Need advice with boiler that continues to fire after tstat stops calling for heat

JSDNJ

I am experiencing an intermittent problem (happened once last season) where my thermostat (ecobee) stops calling for heat, but the boiler continues to fire. I am using a hydronic baseboard system with 3 zones controlled by an Argo zone controller. Each zone is controlled by its own ecobee.

I only noticed because the zone was way warmer than the set temp, and I went down to the boiler to find that zone control LED still lit on the control board and the boiler still firing. I checked the logs and can see the thermostat no longer calling, but the temperature still rising. I shut down the boiler and I power cycled everything, and when it came back up it's back to functioning normally including shutting down when the set temp is reached.

How can I even go about trouble shooting something like this? My ecobee is out of warranty so if it turns out thats the issue I have to buy a new one anyway, but I am worried it could be a wire issue which would be a major pain (finished basement, wires not accessible)

Any help or ideas are greatly appreciated.

Jamie Hall

I love intermittent failures... not. It probably isn't the Ecobee, however, which is something. However, it could be an intermittent short in the wires to the thermostat, and without being able to inspect them that's going to be hard to find. Unfortunately, it could also be a problem with a relay in the Argo board sticking -- which would go along with the situation resolving itself when you power cycled it.

ethicalpaul

Is this system also creating domestic hot water?

Is there another thermostat in parallel somewhere?

You can rule out the ecobee by replacing it temporarily with a thermostat that has no brain (or at least a more minimal brain) to see if the behavior persists.

You can rule some more things out at the boiler but those require more knowledge and a wiring diagram.

HVACNUT

If the LED for that zone is lit, then it's shorted somewhere between the relay and the thermostat. 
Try swapping thermostats AND sub bases with another and see if you get the same issue. 

JSDNJ

Jamie Hall said:

I love intermittent failures... not. It probably isn't the Ecobee, however, which is something. However, it could be an intermittent short in the wires to the thermostat, and without being able to inspect them that's going to be hard to find. Unfortunately, it could also be a problem with a relay in the Argo board sticking -- which would go along with the situation resolving itself when you power cycled it.

If it’s the wire I’ll be in absolute hell. I pulled all new wire before I finished the basement but I did have more than one spool of bad l, brand new south wire that I had to replace. 

I’d rather it be the board. 

JSDNJ

ethicalpaul said:

Is this system also creating domestic hot water? Is there another thermostat in parallel somewhere? You can rule out the ecobee by replacing it temporarily with a thermostat that has no brain (or at least a more minimal brain) to see if the behavior persists. You can rule some more things out at the boiler but those require more knowledge and a wiring diagram.

Not doing domestic water, just heat. 

JSDNJ

HVACNUT said:

If the LED for that zone is lit, then it's shorted somewhere between the relay and the thermostat. 
Try swapping thermostats AND sub bases with another and see if you get the same issue. 

Is there any way I can test the wire for a short? 

The **** of it is now it’s working totally fine, so I could swap the thermostats and it might not happen again and I’ll never know the cause. 

HVACNUT

JSDNJ said:

Is there any way I can test the wire for a short? 

You can check with an electrical meter that reads resistance (Ohms).

yellowdog

do you have zone valves or circs? my mothers place just overheated like yours and the zone valve was stuck open causing it.

JSDNJ

yellowdog said:

do you have zone valves or circs? my mothers place just overheated like yours and the zone valve was stuck open causing it.

I have zone valves,  but the fact that the light on the zone controller was lit makes me think it’s not a stuck valve. 

JSDNJ

HVACNUT said:

JSDNJ said:

Is there any way I can test the wire for a short? 

You can check with an electrical meter that reads resistance (Ohms).

Can I just do a continuity test on the red and white at the boiler? If I have continuity I can assume those two are touching/shorting somewhere? 

Brent H.

Looks like some of the Argo zone controls have both a red and green light. Green to indicate thermostat calling for heat and red for zone valve open. Does yours have both? You only mentioned a red LED.

EdTheHeaterMan

The only way to be sure about the intermittently touching wire completing the circuit to the zone control is to see it when it is happening and remove the thermostat from the wall and see if the zone control stops powering the zone valve. If the zone is still powered then remove the red wire from the thermostat terminal at the zone control to see if the zone control stops powering the zone valve. Then with a meter test for continuity at the red wire to the white wire with the thermostat still disconnected. (I am using red and white but your colors may vary because electric is colorblind) If you get the red and white wire to have continuity with both sides disconnected, (from the thermostat and the control) then you have a wire that is compromised.

There are ways to run wires along baseboards and behind molding to get from the thermostat location to the boiler room. And you do not have to locate the thermostat exactly where the old location is, Just as long as you select a place that represents the overall temperature of the zone you are controlling. Don't use outside walls or place the thermostat near a source of heat like a television or lamp that will offset the room temperature. Thermostat wires should not be 22 gauge wire from the phone company that you got for free (like I did once). Get 18Gauge thermostat wire and always have at least 2 extra conductors in the sleeve in case you have a problem like this in the future.

t300

To the original poster, did you ever discover the issue? experiencing something very similar right now and can't figure it out