Oh hi. There’s a slightly modified screenshot of a page from our building’s Johnson Controls Metasys UI while it was trying to roast our morning show hosts and stage guys to death and I was trying to get it to kindly, you know, not.
This is for the studio air handing unit. It just blasts cold air into the studio and does not have heating features built in. Various people have asked me at times why the heating doesn’t work. It just now occurs to me I could show them this graphic – no heating coils, reheat, or connection to the gas furnace next to the air handler exist for a now obsolete reason: this studio used to originally be lit by a multitude of terrifying hot lights to the point that heating would not be necessary while the studio is in use. Here’s the air handler viewed from outside:
A couple years ago I used to have trouble with the programming on this drive, but that’s long since resolved. The issue I was having was that it was just constantly getting a command to run at 00.00 Hz, which meant no blowy. A quick glance at Metasys showed me that it was calling for 100% chilled water flow to the coil and it was nice and cold inside the air handler, so I just hit battle short on the bypass there to get it going and cool the studio while I investigated. After the fan came up at 60.00 Hz (absolutely fearsome) it sucked one of the doors closed as I walked past it and tore my pants halfway down the side. Nice.
Anyway… Back to looking at the controls. The system cycled once like that, reaching the setpoint temperature and overshooting it slightly, then slamming shut the chilled water valve and letting the studio overheat again. When it had actually cooled the place down I went back up the roof and took the drive out of override, but now it stopped the fans too. Hmm.
This time I set Metasys in override. On each of those control parameters (return fan output, supply fan output, mixed air damper, and chilled water valve output) I could override them to nonzero values and the command would take effect! The only thing that was missing was any semblance of thermostatic control whatsoever. The system was just any degree between on or off I wanted… but once set like that, the studio temp would just drift up or down… I just about froze Tina and Courtney who were sitting right under vents. Aaaaaaaaaa! A call was placed at 8 am for the one and only controls tech in the area, who came out and spent several hours on the hellbeast.
After a while of scratching his head over the way our BACNET system was configured and how it was just spouting communication errors, the controls tech spotted one of these thermostats on the wall of the mechanical room with its display dark. Curious, we thought… I grabbed a meter and tested between the wires in it and found about 3.6 volts AC where there should be 24.
Sorry, I didn’t get a picture of the inside of it but it’s basically just like any normal thermostat, just with a BACNET connection in addition to the normal R, RC, C, Y, G, W, and Y wires. It basically just lets Metasys schedule occupancy and setpoints and monitor the status and temp. The menu system is maddening.
So I walked over to the electrical panel for the air handler it controlled and saw the breaker appeared to be on. I turned the breaker off and back on and the thermostat lit up and the blower started. 26.1 V AC appeared between R and C.
At this point I went back into the studio, wound up the timer switch on the wall that serves as the manual zone occupancy override, and after a couple minutes, the blowers started and the water valve opened until the discharge air temp met the setpoint. (Yes… It’s even adjustable!)
So uhhhhh, what the heck? My only thought is that when that wall thermostat was getting 3.6v (why that and not zero???) it was just getting enough power to make the microcontroller or RS-485 line driver in there wake up and periodically yeet glitches into the BACNET void
The controls tech explained to me that it works like Token Ring. If the token falls out of a powered down thermostat in an empty mech room, does it make a sound? Really this all reminds me of something the Space Toilet used to do wherein you could mess up its canbus network and make the amplifiers blink on and off like holiday lights from hell.
Do you ever look at something and wonder, “why in the actual hell?!”
This is one of the RTU (Roof Top Unit) air conditioners at one of the transmitter sites. It looks like a total pile of garbage but still works for some inexplicable reason. It was made by Payne – their logo still survives on one side but all other identifying marks are gone.
Just look at that glorious weird ductwork. It’s next to the roof kerb where the ducts pass into the building, and then the ducts do a giant whirl around it. There might be an inline heater in the duct at the very end but who the heck knows.
Every now and then, it’ll yeet the evaporator fan belt. Last time, it yeeted the motor pulley too!
