June 27, 2025. Underwriter Laboratories published a new electric sauna heater standard today. The North American sauna industry has long been handcuffed by the restrictions dictated by the current UL 875 standard. Compared to the European EU standard (EN 60335-2-53), electric sauna heaters with UL 875 certificates need to adhere to a few key stipulations which include:
- Over limit switch (the heater must shut off if the temperature sensor fails).
- Temperature sensor location (directly above the heater, 6″ from the ceiling).
- Towel test (the heater cannot ignite a towel draped over the rocks for 60 minutes)
The new standard is better aligned to the European standard in that:
- Higher “high‑temp” trip threshold
UL 875 had a conservative, prematurely activating high‑temp sensor (e.g., ~360 °F/182 °C) to protect wiring and components. The new standard raises that threshold, reducing unnecessary trips and improving sauna usability. - Thermostat‑sensor relocation
UL 875 required thermostat sensors to be mounted directly above the heater—an inaccurate location that often underestimates room temperature, leading to over‑heating and under-heating. UL 60335‑2‑53 allows installing the thermostat sensor over the seating area (Europe‑style), delivering more accurate and comfortable temperature control. - Air‑venting flexibility
UL 875 basically required a supply vent behind or below the heater to cool the high‑temp sensor. This new standard removes that specific requirement, letting ventilation be placed more optimally—improving airflow. - Supports sit‑bench measurements
With thermostat sensors now allowed over benches, room temperatures can exceed 90 °C (~194 °F) more naturally – matching EU sauna traditions – with no need for tricky work arounds.. Example: many sauna installers would coil a bunch of extra wire in the wall cavity, so users could extend the temperature sensor after the fact, on their own accord. - Revised overall safety & documentation
UL 60335‑2‑53 is aligned with the international IEC 60335 family—it updates build‑in warnings, IP ratings, marking, installation guidelines, and includes infrared‑specific safety rules.
The new “go to standard” will likely provide a less costly testing hurdle for European brands. So, we may see more European electric sauna heaters hitting the North America market, even with the threats or realities of tariffs. Further, North American manufactures will be able to test their electric sauna heaters with a few less stringent hurdles.
This is all potentially good news for the American electric sauna user and consumer. Those that have relocated their temperature sensors to a more practical location (vs directly above the heater) in their hot rooms may now be actually in compliance (of practicality and the new standard). And those new to the electric sauna world will be able to build their saunas without tricky work arounds and venting schemes to keep their heaters from tripping.
According to the American National Standards Institute (ANSI), the appliances covered by IEC 60335-2-53 Ed. 4.1 b:2017 are intended for use in the home and in public saunas located in apartment buildings, hotels, and similar locations.
Innertek, the independent testing laboratory, details the safety standards for IEC 60335-2 appliances here. The 60335-2 classifications of “household and similar electrical appliances” are many. As we look at where the new classification nests, well, we start to get a clear picture of where UL is coming from: walking around the house and putting tags on all the different electrical products we American consumers use:
And it’s nice to see “sauna heating appliances” acknowledged. And brought into the category of general household appliances.
8 thoughts on “Electric sauna heaters: UL 60335-2-53 set to “replace” UL 875”
Any idea when we will see these changes show up in products? I’m 2-3 months out from buying a stove.
Wyatt,
The changes are all predicated upon whether and when the sauna heater manufacturers want to go down the road of testing/retesting. I am consulting with two different sauna heater companies right now. The other side of the curtain (the testing labs) are not clear headed about what’s required for actual tests. They are keen to collect money though. To some, UL certification could be considered like Kosher certification. The sticker is what counts, and getting the stickers is a controlled system.
We ended up using fans installed in the vent below our kiuas (Harvia Cilindro) in order to keep the high limit switch from tripping. Do you think there might be an opportunity to retrofit the high limit switch with the new, higher, limit one?
Janet:
A great question. Retrofitting will void the UL875 sticker on your heater. Unless i’m missing a big piece of the UL puzzle:
– Heaters with 875 sticker will need to adhere to UL875 specifications.
– Heaters with 60335-2-53 sticker will need to adhere to 60335-2-53 specifications.
I see no aftermarket “kit” or “now you can do this” instructions to bring a heater from one standard to the next. That would be too simple and practical for the “safety first” industry.
Here’s why:
Certification is for a specific product version
A UL listing applies to the product as originally manufactured, including its design, materials, and construction. If UL standards change, existing products do not automatically qualify under the new standard.
Reevaluation is required
To comply with a new or updated UL standard, the manufacturer would need to submit the product again (or its updated version) to UL for re-testing or review. Only then can the product be listed under the new standard.
Field retrofits are tightly controlled
In rare cases, UL does offer a Field Evaluation Program, but this is for evaluating non-certified or modified equipment on-site, typically one-off industrial machines—not something for homeowners to apply themselves.
UL labeling is controlled
UL marks (stickers) are controlled assets—they cannot legally be issued to homeowners or added post-market except by authorized manufacturers under a current agreement with UL.
Hypothetical exception (rare):
If a manufacturer made a product that already complied with the newer standard before it was formalized, and UL agrees after reviewing documentation, they might allow updating the UL file and labeling new units accordingly—but this doesn’t apply to field units unless they are recalled, retrofitted, or re-evaluated.
I am curious if there has been any new progress with these new standards. I see above that you have been consulting with 2 companies. Any news?
Hi Sue,
Yes, a sauna heater company can test to this new standard. As the rubber meets the road, it’s not as “wow” as initially thought in terms of aligning standards. The towel test and overlimit switch isn’t going away.
Hi Glenn,
I’m in the market for a Tylo Sense Combi heater for a small home build (4×4 ft x 7 ft tall interior). The installation manuals all seem based on the UL 875 standards with very specific suggestions for venting that seem to go against common guidance (e.g. they recommend against mechanical exhaust under the benches). I was hoping the new UL standards would allow for a more optimal venting setup. Do you think this is coming soon, or would it be best to cover all the bases with a four vent setup that can be adjusted (https://www.saunatimes.com/types-of-saunas/electric-saunas/the-a-b-c-ds-of-venting-an-electric-heated-sauna/)? There is a lot of conflicting guidance on this, and I’d hate to end up with a sauna with suboptimal venting or a malfunctioning heater setup.
Thank you so much!
Anton…
Venting, and especially mechanical ventilation with electric heaters, is WAY over played. The four vent set up in the post you reference covers all the bases. With chutes and sliders, you’ll be able to tune the set up to your specific situation. The D vent: wire it for mechanical. And you just may find that you may not need to hook up an inline mechanical vent.
Totally correct regarding the conflicting advice. It’s not a good thing for sauna, the cold feet fear mongering and charts with arrows showing how air is supposed to move in a sauna. I took 17 saunas in 17 days with an electric tower heater and the venting was lame at best. A pebble in the hot room door and a towel swing once and awhile and the microclimate went from 0 to 100 pretty fast.
WAY overplayed.