Air handling unit wont turn off.

It may be backed up with a UPS as well. At least that's what I would do if the controller's memory is so vital.

It's geothermal so it can't be icy cold unless you live on permafrost. I would wear a warm parka instead of paying for a service call!

Yeah its "cool" but it also uses normal air con to bring it down further when its needed so its making it very chilly.
The Memory is on UPS but that doesn't last more than half an hour. And the fans are 415V 20HP Motors and there 4 of them so takes more than batteries to keep them going. The backup generators are off. I'm really lost. I sent down one of my techies and even he got confused as to why they won't stop.
Im very recluctant to pay for a service bill, all I can think is there's an electrical problem, my techie said it could be a relay.. Or contactor stuck on. But the emergency shut off should still stop the fans?

Go to the MCC and open the disconnect. Remember to re-energize in 20 min. To protect the memory.

If you can find the supply to the UPS, plug it into 120V and you can leave the disconnect open.

You are correct, the E-stop should disconnect all power (excluding power to the controller). The E-stop not disconnecting power is a CSA violation (or American equivalent, I'm from Canada). Go to the owners manual and look to see if the unit is CSA certified or if you can see the label CSA anywhere in the manual (CSA stands for Canadian Standards Association but it is an international standard). If it is, they must fix the problem for free.

This is so important of a standard that I will not have any of my designs incorporate equipment without the CSA logo.

There is clearly a serious problem with the control circuit.

The Server Room thermostat should be controlling the unit.

The Emergency Stop button on the unit should shut the AHU completely down, and must be working properly now.

Sounds like this is the installers problem with re-programming the Geo-Thermal system, since first, the system is not temperature controlled, and most importantly, the Emergency Stop does not function. This system should have never been put on line without the proper testing.

Another method you can try is to activate the Server Room EPO system. There should be an Emergency Power Off button by each exit door of the Server Room. I caution you thou, if this button does exist and is activated, it will de-energize the entire Server Room.

Since the servers are not active yet, should not be a problem. If the EPO does shut down the AHU, which it must, you can try reset the EPO system to restore power to the Servers, and the AHU may stay off.

If it does not stay off, the AHU control is wired incorrectly, and you have no other choice but to throw the AHU Main Switch. If you can locate the actual fan unit, there should be a service disconnect locate on or near the fan unit that should only shut down the fan and not affect the Geo system.

If you do end up shutting down the Geo system, my take is that it is the installers issue to re-program the Geo controller. Not your fault the AHU is running wild. And for them to expect you to wait three weeks is very unreasonable.

Give them a call to put them on notice that if they don't get back today or tomorrow to remedy the situation, then you will be forced to shut the AHU Main Switch, and they will need to first wire the system properly and second, incur the costs to re-program.

Not only is the cold temperature a discomfort, the AHU running wild without temp control or a working stop button can be a serious fire hazard by fueling a fire should a fire begin. So let them know that your next call will be to the electrical inspector.

Thanks for all the help guys! There is a server room shut off but this doesn't effect the AHU in the plant room. I went to the Main distribution panel over in the west wing and shut off both AHU Main Breakers (theres an AHU for the other server room which is working fine) Doing this shut them both down and the geothermal alarms went off on the compressor control panel saying the pumps are unbalenced? And the fire alarm panel started beeping saying "POWER FAULT PLNTROOM-01" Now the AHU stopped. But the west wing won't start.
Both Compressors are in safe mode?

NOW.. The fire alarms are sounding the Alert tone every 30 secconds through out the building, the "ALERT" Led is blinking and the panel is buzzing at me. I have silenced them now but its still buzzing and every time I press reset 30 secconds later the fire alarms are beeping again

I have no idea what's going on here

The AHU's must have switches for Freeze protection and Fire protection. Shutting down the AHU must have triggered the Fire protection alarm (it is wired fail-safe so that no power will send a fire alarm).

I suggest turn power to them both back on and reset the fire alarm panel. At least you now know that the fire alarm panel can stop the AHU's!

Next, get the emergency stop fixed. Until then, wear a parka.

So when this system was commissioned, was there a training session?

If no training has happened, why is the system operational?

The FACP is monitoring the AHU system, most likely as a Suervisory zone, to alert offsite in the event the AHU system goes down and affect the Server Room. But should not be sounding a General Alarm.

The installer must come back today, or you need to hire a local electrician to get things back to operational. Document everything that happens, since my bet is you will be getting into a pissing match with the installer.

Yeah, well I own this building, and I was taken down there with the Building supervisor (who handles all this stuff) they showd me the basic on off and emergancy, then how to use the software on the panels.

I can't start any of the Units back up, they just won't turn back on, I reset all the control panels and stuff, both compressors are off safe mode and on standby ready for them to start. Now all my servers in the west wing are getting very hot and slow. So I'm worried if the AHU doesn't start in the next 20 minutes the lots going to go down.
I want the troublsome AHU to stay off! But the west unit MUST start!

The fire alarms are now showing "GENERAL FAULT" and are silenced.

The AHU's will not start until you remove the fault on the fire alarm panel. Get the fire alarm company to come if need be or look at the instruction manual.

An alarm silence and an alarm reset are two different functions. You need to reset the fire alarm panel.

P.S. You should change the title to 'AHU won't turn ON' (I know it's not funny but I just couldn't resist)!

Your system is way out-of-control. Have you ever thought of what will happen if you get a power failure?