What does ADT (A) mean on a Kaeser Sigma Control?
Short answer: Airend discharge temperature exceeded (original Sigma Control). If your Kaeser Sigma Control (original) is showing ADT (A), the controller has logged a specific, documented condition. This page covers what it means, what causes it, what you can safely fix yourself, and when — and why — it takes a technician.
What exactly is the machine telling you?
On first-generation Sigma Control units, the alarm message "ADT" means the maximum airend discharge temperature was exceeded and the package shut down. A "ADT dT/dt" alarm exists for excessive rate of temperature rise.
Which machines show this?
first-generation Kaeser rotary screw compressors fitted with the original Sigma Control — the green-keypad, text-display controller Kaeser introduced around the turn of the 2000s on its direct-drive screw packages. This controller shows faults as short lower-case text messages with a severity letter: (A) for an alarm that shuts the machine down, (W) for a warning it keeps running through — so 'ADT (A)' is an airend-temperature shutdown while 'separator dp (W)' is a clogging separator flagged early. Alarms are acknowledged with the reset key after the cause is fixed. Practical tip: these machines also enforce a minimum start temperature of +3 °C, so a winter no-start in an unheated room is often the controller doing its job, not a fault.
What causes it?
- Insufficient ventilation or ambient above 40°C
- Cooler dirty, or the cooling air outlet too close to a wall
- Oil level low
- Oil filter overdue
Can you fix it yourself?
Often, yes — the manual's own remedy list is ventilation, cooler cleaning, oil level, and an oil filter renewal, all operator-level, then reset after cooldown.
Step by step — what to try, in order:
- Ensure sufficient ventilation and keep ambient temperature below 40°C.
- Clean the cooler; make sure the cooling air outlet is not too near a wall.
- Check the oil level.
- Renew the oil filter if due, then reset the alarm with the reset key after cooldown.
When do you need a technician — and why?
A repeating overheat trip after that cleanup needs a Kaeser service agent to check the thermostatic control and oil circulation with instruments.
If it does come to a service call and you're in Nashville, TN or Birmingham, AL, we maintain independently compiled lists of local companies that service industrial air compressors — real businesses with verified contact information, none of whom paid to be listed.
Related questions
What does ADT (A) mean on a Kaeser Sigma Control (original)?
Airend discharge temperature exceeded (original Sigma Control). On first-generation Sigma Control units, the alarm message "ADT" means the maximum airend discharge temperature was exceeded and the package shut down. A "ADT dT/dt" alarm exists for excessive rate of temperature rise.
Can I fix ADT (A) on a Kaeser Sigma Control (original) myself?
Often, yes — the manual's own remedy list is ventilation, cooler cleaning, oil level, and an oil filter renewal, all operator-level, then reset after cooldown.
When does ADT (A) on a Kaeser Sigma Control (original) need a technician?
A repeating overheat trip after that cleanup needs a Kaeser service agent to check the thermostatic control and oil circulation with instruments. Call a Kaeser service agent if the overheat trip repeats after cooling-system cleanup.
Verified against service documentation: Kaeser Sigma Control (original) documentation for ADT (A) (airsolcan.com)