Another "bought an old kiln help me thread" :)

[Skydve76]

I did a little reading here and there and thought I would just ask some questions.

Background  and where I am at:

This is a Gare Kiln model 2318.  On the silver panel it says 30 amps.  On the sitter it says 45 amps.  The plug on the kiln is an old 10-50p the gray one.

I installed a 240V 14-50r outlet today for the kiln to test it.  I used 8/3 wire and a 40A breaker.  I let the kiln heat up for 10 minutes.  All burners worked.  I have some cone 6 coming tomorrow so I can see if it will hit cone 6.   I assumed the kiln is 30a and the sitter is rated for 45A and is seems to be a generic unit as the Kiln is form Mass. and the sitter from Cali.

I plan to replace the plug with a 14-50p I picked up at lowes and attach the ground to the metal box.  I read on this forum a 60A circuit may be needed which is INSANE.  I HIGHLY doubt that gray 10-50 plug is rated for 50A if that.  I have a clamp on ammeter coming I will see what it is pulling.

Questions:

What circuit am I supposed to use for this?   

Should I replace the coils right off?

What should I do to test this out?

Do I need to seal up hairline cracks?

Thanks!

 

 

 

Edited May 29, 2023 by Skydve76
added close up of silver plate

[PeterH]

Take the gurus advice on what to do about the wiring/breaker.

But, if their response is what I expect,  this is my understanding of why.

>On the silver panel it says 30 amps.  On the sitter it says 45 amps. 

 I think you will find that this means
- the kiln pulls up to 30a
- the sitter can control a kiln pulling up to 45a

So the load your circuit breaker will need to handle is 30a.

But when supplying continuous loads circuit breakers may trip before their rated load.
Information Sheet # 37 Differences Between 80% and 100%  Rated Circuit Breakers
https://cliffordpower.com/wp-content/uploads/2020/01/IS_37_80-versus-100-rated-ATS.pdf

Typical circuit breakers are rated at 80%, so you would need a breaker and wiring rated at 30x1.25=37.5a, i.e. a 40a one. 

> I read on this forum a 60A circuit may be needed which is INSANE.  I HIGHLY doubt that gray 10-50 plug is rated for 50A if that.

You  need an appropriately sized fuse in the plug to protect the kiln and its lead/plug/socket. The breaker prevents the house wiring from overheating (fire risk): hence the house wiring needs to be rated at the full breaker current, not the expected load. 

Edited May 29, 2023 by PeterH

[Skydve76]

 

Ok cool.   The 60a is for the 45 kiln.   My 40a is fine then for my 30a kiln. 

 

How long should it take to get to cone 6?

Edited May 29, 2023 by Skydve76

[PeterH]

As I said don't take my word for it, but I think that's what the gurus will say. I'm just giving a rationale based on my opinion.

[Russ]

Not sure how familiar you are with clamp meter .. but if you do know the correct way to use one this is for others who dont know, the clamp must be centered around only 1 hot to get the correct reading. Then the next hot.... and then added up for the correct  amps.

[neilestrick]

Code requires that kilns be on a breaker that is 25% greater than the draw but no more than 50% greater, so your 30 amp kiln needs to be on a 40 amp breaker. The Sitter can handle up to 45 amps. 

22 hours ago, Skydve76 said:

I plan to replace the plug with a 14-50p I picked up at lowes and attach the ground to the metal box. 

The 14-50 plug is a 4 wire plug- 2 hots, neutral, ground. Your kiln is a 3 wire setup- 2 hots, ground- so you'll have an extra terminal in there that you do not need. I would change out your outlet to a 6-50, which is a 3 wire, and get a new 50 amp power cord with a 6-50 plug. It's always nice to have an oversized power cord. There's no good reason to use that old cord with a new plug.

What size wiring is going from the breaker to the outlet? It needs to be sized to handle at least the amperage rating of the breaker, so if it's a 40 amp breaker you need at least 8 gauge wire. Anything smaller than that will need to be changed. Anything larger than that is just fine. Are there 3 or 4 wires going to the outlet? If there are 4, cap off the neutral because you don't need it, or if you need to run new wire then just run 2 hots and a ground. I'm not a big fan of having unused terminals in outlets and plugs because it just makes things more complicated than it needs to be when doing repairs.

