Originally Posted by ninja_turtle
...2) Why only the elect hyd pumps have an overheat indication ?
Arent the eng driven pumps subject to overheat conditions as well ?...
There is a big difference between the EDP (Engine Driven Pump) and the EMDP (Electric Motor Driven Pump).
The EDP is mechanically driven by the gear box. The heat produced by the mechanical parts are negligible.
The EMDP is driven by a hydraulic-oil-cooled three phase 115 volt ac motor which produce heat like every electric motor does. Hydraulic fluid goes into the electric motor housing to cool the electric motor before it enter the centrifugal pump.
If you do not use the hydraulic power, there is nearly no hydraulic flow to cool the ac motor.
Therefore only the EMDPs are watched by a internal temperature switch.
