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Idea for MORE than 104 F Degrees

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Drewski:
Hi All:

I've been reading lately about how to increase the maximum temperature for tubs (beyond 104) in numerous posts on this forum. Hot Springs obviously has a solution, I know that Jacuzzi tubs allow for "jumper" position changes that can be used to by-pass the limits and, as in my case, you can always pull back the on the temperature probe to “fool” the spa controller.

On spas such as mine, with Gecko control packs, there's no real way to by-pass the 104 limit (even Bubba Stu couldn't figure out how, and THAT'S saying something...) other than backing out the probe. Doing this will get you up to 110 as long as just the circ pump and heater is on, BUT, when the pumps come on, the "real" temp gets read by the probe and the heater kicks off. As a result, the higher temperature can’t be maintained (especially in the winter) and drops to the cooler range.

So, I was sitting in my tub last night contemplating this problem and I came up with an idea (I knew I smelled something burning). Hot tub temps are measured using solid metal probes mounted in the shell and outside the heater. The spa controller monitors each temperature and adjusts the heater, along with shutting down the system if things get too hot (High Limit) or if the temperature readings don't match closely enough (Temp Probe error).

Now, I'm thinking that to measure the temperature with these probes, a weak electrical current is passed through them with the increase in resistance caused by heating of the metal probe used to calculate temperature (someone please correct me if this assumption is WRONG). The return current is weaker, so the spa controller can calculate the temperature using changes in the resistance values.

OK, so let's try this. Build a board with a digital readout and 4 pairs of connectors. The "top" connectors are the wires from the probes, the "bottom" connectors go the spa pack. The board input is from the probes. It senses the "real" resistance values and knows what the "real" temperature is. This value is displayed on the readout. The board also allows the user to "choose" a temperature setting (say up to 110 F), also displayed on the readout. The board output is to the spa pack, using the original probe leads. The board is wired between the probes and the spa pack.

Now, here's the trick. When the “real” temperature is less than the board setting, the board "returns" a resistance value of 80 F to the spa controller using the output connectors. The spa controller then turns the heater on because it reads a "low" temperature. Once the chosen board temperature is reached, the board "returns" a resistance value of 105 F, causing the spa controller to shut the heater off. In essence, the board "bypasses" the temperature sensing capability of the spa controller and allows the user to exceed maximum temperature limits.

I'm thinking such a device could be fairly small, powered by batteries? I know that in my tub, it would be very easy to run the probe wires to this "box" anywhere near the spa control pack.

AND, I know, I know, "it would create all kinds of liability if you made it or sold it." Hmmmm, let's see now, how may "hot rod shops" are held liable for all those aftermarket car parts that create engines with 400 HP in Honda Civics and probably result in hundreds of accidents per year?

OK you guys that are EE's or Biomedical Engineers (VINNY!), any ideas?

Thanks...

Drewski

;D  

windsurfdog:
Duuude,

Back off the 110 degree stuff, man....you don' wan' no stinkin' heart attack.... ;)

BTW--just "summerized" my tub by backing it down to 97.... 8)

txwillie:
Guess being from Texas, I just don't get it. When I first got my tub I set it to 102. Plenty hot. Ran it up to the max of 104, just to see. Too hot. In our mild winters, 101-102 is about right for me.

I've set mine back to 95F, but we've had a little heat wave, air temps over 100F and the spa temp has yet to fall below 98F. Plan to change the water this weekend because it is time, but also to get the temp down.

txwillie

JcDenton:

--- Quote ---I've set mine back to 95F, but we've had a little heat wave, air temps over 100F and the spa temp has yet to fall below 98F. Plan to change the water this weekend because it is time, but also to get the temp down.
--- End quote ---


Maybe you should move to where the temperature inside the tub is warmer than the air outside of it. ;D




This is how we do it in the Great White North. ;D

Jc

jcmsrv:
Hi Drewski
I also have piper glen, (new this may first). I found out that if I run 3 to 4 pumps two to three cycles the water will over-heat to 106 or 107. I know my controls work fine because each morning when I check the water it's right on 104. we found 107 too hot, but 105/106 on cool night ok. Have you tried this???
john

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