ARU Thermal Regulator #77707-0010 Compatible with MasterTemp 400, 250, 125, 200, 300, 333 and Sta-Rite Pool Spa Heaters SR200, SR333, SR400

Worked as a perfect replacement for my Pentair Mastertemp 400. It's been about 2 months since installation and no issues thus far.

Fit and works for my pentair pool heater

It's a cheaper version of a Pentair thermal regulator. The whole purpose of this part is to function as a thermal bypass valve when the water temp passes 120F. In testing it before installing, I ran it under water at 145F, for several minutes, and the bypass valve didn't budge. Pentair one worked fine and opened entirely in about 15 seconds. At 10 bucks cheaper than the Pentair brand, I'm not really sure why I was trying to be a cheapskate but ultimately I just bought the actual Pentair brand one that did its job appropriately. Do not recommend this. I'm not entirely sure what the consequences of this valve not opening are, but I'm not willing to potentially gamble 5k to replace the entire heater to find out.

Regulator did not fit exactly in cap. Had to bend the tabs very carefully with channel lock pliers to get regulator to finally slide in. Otherwise, it has worked fine for a week. Don't know how long this non OEM will last based on some reviews but so far, so good.

A lot cheaper than paying a pool tech $250 to install a drop in unit.

Tried this part after pricing one at the local pool supplier for 5 times as much. Kit had everything needed and the replacement took 5 minutes. Works perfectly. With a salt water pool I have to replace annually so this is a great solution to the ongoing maintenance.

I had the HLS light on my Max E Therm 400 pool heater. I replaced this thermal regulator in less than 5 minutes and I now have perfect heat in my hot tub and pool. It works great!

It gets 2 stars because everything fits at least, although the screwdriver slots on the cap are smaller than the original cap so you’ll need a thinner than normal screwdriver shaft to turn it. The regulator itself looks almost identical to the original and fits the hole, unlike the “genuine” one I ordered on Amazon which is too big. Unfortunately this one doesn’t open up until over 140° so it did not fix the HLS error code issue. It should open at 120° as imprinted on the thing but it doesn’t and the HLS sensor is triggered at 135°. As a result, the HLS error occurs before the regulator opens. Good luck finding a genuine part though on Amazon. I give up and will have the local pool store order one. At least i can complain to a real person if it doesn’t work.

You're better off buying a brand name regulator like Pantair. These bootleg brands are cheaply made and stop working. Don't waste your time and money.