Breaking-in new kiln elements

[JohnnyK]

I'm in the process of installing new kiln elements in my old Cress kiln and I've seen previous mentions of doing an empty kiln firing to break-in the new elements. I would guess that @neilestrickwould be the one most appropriate to chime in on the topic of a first-time firing process.

Thanks in advance for your input!

[neilestrick]

3 hours ago, JohnnyK said:

I'm in the process of installing new kiln elements in my old Cress kiln and I've seen previous mentions of doing an empty kiln firing to break-in the new elements. I would guess that @neilestrickwould be the one most appropriate to chime in on the topic of a first-time firing process.

Thanks in advance for your input!

Yes, an empty firing will build build up a layer of oxidation on the surface of the elements, which will help protect the metal from fumes in future firings. The hotter the better, but generally a bisque firing will do the job. It's also a good idea to put some cones in the kiln to make sure everything's working properly with the new elements.

[JohnnyK]

45 minutes ago, neilestrick said:

Yes, an empty firing will build build up a layer of oxidation on the surface of the elements, which will help protect the metal from fumes in future firings. The hotter the better, but generally a bisque firing will do the job. It's also a good idea to put some cones in the kiln to make sure everything's working properly with the new elements.

SO would it be a good idea to put 3 or 4 shelves in with cones at each level to check the heat distribution? How about firing to ^6 where I usually glaze fire to?

[neilestrick]

51 minutes ago, JohnnyK said:

SO would it be a good idea to put 3 or 4 shelves in with cones at each level to check the heat distribution? How about firing to ^6 where I usually glaze fire to?

Yes to all 

[JohnnyK]

I just replaced the elements, which was an interesting task. The coils were about 3" too long, so I had to straighten and shorten the overall length. Man, I didn't realize how strong that coil wire is. It took quite an effort to do the straightening, Anyway, I got it done. I installed 4 shelves with posts and 2 cone sets, one near the bottom peephole and one near the top. It seems to me that the bottom of the kiln is running slightly cooler than the top and the top set (which is in the front) is dead on for cone 6. The firing was the pre-programmed ^6...

The next run is going to be a bisque firing, then on to glaze firing. Comments anyone?

[Dick White]

A couple of thoughts about the elements that were too long. My impression from your description, you flattened out several inches at the end of the coiled part, poked it through the hole in the brick, and cut it off at wherever/however it connected to the supply wire. I think that will cause two problems. 1) The doubled up end of the element wire past the end of the coils allows that part of the wire sticking through the brick to the connection to NOT heat up. The elements only get red hot and heat up in the single thickness of the coils. Now you have a red hot connection. 2) The resistance of the element is proportion to the length of the wire in the coil. By shortening the wire by the several inches you flattened and cut off, the resistance of the element is lower, which will cause it to heat hotter and draw more amperage. How much is uncertain without measuring the actual resistance and doing the Ohm's Law calculations.

The above said, how does one shorten the element coil? The opposite of how one lengthens it if too short. To lengthen, stretch it either by pulling it end to end until the coils separate enough to give the necessary additional length, or firmly grasp a section at a time in both hands and muscle your hands apart, until the whole coil is longer. The opposite is how to shorten it. Grasp short sections in both hands and push them together, until you have scrunched the whole length. This preserves the doubled ends and the overall resistance.

As for the cones, you didn't get a good 6 in either set. With the self supporting cones, a proper bend is when the tip is level with the top of the pyramid pedestal. Obviously, 5 is over and done as it should be, but both 6s are not yet drooping to level with the top of the base. And yes, the bottom is running cooler, which is a common problem with kilns that have only one thermocouple. The only solution is through loading - less ware on the bottom shelf so that it doesn't have to work so hard to heat it all. Remember that above red heat, convection stops. At that point, heat transfer is through radiant energy directly from the glowing element to the ware. (Ware around the outside of the shelf is heated by the elements, and in turn that ware radiates heat to its neighbors in the middle.) If the lower section of the kiln is already running behind because of convection earlier in the firing moved heat up, once it goes radiant, it has more heatwork to make up. So, decrease the load and that section will begin to catch up. But, all that said, don't get too excited to tweak the thermocouple offset in the controller until you have run a few full loads.

