Thermal Regulator problems

[finatic]

This is the second time in the past year I have needed to replace the thermal regulator (thermostat) in my Sta Rite MaxETherm.
This is used on a ~1200 gal. saltwater in ground spa.

This one is 6 months old. They have rarely lasted past 1 year.

Here's the one I just pulled. You can see the crack in the center shaft and it is completely frozen.

[attachment=0:mik7pnhz]ThermReg1.JPG[/attachment:mik7pnhz]

I thought I kept very close eye on my water chemistries but clearly there is something not right. Is there a specific thing like ph or hardness that might be accelerating this problem? Can anyone offer any advice on how to get these things to last longer or can I just leave it out. It's become a bit of a PITA.

The heater works well without it right now- no error codes!!!

 

[waste]

Welcome to TFP!!

It certainly looks like something's wrong.

The color doesn't look right, so I suspect a chemistry issue.

Can you post some test #s and tell us how you came by them?

 

[finatic]

Thank you waste!
I am glad I came across this forum. Lots of very knowledgeable people and good info to be found.


The pool is exposed aggregate.
I find I need to add acid often due to the pH continually drifting upward.

Here is a snapshot from today: (I dropped this off at the local pool store for a complete analysis, it's usually pretty close to what I get)

TC: 5 ppm
FC: 5 ppm
pH: 7.8
AD: 1
TA: 85 ppm
CH: 215 ppm
Stab: 30 ppm
Salinity: 3200 ppm

 

[Ohm_Boy]

Odd.
To me, that "thermal regulator" sure does look a lot like an automobile cooling system thermostat. On my truck, one of those has lasted for pretty near to 20 years in the ralph-awfulest mess of liquids similar to water with a wide range of antifreeze dilution and some varying consistency lumps of rust and stopleak, over temperatures from freezing to around 230*F with absolutely no consideration for ph or calcium or algae, and while it may fail tomorrow, it hasn't batted an eye yet. I cannot imagine what might could cause that kind of split.

 

[Bama Rambler]

You're not pouring the acid in the skimmer are you? Just asking!

 

[finatic]

Good question, Bama!

I usually pour it on the opposite side of the spa from the skimmer near a jet to get it dispersed well before going into the skimmer. Usually needs only about an ounce every few weeks.

 

[finatic]

Odd.
To me, that "thermal regulator" sure does look a lot like an automobile cooling system thermostat. On my truck, one of those has lasted for pretty near to 20 years in the ralph-awfulest mess of liquids similar to water with a wide range of antifreeze dilution and some varying consistency lumps of rust and stopleak, over temperatures from freezing to around 230*F with absolutely no consideration for ph or calcium or algae, and while it may fail tomorrow, it hasn't batted an eye yet. I cannot imagine what might could cause that kind of split.

That's exactly what it is, only a lot smaller. I don't know why they corrode so quickly but salt water may be a different animal from antifreeze???

 

[finatic]

Spoke with the Pentair/Sta Rite tech today.
His opinion is that high pH is to blame for the repeated malfunctions of the TR.
pH does drift up to 7.8-7.9.
Skeptical but I will try to control it more tightly and see if that makes any difference this time.