120V Oven With 240V Type Element

[tigercreek]

I recently picked up an old 120V Blue M oven for curing. It works fine as it is BUT it has no timer controls. I thought I would just make a new panel using a PID controller to take care of everything. Not as simple as I thought.
The problem that I'm having difficulty resolving is the power to the heating element. The existing element works like a 240V element with continuity and power input on each leg. With this being a 120V oven I'm trying to understand how Blue M accomplished this. I'm not sure how the neutral or an additional 120V on a different sine is added to complete the circuit and allow the element to function.
The only information that I can add is that this is a 120V 30 amp oven. The heating element has continuity and 7.5 ohms resistance. The SN plate designates Line Current L1 @21 amps and L2 @21 amps. On the board wiring L1 is the 120V hot wire and L2 is the neutral.

 

[tigercreek]

Well, I may have started crying too soon. I just heard from a support rep for these ovens and he confirmed that the hot is connected to one side of the element and the neutral to the other. I've just never come across a 120V element with continuity and was afraid of completing the circuit and letting out the magic smoke.

 

[fitter30]

7.5 ohms @120vac=16 amps
7.5 ohms@ 240vac= 32 amps
Is there a fan or just the element?

 

[wyliesdiesels]

Where did you get 240v? What does the nameplate say for voltage?

as said above. 7.5ohms equals 16a so there's another 5a draw for something else? convection fan?

 

[tigercreek]

Yes, there is a 3 amp fan.
They mystery behind this was solved and confirmed by a member of their tech support team.
Even though this element has continuity and a low ohm rating it is to be connected like a 120V element with hot on one leg and neutral on the other.
I was using 204v element as a descriptive reference since they have continuity through each leg.
The pics show what I was looking at.

 

[nsula_country]

We have a Blue M in the lab. 3P 480 though.

HD Industrial grade for sure!

CT

 

[fitter30]

Looks like it might have a scr control on elements. That would explain the lower amp draw.

 

[tigercreek]

A follow up.
The 120V oven is rewired and operational. A thing to note is that the wires going to the element ARE hot/neutral specific. Both wire colors coming from the element were black which lead to my initial confusion about the entire situation. Wiring the "wrong" black wire from the element to the hot wire results in no heat. After figuring this out it became smooth sailing. Created a new panel and it's back in business.

 

[Bert_]

A follow up.
The 120V oven is rewired and operational. A thing to note is that the wires going to the element ARE hot/neutral specific. Both wire colors coming from the element were black which lead to my initial confusion about the entire situation. Wiring the "wrong" black wire from the element to the hot wire results in no heat. After figuring this out it became smooth sailing. Created a new panel and it's back in business.

The element doesn't care. It just wants 120 volts between two wires. Whatever controls the element might care about which wire is neutral.