It looks like someone replaced the motor in this thing’s history and when they installed the new one, they found the shaft key didn’t fit and left it lying in the bottom of the cabinet and just tightened the set screw against the shaft. This worked until it eventually started slipping and the pulley spun on the shaft. I found it with the belt off and the pulley dancing around on the shaft. When I turned the power off, the pulley fell onto the roof. The shaft bore now measured 5/8″ on one side, 3/4″ on the other — it had become conical!
I got a new pulley and shaft key from McMaster and put it all back together, it works, but sounds a tiny bit more like a lawnmower. I don’t think it’s all that much longer for this world, honestly.
So on another note, Carrier got away from belt drive fans on their newer RTUs! Look at this monster that just went in at the other site..
The evaporator fan, which moves the air to be cooled from indoors, is now a big vaneaxial type. It’s amazingly quiet too. Smaller vaneaxial fans can be found in 1 rack unit servers where they are most definitely NOT quiet, and larger ones are used in tunnel and parking garage ventilation.
I dunno, it seems like replacement of the Payne at the aux site is low on the priority list but I’m a little concerned that we’ll find it should have been higher on the list if we have to broadcast from there for a while over the summer. I can only imagine how many kilowatt-hours are being wasted via that pile of rusty crap. Somehow I’m imagining it being 10 SEER or less…
This post contains large amounts of angry hissing and swearing. You’ve been warned.
I was doing the weekly inspection checklist at the transmitter site when this….. Space Station Toilet….??? went thunk, plunk, and cycled out of Beam On. The display forlornly moaned of a low anode coolant flow alarm. I know the issue is with the flow sensor.
It’s in the middle of all this so I did not try to undertake the replacement single handedly. Look at this glorious mess!!!
But then my attention was drawn to the fact that it started getting warmer in the room… and it just kept getting warmer. Luckily, it was about 68 outside with a strong Delta Breeze, so I just opened all the doors and started to investigate the attempted thermal runway. On the roof I peeked into one of the large RTU (Roof Top Unit) air conditioners and saw a winter wonderland of ice. Hmm.
Not good. So why’s this thing icing up? It’s practically brand new! I called the HVAC company we have a service contract with and their dispatcher literally told me she was going to see if anyone felt like helping us out today. (No.)
Time to gather tools and investigate.
Definitely a low head pressure situation… but why? Remember, PV=nRT even for insufficient levels of T[emperature], so maybe it’s just running too cold due to low heat input into the system. Let’s open up the other side…
Note three things in this photo: 1) motor sheave spinning. 2) fan sheave barely spinning. 3) harder to see but— water flying everywhere including spraying on that poor little ABB drive!
Click, power down, go gather more tools, climb up and down the ladder about a zillion times…
I set the thermostat below to system off / constant fan and properly tensioned the belt, which DerpCo HVAC’s techs do not know how to do… At all… then restore power.
The fan didn’t start. The little ABB drive’s cooling fan wailed, but it just wasn’t coming on. Why? Finally on a whim I twisted the red and green thermostat wires together and it ramped politely up to full blast with no slippage. Guess the thermostat just isn’t letting constant fan be a thing. That’s fine…
Slowly but surely, the room temperature started creeping down.
I always wonder if I’d get in trouble for naming and shaming DerpCo HVAC. They’re a large, probably national company, and are far more interested with their prime directives of union busting and bumping out any employees with seniority than they are with providing proper service to their customers. I hate dealing with DerpCo mostly, though they have *one* tech locally who actually knows what they’re doing.
good jorb sweaty, totally glad we’ve been paying for a maintenance contract on this thing all this time
Upon having the staff working below complain they were pretty much freezing down there and looking in this confusing mess and seeing a suspiciously weak output air temperature… it was time to go investigate so I can tell the HVAC company how to fix it.
They do not successfully ever do diagnostics. I basically have to tell them what’s wrong and have them fix it.
but at least there’s no variable frequency drive involved. just a toasted drive belt that’s about two days from snapping off like an over-fried onion ring and leaving us shivering.
i don’t know i’m six days into what should have been a four day work week and my brain is just a bunch of aktivschaum.
anyway I found the thing having trouble lighting, short cycling, and periodically letting out gas farts because the “intermittent pilot” (a high voltage spark ignitor) was all fouled with crap… along with the venturis to the burners…. and pretty much….. everything
can i go home already?? youtube is recommending a video to me called “calm your anxiety”.
