Sauna woes

My new Sauna never got over ~150°F – not exactly how it is supposed to be. It took quite a bit of research and hands-on tinkering with the control unit until I got it working correctly. Neither the manufacturer of the hardware nor the vendor of the kit were particularly helpful in this, so I think a summary of what I learned in the process could be useful for a larger audience.

Sauna kits in the US usually come from Canada. After researching options and prices for years, I ordered mine from SaunaFin in Toronto. I opted for a 5×8 clear cedar kit with several upgrades: a cedar door, a double L-bench, a Tylö Deluxe heater with remote control, extra cedar to finish the outside, and little things like headrests, thermometer, bucket / ladle, and of course a timer. Overall, my purchase experience was very positive. The material arrived on time and with minimal damage (despite UPS freight shipping), the price was reasonable, and the cedar was of high quality. Everything fit and nothing was missing. It took about two weekends to build it.

I don’t want to get into the details of construction, because the process is sufficiently documented elsewhere, such as in the instructions for the electrical wiring that Saunafin provided.

I did, however, have issues with operating the sauna that I want to summarize, because this information is nowhere else on the Web, and because the heater manufacturer, Tylö, who maintains a US representation, did not respond to my requests for customer support. Shall we assume that Tylö is taking preemptive action to protect themselves from law suits? They ship sauna ovens that cannot be operated without altering them, but if something goes wrong, they can always say to the judge: Well, not our fault that the house burned down – they altered the oven! Honi soit qui mal y pense.

My problem was 2-fold. First, the heater’s thermal limit switches kept tripping during normal operation. Second, the sauna did not reach my target temperature of about 190°F because the thermostat shut off the heater at 150°F. It turned out that these two things were unrelated, and here is what I did to fix them.

Tylö Temperature Limit Switch

The Tylö heater has two temperature sensors tucked into the handle on top of the unit. These sensors each trigger a limit switch when they get too hot. Unfortunately, they always got too hot. This is poorly documented.

The Tylö manual simply states that frequently tripping limit switches indicate a ventilation problem. In other words, the heat supposedly does not get transported away from the heater fast enough, and hot air backs up around the top of the heater, which leads to overheating. Tylö says that cross-ventilation is always required. There must be a cold air vent below the heater and a hot air vent at the top of a wall diagonally across from the heater.

Saunafin simply states in their instructions that cross ventilation is optional, because they undercut the door and that this gap provides enough ventilation to circulate the air in the sauna. I had installed a top vent, and I had the undercut door. The top vent is closed during normal operation, otherwise I would heat the outside.

My first intuition was to rearrange the rocks on the heater. I thought that I had packed them too tightly so that they were blocking the flow of air. Removing rocks or rearranging them did note solve the problem, though.

Suspecting a flaw in the layout of my sauna, I contacted Saunafin about this issue. As it turns out, this was a known problem, because I received very specific instructions for how to address it – by disabling the temperature sensors on the heater. Sort of. I was not ready for that, figured that Tylö must know better how to install their heaters, and cut a hole into the finished sauna to allow for cross-ventilation.

I had found this vent grill on Amazonthat was a perfect fit for the job, and in less than an hour I was ready to try out cross-ventilation. It made no difference. The limit switches tripped again. The Tylö manual states that you should call a professional to reset the switches, which is nonsense. The switches are two red buttons on the back of the unit, near the bottom where the electrical connections are. The problem with these switches is that they cannot be reset until the sensors have cooled off quite a bit, at which point I had lost interest in the sauna for the night. The only option left was to accept that the problem was with the heater and not with my sauna. I decided to move the senors a little further down, which was easy enough to do. This radical step took care of the issue, just as Saunafin predicted. Whether it was the right thing to do I still don’t know (Tylö never responded to my request for advice).

Temperature confusion

My other issue – the sauna temperature peaking at 150°F – remained, however. I had installed the sensor for the thermostat at the right height and far enough away from the heater, so that was not the issue. Saunafin suggested that the thermometer may be bad and that the temperature was actually higher than I thought. Funny, since they had sold it to me in the first place. So I went online and found a decent replacement here – even with a Celsius scale.

And Saunafin was right again. The new thermometer reported over 80°C when the thermostat shut off at the highest temperature setting. This is equivalent to almost 180°F and is warm enough for me. It still bothers me that I cannot go higher, should I want to. I suspect that there is a potentiometer in the TS30-01 control unit where the temperature limit can be adjusted, and maybe I will open it some day to find it. For now, I am happy with the sauna’s performance and looking forward to many cold winter evenings.

Six months later I finally got around to figuring out how to adjust the temperature limit of the TS30 controller. These units use a sensor that consists of a capillary tube and a bulb containing freon. Temperature changes around the bulb result in a change in pressure in the capillary tube, and this pressure change actuates mechanical switches in the dial. There are 4 switches, each with a separate temperature setting. This is how the heater’s stages are operating. When a limit is reached, the switch shuts off power to one of the heating elements. The switches are spring-loaded, and this enbles us to change the limit temperature. Here is my recommended process for raising the temperature limit of the Tylo TS30 controllers beyond 200°F:

1. Set the temperature to max and heat up the sauna until it reaches operating temperature
2. Disconnect the power by switching off the breakers
3. Remove the black plastic frame and the two screws that hold the face plate in place
4. Pull the black knob off the temperature dial
5. Remove the 2 screws that were behind the knob
6. Pull the face plate out and push it down
7. Push the temperature controller in and pull it out from behind, as shown in this picture:

   

8. There is strip of duct tape that covers four holes (blue arrow in picture). Pull it off.
9. Now the adjustment screws are accessible (red arrows in picture). Turn them clock-wise in equal amounts to raise the temperature limit. Remember that each stage has its own limit, and by turning the screws in equal amounts, the dynamic characteristics of the system are preserved. Start by turning each screw 1/2 turn. By turning the dial (now without the knob on), you can find out the amount of change that you have made (this is why I recommend that the sauna is heated for this process), because when the limit temperature is reached, you hear an audible click from the switch.
10. Put everything back together and turn the power on
11. Run the heater for 15-20 minutes to see if the new temperature setting is where you want it to be
12. If not, repeat

I initially turned the screws too much (several full turns) and the temperature soared past 200°F right away once I turned on the power. This caused the heater’s limit switch to trigger again – a problem that I thought was already solved. I had to repeat the process by now lowering the temperature limit in several steps. I also had to lower the temperature sensors behind the heater further to avoid unwanted shut-offs.

Ideally, you want the desired top temperature to be somewhere near the maximum position of the temperature dial. Otherwise, someone could accidentally turn up the heat to a level that might be damaging or dangerous. There is a delicate balance between that and the position of the limit switch sensors behind the heater. It took a few iterations to get this right.

Also, because the factory temperature limit settings for each of the stages are optimzed to work together for the most energy-efficient operation of the sauna, there is some risk of ending up with a less ideal temperature characteristic of the system. By turning the screws in equally small amounts, this should be mitigated.

Now I get 90°C/200°F – much better and now there is nothing left to wish for.