Date: 202001
Local time of day: 0001-0600
Location: ZZZ.Airport, US
Flight conditions: IMC
Light: Daylight
Aircraft: EMB ERJ 170/175 ER/LR
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Climb
Aircraft component: Air Conditioning and Pressurization Pack
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Pilot Not Flying; Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Weather / Turbulence
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Issued New Clearance; Flight Crew Diverted; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Landed As Precaution
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: [In preflight we] informed the flight attendants about the following write ups: - NE 25-XX-XX; Emergency Equipment Compartment for gallery 2 - MEL 21-XX-XX-X; Pack flow control valve - MEL 21-XX-XX-X; Air conditioning packs.Captain informed the flight attendants about the inoperative pack 1 system and that would mean the pilots in the cockpit will have to adjust the air conditioning for the cabin and that if [they] needed adjustments in the cabin; they should feel free to call the cockpit for the necessary adjustments. First Officer did the external walk around and did not notice anything unusual in accordance to the MEL during the walk around. During the climb out to FL310; an EICAS caution message appeared - 'Bleed 2 overpress'.First Officer said; 'cancel and identify'; at that point; Captain said; 'Bleed 2 overpress'. Captain then referenced the QRH for Bleed 2 overpress. While running the QRH the message persisted. Captain referred to the ECS page; which showed both packs 1 and 2 valves closed and both at about 3psi.The QRH calls for 'Affected Bleed button - push out then in'; once that action was preformed; the psi on pack 2 gradually increased; then dropped down back to about 3 psi. [After] the QRH for Bleed 2 overpress had been performed; we got an EICAS warning message - 'Cabin Altitude Hi'. Both pilots donned the oxygen mask at 100% as the EPC calls for. Captain then requested to descend down to 10;000 ft. due to the Cabin Altitude Hi. Even though communication was established between both pilots; First Officer had a loud squelching noise out of his oxygen mask; [so] Captain stayed on the radios with ATC. Control center then gave flight a heading and a descent clearance to 10;000 ft. Captain completed the EPC and QRH for Cabin Altitude Hi as First Officer maintained proper control of the airplane. Captain then requested vectors back to [departure airport] as the weather was better than the other airports in the area and this also gives the opportunity to burn extra fuel so as to not land exceeding the landing limitation. ATC advised that [another] airport was closer; but the weather was reported 'broken at 500 ft. and low visibility'. After coordinating with dispatch; Captain then requested vectors to [the closer airport]. At this point; Captain had informed the flight attendants and passengers that; instead of returning back to ZZZ; and after coordinating with dispatch; we plan on diverting to ZZZ1; were we have the maintenance resources and the ability to switch aircraft. Due to the hi cabin altitude; the cabin masks had deployed and had been used as instructed by flight attendants. Control tower vectored [us] to for the ILS. Before landing; Captain and First Officer made sure that we were within the landing limitations.




Synopsis: E175 Captain reported that a loss of cabin pressure resulted in a diversion.