Thanks, here is what Sup. 12 Part E Offshore helideck takeoff says:
ECS enviro (if fitted)
Confirm SOV 1 & 2 switches selected to NORMAL. Select ECS CONTROL switch to MAN HEAT and hold MAN HEAT switch to increase until ITT increase noted on both
engines, and HEATER ON advisory illuminates. Select ECS CONTROL switch to OFF, note ITT decrease, on both engines, and HEATER ON advisory extinguished.
RFM rev. 22 but the revision for this specific page is no. 10 according to the index.