I have a server room cooled by three wall-mounted units, two 2.5 ton and a 2 ton. At a minimum, I'd like to monitor discharge airflow and temperature and be able to post the results up on a web app in real time. What I don't have is a bottomless bucket of money to throw at it. Is there something cheap and reliable I can cobble together from off-the-shelf parts? Thanks.
A camera pointed at a thermometer and a couple cameras pointed at the fans with streamers off the back to show air flow?
Not sure what your existing data/communication environment is, but there are a number of internet-enabled temperature data loggers that will make results available online for a few hundred dollars. If you have an existing computer to handle the data you can go even cheaper and just run any USB logger that outputs in Excel. At that point it's not hard to set it up to send out alert emails etc as needed if the temp exceeds alarm thresholds etc. I highly recommend Omega, their stuff is well made and reasonably priced. http://www.omega.com/ You wanting to monitor airflow makes it significantly more complicated. Can you get what you need with temperature only? Perhaps measure air temp change across the coil (or coil refrigerant outlet temp) to determine whether air is flowing. All other things being equal I'd recommend a system that reads thermocouples rather than RTDs or other similar sensors. TCs are generally a bit less accurate but are much cheaper, more flexible, and more robust.
Temperature alone won't tell me if an evaporator is iced up. Edit: I see your suggestion about measuring coil refrigerant outlet temp. All three units don't run at the same time (they can, but only if it's really hot out or there's a high human load in the room), so I'd have to be able to tell the difference between normal cycling (guessing that it would range from room temp to hot), a dead unit (steady room temp, but that can be normal for the unit with the higher setpoint), and a frozen unit (cold). Also, if a fan motor fails, I'd like to know sooner, rather than later.
What brand are your wall mounts? Mitsubishi? What brand is the rest of the building and does it have a BAS system? We run Trane units with the Tracker BAS on the main buildings and main server room. Mitsubishi split systems for smaller data rooms. Mitsubishi does not offer remote monitoring. We use some Trane sensors in the rooms with Mitsubishi units (temp, AC power & on/off) and can get basic monitoring and data logging of the room on the Tracker. Tells me the temp, if the unit is running and, if AC power is lost.
Only the 2-ton has a brand name on it, and that's a Liebert. The other two are plain beige boxes. Most of the rest of this building is zoned and running on unmonitored units. The five units I can see are Trane XE-series. One area over here uses a rooftop chiller (modified to cycle), and I don't think it has monitors, either. The pressroom area has a 25-year-old homebrew panel that just has red LEDs on it to show if something is running or whether a damper is open or not. So no, there is no existing system on which I can piggyback. I have a standalone temperature and power monitor in the room that calls our internal emergency number, but if things get bad enough that the temperature goes out of bounds, it's already too late. I've got ~10kW of load in a 400 sq. ft. room, so it'll get really hot really fast if the A/C goes down. I have redundancy by having three units, but if no one notices that one is dead and then a second unit goes down, I'm screwed.
I do have a panning IP camera in there, so I could use the streamer idea, but that won't call me if one quits. Someone here who used to work for Borders said that their motion sensors would go off when the A/C would start moving hanging banners around, so he suggested using a motion sensor in reverse.
if you have an APC UPS in the room they have add-on temp/baro sensors and monitoring software that is customizable for alerting.
I'll have to look at that. We have a Symmetra PX 20kW unit in there. Not sure how a barometric pressure unit helps, with no ducting available to measure. Separately, I see that there are some hot-bulb velocity sensors that may work.
How about a cheap weatherstation? the air speed thing in front of the main vent and a thermometer. Added bonus, humidity which will tell you if you have an icing problem. I had a cheap one that connected to the internet. Or webcam. This thread needs more duct tape.
i've had a very different experience with them. I installed a very pretty basic 8-channel alarm dialer to monitor some pressure switches at a remote site. Part of the functionality that I (over)paid for is the ability to phone into the system to check status. When that functionality failed, a call to tech support put me in touch with a totally unhelpful and nasty engineer who told me that the unit was an old design and wouldn't accept calls from either a cell phone or digital phone. so, analog only? good luck finding a payphone.... EDIT: BTW, pressure switches would be a one way to measure air flow if you just needed a flow/no-flow indication (depending on your setup). they wouldn't necessarily be able to give you a flow RATE.
I have a Netbotz 500 in our datacenter. It has airflow (ft/min) dew point temperature sound and later on you can add cameras, door sensors, etc. Not cheap but has worked for 6 years. Youtube: https://youtu.be/K6ttT-xfeWI
Yeah, a Netbotz or similar is probably the best answer. But can I point out that there's a horrible inconsistency here? This is a server room which is important enough to someone that you've got redundant cooling provision and are concerned enough to want to monitor it for faults BUT the a/c units are unknown brand? That implies to me that they're old and/or of some questionable manufacturer and therefore their condition is probably suspect. If you aren't already, you need to be giving the bean counters earache about properly supporting the server room and replacing these units. Any decent split system will have in-built (or as an optional extra card) fault diagnosis with output signal. Mitsubishi, Panasonic, Daikin. Good luck with all that. Brian
While I appreciate the sentiment that modern A/C would be better, I have to work with what I have for the foreseeable future. $1400 for a Netbotz may be out of reach, but at least I know it exists now.
So I bought one of these: and one of these: We'll see if I can make this go. This is a temperature-compensated sensor, and I'm hopeful that I can pull the temperature from it, too.
Someone suggested a Pi, I was about to say an Arduino. You may be lucky enough and find a sketch already completed online for your needs. Airflow would probably be easier if you could find out the volumetric flow rate of the unit at a constant rate and figure it in whenever the fan kicks on. edit: nevermind about the airflow. I see why you need it.
Both pieces arrived yesterday. Looks like I have a bum probe, because I'm not getting ambient temp data from it. The wind speed part works, though, which is cool. I have e-mail in to support on the probe problem.
I have a couple of arduinos operating, logging temperature and humidity samples to SD card and also browser accessible, but not emailing me on overtemp. Code size is on the edge of the limit for standard Arduino and they hang a bit. (I use Freetronics Etherten). To overcome that, I use the Mega for stable operation (Freetronics EtherMega is the equivalent I use). If you want a out of the box package without any coding, etc....check out ControlByWeb X-300. These are neat as they can run in monitor mode and also thermostat mode, either of which might suit your requirement. they also can log and email and SNMP on overtemp and also have a 3 relay contact outputs as well....also capable of running up to 8 One-wire temp sensors. Only bummer I found with these is no SD card, so log is lost on power cycle, unlike the arduino.... Either option might sort you out...
