. I thoroughly appreciate all of the insight on this subject!

[DWyatt]

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Glad to hear that you are ready to finish up, hope that you get good weather.  I am still messing with door seals even after a few years of use.  What did you find best for gasket material, weather seal?

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I am using a combination of gaskets on the doors. I think I about bought Lowes out of weather stripping when I was there. Along the hinge side, I have two rows of seals that are 3/8" - 3/16" seals. Along the top, I mounted a 2"x2" aluminum angle that has the same seal that the door will press against when latched closed. The bottom of the doors will seal against the floor structure. For that I got seals that expand from 1" - 3/8" which will be mounted on the face of the floor framing. For the gap between the doors, I am using the same thick seals that will smash together as the doors close. The big door on the kiln also faces NE which should help keep it out of the weather as much as possible. The goal is to challenge the seals as little as possible.

[DWyatt]

Conduit and wire is installed. Just have to finish things out. I have the box for the controller. Just need to install it, then I'm ready to run the first load! Oh and I also got the small door installed, but it was too dark for a picture.

[blackhawk]

Maybe you haven't gotten that far, but I would suggest having 4 extra fans instead of 2.  I needed that to get the air speed up through the stack.  I did my extra fans at 90° instead of at an angle.  I didn't try them at an angle, so I'm not sure if there will be a difference.  One thing that Stan suggested was to put a 45° angle piece of plywood along the wall/ceiling opposite the fans.  When the fans hit that sharp corner a good amount of air gets deflected back.  The angled piece helps push the air down that far wall and then through the stack.  I tried it both ways and it did make a significant difference.  If you don't have on already, I suggest getting an air flow meter.  I have a Kestrel brand and it really helps to check your airflow through the stack and be sure it is even.  

[DWyatt]

Thanks for the heads up. I had planned to run the kiln with the two auxiliary fans, but I spaced them toward the edge of the stack so I have room to add two more if needed. Yes, on the deflectors. I haven't added them yet, but I plan to. I appreciate the reminder!

I am basically ready to run the first load. This weekend I finished getting the power cord run into the kiln unit, got all the seals put on the small door, finished the electrical, and installed the cam lock trailer door latch on the big door. I have to put the seal on the bottom of the big door, get my 45 degree angle pieces installed at the top corner of the wall, and mount the wet & dry sensors. I can finally see the light at the end of the tunnel! 

[Magicman]

This is getting Exciting...

[K-Guy]

Unfortunately your electrical will all have to be redone, it must be in water tight boxes and be in aluminum or plastic conduit. The steel will quickly rot due to the tannic acid in the wood.

[DWyatt]

K-Guy, you're probably right. Dad's kiln has been in operation like this for 25ish years and never had an issue. So if I have to redo things every 25 years, I'm okay with that.