I would only change the elements if they need it. Unplug the kiln, turn on the Sitter and all the switches, and measure the resistance (ohms on the meter, little horseshoe symbol) at the two hot prongs on the power cord.  It should be around 8 ohms- 240 (volts) divided by 30 (amps). You can also check each element by turning on each switch one at a time. Each element should measure around 32 ohms.

[Skydve76]

36 minutes ago, neilestrick said:

Code requires that kilns be on a breaker that is 25% greater than the draw but no more than 50% greater, so your 30 amp kiln needs to be on a 40 amp breaker. The Sitter can handle up to 45 amps. 

The 14-50 plug is a 4 wire plug- 2 hots, neutral, ground. Your kiln is a 3 wire setup- 2 hots, ground- so you'll have an extra terminal in there that you do not need. I would change out your outlet to a 6-50, which is a 3 wire, and get a new 50 amp power cord with a 6-50 plug. It's always nice to have an oversized power cord. There's no good reason to use that old cord with a new plug.

What size wiring is going from the breaker to the outlet? It needs to be sized to handle at least the amperage rating of the breaker, so if it's a 40 amp breaker you need at least 8 gauge wire. Anything smaller than that will need to be changed. Anything larger than that is just fine. Are there 3 or 4 wires going to the outlet? If there are 4, cap off the neutral because you don't need it, or if you need to run new wire then just run 2 hots and a ground. I'm not a big fan of having unused terminals in outlets and plugs because it just makes things more complicated than it needs to be when doing repairs.

I would only change the elements if they need it. Unplug the kiln, turn on the Sitter and all the switches, and measure the resistance (ohms on the meter, little horseshoe symbol) at the two hot prongs on the power cord.  It should be around 8 ohms- 240 (volts) divided by 30 (amps). You can also check each element by turning on each switch one at a time. Each element should measure around 32 ohms.

Hello, I have a 40A circuit, with 8/3 NM wire.  I was confused if my kiln pulls 30 or 45 amps.  So thats all cleared up and my circuit is fine.

Ill check the elements as you said.

 

Do you think it is worth firing it to cone 6 for testing (empty) or should I just get some pots going and fire them up?

EDIT: BTW in my area its illegal to install anything but a 14-50 or 14-30 after any house built after 1996.  So I went with 14-50r, I have an adapter for now but plan to put the 14-50p on it with ground wire attached to the casing (hot, hot and neutral going to the spots they are on now)

Edited May 30, 2023 by Skydve76

[neilestrick]

10 hours ago, Skydve76 said:

EDIT: BTW in my area its illegal to install anything but a 14-50 or 14-30 after any house built after 1996.  So I went with 14-50r, I have an adapter for now but plan to put the 14-50p on it with ground wire attached to the casing (hot, hot and neutral going to the spots they are on now)

That's an odd ruling, because that would mean a kiln would not be hooked up according to manufacturer's recommendations, and in the case of a UL listed kiln it would require changing the plug and possibly negating the UL Listing. @Bill Kielb have you ever heard of that rule? 

Ground wire should be attached to the appropriate ground terminal all the way through from the breaker box to the kiln box. The neutral should not be used at all. Adapters and extension cords are not safe for use on kilns.

I wouldn't fire any pots until you test it, but I wouldn't run a test until you measure the element resistance.

[Skydve76]

42 minutes ago, neilestrick said:

That's an odd ruling, because that would mean a kiln would not be hooked up according to manufacturer's recommendations, and in the case of a UL listed kiln it would require changing the plug and possibly negating the UL Listing. @Bill Kielb have you ever heard of that rule? 

Ground wire should be attached to the appropriate ground terminal all the way through from the breaker box to the kiln box. The neutral should not be used at all. Adapters and extension cords are not safe for use on kilns.

I wouldn't fire any pots until you test it, but I wouldn't run a test until you measure the element resistance.

Hey I read your post too late.  I thought you said to use a 10-50 sorry. 

A 6-50 is fine.

Why are rv extension cords not recommended?  It's stronger than the wiring in my house. 