[Min]

4 hours ago, Dick White said:

The opposite is how to shorten it. Grasp short sections in both hands and push them together, until you have scrunched the whole length. This preserves the doubled ends and the overall resistance.

+1

This! 

[JohnnyK]

6 hours ago, Dick White said:

 The elements only get red hot and heat up in the single thickness of the coils. Now you have a red hot connection.

I learn something every day... Is there any way to salvage the single wire portion? It is too stiff to twist another wire to it like from the factory. What about tying another piece of wire to the singleton with some finer nichrome? The difference in resistance is about 0.2 Ohms, which calculates to about a 1 Amp increase in current...

[neilestrick]

L&L does not twist the ends on a lot of their elements, especially the beefy ones. The elements on my eQ2827-3 are not twisted, and they do not glow when the kiln is firing. I think that a straight wire does not heat the same as the coiled wire, which makes sense because I know that coil density is one of the factors in element design. I've sent an email off to L&L to get more information on this, but for now I would say that @JohnnyK your elements are going to be fine. The resistance difference is not going to be an issue at all.

[neilestrick]

Some more info on non-twisted ends HERE. I'll have more info on this later today. I'm going to see if there's something about the L&L element connection system that makes non-twisted ends more viable than other element connection types (crimp, screw). There is no difference in element life between the twisted and non-twisted in L&L kilns. They are not more likely to burn out at the element connections or through-hole or anything like that.

[neilestrick]

@JohnnyK I just had a nice conversation with Steve at L&L, and he confirmed what I said above. The non-twisted end will not heat nearly as much as the coils inside the kiln do. For one, the coils feed off each other and run hotter- this is why they get hot spots when they bunch up at the corners. Plus the coils are in an insulated environment, whereas the end can dissipate heat fairly well, assuming the control box has good air flow.

That said, there are a couple of things that may be an issue with your Cress compared to the L&L. First, the L&L element connection has a much greater surface area in the connection by using bolts, nuts, and washers. Plus all of that hardware is stainless steel, which is more durable and won't expand and contract as much as brass or copper connectors. The second potential issue is frying out the feeder wires if they're pressed up against the element connections when you close up the box. The L&L control box design directs the wires away from the connections so it's not an issue with their kilns.

At this point I don't think there is really anything you can do besides fire the kiln and see what happens, but I think there's a good chance it will be fine.

[JohnnyK]

2 hours ago, neilestrick said:

Some more info on non-twisted ends HERE. I'll have more info on this later today. I'm going to see if there's something about the L&L element connection system that makes non-twisted ends more viable than other element connection types (crimp, screw). There is no difference in element life between the twisted and non-twisted in L&L kilns. They are not more likely to burn out at the element connections or through-hole or anything like that.

 

4 minutes ago, neilestrick said:

@JohnnyK I just had a nice conversation with Steve at L&L, and he confirmed what I said above. The non-twisted end will not heat nearly as much as the coils inside the kiln do. For one, the coils feed off each other and run hotter- this is why they get hot spots when they bunch up at the corners. Plus the coils are in an insulated environment, whereas the end can dissipate heat fairly well, assuming the control box has good air flow.

That said, there are a couple of things that may be an issue with your Cress compared to the L&L. First, the L&L element connection has a much greater surface area in the connection by using bolts, nuts, and washers. Plus all of that hardware is stainless steel, which is more durable and won't expand and contract as much as brass or copper connectors. The second potential issue is frying out the feeder wires if they're pressed up against the element connections when you close up the box. The L&L control box design directs the wires away from the connections so it's not an issue with their kilns.

At this point I don't think there is really anything you can do besides fire the kiln and see what happens, but I think there's a good chance it will be fine.

All good to hear, Neil. The original connections were screws, nuts and washers through a loop on the element and a crimp connector on the feed wire. Euclids provided me heavy brass couplings with stainless steel clamp screws. As for the feeders, I cut the loop off the crimp connector leaving the crimped portion on the end of the wire. The connections are solid and the feeders stick out away from the connectors. Ther is plenty of room in the well-ventilated box cover for the wires. On the next firing, I'll check the connectors to see if there are any problems.

[neilestrick]

2 minutes ago, JohnnyK said:

The original connections were screws, nuts and washers through a loop on the element and a crimp connector on the feed wire.

I always liked that type of connection. Simple and solid. It was fairly common a long time ago, but nobody uses it anymore.