Thermostats for hydronic radiant system

quattrobreck

I have a 3-zone whole-home hydronic radiant system. The 4th zone is hydronic baseboard for the basement. Each zone is controlled by a NIX SP-84M pump controller. The radiant system is the sole heat source for the house with the baseboard solely for the basement.

I am currently using 2-wire old mercury honeywell circular thermostats for each zone. The below picture only shows zones 1 & 2 wired but as of today, zones 3 & 4 are also wired.

I am wondering what options I have to upgrade my current thermostats with something more modern? I am of the set it and forget it mind with the radiant system but the baseboard may fluctuate with raising/lowering the temperature. Zones 3 & 4 have 7-wire going to them but Zones 1 & 2 only have 2-wire. I would prefer to stick with 2-wire but I have the ability to run new wires for zones 1 & 2 if that would lead to my best options for an upgrade with thermostats. I do not want to change the pump controller at this time.

Jamie Hall

My first reaction is… if you are of the set it and forget it turn of mind, as you say, or might just turn up the baseboard in the basement when someone is down there…

You can't beat the thermostats you have for reliability and precision (that is, they will always work at the same temperature every time — if that is off of reality, they may just be slightly off level, which is easy to fix). They will last forever. They need no batteries. They only need two wires.

And so on.

There are any number of modern thermostats with all sorts of bells and whistles. Some are two wire (they require batteries) and some are three or even more wires. They don't work as well as the ones you have, but yes, they are modern.

So what additional functionality are you looking for?

quattrobreck

https://forum.heatinghelp.com/discussion/comment/1809660#Comment_1809660

I'll be honest, its mainly from an aesthetics standpoint to replace the current mercury thermostats to something digital. Having to switch to battery power is not ideal. There are a handful of times in the winter the house is empty for 2-3 weeks at a time, so lowering the temperature after leaving & raising prior to arrival would be ideal but not necessary or game-changing.

I do have the ability to run new 7 wire for zones 1 & 2 and zones 3 & 4 already have existing 7-wire ran but are currently only using red/white wires into the NIX controller & existing thermostat. I do have access to a 24V outlet near the pump controller. Here are a few additional pictures of the pump controller. Zone 3 wire is not pictured but that is the baseboard heating.

heathead

Ok if you leave the house for 2-3 weeks during the winter, and if you have Wifi at the house I would get at least one wifi thermostat. You can set them up to alert if the temperature gets to low. Still better to have someone check on the house daily but it's an extra safeguard.

Jamie Hall

Ah yes. Wi-fi, that magic servant which alerts you when things go wrong.

Except when the power fails, which is when the heat will go off and the house will freeze. Much much better to have someone reliable (you may even have to pay them) to check the house — daily if it is below freezing and the water is left on.

On the more general question, if it's a matter of aesthetics, then go ahead. As I say, there are many digital thermostats available, some with wi-fi, some talk to home automation systems. If you have power and can run the extra wire or have it already, that's a plus. They take some programming to get them to cooperate with your system.

Just remember that they won't be as reliable as those old-fashioned ones which you have now.

DCContrarian

I like this one:

https://www.supplyhouse.com/Azel-Technologies-D-135E-Digital-Non-Programmable-Heat-Only-Thermostat-with-Setpoint-Memory-24-VAC

Digital, can be powered off of the 24V transformer power, remembers its settings if power is lost. 27 bucks.