nobody wants to fix the cafe's troubling nest thermostat. not xiaowu the HVAC guy who usually does all the repair work whenever something breaks down, not the handful of professional nest installers whom i contacted in early spring. some never responded, some i e-mailed but never got any traction, and the one installer (victory) who did come (late) took a look, said all the right things, but then disappeared off the face of the earth even when i tried to contact them afterwards (one of the guys stole our screwdriver no less). what is it about our particular setup that makes HVAC specialists so afraid?
but i've done enough research on my own, scouring online discussion boards, watching youtube installation videos, reading all the explanations and hack attempts, that i like to think i already know a lot about the nest thermostat. i've also installed it at my own place (december 2014, running my own common wire when one wasn't available) and my father and i hacked a solution for the nest thermostat at my parents' place (november 2016).
so the trouble started last october when we installed a nest thermostat at the cafe, replacing an old school dual heating and cooling mercury-switch honeywell thermostat. that should've been a cause for celebration, a step into the future. having the ability to control the heat remotely and turn it down for those times when my parents forget was be a blessing. i wired it by the book, borrowing an unused wire from the AC roof unit and connecting it to the unused common on the control board. everything was going according to plan until we switched on the nest and it said it couldn't detect neither Rc (cooling) or Rh (heating). after some trial and error, we found out that if we pull out the common wire the thermostat will work fine, even though it shouldn't. but we left it as is since it was working and all seemed right with the HVAC world.
but over the weeks we began to notice that the basement furnace will make these loud intermittent clicking noises, like it was trying to ignite the furnace but couldn't. it never happened when it was heating, only when it wasn't. the most likely explanation was the nest thermostat still needed a common wire. the common provides power for the thermostat, and without it, it will try to sip power from the furnace, causing it to fire intermittently.
my father finally managed to get xiaowu to pay a house call (to fix a few other things). i figured him being the professional, he'd find a fix. but afterwards my father told me xiaowu couldn't make any sense of it either, and suggested we run new thermostat cables. while we waited for him to return (he kept putting it off), we did our own sleuthing mid-december and discovered that the common wire coming from the AC unit was actually 18VAC, not 24VAC. so it was definitely something wrong with the wire. fortunately there was one extra spare so i simply replaced the wire. when i measured it again from downstairs, it was the supposed value of 24-25VAC. wiring every back up, i put back the nest thermostat. it now accepted the common wire which you'd think is a good thing, but now it was firing the basement furnace non-stop, scary enough that we removed the nest thermostat after a few seconds. out of ideas, we went back to reliable mercury switch honeywell thermostat. sure, you couldn't control it remotely over via wifi, but at least it'd never repeatedly trigger the furnace when it wasn't turned on.
when spring came around i thought it'd be a good time to contact some nest-recommended professional installers. sure, it'd be expensive, but at least it'd fix our problem once and for all. that was before i found out nobody wanted to touch our system. something to do with a two transformer system - one transformer from the AC, one transformer from the furnace - a headache nobody wanted to tackle. as the weather was getting warmer, it was time to make the switch from heating to cooling. instead of using the honeywell thermostat, i decided to hook up the AC wires (Y-G-Rc-C) to the nest thermostat, which had been sitting on a shelf unused gathering dust all winter. the nest had no problems accepting the AC (a much newer unit by several decades compared to the basement furnace), and we didn't have anything to worry about, at least for the summer.
but now mid-october, with the temperature turning cooler, it was once again time for heating. we sort of kicked the can of our malfunctioning nest thermostat, but now it was time face the problem again. one thing i don't remember trying is to just use the common from the AC while connecting the heat. so the furnace would connect to W-Rh, while the common would be on Rc-C (disconnecting Y and G). i saw this wiring for an external 24VAC setup, and figured we could trying matching it, except we'd be using the AC as the common. i think in the past we tried connecting just the C wire which didn't work and the nest wouldn't even allow us to continue until we fixed the wiring. having a year to digest what we did, i now realize it didn't work (just W-C-Rh) because the C was an open loop. when we wired it again this time (Rc-C, W-Rh), there was no problem. the nest thermostat accepted the wiring, but did throw me an N72 error. from a youtube video i learned that N72 is a minor error, the nest will say this in certain conditions, like wiring in a C common wire from an external source. everything is still okay, and like the video said, the nest will still allow you to continue despite the error message. in fact, we were able to test the furnace, it turned on no problems, and we also increased the room temperature by 1 degree as an additional test, it passed as well.