Apparently that heat exchanger isn’t original. We had another one of these units on which the heat exchanger cracked and Modine has entirely washed their hands of this series – no parts available anymore. The new one that was installed in its place is twice the physical size, makes huge banging and whistling noises, took ONE YEAR from order to delivery, and required a weird custom roof curb to sit in. Charming.
oh and the video is actually a pretty awesome lo-fi compliation
The pin was never securely inserted and latched into the housing of the fan connector! Welp. Lacking the correct tooling for this connector series (I have yet to be able to identify it!) I broke the rounded end off one of those plastic stirrer sticks from Starbucks and used it to prod the thing into place. It snapped in and I plugged the fan in and it’s happy again. Speaking of fans and drama, this greeted me with a rhythmic pounding noise from the office roof yesterday morning. I sent the HVAC contractor a photo of it and he arrived at the door at 9 AM laughing with a replacement propeller in hand. The cause of this one appeared to be that the “belly band” mounting Trane uses for the fan allowed it to slip down.
By design, these Trane units have a behavior that I consider to be just this side of “broken by design”. When the thermostat calls for cooling, the compressor starts and pumps gas (R-410A in this case) into the condenser, where it gives up heat into the metal finned tubes, condenses into liquid, and is sent to the output lines and into the building to boil inside the evaporator coil, cool the air down there, and come back to the outdoor unit as gas… the usual vapor compression refrigeration cycle. As the condenser heats up, the gas head pressure leaving the condenser starts to rise due to thermal expansion. You can hear the sound the compressor makes change as the head pressure rises, and I’m guessing the motor current starts climbing too. Once it rises to a certain point, a pressure switch trips and starts the fan, which cycles on and off based on the head pressure.
This causes it, in practice, to cycle in about 5-10 second intervals, repeatedly flexing and stressing every part of the nasty stamped sheet metal assembly up there.
The first time I encountered a unit like this in the wild, I thought I was hearing it repeatedly overheating and tripping a safety cutout. I had to ask an HVAC contractor if that’s normal. They said that (sadly) it is. Why?! I guess it might save a LITTLE power, but I don’t think it’s worth the reliability problems.
On a side note, my parents’ house had some ancient Sears “Good Neighbor” condensing unit that was made by Whirlpool, part of a retrofit from the 1970s or so (best I can find from trying to Google the thing). It claimed to be a two-speed condenser, but in reality, was a single speed compressor paired to a two speed fan that’d switch between high and low as needed based on the compressor discharge line temperature/pressure. It never outright STOPPED if the compressor was on. Yes, this was done… better… over four decades ago. Sigh.
It may be worth noting this was a pretty small R-12 system, couldn’t really fight the Florida heat well, but lasted a LOOOONG time. The condensing coil was much smaller than it is on modern high efficiency systems and I remember the temperature of the air coming out of that condenser being fearsome. You couldn’t comfortably touch the top of the unit after it’d been running.
Hey, let’s also try to give it variable speed fans, based on…. uhhhhhhh…
Whatever This Shit Is. Uhhhhhhhhhhhhhh—-
Now let’s put a water misted cooling pad system on the air inlets and make it look like something that was field expediently whacked together in the back of a barn OH FUCK GO BACK NO
Here’s the end result. At some point someone cleared out the electrical cabinet of everything but the main disconnect and rebuilt it with……a mountain of weird shit. This is the left side where the contactors for the compressors and fans would have normally been. I don’t know what the deal is with that thing that looks like a transformer, it’s just an 3 phase “reactor” – an inductor.
Not particularly visible at the bottom: a set of current transformers on the Turbocor’s power wires that set off the water misters when it begins to spool up, and a pair of fans rigged in the bottom to keep the VFDs cool…ish. They’re powered through the barrier strip on the far right.
In the compartment which would have formerly held the logic board that controlled the old setup, the two relays to the left of the Turbocor interface board turn on the cooling fans at the bottom, and…. well, I have no idea what the second one does. I couldn’t trace this out and there’s no documentation left with it. In short, I have already run out of fucks to give.
Um, what the fuck happened to R12? Again, lack of fucks to give, the thing still runs ok. Not sure what the LEDs are indicating but when D5 through D8 flicker periodically.
