was able to program how i needed it to work. A spa alarm

Thermostats work nice you can set the dip differential where you want it. You can use it on heating control boxes. Or refrigeration units set your temp and your differential.

Took me a while to get it set up but it works perfect holding the temperature of 104

Easy to hook up, simple to program, will buy again!

I've been using these for 8 years in an application where they switch constantly day and night. Combined with RIB relays to isolate the loads from the controllers, these have been flawless. These do exactly what they should do year after year. These harken back to a time when things were built to last and do the job they are supposed to do. It's a shame so many products fail to produce the bare minimum. I have 4 of these (actually the other 3 are pre Penn and one is pre 421 designation) running in various tasks in my house and will always go to Johnson Control (now Penn) for this application assuming they continue to build a quality product.

This was a gift and I do know it is being used. So it must work.

Installed on a walk in cooler. I found it easy to program and install compared to some other brands.

The unit works flawlessly. Converted my Arctic King chest freezer into a Chest refrigerator at a constant 36 degrees. Success was by Trial Error over. Several Days. I NEVER Figured out the insructions worded and written by an Electrical Engineer with an advanced degree. DEFINATELY BUY this unit. FLAWLESS Operation.

Good product

This product did not work. Not at all!

The best durable temp control on the market I have 2 the oldest is an a21 8 years old and still working. johnson controls builds a good product usa made... hoo ra!

This is a boring product, as it should be. Once I deciphered the instructions and got it wired up and configured, it's worked without any fuss. The menu system isn't the most obvious, but once you figure it out, it's acceptable.Our fridge went out and I used this to convert a wine/beer fridge which only went down to 40F.I chose this over other cheaper ones because it has an anti-short cycle mode which is important for refrigeration to keep from damaging the compressor.