Induction Motor Oil Sump Heater Connection

[NomadicOwl]

Attached is the image of oil Sump Heater for 700HP Siemens Motor. Could anyone please explain me the diagram and how to connect it to power supply.

 

[Gr8blu]

There are three (single phase) heating circuits shown.

Circuit #1: (H1-H2-H3) is the main anticondensation heater circuit for the machine, and each heating element (indicated by the squiggly resistor symbol) sees 120 V. This requires that there is either a 120 V supply connected across the heating elements (H1-H2 gets 120, H2-H3 gets 120), OR 240 volts is supplied across H1-H3 with H2 left OPEN (NOT grounded!).
Circuit #2: (SH1-SH2) is the bearing sump heater at one end of the machine. Supply 120 V across SH1-SH2.
Circuit #3: (SH3-SH4) is the bearing sump heater at the other end of the machine. Supply 120 V across SH3-SH4.

Alternatively - jumper SH2-SH3. Then apply 240 V across SH1-SH4.

Converting energy to motion for more than half a century

 

[petronila]

NomadicOwl,

What Gr8blue is expaining is correct. However, regarding the space heaters connection just note the 120 V is a parallel connection (4 resistance connected in parallel)and the equivalent resistance is R/4; for 240 V connection the equivalent resistance is R (resistances connected in series - parallel).

Because Watts = V squared/R then R= V squared /Watts. For 400 Watts and 240 V we have a Resistance of (240*240) /400 = 144 Ohms and for the 120 V connection R= 144/4 = 36 Ohms and same 400 Watts = (120*120)/36 = 400.

Best Regards and Happy New Year.

Petronila