I’m fairly sure the Turbocor must actually be capable of commanding variable frequency fan drives to cool the condenser, but oops, someone put that weirdass blue pressurestat in place instead. That thing is fucking weird. It sits there and does nothing until the pressure is like 4 PSI below setpoint, then the command voltage it sends just abruptly leaps up from 0 to 10v, making the variable frequency drives… not so variable…
Anyway the reason I had to mess with this thing is one of the drives lost a 24VDC cooling fan. Our HVAC contractor looked into ordering a new fan and found out that a replacement would be at least SIX MONTHS OUT. The original, an NMB 3110KL-05W-B50 (80mm, ball bearing, 24v, 0.15A) appears to be Fuck You NLA. In fact, almost all 80mm 24VDC fans appear to be unavailable. I begrudgingly, out of desperation, dug into my own supplies and grabbed a little switching buck converter that’d take the 24VDC from the VFD and step it down to 12V to run a fan that actually IS available and extremely common.
Now the dumb thing spits out cold water again and I’m not quite as mad. I’m still going to swear at the fucking bellend thing though.
I’m a little annoyed with having to deal with air conditioning nonsense right before a weekend I don’t get any time off from work because we’re so understaffed. We have an HVAC contractor who is supposed to deal with this but they’re completely clueless when it comes to large systems. They have one guy in the company who understands the Metasys controls and somehow I know more about them than he does.
The last big issue I had was with this one air handler / fan coil unit on the roof that cools both control rooms and our newsroom via a Medusa head of VAV boxes. First it had been shutting down, it turned out the variable frequency drive was on an HVDC overvolt fault and didn’t automatically restart. I programmed it to do so. The service company looked at me like I was speaking Martian COBOL when I explained this to them.
I also asked them if the belts to that blower it runs were too loose. They don’t know. They couldn’t advise me on this and didn’t know how to check. I’m not touching this with a social distancing pole.
Today it was acting up in a different way and I found Metasys reporting the cold duct pressure was 0.1″ water column. When I opened the blower access door on this totally turdly air handler, it jumped up to 0.7″ and the VAV boxes actually started, you know…… working. Opening the door took an unreasonable amount of force and only after I opened the door, the system started calling for less than 100% blower speed. Hmmmm.
Gee I wonder why there’d be that much airflow restriction on the inlet? Let’s see, shall we?
These coils were supposedly cleaned! Uh…. No.
On a side note, the fact that our chiller’s variable output capability is simply not used and instead it was just saddled with this foam rubber covered Chipotle burrito tank and set to on/off cycle makes me wonder
Here’s to hoping this hot weekend goes uneventfully.
Variable frequency AC drive controllers are all sorts of amazing. They rectify AC power to DC then give you 3 phase AC at the desired frequency to let you run the motor at the desired speed, anywhere from just a few RPM up to full tilt. They can also, if misconfigured, drive you up the wall at 60 cycles per second.
I’ll save you the pain of having to watch me scream about Johnson Controls Metasys, here’s the data showing that this one air handler is not happy. This graph is showing its air output temperature. This morning I came in to find half the facility nearing meltdown and decided to see if I could do anything about it.
There’s the drive for that unit’s blower. I found it shut off on a DC bus overvolt fault. The automatic fault restart was not enabled, so it just sat there.
I restarted it and watched it ramp up to full speed…. fearsomely. After it’d let the place cool down a while I revisited the settings. This Yaskawa controller actually has pretty good documentation and a setup routine designed to aid in quick deployment (I CANNOT say that for all the controllers I’ve come across in the wild). Right away I noticed the amperage and wattage limits set in the controller did not match the motor, which did not appear to be original to the unit.
Yeah uh I’m gonna have to recommend you not do that. I filled out the proper values in there, turned on fault restart, and ran the auto tune, which sounds like angry crickets on this unit.
Aside from the drain pan looking suitably foul, I’d say it’s happy again.
I dunno, I realize that variable frequency drives are probably a bit of crazy black magic to a lot of HVAC people, but pleeeeeeeeeaasseeeee make sure you have the thing configured right for whatever motor you’ve wired to it! It does make a lot of difference!
Oh, and the Johnson Controls corporation is a bellended bagbiting cockwomble. There i said it ok