T902_O: Envelope Protection Fault
On the VSODC, this fault would be displayed on the seven-segment LED as a number 31.
The Drive LED's will likely not display any fault codes.
This is an operational fault, similar to an overcurrent except it occurs when the compressor is actually running. The Envelope is an operating current range based on compressor speed and load. If the current, while running exceeds the programmed envelope, the unit will fold back. If the compressor is already running at its lowest speed, it will shut down and display a 31 on the VSODC control momentarily. The unit will restart after the anti-short cycle timer as run.
In order for this fault to show in the EcoNet fault history, it must have occurred 15 times in a 24 hour period.
Generally this will happen when the system is overcharged because the compressor is working harder than it should.
This fault will not result in a system lockout
Reduce the system charge slightly
Early production dates, before mid 2017 had a slightly tighter operating envelope than they do today. If verifying the charge did not help it's possible to change the envelope. You must look at the date code on the drive board. If it was manufactured in 2017 or later, you can simply order a new model data card that is marked in parts to be after W5017. If the drive on the other hand was built in 2016 or earlier, you will need a new drive and a new memory card. If you have a drive after 2017 and for some reason you think a new drive will help, it will NOT. Yes, it will run, but no better than it did before. You just need the memory card to unlock the less conservative drive parameters. If you attempt to just use a new memory card on an old drive, it will not run and you will likely end up with an "A925_O Compressor Model Unknown" fault.
Do not just arbitrarily replace a drive and model data card for an upgrade if you aren't having envelope faults, nothing else changed. If you are having the envelope faults, check the charge before messing with the drive and/or memory card.
