You sit down in your favorite area of your home for some relaxing peace and quiet. You then realize that it’s a little chilly, so you walk over to the thermostat and turn up the temperature but 30 minutes later, you check and it’s still reading the same temperature! What is going on? Is my thermostat bad? Is my boiler broken? If you have a hydronic or hot water boiler and one area of your home isn’t heating, this can be troublesome.
First, check the other thermostats, if they are all reading the correct temperature and the rest of the home is warm, your boiler is likely fine. Let’s go back to the thermostat in the room, not heating. Take a look at the settings. Is it on heat? if so, move the temp up and down to listen for a “click” this is the activation of electricity being sent to the boiler zone valve.
Hydronic zone valves allow a single boiler to control heat independently in different areas of a home by its thermostat. The photo above shows a total of five zones, so there will be five thermostats in this home. When a zoned area of a home stops heating correctly, the likely culprit is the zone valve. When a thermostat calls for heat, a signal is sent to the corresponding zone valve, telling it to open up and allow water to flow through that specific area of the home while simultaneously sending a signal to the boiler to turn on as well if needed. Some zone valves have a “manual” bypass switch which allows you to manually open the valve if necessary in an emergency or till you can get service or replace the valve. Most zone valves also allow you to replace the control head/motor only while leaving the soldered body in place. This way you don’t have to drain the boiler or line and can just replace the bad control. You can test these by checking incoming power, if you get 24-volts, then the thermostat is working and the valve control needs replacing.