Fixing the heating system - again...
I've noticed over the last several days that the main part of the house is cooler than it ought to be. I had (incorrectly) assumed that this was due to the fact that the house is pretty drafty, a problem that I'll deal with as soon as I can afford to. The thermostat was reading 18.5°c though it was set for 21°c. It was definitely calling for heat, but when I checked the radiators, they were cold. Uhoh...
My first worry was that the boiler had conked out again. Checking it, I found that it was also cold; Attempting to reset it didn't do any good. Turning up the thermostat in the bedroom made the boiler fire up properly, so I knew it was okay. *whew!* I began to wonder if the connections to the hallway thermostat were questionable, but all of the wiring seemed intact. A major problem was that none of the wiring was labelled properly. Tracing the wiring, I found that the bedroom valve was wired into the block labelled hallway, and vice-versa. We never had an issue with incorrect temperatures before, so I figured something else must be amiss. It was past midnight at this time and I was tired; The house was cool, but not freezing, so I decided to call it a night and that I'd deal with it in the morning.
My first concern when I started this morning was to correct the labelling so that I knew which circuit (bedroom or hallway) I was working with. Fortunately, from downstairs you can see the supply and return pipes, so it was easy to confirm which circuit was which. The labels on the wiring block were backwards, but the wiring had been reversed to compensate. So a negative-negative made it all right again. AURGH!!! The bottom line is that when the control-valves were replaced back in 2007, whoever installed it didn't pay proper attention to what he was doing, and trimmed the wires before making sure he had them in the right places according to the original labelling. Then to correct his mistake, he just switched the wires from the thermostats around instead of re-labelling the panel. It took me a few minutes of probing with a multi-meter to confirm which circuit was which, and re-label everything.
Once I knew which was which, it was a matter of finding out why things were not working properly. A Zone-Valve has two jobs: 1) A small synchronous motor inside turns a shaft that opens or closes the actual water-valve to which it is mounted; 2) a cam activates a micro-switch that tells the boiler to fire up. When I tried re-powering the system, I could hear the zone-valve starting to open, and a brief click as the boiler would start to fire up, then shut off again. I removed the control-section from the brass valve (they just pop off by sliding a switch) and removed the cover to get a look inside. Under the cover was the synchronous motor, and hidden beneath it was the micro-switch. As you can see in the image, there's a larger metal slide sitcking out; This allows you to force the motor (and valve) into the open position for removal and/or trouble-shooting. By moving this lever, I was able to confirm that the cam was rotating properly and pressing the switch. Using a small screw-driver, I clicked the switch on and off several times, listening to it "click" each time.
I turned the power on again, and watched the motor slowly turn the valve-control shaft, and also engage the switch. This time, the boiler fired up! Shutting it off again, the motor slid back to the off position, and I put the control-module back onto the water-valve. Once more powering up the system, I confirmed that it was now working properly. My guess is that the switch must have gotten stuck, or dirty (or something) and that by manually clicking it several times it cleared the problem and now it's working again. I turned the power off one last time, removed the control and replaced the cover, then put everything back again and restored the power.
Everything is working properly now; The boiler is running properly, the zones are correctly wired and labelled, and the house is warming up again. What bothers me the most is that if the switch had totally failed, I'd be faced with having to buy an entire new control module for about $75 to replace a $2 switch. The switch is a removable part if one knows how to take these things apart. Fortunately, I'm one of these people who knows how to take things apart (putting them back together again can be another matter!) Once we're safely into the Summer and I can shut down the heating system for a while, I plan to get a better look into the control-module and get a couple of extra switches, just to be prepared.
My first worry was that the boiler had conked out again. Checking it, I found that it was also cold; Attempting to reset it didn't do any good. Turning up the thermostat in the bedroom made the boiler fire up properly, so I knew it was okay. *whew!* I began to wonder if the connections to the hallway thermostat were questionable, but all of the wiring seemed intact. A major problem was that none of the wiring was labelled properly. Tracing the wiring, I found that the bedroom valve was wired into the block labelled hallway, and vice-versa. We never had an issue with incorrect temperatures before, so I figured something else must be amiss. It was past midnight at this time and I was tired; The house was cool, but not freezing, so I decided to call it a night and that I'd deal with it in the morning.
My first concern when I started this morning was to correct the labelling so that I knew which circuit (bedroom or hallway) I was working with. Fortunately, from downstairs you can see the supply and return pipes, so it was easy to confirm which circuit was which. The labels on the wiring block were backwards, but the wiring had been reversed to compensate. So a negative-negative made it all right again. AURGH!!! The bottom line is that when the control-valves were replaced back in 2007, whoever installed it didn't pay proper attention to what he was doing, and trimmed the wires before making sure he had them in the right places according to the original labelling. Then to correct his mistake, he just switched the wires from the thermostats around instead of re-labelling the panel. It took me a few minutes of probing with a multi-meter to confirm which circuit was which, and re-label everything.
Once I knew which was which, it was a matter of finding out why things were not working properly. A Zone-Valve has two jobs: 1) A small synchronous motor inside turns a shaft that opens or closes the actual water-valve to which it is mounted; 2) a cam activates a micro-switch that tells the boiler to fire up. When I tried re-powering the system, I could hear the zone-valve starting to open, and a brief click as the boiler would start to fire up, then shut off again. I removed the control-section from the brass valve (they just pop off by sliding a switch) and removed the cover to get a look inside. Under the cover was the synchronous motor, and hidden beneath it was the micro-switch. As you can see in the image, there's a larger metal slide sitcking out; This allows you to force the motor (and valve) into the open position for removal and/or trouble-shooting. By moving this lever, I was able to confirm that the cam was rotating properly and pressing the switch. Using a small screw-driver, I clicked the switch on and off several times, listening to it "click" each time.
I turned the power on again, and watched the motor slowly turn the valve-control shaft, and also engage the switch. This time, the boiler fired up! Shutting it off again, the motor slid back to the off position, and I put the control-module back onto the water-valve. Once more powering up the system, I confirmed that it was now working properly. My guess is that the switch must have gotten stuck, or dirty (or something) and that by manually clicking it several times it cleared the problem and now it's working again. I turned the power off one last time, removed the control and replaced the cover, then put everything back again and restored the power.
Everything is working properly now; The boiler is running properly, the zones are correctly wired and labelled, and the house is warming up again. What bothers me the most is that if the switch had totally failed, I'd be faced with having to buy an entire new control module for about $75 to replace a $2 switch. The switch is a removable part if one knows how to take these things apart. Fortunately, I'm one of these people who knows how to take things apart (putting them back together again can be another matter!) Once we're safely into the Summer and I can shut down the heating system for a while, I plan to get a better look into the control-module and get a couple of extra switches, just to be prepared.