lincoln 1300 series pizza oven

[arnoldbta]

I just replaced the element, hi limit thermostat, and seal on a 1300 series countertop pizza oven. 240 volt/single phase. I recommended replacing thermocouple as well, since I believed that is what caused oven to burn up element and hi-limit. Customer chose not to and a few days later the oven was burning pizzas and eventually shut down opening the hi-limit thermostat. The hi-limit is supposed to reset and close when you push in the reset button, but the previous part and new part would not. I was wondering if someone with a little more experience could tell me if this is common for this part, or is it normally resetable. I have a thermocouple and a new hi-limit I am about to replace. I have ohmed the potentiometer to make sure there were no dead spots and it checked out OK. Also I am curious if there is anything else I need to check that cud be causing unit to keep calling for heat when it should be satisfied.

Any advise may be helpful.

[jorogas]

If that oven uses SSRs you might check for one stuck closed.

[arnoldbta]

Update

Oven also burned up element again when it messed up the hi limit. After replacing the hi limit and the element I discovered when the air thinned out and the oven was around 500 degrees it began opening and closing on the air switch instead of the thermostat. When it does this rapidly it heats up the mercury contactor and causes it to stick closed. Resulting in damage to the element and hi limit thermostat. So heads up to anyone that runs up on this oven with a bad element and hi limit t-state. Make sure you check and make sure it is not losing power to the contactor because the air switch is opening. Power comes out of the control board to the hi limit then to the air switch, then to the contactor, this then allows 240 volts to go to elements.

I had to let the oven heat up and operate for sometime before it would start opening and closing on the air switch.

Again just a heads up if you come up on one of these ovens with both of these parts failed. I had to learn the hard way.

[smurphy]

Just wondering. Was there something wrong with the motor? Also, my opinion, I hate these ovens.

[arnoldbta]

Just wondering. Was there something wrong with the motor? Also, my opinion, I hate these ovens.

No. For now I have it wired bypassing the air switch. The air switch is what was causing the mercury contactor to stick in the closed position. Instead of replacing the air switch with a new one , mainly because the customer already had almost a grand sunk in the repair already, I just bypassed it to make sure that was what was causing the element and hi-limit to fail. It has been operating for almost two weeks now without fault.

Only problem with bypassing the air switch is if the main fan motor were to fail there is nothing to kill power to element, unless hi-limit switch opens. This could also cause the element to burn up.

I had no concern about the motor going out, and I recommended to customer if this bypass fixes our problem we should replace air switch. Doubtful he will as long as it continues working.

I have only ran into a handful of these, and usually you are changing the thermostat, hi-limit, element, or the motor. This one definitely threw me for a loop.