so everything was working, and all seemed well in the HVAC world once again. but the real test wasn't whether or not the nest thermostat could turn on the furnace, it's always been able to do that. what we wanted to know is if left alone, will the nest thermostat try to steal power from the furnace (thereby causing the intermittent clicks) or will it behave and take power from the provided AC-supplied common wire?
in the meantime i helped my father take down 2 window AC units from the apartment bedrooms. in the past we simply left the AC's in the windows all season because 1) they were too dirty to move, and 2) they were too heavy. but these new AC's we've installed are much lighter, and taking them down will lessen the draft coming into the bedrooms come winter. currently a male astrophysicist is living in the small bedroom and 2 other male astrophysicists are sharing the larger bedroom. i was surprised they left their doors opened, i guess none of them have much to steal. after taking down the AC's we moved them into the basement. i was admiring the plastic wash basins, which i realized last night are the perfect containers for growing lotuses next season.
afterwards i rode to belmont to check on the solar batteries, water the lawn, and do some weeding.
i should've realized something was wrong with the nest thermostat when my father called me around 3:30pm. he said he started hearing the clicks again, said they were different from last time, put the phone up to the furnace for me to hear as well. they sounded like somebody knocking or hammering on a door. although he said we could fix it tomorrow, i told him i would come down immediately. i went via bicycle, figuring it'd be easier to get back home come rush hour.
so the Rc-C common wiring hack from the AC didn't work. i couldn't figure out why, but our final solution was to use an external 24VAC power source. we actually had a 24VAC transformer (MG ELECTRONICS MGT2420, $13.55) that we purchased back in april 2017, when we discovered that turning off our furnace for the season would also cut power to the nest thermostat. the transformer was a potential fix but my father figured out a way to have a separate 24VAC switch from the basement to the thermostat so we ended up never using the transformer. this seems like such a common problem (smart thermostat requiring an unavailable common wire) nowadays that i've seen specialty plugs being sold on amazon just for this purpose. the kind that we got is a big ugly heavy transformer, didn't even come with wires, which you have to provide yourself.
ideally you'd want to hide the transformer wires inside the walls, but we decided to do a temp hack job, just to see if it'd even work. we unscrewed the rectangular thermostat baseplate so there'd be some clearance for the wires to go underneath and then into the nest. i wired it exactly the same way i did before, except the Rc-C wires were now coming from the 24VAC tranformer. like before, it threw out an N72 error, which i learned to ignore. it allowed us to continue and we were able to run a heating test without any problems. but like before, the problem isn't with the heating, it's with the thermostat when it tries steal power when its battery begins to run low.
only time will tell if the external 24VAC transformer hack will work. we taped the wire to the wall to prevent anyone from accidentally snagging it. my father seemed optimistic, but i've been fooled so many times before, i'm sort of hopeful but guarded. even if it was does work, this is a hack, and come late spring, we'll need to switch the wires inside the nest for AC cooling. we'll also need to find a way to hide the exposed wires. but all those are things for the future; right now we need to worry about if this fixed it or not.
my aunt showed up unexpectedly. we thought she was hire to pick up some xian bread jason's father had made before they returned to china, but she came to tell my parents' that matthew's father passed away on saturday.
when i came home there are two packages for me in the foyer: a pack of alligator clips and a solar-powered rubber cork stopper string light. the cork stopper light is cool, not sure how much electricity it can actually store. the rubber cork is also completely sealed, so no way to replace the battery. the cork isn't very elastic, i couldn't really squeeze it into a bottle, it's more of a solid stopper, but cool nevertheless. speaking of solar string lights, my amazon seller finally refunded by $7 for the handful of solar mason jar lights that leaked water. i brought a few home to test, so i could figure out where exactly is it leaking from, so that maybe i could fix it with silicone caulk.
i had some bread and the remaining drumstick for dinner but it wasn't enough so i heated some soup from a can. still haven't gone to the super market this week, need to figure out what i'm going to make for dinner the rest of the week. my parents are off to bermuda next week so i'll need to forage for myself for the entire week.