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That's interesting. I never knew that and I use these so frequently. Great info

interesting

So i just converted a Marsal Pizza oven from that old style pilot safety (long red button ) to a modern valve like you see on a deep fryer , and i used the plain ol asbestos thermopile , and after 20 min the wire went from white to a brown...

I wondee if i need to swap in the shielded type

Originally Posted by Snapperhead

And whats the benefit of the metal shielded one ??

By shielded ones, do you mean the "armored" ones like THIS?

They're used in high-temperature applications. For instance, they're preferred for use in deck ovens - which commonly operate at temps above 500°.

I know you didn't ask for this, but here I go:

Consider that the hot & cold junctions are both within the actual sensor body. The tip is impinged upon by the pilot flame to create the HOT junction. The mounting point is the COLD junction. The difference in temperature between the two creates the output voltage. If those two points were the exact same temperature, then there'd be NO output voltage. That's the way thermocouples work.

A thermocouple puts out 30mVDC max.
A thermopile puts out 750mVDC max. A thermopile is merely twenty-five thermocouples (encased in a larger body) connected in series.

Back to the hot/cold junction thing:
MOST thermopiles (and thermocouples) can dissipate enough heat at their mounting bracket to allow that point to serve as the COLD junction. That's why it's important for it (them) to be properly mounted. They can't just flap around outside of their mounting bracket...and the mounting bracket needs to be properly secured to wherever it's intended to mount. That mounting point serves as the "heat sink" to give you that cold junction.

The armored SHIELDING:
Again, for higher temp applications where the thermopile's working environment might come closer to FLAME temperature (therefore lower voltage output), the armor simply acts as an additional heat sink.


AS FOR THE COSTS ($10 vs $30):
I always prefer OEM. RobertShaw seems most prevalent in that regard.
Honeywell? Maybe... I just don't like their thermocouples, though. They use aluminum instead of brass as a collar, which makes them a bigger PITA to remove for replacement since the thread are more screwed up from all the heat they must endure.

It really depends on where you are going to use it and the aggressiveness of the pilot.

Frymaster, Imperial, Pitco, Dean, Southbend, Anets.... as far as I can tell they all use a Robertshaw 1950 series t’pile. Maybe the Pitco one is a different manufacturer, maybe. And that’s just the metal sheath that separates it from the others.

Does the metal sheath offer just a little more protection?


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Thermopiles

Does the 10 dollar one last just as long as the 30 dollar one ??

Side by side they look pretty durn similar

And whats the benefit of the metal shielded one ??