CityRail has to limit the number of Waratahs because the trains are too power hungry. Picture: John Grainger Source: The Daily Telegraph

CityRail has to limit the number of Waratah trains running up hill on the North Shore Line because the power-hungry trains draw too much energy on the climb towards Hornsby.

The problem will also affect passengers catching trains on the Western Line because the two lines are linked.

It means only a certain number of Waratah trains can be on the line at any one time, with passengers destined to be crammed on to 30-year-old non-airconditioned trains more often until the problem is fixed.

RailCorp is upgrading power supply across the network, but work is not expected to be completed on the North Shore Line for at least two years.

“The North Shore Line is the worst affected because of the steep grades and the trains have to use much more power,” one source said. “Why they would leave that line for so long before upgrading is anyone’s guess.”

The power supply problem is similar to one that affects newer trains in the Epping to Chatswood tunnel, where the steep grades means more modern trains are unable to access the line.

Other glitches continue to plague the new trains, with Downer EDI installing new software to try to fix a fault that causes the doors between carriages to open by themselves.

A spokesman for CityRail said a program of infrastructure works was being carried out across the network, including on the North Shore Line, to upgrade the electrical systems for the Waratah trains as they are rolled out.

Software upgrades were “routine” across all train fleets, she said.

CityRail has taken possession of 12 of the new trains from Downer EDI’s Hunter Valley workshop, with 11 in operation across the network.

But the program continues to slip behind schedule. In February Downer EDI promised to deliver 12 trains by June 30, but the last train arrived in July.

The company will provide a full update when it announces its full year results today.