Date: 201302
Location: ZZZ.ARTCC, US
Flight conditions: VMC
Light: Daylight
Aircraft: B737 Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Climb
Airspace: Class A ZZZ
ATC / advisory: Center ZZZ
Second aircraft: EMB ERJ 170/175 ER/LR
Reporter organization: Government
Reporter function: Enroute
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Workload; Time Pressure; Communication Breakdown
Second reporter function: Captain
Anomaly: ATC Issue All Types; Conflict Airborne Conflict
Detector: Person Air Traffic Control; Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Separated Traffic; Flight Crew FLC complied w / Automation / Advisory
Contributing factors: Human Factors
Primary problem: Human Factors

Narrative: I was working Sector XX with Sector XY. I was then assigned to open Sector XX from Sector XZ. Sector XY is at the end of the aisle-a long distance from Sector XX. Since there were only a few ZZZ aircraft and not much volume in Sector XX; I said I was ready to take Sector XY. I soon realized after the CS entry was made that Sector XY had a lot of traffic; and the Controller was working a push. He was told to give Sector XY to Sector XX and he did. Shortly after; I had two aircraft I was trying to space on one route. A restricted area was active; and I had a D-Side. I put speeds on the arrivals; only climbing the second arrival to FL200 until the speeds worked out. Once the speeds were working; I climbed the B737-700 to FL220. There was a ZZZ arrival in level flight northbound at FL210. On the bigger range; I took a second look and realized it wasn't going to work; therefore I started a left turn to 100 heading on the B737-700; and a left turn on the Embraer 175 to a 360 heading. I asked for a report from the B737-700 being level at FL220. Both aircraft responded to TCAS. I believe the Embraer 175 descended to FL205; and the B737-700 reported level at FL220 before a loss of separation occurred. The D-Side immediately pointed out the the B737-700 to Restricted Area advisories as I had to use their airspace. The pilot of the B737-700 kept inquiring about what happened; however I still had a high volume/complexity with aircraft that needed clearances and I could not answer him. I was assigned a position to work for my first rotation; and asked to work an unusual combination (XX/XY). I said yes because on the shifts I work (mostly nights and weekends) Sectors XX and XY are fairly slow; and that was the impression I got if they were going to be combined. I had no idea Sector XY was working a push. The Supervisor and the Sector XY Controller both knew this; and neither one said let's wait to combine until after the push. It would have been nice had the Supervisor said it's a little busy in XY; but not in XX; or something to give me a head's up. Routinely; Supervisors are making decision to split or combine sectors too late; and often controllers are working busy pushes and tasked with giving briefings during this time. I know it's not a science; but it's like if a controller is busy and the supervisor didn't split it out in time-if something were to happen then the supervisor might get in trouble for not having it split-so out of fear of getting in trouble; they irrationally split sectors in a hurry-which actually can cause something to happen or things to get missed. In this case it was combining sectors-but can't we wait until after the push? Why did it have to happen right then? I said I was ready-but I did not have all the information-the supervisor did; as well as the Controller working the traffic knew it was busy.


Second narrative: While on vectors we received a RA. We were on vectors from initial takeoff and these vectors lasted until after the RA event. As we were turned left and right during our climb; we finally leveled off at FL200. After a couple of minutes at FL200; we were given a right turn to a heading of 270 degrees and a climb to FL220. As we approached FL210; we were given another turn back left and it was at this time we received the RA. The Pilot Flying disengaged the autopilot and initiated a climb as directed by the flight instruments to ensure a safe RA conclusion. I also heard on the radio at this time; another aircraft executing a RA. After the RA event; controllers continued with vectors for our aircraft until we were switched to another frequency.


Synopsis: Enroute Controller working combined positions encountered unexpected busy traffic and experienced a loss of separation.