00-410839-00004 & 721027-1 — 36 in Two-Lead Thermopile, 250–750 mV

36-inch two-lead millivolt thermopile (Robertshaw 1950-53B type) used on current Vulcan LG, VEG and 1GR fryers. It is also the OEM-designated replacement for 721027-1, which additionally covers Cecilware, Imperial, Tri-Star, Star, Southbend and Keating equipment. Not interchangeable with the coaxial 1951-53F type.

Availability Status

Currently in production

Current production part in 2022-2026 Vulcan fryer catalogs. This number supersedes 721027-1, which is no longer orderable from the OEM.

Source: public distributor listing, checked 2026-10-19. Availability changes; re-check before ordering.

Market Reference

seen at $65.22, Non-OEM, made in Mexico. 90+ units sold in recent months.

Source: public product listing at a major US parts retailer, checked 2026-10-20. This is a market observation for reference only — it is not an offer, a quotation, or a commitment to supply at any price.

Compatible Models

Vulcan

LG300
LG400
LG500
1VEG35M
1VEG50M
1GRC
1GRD
1GRM

Other equipment covered via 721027-1

Cecilware fryers
Imperial IF / IHR / IR fryers
Tri-Star TSF fryers
Star fryers
Southbend fryers
Keating griddles
Wells gas grills
Cleveland gas steam generators
Groen CHFP / NHFP braising pans

Cross-Reference / Interchange Part Numbers

This item is listed under the following part numbers across manufacturer documentation and distributor catalogs:

00-410839-00004
410839-00004
410839-4
721027-1
00-721027-00001
51-1121
Robertshaw 1950-53B
00-497301-00001
2J-Y9270
STA2T-42195

Cross-references marked as reported come from distributor interchange tables rather than manufacturer statements. Always verify against your equipment's parts manual before ordering.

Specifications

Type	Two-lead thermopile, 2 poles
Output	500 mV catalog designation; operating band 250–750 mV
Lead length	36 in
Robertshaw equivalent	1950-53B
Weight	0.2 lb (721027-1 variant)
OEM supersession	721027-1 is superseded by 00-410839-00004

What to Verify Before Ordering

These are the points that most often cause a wrong order on this specific part number. They are not generic advice.

Two-lead, not coaxial — Even though it shares 36 in length and 250-750 mV output with the coaxial 00-348358-00001, the terminal arrangement differs. Check the terminal type before ordering, not the length.
Supersedes 721027-1 — The older 721027-1 is no longer orderable from the OEM. Confirm which number your unit was built with.

Compiled from manufacturer catalog strings and distributor listings. Verify against your own equipment's parts manual before ordering. This is not an offer or a quotation.

As the OEM parts catalog lists it

Vulcan’s own catalog carries this number on the pilot page. According to FORM F-37136 Rev. A (January 2024), the line reads “00-410839-00004 Thermopile” — the catalog gives no thread, which is consistent with a lead-type device rather than a screw-in coaxial one.

Item	Part no.	Name of part (verbatim)	Amt
26	`00-410839-00004`	Thermopile	—

Source: Vulcan-Hart, LG Series Fryers replacement parts catalog, FORM F-37136 Rev. A (January 2024), Pilot and manifold assembly, p. 11. Retrieved 2026-10-27: https://www.webstaurantstore.com/documents/pdf/lg_series_fryer_gas_parts_catalog_f37136_02-24_.pdf. Quoted under fair use for identification; the manual is the publisher's document.

The electrical detail (36 in, 250-750 mV, Robertshaw 1950-53B) comes from distributor specifications, not from this catalog page.

What it fits and where it is used

Standing-pilot millivolt generation on current Vulcan LG, VEG and 1GR series fryers, and — through the 721027-1 cross — on a much wider set of gas fryers, griddles and steam equipment. The two leads connect to the gas valve and the thermostat circuit.

What it does and how it fails

A thermopile is a stack of thermocouples heated by the standing pilot. It generates the millivolts that hold the safety magnet in the gas valve open; there is no external supply. This is a two-lead unit: two conductors, polarity matters. A coaxial thermopile is a different part, not an adapter question.

Symptom check — is this two-lead thermopile the cause?

Symptom	This part?	Check first
Pilot lights but dies when the knob is released	Yes, possible — weak output or a bad connection	Pilot flame envelope and orifice, terminal tightness, then measure output
Pilot holds, main burner never lights	Possible — output collapses under load	Thermostat call, gas-valve operator, output measured at the valve terminals
Burner drops out after a few minutes of running	Possible — output falls as the pile heats	Output under load; corrosion or heat damage on the leads
Pilot will not stay lit at all, flame looks fine	Possible — reversed polarity or shorted lead	Lead routing, pinched insulation, correct replacement type

How to test it before you replace it

With the pilot lit and the main valve off, measure DC millivolts across the thermopile leads (open circuit). Compare with this record: 500 mV catalog designation; operating band 250–750 mV.
Reconnect and measure again at the gas-valve terminals while the thermostat is calling. A large drop between the two readings points at the leads or the connections, not the pile.
Clean the pilot orifice and check that the flame plays on the thermopile body — a flame that only licks the tip produces millivolts that hold a magnet but cannot open the main operator.
On a two-lead unit, confirm polarity: reversed leads generate the same voltage with the wrong sign and hold nothing.
Check lead length (36 in) and routing before ordering — a longer lead is fine, a shorter one cannot reach the valve.

These are standard electrical and gas-side checks for the device family, not a service manual for your fryer. Work with the appliance isolated, and have gas-side work done by a qualified fitter. Where this page states a value, it is copied from the specification table above; where it does not, the reading is only meaningful against your appliance manual.

Substitutions that fit but do not work

Coaxial for two-lead. Same thread, different circuit: the coaxial body is the return path and will not work in a two-terminal pilot lead set.
'Universal' piles with adapters. Adapters add a connection in the millivolt circuit, and every connection is a place to lose the signal.
Thermocouple vs thermopile. A thermocouple holds a pilot; a thermopile also drives the main operator. Fitting one where the other belongs gives a pilot that lights and a fryer that never heats.

Related records and guides

Frequently Asked Questions

Can I use this in place of 721027-1?

Yes — the OEM designates 00-410839-00004 as the replacement for 721027-1.

Is it interchangeable with the coaxial thermopile?

No. This is the two-lead 1950-53B type; the coaxial 1951-53F type (00-348358-00001 / 00-410839-00001) is a different part and will not substitute.

What output does it produce?

The catalog designates it as a 500 mV thermopile; the operating band across the family is 250–750 mV.

China Sourcing Notes

Capillary, millivolt and high-limit thermostats in these part families are produced in volume in China. Public supplier directories list manufacturers concentrated in specific industrial clusters: Zhongshan (Guangdong) for capillary, millivolt and deep-fryer thermostats; Wenzhou (Zhejiang) for capillary, gas, immersion and mechanical thermostats with OEM/ODM capability; and Jinan (Shandong) for gas-valve and thermostatic gas-control components. When sourcing these parts from China, verify: dimensional drawings, sensing-bulb and capillary specifications, temperature accuracy, electrical ratings, cycle-life testing and applicable safety certifications (CE / CQC / UL). A high-limit safety thermostat must not be substituted on the basis of physical fit alone.

Sources & Compilation Note

Compiled from Vulcan OEM parts manuals, Parts Town and PartsFe listings, and Robertshaw 1950-53B specification data.

Part numbers and specifications are reproduced as published by the sources listed above. This page is a reference compilation for identification purposes. Last compiled: 2026-10-31.