[Skydve76]

BTW this is the RV cord I got:
https://www.amazon.com/dp/B08HGLV1L3?psc=1&ref=ppx_yo2ov_dt_b_product_details
You have me doing more research now.  Its interesting with the EV charging market there are all kinds of adapters and extension sords being used all over with 240.  That doesnt mean its safe but it is becoming common practice.

Since I went 14-50 what cord should I use on the kiln, is one for an oven ok and what is the max length?

[Bill Kielb]

2 hours ago, neilestrick said:

That's an odd ruling, because that would mean a kiln would not be hooked up according to manufacturer's recommendations, and in the case of a UL listed kiln it would require changing the plug and possibly negating the UL Listing. @Bill Kielb have you ever heard of that rule? 

I have only heard of local rules affecting the wiring of stoves so as to include a full rated neutral in all installations. With respect to three wire loads, I am not aware of making neutrals mandatory. There are very specific requirements to grounding and bonding to avoid voltage / currents appearing where they should not. With respect to cable ratings, buy the appropriate one for the appliance, there are too many nuanced and tested criteria that really impossible to know with respect to something being “stronger”.

My suggestion: If you have a three wire system, do NOT wire the neutral, wire as the manufacture specified

Edited May 30, 2023 by Bill Kielb

[neilestrick]

1 hour ago, Skydve76 said:

BTW this is the RV cord I got:
https://www.amazon.com/dp/B08HGLV1L3?psc=1&ref=ppx_yo2ov_dt_b_product_details
You have me doing more research now.  Its interesting with the EV charging market there are all kinds of adapters and extension sords being used all over with 240.  That doesnt mean its safe but it is becoming common practice.

Since I went 14-50 what cord should I use on the kiln, is one for an oven ok and what is the max length?

Any time you add a plug into the system it's another weak point, so the fewer the better. Not using an extension cord is most likely a physical safety thing rather than an electrical thing. A long cord is far more likely to be tripped over, which could cause the kiln to be pulled off the stand while hot. An RV isn't going to tip over and start a fire if you trip on the cord.

A 6 foot long, 3 wire, 50 amp oven cord would work fine. If you get a 4 wire that matches your outlet, just don't use the neutral wire.

[Bill Kielb]

The six foot rule is in place for several reasons but one of is that it becomes a reasonable approved means of disconnect within six feet of the appliance.

[Skydve76]

FYI my kiln currently has a 10-50p on it.  I havent opened it up yet but does it just ignore the neutral?   There is on the side of the sitter what looks like a 120v plug but the tanks are rotated 90 degrees (horizontal). 

 

If it doesnt need the neutral, does that mean my current kiln just uses two hots only?

[Bill Kielb]

3 minutes ago, Skydve76 said:

FYI my kiln currently has a 10-50p on it.  I havent opened it up yet but does it just ignore the neutral?   There is on the side of the sitter what looks like a 120v plug but the tanks are rotated 90 degrees (horizontal). 

 

Post a picture. North America is one of the few places that use split phase so The neutral is not used in a three wire load. Just two legs and a Ground. The ground Carries no load, just a safety usually bonded to the shell of the kiln. This kiln appears to be built in the UK which likely means a single phase 240v circuit. A neutral and one hot leg @ 240 v.plus a ground. Here, since we split our phases in residential it will just be two hot legs and of course the ground.

[Skydve76]

Here is the plug, a 10-50p that is 2 hots and a neutral,  no ground.

When I put my 14-50p on it, I will attach the 2 hots where they are now, and the neutral where it is now (if its just capped off inside Ill do the same).  In terms of the ground that will be present, I will attach it to the shell of the sitter.  Does that make sense?

[Bill Kielb]

Show us a picture of where these are attached inside the kiln presently with a bit of an overview of the wiring (picture)  but yes, that sounds correct.

Edited May 30, 2023 by Bill Kielb

[neilestrick]

Yes, pics inside the kiln. I've never seen this model of kiln with a neutral, nor have I seen a 3 wire plug with a neutral and no ground, but hey that doesn't mean they don't exist. An ungrounded kiln would not be safe, though. Even though the 10-50 is technically 2 hots and a neutral, ungrounded, they are probably using it as a 2 hots and ground. No guarantee that cord is the original. Post some pics of inside the control box and that will clear everything up.

