Mechanical capillary thermostats are among the most replaceable parts in a commercial kitchen — but only like-for-like. A replacement with the wrong range, bulb or rating will fit the hole and still be wrong: temperatures off, contacts welding, or a safety device quietly replaced by a control. This guide is the identification routine we work through with service buyers: what to read, what to measure, and what to send for a cross-reference.
Start with the rating label
Most controls carry their identity on the body: model, temperature range, current and voltage rating, contact form. Photograph the label before removing anything, and photograph the wiring before disconnecting it. If the label is gone or unreadable, do not guess — work through the checklist below from the part itself and from the appliance it serves. When you contact us for a cross-reference, the original part number or a clear photo of the rating label is the single most useful thing you can send: from it we match mounting, ratings and capillary length.
The identification checklist
| Parameter | What to record | Why it matters |
|---|---|---|
| Temperature range | The dial's maximum marking, or the label range (e.g. 50–300°C) | An oversized range loses dial resolution and accuracy across the working band |
| Differential | Note the cycling behaviour if known (narrow or wide swing) | The on/off differential is built into the design; a mismatched one changes cooking results |
| Bulb size | Diameter × length in mm, and whether it sits in a well or clamps on | The bulb must fit the existing well and read the same point as the original |
| Capillary length | Routed length from bulb to control, following the original path | Too short will not reach; the sealed system cannot be extended or shortened |
| Mounting & shaft | Panel fixing pattern, shaft type and length, knob fit | Decides whether the replacement physically installs like the original |
| Contact rating | Current and voltage on the label — 16A, 20A or 32A class | Under-rating is the classic early-failure cause; match or exceed, never go below |
| Terminals | SPST or SPDT; faston size and orientation | Must land the original wiring without modification |
| Reset type | Automatic, or manual with a press-to-reset stem | Tells you whether the part is a control or a safety limiter — see below |
Control or limiter? Do not swap their jobs
The reset test settles it: a control resets itself as temperature falls; a safety limiter stays open until someone presses its reset stem. The two are not interchangeable. Replacing a limiter with a control removes the appliance's over-temperature protection; replacing a control with a limiter leaves it tripping and locking out in normal service. Both mistakes appear in the field, and both trace back to skipping the reset row of the checklist. The full control-versus-limiter logic is set out in our specification guide.
What to send for a cross-reference
Send: the part number or label photo; the checklist readings above; the appliance type and its power rating; and one photo of the installed part showing bulb and routing. With that set, a cross-reference is normally a single match, not a shortlist. If the failed part came out of a gas appliance, say so — gas equipment uses millivolt controls, covered in our gas thermostat guide, and a mains-rated lookalike is not a substitute.
Mistakes that come back as callbacks
Oversizing the range “to be safe” and losing accuracy. Kinking the capillary during installation and strangling the sensing fill — routing rules are in our installation guide. Leaving the bulb loose in an oversized well so it reads late. And the most dangerous: bridging out a limiter that “keeps tripping” instead of finding the fault it is reporting. A tripping limiter is a symptom; our troubleshooting guide works through what it is telling you.
Certifications
Our thermostats are produced under a TÜV-certified quality system — certificate R50309054 (EN 60730-1 / EN IEC 60730-2-9), verifiable on Certipedia. Confirm the approvals carried by the specific models you select.
FAQ
Can I replace a 16A thermostat with a 20A model?
Generally yes, if the range, mounting, bulb and capillary all match — a higher current rating in the same duty is headroom, not a mismatch. The reverse is never acceptable: a lower-rated control in a heavier circuit will weld its contacts and fail early.
The old thermostat has no readable label. Can it still be matched?
Usually. Work from the equipment instead: its type and rated power, the dial's maximum marking, the bulb's measured diameter and length, the capillary's routed length, and the shaft and terminal pattern. Send those with a photo of the control and the appliance rating plate, and the match can normally be narrowed to one specification.
Can I shorten a capillary tube that is too long?
No. The bulb, capillary and bellows are one sealed, calibrated system; cutting or crimping the tube destroys it. Order the correct length, and coil any modest excess in a wide loop, never kinked — the installation guide shows the routing rules.
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