Two Stage Temperature Control w/ Sensor (24V Input)

I have a remotely located Coal fired Boiler that is supplying hot water underground to my pole barn ceiling hung fan coil unit. Rather than going through the effort of isolating the pole barn with a glycol system. I use this two stage thermostat for freeze protection. The first stage anytime that it senses the pipe with the remote probe being below 50°. It'll run the circulating pump via a RIB Relay with a 10° differential. That's freeze protection. The second stage is hooked up through a relay as well that when the thermostat in the pole barn is switched to heating mode and is calling for heat which I can control remotely, the 2nd stage will allow the fan unit blower to kick on as soon as the temperature reaches 120°F. ( to prevent cold blower air. There are a few more items in the control logic that I have in place for precise control. As I am a retired HVAC tech.It worked perfectly this winter.

I bought 2 of these to control my outdoor wood boiler. They do work! Easy to program and install. But I am not impressed with the build quality as follows: 1.) Sensor probe thermistor is plastic covered, and it will soften at temps well below the units high rating. They could have have used a metal covered sensor. I simply used some HVAC foil tape and then used silicon heat sink compound on that and inserted in a thermo well.. All good. Problem solved. 2.) Terminal connectors are really poor quality. The type used do not open up completely and thus given the tight quarters to inset the wires it is a challenge. Good quality connectors that drive open completely would be the better choice. 3.) LCD display does not stay lit. 4.) Entry hole for 24v powered model is too small for basic TSTAT wire. It can be drilled larger if needed, but really they should be able to figure that out. 5.) They do not supply plastic low voltage snap in cable inserts for the SPDT wiring inlet. Not all of us will use this for 120V on up applications but might like one for 24v or low voltage switching, so they can at least throw one in the box! 6.) Unit is slow to respond to temp changes, if temp is either on the increase or decrease and the temperature at the probe reverses (ie High to low, then low to high), the unit will take a minute or two to respond. I find that odd, but most likely do to a low linear scan rate of the probe by the unit. Over all I am keeping these as I already installed them, we will see how durable they are over time. Hopefully the time will not be short. I would recommend, this but beware of the units short comings.