Adding Switch To RTC-1000

[lbailey]

I'd like to add a 3 position switch to my Bartlett RTC-1000 that would allow me to select top, side or both sets of elements. It is running my Olympic GF314ETLC.

Seems possible, has anyone done this? If so, can you share details and/or suggestions?

Thanks

[Tony Smith]

It's easy to add two switches, one to control the top (on or off) and another to control side (on or off). It's more of a challenge to combine the two because you need three positions: top; side; and both. You could order a double pole, triple throw switch, they're just not readily available at your local Radio Shack. Just splice the switch into the 12V line the activates the relay. These are low current, typically <0.5 Amps at 12V, so you can use a small toggle or rocker switch.

I did this on one of my evenheat kilns years ago. What I found was neither set of elements was powerful enough to get the kiln to fusing temperature by themselves, and the top element couldn't get the kiln to slumping temperature by itself... so I never used the switches after the initial experiments.

I hope this helps.

Tony

[lbailey]

Perfect!

Thanks Tony

[Brad Walker]

[quote="lbailey"]I'd like to add a 3 position switch to my Bartlett RTC-1000 that would allow me to select top, side or both sets of elements. It is running my Olympic GF314ETLC.

Seems possible, has anyone done this? If so, can you share details and/or suggestions?
[quote]

Check if your GF314TLC has a infinite switch on the side. If it does, you probably already have the ability to run side only, as well as both side and top. Just turn the dial to off, which cuts the power to the top elements only. If you also want the ability to run top only, then of course that won't do everything.

You might also check with Olympic. Because of the way that kiln is wired, it may not be as simple as Tony suggests. (But if it is, I'd believe every word Tony says!) I do know that Olympic frequently wires kilns with all 3 positions, so there may be more than one way to get there. You'll need the kiln's serial number when you make the call; they've had several different wiring configurations for that kiln.

[lbailey]

Ah ha......

I'll call Olympic with the SN this week. It does have the infinite switch on the side as you suspected but I have always left the top elements set to full. And I do need it to top fire only, so some sort of switch is likely needed. (Gotta turn off the side elements somehow......)

Thanks for the heads up.

[Tony Smith]

The RTC-1000 technical manual is on the Bartlett website. http://www.bartinst.com/kilns/2
On page 5 of the manual is an illustration showing the outputs from the board to the relays. This controller will run three zones. I expect your kiln only has two zones - top and side. To turn off the side elements, identify which relay controls them then trace the light gauge wires back to the board. One of the wires connects to an output and yhe other will be paired up with the return from the other relay. Install the switch in the wire that runs from the output to the relay. If you only want to shut off the side elements, then it's one SPST switch.

Tony

[lbailey]

Thanks Tony. It actually has 3 relays (I've replaced them), top, upper side and lower side. I assume a single switch for both side relays will do, right?

[Tony Smith]

It depends if both side relays are wired together as a single zone or if they operate independently. Either way, a DPST toggle switch will do the job. Break one control line on one side of the switch and break the other on the other side of the switch.

Tony

[lbailey]

Here is the schematic that Olympic sent. Lid relay and rheostat on top, notice that one of the side relays control one element while the other controls a pair of elements. Couple of questions for the experts here:

- Why would the bottom relay that controls a pair of elements have one element with a 25 ohm value while all the others are 16 ohm?
- If I were to measure ohms (multi-meter across both ends of an element, isolated from rest of controller, power off, disconnected from wall, etc), what values would we expect to see? Anything relative to the values in the schematic? All over the place due to (unknown) times fired?
- If I replace all elements at the same time, would you expect that 25 ohm element to be a different PN?
- At what point does a high or inconsistent value (compared to the other elements) dictate replacement of the elements? In other words, what range of values is acceptable?

Tony, assuming that the 3 relays are numbered 1 thru 3, bottom to top in the schematic (the top component with the light is the rheostat) it seems that you are suggesting a switch to turn off/on the side elements should be across the LH 12v side of Relay 2 and the RH 12v side of Relay 1. Is that correct?

Thanks for the help, trying to careful here....

[Tony Smith]

It's interesting that Olympic is using a single zone of a three-zone controller and wiring all three relays in parallel. I suppose it would allow them to use a single-zone controller without having to change the wiring.

To answer your questions, one element has a higher resistance because it is longer than the others. I'm sure it would have a different part number. With the power off, and the kiln unplugged (there is always power at the relay even with the controller turned off) you should be able to measure the element resistance at the relay. The resistance will only change if the element is damaged in some way. An oxidation on the element is normal, but severe corrosion will create a hot-spot in the element and will eventually fail. Elements will last for years if they aren't severely corroded or mishandled. I would expect an element to be within 3, maybe 5 ohms of nominal unless it was damaged or otherwise compromised.

From this schematic, you can break the red wire between relays 2 & 3 (just to the right of where it says 240/208) and install a SPST switch. You don't need to break both sides.

Tony

[lbailey]

Thanks Tony, this place is great for new guys like me. Hope to pass it on some day.....