518 VS T6 Hydronic - 561 vs T6 WIFI - Outdoor Reset Mixer

joshavan

Recently moved into a home built in 1995 with the same age radiant floor heat throughout the entire house. 8 zones all on mechanical thermostats with 3 wires at each location unfortunately that means no slab/floor sensor at any of the locations either. Boiler is an old Weil-McLain that requires return temps to be above 140-160 to avoid condensation. DHW tank also runs off the boiler which unfortunately means I need to maintain those boiler temps even in summer. Mixing valves are manual and can be set from 75-175. Currently mixing valves are at 90 degrees which is maintaining warmth, only a low of 30-40s so far.

1. I am planning on limping this system/boiler along till it fails and replace it with something that can do outdoor reset properly and far more energy efficient. My question is if I have one zone that I struggle to keep at a consistent temp should I try an outdoor reset mixing valve or just deal with it until I replace the boiler?
   1. https://www.supplyhouse.com/Taco-I075U3R-1-3-4-3-Way-Outdoor-Reset-I-Series-Mixing-Valve-Union-Sweat
2. I am looking at changing out some of the thermostats with ones that have the PWM/CPR/HCR to help maintain a more even temperature. Do the wifi/smart thermostats have any ability to learn or adjust based PWM/CPR/HCR for outdoor temperature or solar load on a daily basis? If you have any other suggestions for thermostats than the ones listed below tell me why.
   1. Non wifi I am looking at the following, any suggestions between the two and why would be great.
      1. T6 Hydronic - https://www.supplyhouse.com/Honeywell-Home-TH6100AF2004-T6-Pro-Hydronic-Programmable-Thermostat-w-Slab-Floor-Sensor-1-Heat-Only
      2. Tekmar 518 - https://www.supplyhouse.com/Tekmar-518-Thermostat-518-One-Stage-Heat
   2. Wifi Programable I am looking at the following, any suggestions between the two and why would be great. I am leaning towards the Honeywell thermostat so I have the ability to put wireless sensor where I want to actually monitor temperature instead of at the location where the wires are.
      1. T6 Pro Wifi - https://www.supplyhouse.com/Honeywell-Home-Resideo-TH6220WF2006-T6-Pro-Smart-Wi-Fi-Programmable-Thermostat-2H-2C
      2. Tekmar 561 - https://www.supplyhouse.com/Tekmar-561-WiFi-Thermostat-One-Stage-Heat

GroundUp

T6 without question, WiFi or not. The Tekmar stats are clumsy and in my opinion, garbage in comparison. I can't even count how many 518s I've had to throw away, they almost never make 5 years. The Tekmar app (if using WiFi) is all but worthless and without a floor sensor, there is no reason to spend the extra $100 on the 561 over the T6. The only thing the 561 is good for is the floor sensor capability.

joshavan

Thanks