ReplyNow, that's is why you join the HVAC-talk. The site that can screw you up even more than you have right now.Originally Posted by HVAC_rookie
Regular Guest
I work at an office with a critical server room, and in it we have a Sensaphone 800 that has been alarming us more than usual these last few months -yes I know it's summer and it's hot... Anyways, this year we've had professional air-balancing performed, sealed up lot's of little heat leaks around the server equipment, and opened up 2 more ceiling exhausts in the hottest spots all to no avail (all under the guidance of the contractor that performed the initial install); our system seems to be struggling more than ever! Our IT manager assures us no new servers have been added and the current activity with the machines is nothing special -mostly idle.
I'm an Administrative Assistant who got tasked on investigating this issue. I've consulted our HVAC preventative maintenance team and ruled out leaks, HVAC performace issues, refrigerant levels, and have confirmed the HVAC is more or less performing the same as always.
The room always feels cool (i.e. below 71), so I'm also looking into calibrating the respective temperature sensor connected to the Sensaphone).
Any suggestions how to proceed? We're in keep-it-cheap mode, so I'm trying to rule out all the inexpensive possibilities first.
I have more information, just not sure if it's all relevant. I'm baffled why the new exhaust holes didn't seem to help -is it possible too many exhausts could have a negative impact on the system's pressure?
Professional Member*
Now, that's is why you join the HVAC-talk. The site that can screw you up even more than you have right now.
Professional Member*
I'll start it up.
Am I missing something.......is the sensors getting above alarm point or no? Why does your server room have exhaust holes? The room feels 71 degrees.......is it? What kinda of AC setup do you have? Hopefully not portables or mini splits?
Regular Guest
Yes, sensors are getting above alarm point and calling my cell phone at 2am on weekends : (
Our server room is compartmentalized; cold area in front of the servers via ceiling supplies, then the back of the servers are walled-off so all their exhaust is trapped and vented into ceiling ducts and transferred back to the HVAC units.
We've got 3 x 5 ton Challengers installed in 2007, and maintained every 2 months. Other than a busted bearing several months back, they seem healthy, but they do run 24x7.
I noticed a slight hint of humidity the last couple days.
Professional Member*
Where are the alarm sensors located and what temperature is that area?
Professional Member*
It happens at 2 am on weekends. Coolest part of the day. Is it a busier time for the servers? Same? Less? I would look into a timed schedule function. The unit may be off and it takes that much time for the space to heat up. Or something else is off and the heat load on the unit increases as it tries to pick up the slack. What is the actual space temperature measured when that happens? Or does anyone even respond to investigate?
Regular Guest
Alarm sensor(just 1) is located in the exhaust duct -I'm aware that most people don't like this, but our contractor designed it this way. We're trying to convince the IT manager to allow us to relocate the sensor nearer the cool-side of the machines to instead monitor the supply-air.
2AM is not a busy time for the servers, on the contrary the overheats never seem to be spurred by increases in server activity at all; I've asked our IT manager about server load many times and she always assures me that due to the timing there is no correlation -I know it's hard to believe, for me too, but she stands by this fact. The alarm pops at random times, 1/2 in the day, 1/2 in the middle of the night, I just recollect the ones that ruin my weekend more vividly than the others.
As far as I can tell, none of the AC units EVER turn off because they never reach their set point. Although, when 1 of the 3 AC units fails (every 18 months or so) the room does warm up pretty darn fast (room temp goes from 70 to 80 degrees in about 20 minutes and will climb to 90 degrees in about 60 minutes if we don't start shutting stuff down).
Any chance someone can consider my exhaust question from earlier? Just wondering why more exhaust holes seemed to do more harm than good...
Professional Member*
I would have the sensor next to the cooling thermostat.
Regular Guest
Why?
Professional Member*
With the information you gave it seems to me that your units were barely cooling the room well enough to begin with. If the room was opened to the Plenum above the ceiling your units can't handle the extra load. Is this a dropped ceiling? Also, is the Plenum above the computer room open to other areas of your building or is it closed in all the way up to the actual ceiling? I think I would try to put the ceiling tiles back in to see if that will stabilize your temps.
Professional Member*
So it senses the same temperature that operates the cooling equipment.
Where is the thermostat now?
Regular Guest
@dunkman, What's the advantage with sensing the cooling equipment? Sensor's currently in the exhaust ducts.
@j3hvac, the ceiling tiles were there before so I don't expect that would improve anything -sort of a been there, done that. Our exhaust ducts are a sealed system, no heat is allowed to escape anywhere, it's all circulated back to the AC units.
Professional Member*
Forgive me, I'm trying to understand. Do you mean the sensor is in the exhaust of the servers, or by "exhaust ducts" do you mean the cold air supplies?
BTW, what's a Challenger?
Professional Member*
I have been scolded for my reply to this post because I don't have the * by my name. So I will go through the proper channels before I post anything else here. Sorry Mods!!
Regular Guest
@dunkman, by "exhaust ducts", I am referring to the hot air exhaust ducts that begin at the ceiling and carry the hot air back to the units. Thanks for asking
Challenger 3000 - is the make/model of our HVAC units
Regular Guest
@j3hvac - lol, I saw that! Rules are rules, glad I read em so I noticed you lacked that little star. Nevertheless, I appreciate any input and would still love to hear you back up your theories if you can find a way. You seem to know more about HVAC than me, so that's enough to make you qualified in my book.
Professional Member*
I'd expect that the building/house AC is being shut off/back at night. This can cause the increased load in the space, that eventually causes the High Temp Alarms. Check with the Building HVAC guys to see if the Building/House AC is on a schedule.
Professional Member*
Maybe I missing some facts......You are venting supply air from units via ceiling registers(via a upflow ducted challegers). I can get that, but what about the returns? You mention ceiling exhaust openings? Normally you would have a hot isle behind the racks. It would be sealed and returns from CRAC's would pull from.
What kinda of Challengers are they? Water cooled or air cooled dx? Split or self-contained? Or are they chilled water?
Professional Member
Dunkman, a challenger is a Liebert unit.
Chaos equals cash$$$
Professional Member*
LIEBERTS! Why didn't somebody say that before? Now I just feel silly. We have a bunch of those around here, none are ducted units though.
Total of 15 tons, I wonder if you're short on capacity. I'm not real sure how anyone would fix this one over the internet, Lieberts are complex enough in person.
Personally I would seriously consider purchasing a data logging device that can record temperature so you can look back and verify the actual temp when you get an alarm. You said it feels 71 in there. You might just have a bad temp alarm.
Another thought, do they have economizers???
