Element connectors, overall new kiln project.

[cadenrank]

Hello all! 

Today, I got the 8 awg cable that supplies my one kiln upgraded to a 6 awg cable. The intention of this is to upgrade my elements to a different resistance configuration that will both supply the kiln with more power and hopefully more even heating, as well as make replacing elements easier (as I won't need to get them custom made, and hopefully won't have to do any stretching of elements, discussion of this project for this kiln has happened in the past on another topic of mine here, but about time for new elements, so progress towards getting the circuit ready for that transition is underway) 

This kiln currently pulls around 30 amps (8 sided, 5 brick layers deep. Skutt 822 is the most  similar model.). At the end of this project, it should pull roughly 34.7 amps, with the new elements on the 6 gauge copper, and a 50 amp breaker circuit that's now finished for this kiln.

During my last element change I used some of these types of connectors: 


I like these connectors because of how easy they are to connect, and they allow for changes to happen and repairs to happen much more easily than the crimp on connectors. My issue with these is that over the life span of these elements, I've had 4 of the 10 fail. They corroded, and eventually burnt out at the connector, leaving them unusable because the wire had melted where it burned out and essentially welded the connector to the element tail.

This kiln is an older model kiln with entirely new components and wiring. The kiln originally came with brass nuts, bolts and washers as element connectors which I wasn't a big fan of at first, however, of all the types I've tried (the ones pictured, Skutt's crimp on barrels, and Paragon's version (which I mostly don't like because of cost)), I think the nut and bolt connector is the one that I like, and feel the most comfortable with. All of the connectors like the ones pictured above that have burned out I replaced with the old original brass nut and bolt and washers that I saved, and they still look perfect and feel the most secure to me while being relatively easy to perform repairs or replacements with in the future. 

So that being said, my question comes down to material. I don't have enough of the original brass nuts and washers to do the whole kiln with them once the new elements go in, so I'll need to purchase more and I'm just wondering what size as far as bolt goes, material they're made of, etc.  Is brass the best option? Stainless? Are the brass nuts/bolts/washers I'd find in big box hardware store good to handle the heat and voltage/amperage that will be passing through it? Any other recommendations on where to get some that would if not? 

Thanks as always for any information and any help!
-Caden

[neilestrick]

I've had good luck with the connectors you show above, and ConeArt uses them in all their kilns. Are those tinned copper? I usually use raw copper, as does ConeArt. Not sure if that matters or not. One tip, make sure you're putting the wire at the bottom in the V and the element at the top, so the bolt pushes on the element. That'll give a tight connection. You may also need to re-tighten them after the first few firings just to be safe.

Bending the end of the element into a circle and putting a bolt through it is a great connection. Use stainless steel, put a washer on each side, use a lock washer, and connect the feeder wire to it with a high temp ring terminal. Totally old school and very good. I'd use a 10-24 bolt.

[cadenrank]

I really liked the one's pictured (they're from TheCeramicShop, who say's "They are made of zinc coated copper for higher resistance to corrosion, and longer connection life"). Price was good, and I was confident in the connections when I made it, but the amount of times these have failed now have made me weary of them in general. I believe I did put the element on top in them, but not certain. And each time I've had a burnout (4 of them now) I've tightened all of the others while I had the box off. I just feel the washers bolt and nut is much more secure in combination with crimped on ring terminals on the wires, while still being able to take them off easily during changes or other maintenance. I never had any issues with corrosion or burn outs on them or getting them off when they needed to come off. 

24 minutes ago, neilestrick said:

Use stainless steel, put a washer on each side, use a lock washer, and connect the feeder wire to it with a high temp ring terminal. Totally old school and very good. I'd use a 10-24 bolt.

Thanks for the information! I figured stainless hardware would be fine, but wanted to double check before I went and bought some. I think this is the route I'm going to go. 

[Bill Kielb]

1 hour ago, cadenrank said:

So that being said, my question comes down to material. I don't have enough of the original brass nuts and washers to do the whole kiln with them once the new elements go in,

This may help - I like those as well but their mass is small so I personally have seen them fail on the highest loaded elements in the least cooled ares. They are not big enough or have enough surface area to keep the connection cool for the amount of cooling  air passing them.

Improving the cooling airflow can help if the convective flow from bottom to top can be improved. Reducing leaks out of the kiln by stuffing with high temp insulation can help for radiant and convective losses as well.

The simplest solution has been to extend the element pigtail more and position for best convective cooling, just to get some additional cooling to the connection.

conductivity plays a role so copper best, brass next,  followed by steel / stainless.  An old easy connector to build  is drill a brass bolt, use the bolt and two washers. Sandwich the wires between the washers through the drilled hole. Increased  convective cooling (heat sink)  easy to achieve this way, thermal conductivity less of an issue but surface area as well as mass very important. So this can be done with steel and stainless, just harder to fabricate and not thermally as conductive.

1/4” - 3/8” X an inch or two (Cooling surface area and mass) simple brass bolt and nut depending on the clearance in your cabinet can last forever and be very economical and easy to build.

Edited December 31, 2023 by Bill Kielb

[Mark C.]

How about copper split bolt connectors . Electricians like me use them on all large wire connectons as they are made for large amp draws. They are usually all copper and a brass nut. They are spendy and come in a variety of sizes. Also I use copper coat on these connections as that keeps out all corrosion. Never had one fail.

Edited January 1 by Mark C.

[cadenrank]

1 hour ago, Bill Kielb said:

 I personally have seen them fail on the highest loaded elements in the least cooled ares. They are not big enough or have enough surface area to keep the connection cool for the amount of cooling  air passing them.

Improving the cooling airflow can help if the convective flow from bottom to top can be improved. Reducing leaks out of the kiln by stuffing with high temp insulation can help for radiant and convective losses as well.

This makes sense. 
 

1 hour ago, Bill Kielb said:

The simplest solution has been to extend the element pigtail more and position for best convective cooling, just to get some additional cooling to the connection.

conductivity plays a role so copper best, brass next,  followed by steel / stainless.  An old easy connector to build  is drill a brass bolt, use the bolt and two washers. Sandwich the wires between the washers through the drilled hole. Increased  convective cooling (heat sink)  easy to achieve this way, thermal conductivity less of an issue but surface area as well as mass very important. So this can be done with steel and stainless, just harder to fabricate and not thermally as conductive.

Good to know. I'll see what they have at the store. 

 

7 minutes ago, Mark C. said:

How about copper split bolt connectors . Electricians like me use them on all large wire connec tons as they are made for large amp draws. They are usually all copper and a brass nut. They are spendy and come in a variety of sizes. Also I use copper coat on these connections as that keeps out all corrosion. Never had one fail.

I never thought of a split bolt. I'll see what I can find! 


Thank you everyone, again, for the help! 

[Mark C.]

I used these from Euclids when I rewired my electric -brass and stainless -I added some copper coat as well to insure great long term corrosion free connection 

https://euclids.com/products/element-connector-large-2-screw?pr_prod_strat=e5_desc&pr_rec_id=82bd0e954&pr_rec_pid=5133891010605&pr_ref_pid=5133812236333&pr_seq=uniform