A commercial steamer — a convection steamer, a pressureless steamer, a countertop steamer for vegetables, rice and dim sum — cooks with wet heat. A boiler or steam generator turns water into steam, the steam fills the chamber, and the food cooks at the steam temperature, close to 100°C at atmospheric pressure. The control problem is a wet one: the chamber thermostat works in saturated steam, the boiler thermostat works against a water level that can fall, and the sensing bulb lives where scale forms fastest. The safety problem is the boiler running dry. This guide works through the two circuits a steamer needs — chamber and boiler — and the protection that keeps a dry boiler from becoming a fire.
Two circuits: the chamber and the boiler
A steamer has two temperatures to hold, and they belong to two different controls. The chamber control holds the steam chamber at its working temperature, cycling the steam supply as trays go in and out and the door opens and closes. A small countertop steamer draws a modest single-phase load and sits inside the AG16-K (50–400°C, 16A / 20A); a larger floor-standing steamer with a heavier boiler steps up to the AG32-1K (up to 32A, single-pole compulsory OFF). Three-phase steamers switch all phases on one control — the AG32-3K three-pole control (16A / 32A / 50A, up to 400V, 50–350°C) is built for that duty. The boiler control is the second circuit: it holds the steam generator itself at steaming temperature, and it is the circuit that needs dry-boil protection. The same two-circuit thinking applies to combi ovens, where the cavity and the steam generator are controlled separately — covered in our combi oven thermostat guide.
Gas-fired steamers are a different circuit again: a millivolt gas thermostat such as the ARB-33 (200–400°F, 5 VDC) covers the boiler on its range, and our gas thermostat guide covers that control. Whichever fuel the steamer burns, the control thermostat is an automatic-reset device — it cycles the heat on and off in normal service — while the boiler's protection must be a separate manual-reset limiter, covered below.
Bulb placement in wet steam
The sensing bulb in a steamer lives in the wettest place a capillary thermostat ever works: saturated steam, condensate dripping from the chamber roof, splashes around the control body. Permanent wet duty is exactly what waterproof sensing is built for: the TY316 waterproof variant (16A, 50–380°C) covers chamber control, and the TY316-8 brings the same waterproof construction to a manual-reset limiter tripping at up to 380°C. A standard sensing bulb in a steamer chamber corrodes and drifts; a waterproof bulb keeps reading true through wash-downs and descaling.
Place the bulb where the steam actually flows past the food, not where condensate drips on it and not in a dead corner behind the trays. A bulb sitting in a drip reads cool condensate and lets the chamber overshoot; a bulb in still air reads late and the steam supply hunts. Hard water is the other enemy: scale coats the bulb just as it coats the boiler, insulates it, and makes the control respond late, so descale and clean the bulb on the equipment maker's schedule. The seating and routing rules are in our installation guide, and the same waterproof logic applies to pasta cookers, where the bulb sits immersed in boiling water — covered in our pasta cooker thermostat guide.
Sizing the control to the boiler
Size the control to the boiler's continuous draw, not to the size of the chamber: a small steamer with a heavy boiler element is a heavy switching load, while a large chamber with a modest boiler is not. Match the current rating with margin, and remember that a steamer earns its 100,000-cycle rating in short, sharp bursts — every tray is a full steaming call followed by a door opening and a temperature dip. The table below covers the common steamer duties; the exact setpoint and trip point are properties of the equipment, not of the thermostat.
| Model | Rating | Range | Reset |
|---|---|---|---|
| AG16-K | 16A / 20A · 110V / 250V | 50–400°C | Automatic |
| TY316 | 16A · 110V / 250V | 50–380°C | Automatic |
| AG32-1K | 16A / 20A / 32A · 110V / 250V / 380V | 50–450°C | Automatic |
| AG32-3K | 16A / 32A / 50A · 110V / 250V / 400V | 50–350°C | Automatic |
| AG32-2S | 16A / 32A / 50A · 110V / 250V / 400V | Trip up to 400°C (double-pole) | Manual reset |
Technical data is a catalogue reference. Confirm final ratings, dimensions and approvals for the selected model before ordering.
Dry-boil protection: the limiter that must not reset itself
A boiler that runs dry with the element still powered climbs fast, and an automatic-reset device would simply cycle the element back on into an empty, overheating boiler. The limiter on a steamer boiler must cut the circuit completely and stay cut: the AG32-2S double-pole manual-reset limiter (16A / 32A / 50A, trip up to 400°C) is that device, cutting both poles of the boiler supply. Manual reset forces a check — is the water feed blocked, is the level control stuck, is the element damaged — before the boiler can fire again. The same dry-boil logic protects water boilers, where the same double-pole limiter guards the tank — covered in our water boiler thermostat guide.
Set the limiter's trip above the boiler's maximum working temperature and below the damage point of the element and the boiler shell. Trip points are factory-set to your specification; our specification guide covers the full ordering checklist, and our safety limiter guide works through the setting logic.
Certifications
Our thermostats are certified by TÜV Rheinland, UL and KEMA-KEUR — see our Certifications page for the certificate number and verification route for each model. Confirm the approvals carried by the specific models you select.
FAQ
What temperature does a commercial steamer run at?
The steam chamber runs close to 100°C at atmospheric pressure for a pressureless steamer, and the thermostat holds it there while trays go in and out. The boiler itself runs hotter to make steam. The exact setpoint is a property of the equipment, not of the thermostat.
Why does my steamer take longer to cook than it used to?
Usually the sensing bulb: scale from hard water coats the bulb, insulates it, and makes the control respond late, so the chamber spends more time below temperature. Descale the boiler and clean the bulb on the equipment maker's schedule, and check the bulb position before replacing the control.
Why does my steamer keep tripping the limiter?
Usually one of three causes: the boiler ran low on water or dry, the sensing bulb is scaled or misplaced so the control responded late and the boiler overshot, or the water feed or level control has failed. A manual-reset limiter is doing its job when it stays tripped — check the water feed, the bulb and the element before resetting, and have the control tested if the trips keep coming.
High-Current Control Thermostats · Manual Reset Safety Limit Thermostats · Capillary Control Thermostats