This day is fired.
So, I've been thinking about getting intelligent thermostats. Probably Nests, but the jury's still out on the brand.
Two things need to be different to make that happen:
1: I need to pull new wire to the thermostats, because the intelligent ones require power, and the wiring I have will not support that.
2: they usually have occupancy sensors, and the thermostats are currently in rooms not frequently, y'know, occupied.
So I decided to pull new wire to new locations. Zone 2 thermostat will be moving from my office to my bedroom. Zone 1 thermostat will be moving from the living room to the dining room. Those wires are now in, at least as far as the basement; the hard part (fishing into the walls) is done.
While I was researching the arcana of residential thermostat wiring, I discovered that the wiring done by my previous heating contractor was...nonstandard. For one thing, rather than install a piece of 5-conductor cable (the standard now and indeed at the time of the work) or even 3-conductor cable (the older standard, and the number of conductors required) between the two zone valves, he had chosen to use one conductor each on three pieces of two conductor cable. Color coding standards? What are those? So I replaced that with a length of 5-conductor, adhering to the color coding standard, and following the wiring diagrams supplied with the valves.
And when I powered it all on, the magic smoke came out of the main furnace control box.
"WTF‽" Says I.
The relay inside that control box was buzzing, but not pulling all the way over. When I pushed it over with a screwdriver, the furnace fired up. But it wouldn't stay running without me leaning on it.
Turns out that even though the furnace wiring had an external 24VAC low-voltage transformer, which was in use when I started, the control box was also supplying 24VAC across its "thermostat connect here" leads. So when I straightened out all the funny wiring, and I didn't touch the last leg, leading to the control box (because see below about how hard it is to get into the control box)...turns out that last leg was color coded backward. So when I hooked everything up again, I was connecting the two transformers up hot-to-ground, ground-to-hot. They both could have blown. But since only one did blow, it was inevitable that it would be the one inside the $550 control unit, not the basically identical $12 one next to it.
Luckily, "I got a guy." In this case my guy is the manager at an HVAC supply house who is a customer of mine. So the control box cost me "only" $220 cash out the door.
But when I got it home, I discovered that it was not the same unit; it's a "functionally equivalent updated model." Specifically, where the old one had 8 wires needing to be hooked up on 8 screw terminals (Two each for 120VAC in, Pump, Burner, and Thermostat/24VAC out), this one has 9 wires (All those, but the 24VAC side has separated the Heat Request and Neutral into separate lines, which is a good improvement), and ONE of the burner wires now wants a spade connection. Again I say: "WTF‽" So another trip out to buy some spade crimp-ons, a little swearing to get the control box back into the little annoying niche it must be in (after the furnace was installed, someone re-routed some pipes, and there is now about 1/8" clearance in front of the box.)
The furnace is now running. Hopefully the other part, where it shuts down when the desired temperature is reached, also works.
(originally posted on dreamwidth. I'd like to keep all my comments in one place, so I'd rather you comment there by creating an openID cross-site login.)
Two things need to be different to make that happen:
1: I need to pull new wire to the thermostats, because the intelligent ones require power, and the wiring I have will not support that.
2: they usually have occupancy sensors, and the thermostats are currently in rooms not frequently, y'know, occupied.
So I decided to pull new wire to new locations. Zone 2 thermostat will be moving from my office to my bedroom. Zone 1 thermostat will be moving from the living room to the dining room. Those wires are now in, at least as far as the basement; the hard part (fishing into the walls) is done.
While I was researching the arcana of residential thermostat wiring, I discovered that the wiring done by my previous heating contractor was...nonstandard. For one thing, rather than install a piece of 5-conductor cable (the standard now and indeed at the time of the work) or even 3-conductor cable (the older standard, and the number of conductors required) between the two zone valves, he had chosen to use one conductor each on three pieces of two conductor cable. Color coding standards? What are those? So I replaced that with a length of 5-conductor, adhering to the color coding standard, and following the wiring diagrams supplied with the valves.
And when I powered it all on, the magic smoke came out of the main furnace control box.
"WTF‽" Says I.
The relay inside that control box was buzzing, but not pulling all the way over. When I pushed it over with a screwdriver, the furnace fired up. But it wouldn't stay running without me leaning on it.
Turns out that even though the furnace wiring had an external 24VAC low-voltage transformer, which was in use when I started, the control box was also supplying 24VAC across its "thermostat connect here" leads. So when I straightened out all the funny wiring, and I didn't touch the last leg, leading to the control box (because see below about how hard it is to get into the control box)...turns out that last leg was color coded backward. So when I hooked everything up again, I was connecting the two transformers up hot-to-ground, ground-to-hot. They both could have blown. But since only one did blow, it was inevitable that it would be the one inside the $550 control unit, not the basically identical $12 one next to it.
Luckily, "I got a guy." In this case my guy is the manager at an HVAC supply house who is a customer of mine. So the control box cost me "only" $220 cash out the door.
But when I got it home, I discovered that it was not the same unit; it's a "functionally equivalent updated model." Specifically, where the old one had 8 wires needing to be hooked up on 8 screw terminals (Two each for 120VAC in, Pump, Burner, and Thermostat/24VAC out), this one has 9 wires (All those, but the 24VAC side has separated the Heat Request and Neutral into separate lines, which is a good improvement), and ONE of the burner wires now wants a spade connection. Again I say: "WTF‽" So another trip out to buy some spade crimp-ons, a little swearing to get the control box back into the little annoying niche it must be in (after the furnace was installed, someone re-routed some pipes, and there is now about 1/8" clearance in front of the box.)
The furnace is now running. Hopefully the other part, where it shuts down when the desired temperature is reached, also works.
(originally posted on dreamwidth. I'd like to keep all my comments in one place, so I'd rather you comment there by creating an openID cross-site login.)