PID question

Well I have a small kiln I just built that is 3.5"x4"x18" and I used 35" of kenthal A1 I could have used about 30". I bought it coiled from a pottery place for about 40 bucks. it was 40" and I stretched it out and just cut off the end and twisted it up works great, fired it off about 20 times so far. Ramps FAST!
 
How did you know to get that much? What gauge, coil size, and are you running 220/240v?

How do you find out the wattage to run or that you are going to run? Electrical stuff is not my strong suit so I always make certain it is correct done and saftey first.
 
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Duralite sells pre-coiled elements. You can pick the Wattage/AMP rating you need and they list what length each element needs to be stretched to for optimum performance. I did not comparision shop when I bought mine from them but the price seemed reasonable. They can also supply high-heat wire for the element leads and have pin/staple wire for fixing the element into place, along with various other supplies.
http://www.duralite.com/store/scripts/prodView.asp?idproduct=108
 
I am sure this is a dumb question, I see the amps and watts listed for the coils so are the watts the temp I wish to reach? I am running a 240v system with a 40amp SSR. 2200*F is plenty hot for my needs.
 
Erratus Animus said:
I am sure this is a dumb question, I see the amps and watts listed for the coils so are the watts the temp I wish to reach? I am running a 240v system with a 40amp SSR. 2200*F is plenty hot for my needs.
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No, the Amp rating tells you what the required amount of current is for that element. The wattage is a measurement of energy used over time and does not indicate the temperature that the element can operate at. They typically operate over 2200F, I believe, but the max temp you can run in the oven may depend on other components such as the PID or thermocouple. The element itself should handle heat treating temps for steel without problem.
 
I run 50' of 14 gauge A1 that I coiled myself. It runs just over 20 amps and 4400 watts. The bigger the diammeter wire the longer it will have to be as bigger means less resistance. To figure it out you need resistance per ft and watts you plan to run. 4400 watt devided by 220 Volts = 20 amps 220 volts devides by 20 amps = 11 ohms of resistance. This divided by the ohms per ft gives you the need length. I got mine from Pelican Wire co.
http://www.ec-securehost.com/PelicanWireCo.Inc./Bare_Resistance_Wire.html

Kathal A1
12 gauge .1335 ohms per ft 50 ft =5.675ohm or 39 amps of 220V 220x39=8580 watts
14 gauge .2124 10.62 ohm or 20.7 amps of 220V 220x20.7=4554 watts
15 gauge .256 12.8 ohms or 17.2 amps of 220V 220x 17.2=3784watts

The shorter the wire the less resistance and more amps
4400 watts/220v=20amps 220v/20 amps= 11ohms 11/.256(15gauge)=43ft
about the same as 50 ft of 14 gauge, but, the 14 gauge will handle the amperage better and last longer
The bigger the wire the more amps it will handle and the longer it will last
 
I purchased my PID controller and TC from Auberins as did other s here. I got a controller that can be programmed as to help with stainless and for annealing allow steels. The Kanthal wire I purchased pre rolled for around $25 delivered off of Ebay. You can email the guy with your oven size and he will roll what you need. I went with 50' of 16 guage.

PM me is you want the Ebay link.


Seth
 
16 gauge .335 ohm per ft. 50 ft = 16.75 ohms for 13 amps of 220V 13x220=2860 watts
if you wanted to run a bit more say 15 amps for 3300 watts you could cut your 16 gauge length down to 41 ft

The bigger the wire the longer it will run under the same amperage and wattage.
15 gauge wire at 15 amps will outlast 16 at 15 amps.
 
One thing I want everyone to realize is that you should use the largest wire size(that you can get the length to fit in) possible to achieve you amperage/wattage goal. Say I wanted a oven that ran 15 amps of 220 and therefor 3300 watts/. I could run the 41ft of 16 gauge mentioned above for that goal or 57 ft of 15 gauge to hit the same goal. I could also run about 23 ft of 19 gauge and hit the same goal. But, the 19 gauge would burn out in short order under that kind of amperage, it would be difficult to get a 57 ft piece of 15 gauge and then get that much coil in a oven small enough for 3300 watts. So, for that range 16 gauge is best.

In my case I figured 50' of wire is about as much coiled wire as one can get in an decent sized knife oven. My shop wiring can support a 20 amp oven so, I went with the 50' of 14 gauge. If you can only run 15 amps 16 gauge would be the wire to use.

On 110 at 20 amps you are limited to 2200 watts. There you need 5.5 ohms of resistance so you could run 26 ft of 14 gauge which would support the 20 amps and last well.

Many people have a hard time getting the fact that to increase to wattage from a given wire size you need LESS wire to give you less resistance and more amperage. Also that wire size is the what limits the amount of amperage it can handle. A 16 gauge wire doesnt care if the voltage is 12 volts or 120000 volts. It will handle 15 amps of either. In the case of the 120000 volts and resitance wire being the load you better have enugh of it though.
 
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