The last one I saw had a fixed limit at 108 degrees.
You won't find a contractor to set it any higher, because your asking him to present a dangerous condition that can cost him his job, company and freedom. I'm not willing to do that either.
Not to long ago, a plumber here was asked to set the customers water heater to 180 degrees. He advised them that it was dangerous, but was sweet talked into it. When one of the kids recieved 3rd degree burns, who did the customer go after? You guessed it- the plumber. He lost his license and business in the suit.
I don't mean to give you a speech, but just to let you understand why we must stick to the rules, because people will turn on you when they are in trouble.

Isn't 106 degrees considered scalding? Your tub has a maximum setting to protect YOUR health.

Turn your shower up to as hot as you can stand it and measure the water with a thermometer at that point. I bet it isn't above 104 degrees.

Looks to be around 110F. for most people.

HTH
Chris

Here is a link that might be useful: Bathing Scald Escape Time

Elevating your body above 108f degrees causes death. When I worked for a Cancer radiation treatment manufacturer, the leading one in the world, the expected treatment, used world-wide, elevated the temperature in the cancer cells to above 108 degrees. The cancer cells died, and the good cells grew back quicker than the cancer cells. Submerging yourself into water that is that hot will shut down the body. This is the reason NO ONE will help you. It would be cheaper to use a gun to your head. A bullet only costs about a buck. It is against the law in the USA to commit suicide. Assisting in suicide is also against the law.

Thanks, everyone, for replying!

Daddo: I understand completely. In fact, that is exactly what most have told me. I dont want to get anyone in trouble. Its just that this seems a new and arbitrary rule imposed by either government or insurance companies, or most likely both. For "ever and ever" meaning since the late 60's, hot tubs could go way up past 104 and all. This new 104-F rule must have been imposed during the 90's at some point. I just wish I could find a schematic of the regulator on this thing and alter it myself so no-one is liable but me.

baymee/saltceder: I dont know what scalding temp is for the average person, but my Rheem house hot water heater goes up to 150-F. I have it set for 120-F because of the gas usage. I have run 150-F water over my hands and although quite hot and flinch-inducing, it does not burn and once used to is just uncomfortable as hell. I assume that since we are made up mostly of water that in order to "scald" it must be 212-F or "boiling". After all, our own body temp average is about 100-F, so 10-degrees in either direction is not going to kill us. Hell, I had a fever once for higher than 104! I have breathed in air in excess of 120-F for hours and lived to tell the tale. and last year a freak heat wave made it 110-F during the day for 2 weeks, and it was hotter inside my house. I lived, but not well. :( Thats why i am installing air conditioning this year.
The thing is, different people have different hottub techniques that they like. Some like a long sit in tepid water (100-104-F) and some, like me, like a short 5-10min stay in 110+-F water with all the jets workin on my back muscles. I ride a motorcycle and I get cold down to the bone. The best thing is a 5-10 min. tub at 110. For me anyway.
I think the insurance people or whatever are mostly concerned with dehydration or heat stroke, not scalding. I just dont like it when an entire system gets dumbed down to protect a few Darwin award candidates.
I guess I will pull my old 1992 gas heater out of storage and convert to propane and install it. :( Bummer, that damn mini-max thing cost me as much as a new TV!!

egor; The real problem is the risk of rising the body core temperature. The longer you stay in the tub, the higher your body temperature rises and as stated 108 degrees can cause stroke, brain damage and death.
Your hands are tougher and the skin different than other parts of the body. Ever wonder how it is you can sip on hot coffee that will scald your skin on your legs?
Are you sure your thermometer that was reading 110 is calibrated?

Temperature of water and time to cause bad burns.

-------------------------------------
150°F (66°C) 2 seconds
140°F (60°C) 6 seconds
125°F (52°C) 2 minutes
120°F (49°C) 10 minutes
-------------------------------------
When submerged in hot water, there is no way for the body to cool itself and your body WILL approach the 110 degrees, but only after you are unconsious.
In 110 air temperatures, your body can cool itself by evaporating sweat, encreased blood flow, dialation and blood encrease to the surface of the skin in order to protect your core temperature.

When I hear the results of the hottest prolonged shower you can stand under, measured with an accurate thermometer, I will believe that you can withstand 110º for more than a few seconds. Otherwise I will have to assume you have lost nerve function.

daddo, bob,baymee: I'm no doctor or scientist, and I understand and wouldn't presume to argue your facts. They seem reasonable to me. Its just that I have been doing this on an almost daily basis for 30 years! But as pointed out, I only stay in for 5-10 minutes, maybe an all time record stay of 30 minutes at those temps. Once "me bones" has warmed up, it is quite uncomfortable to saty in and even though I grew up in the 70's, I still have enough brain cells left to get out before serious damage is done.
My thermometer I use is actually a highly accurate one used as a proccess control thermometer in commercial darkrooms where chemicals must be exactly the right temp. I kept it from my old days in that business. I will do another test today just for fun. If I dont post back, you'll know what happened! :)
saltceder: I dont know, that sounds like it may work, but would require much trial and error. ....maybe...
If I can find the thermostat sensor, and can remove it without disabling the whole unit, maybe I can then hook up a simple electrical switch that turns the pump off at 108-110 or something.