[Dick White]

1 hour ago, neilestrick said:

... nor have I seen a 3 wire plug with a neutral and no ground, but hey that doesn't mean they don't exist...

Back in the day, dryers (with a 10-30 plug) and stoves (with a 10-50 plug) used 240V from the two hots for the heating circuits while the controls and interior lights used 120V from one of the hots plus the neutral. Apparently, independent grounding wasn't a high priority back then for those household appliances as chassis grounding was permitted through the neutral, though the  really old120/240V kilns that we sometimes get involved with here all use proper 4-wire grounded circuits. In '96, the code changed to mandate separate grounding everywhere, hence the change to 14-30 and 14-50 for all new dryer and stove circuits. There is still a neutral for any 120V components in the dryers or stoves, but now there is a separate safety ground. However, you can still get a 10-30 cord for a new dryer if you are installing it in a grandfathered pre-'96 house.

I too suspect it is unlikely that this kiln has anything in it running on 120V (that would need the neutral), and therefore should be fine with a fresh 6-50 power cord, with the circuit in/on the wall running a straight double 240V 40A breaker and 8 /2-with ground cable to a 6-50R outlet. 

[neilestrick]

18 minutes ago, Dick White said:

I too suspect it is unlikely that this kiln has anything in it running on 120V (that would need the neutral), and therefore should be fine with a fresh 6-50 power cord, with the circuit in/on the wall running a straight double 240V 40A breaker and 8 /2-with ground cable to a 6-50R outlet. 

I should have specified that I was referring to kilns, not other appliances, but I get what you're saying.

And the serial plate doesn't specify 120/240.

[Skydve76]

1 hour ago, Dick White said:

Back in the day, dryers (with a 10-30 plug) and stoves (with a 10-50 plug) used 240V from the two hots for the heating circuits while the controls and interior lights used 120V from one of the hots plus the neutral. Apparently, independent grounding wasn't a high priority back then for those household appliances as chassis grounding was permitted through the neutral, though the  really old120/240V kilns that we sometimes get involved with here all use proper 4-wire grounded circuits. In '96, the code changed to mandate separate grounding everywhere, hence the change to 14-30 and 14-50 for all new dryer and stove circuits. There is still a neutral for any 120V components in the dryers or stoves, but now there is a separate safety ground. However, you can still get a 10-30 cord for a new dryer if you are installing it in a grandfathered pre-'96 house.

I too suspect it is unlikely that this kiln has anything in it running on 120V (that would need the neutral), and therefore should be fine with a fresh 6-50 power cord, with the circuit in/on the wall running a straight double 240V 40A breaker and 8 /2-with ground cable to a 6-50R outlet. 

Thank Dick, this is what I had read about 10-30 as well.  I went ahead and installed a 14-50 with 8-3 wire.  The reason I thought is its more versatile in my garage.  Perhaps a heater with a timer will be in my future for my garage.

Ill get pics of the kiln, with the 10-30 on it, it implies it is using the neutral as a ground.    if I put a 14-50P on it, I assume I attach the ground to the ground lug and leave the neutral capped off

[Dick White]

Yes, always connect the green (or bare) ground wire to the ground lug of either plug or receptacle, so that the case is grounded at all times.

[Skydve76]

Sorry for delay just got back onto this project.  As you can see from the pics, the 3rd wire (center) which is neutral on the plug, is being used as ground.  

Im not sure why, but the kiln has a 6-15p on it the outside of the sitter, what is that for?

 

I didnt ohm out the elements yet, is there any advantage to cleaning all the connections, everything is a bit dirty.

[neilestrick]

So it is a 3 wire system, no neutral. The 6-15 receptacle is for adding on another ring, which was common on a lot of the old kilns. I would just unhook that if you don't have the ring.

Is the wiring really dirty, or is it the old waxy cloth wrapped wiring?

[Skydve76]

This is a 10-50p which is no ground just nuetral.  So maybe the cord is not the original and it's hooked up incorrectly.

 

The wiring is a bit rusty too.