I have a 225 with an occasional trip of this code t099 when off for a while. This translates to econo pressure is less than 12# less than suction pressure. I have watched this pressure from the navigator and on a start-up it climbs slowly, so after a reset it will be fine. This is on circuit b the single stage compressor. So maybe there is a shrader under the transducer from the factory that is not open fully or what. This is not a brazed plate economizer it is the tank style. So here is my scenario- the exv doesn't close off 100% so the evap fills with liquid above liquid level setpoint, then when the chiller starts up the exv stays closed until level drops and due to it being closed the econo pressure will drop below suction pressure on a cold start up. But this backpressure valve from the oil separator with the 3/8 line does what for the system? I would think if this was open to the econo pressure line then this would cause the pressure to rise faster? Am I over thinking this or am I close? With this type of econo tank I can not see the valve operate through the sight glass because there isn't one. But when I use the test mode and I open then close the valve you can hear the refrigerant equalizing well after clicking from the valve closing occurs.