And another nut bar hit's this site. You have been given most perfect advice from some of the best boys on this site. Why don't you listen ? 104F is the safest temporary temperature rize for the human body not to excede a 15 minuet time frame. After you alter the thermostat canceling your U.L. approval your tub now become not legal and insurance companies love that. How are you going to alter the high limit after you screw with the stat ? Most of those tubs come with timers. Is that going to be altered ? Do you have any idea how poisonous chlorine gets after it is heated behond safe levels ? And what is that safe level ? Do you have any idea how stupid it is to shut off the pump with over heated water ? I guess not. The water now does not move. You are now in a poaching tub. Sorry, i take that. I know you will leave the tub when you get too hot, but let's say your not feeling well. Had a bad day. Under medication or not up to snuff. Fall asleep, Wake up dead. Then what ? It could happen. I was a power engineer at a holiday inn for years and have pulled many unconscious people from the wet sauna ( and we locked it off at 104F. with an outside manual timer maxed out at 15 minuets. We took the water away because they were flooding the heating elements and shorting them out so they went to
the pool and poured chlorinated water from empty beer cans onto the heaters. Chlorine poisoning and burned lungs.
Nice vacation. I guess you have already made up your mind
and we will not turn you. Good luck and be carefull. Maybe
warmer clothing when riding your bike ?

LOL!! So I'm a "nutbar"? Oh well, I ve been called worse, and you may be right. I mean there is a first time for everything, and maybe the thousands upon thousands of people who have hot-tubbed in the past 30-40 years at 108+ will suddenly realize you are correct and keel over and die! :) Of course there are the millions of people around the world who soak in hot springs above 105 and have lived to tell the tale!
All jokes aside, kalining, I do respect the advice given to me on this website and dont wish to demean anyone.
Before this new setup, back in the dark ages (before 2003), we controlled the heat in our hot tubs just the way I described. The heater was "full on" until a thermostat or actual person turned the pump off. The heater would shut down almost immediately and the remaining water in the exchanger would just absorb the excess heat. Nobody par-boiled or died of chlorine gas explosions.
I know you think I am a nutcase, and I'm ok with that. The same thing was told me when I said I would build a biodiesel proccessor and make my own diesel fuel. That was 10 years ago and everybody laughed and called me a nutball. nobody laughs anymore and I havent spent a dime at a gas station in over 6-years!

My hat goes off to you with the biodiesel. GOOD for you. I've wanted to do that for years, just never got around to it. Thing is " they " changed the rules about hot tubs.
Must have been a reason. I'm sure you have it under control. No one here wants to see a fellow poster hurt
themself including myself. Sorry for the blast but i have
seen what can go wrong. I need you aroud so i can talk to
you about biodiesel. If you will talk to me that is. Hope
you get it sorted and don't get hurt. Again good luck.

No worries, kalining! I'm thick skinned and probably the first to admit I'm not the sharpest tool in the shed. :)
I have no intention of killing myself or others with my hot tub problem. I am just not familiar with these new heaters and was hoping to avoid the whole "You'll shoot your eye out, kid" argument. But alas, it happened anyway. I appreciate everyones concern and good, well thought out advice here.
If you wish to try making bioD, I am more experienced than most, and would be happy to discuss it with you. My email address is eric@eprepservices.com and I even made a little web page for our BioDiesel club, but dont use the email address there. Use the one above!
http://www.santabarbarabiodiesel.com

I was in charge of heating our building for 3 years with waste oil, vegetable and motor oil. We saved about $10K in heating costs, but the supply of oil was so varied, our furnace was down more than it ran.

We sent the prototype to a sister plant and went without heat last winter because I never had time to build a boiler room.

This year I intend to have a waste oil boiler and a coal boiler installed (with the emphasis on coal), so we don't freeze again this winter.

Quote-"We sent the prototype to a sister plant and went without heat last winter because I never had time to build a boiler room."
___________________________________________________________

Wally Mart- Space heaters @$15.00 a piece. LOL.

baymee, we're off topic now, but curious:
why was your waste oil heater a "prototype" ? Why did you send it off to another plant if the problem was "supply" side?
just curious!

You prolly already know this but one of the 1st things I tell people who want to burn waste oil, or process it into biodiesel like I do, is that you absolutely must 1st find a reliable source of high quality (water free, low acid, low FFA's) waste oil. Everything else is secondary. Of course, comming right up on the heels of that issue is finding a reliable person to go and collect the grease. Its a dirty job and most people burn out after a few months.

My company was going to begin production of waste oil boilers and they had a Shenendoah burner and an old tobacco barn furnace of about 400K btuh. Nobody wanted to operate it, and since I believe in recycling, I said I would do it. On the cold winter days it required 30 gallons of waste oil a day. You can see that it was a challenge to filter that much oil and still run a coal stoker operation. The heated area is about 70K sq. ft. with 30 foot ceilings, brick and glass walls and NO insulation anywhere; an old silk mill.

Almost every day the fire was out and it would take 6 hours of continuous use at 3 gpm to bring the temp up to 60. Sunlight also helped.

The prototype was sent out to be used in another building, but they left it sitting in the corner and we had no heat.

The order came down to install two new boilers, one of them the newly designed waste oil boiler, however, with the price of oil, I spent the entire year dealing with coal stokers.

This year I am determined to get it running.