ECN Forum Forums Technical Discussion Electrical Theory and Applications Discussion for: Forward / Reverse motor control

Scott,

I think you are doing a great job with the drawings. They don't have to be perfect, the discussions that follow usually clear up any problems.

Being consistent with industry/trade standard conventions is the key concern. Too much slang or misuse of terms can lead to major confusion (i.e. "phase" being used to describe "ungrounded" conductors).

Scott,
why do you and most others who draw motor control schematics continue to show 3 overload contacts? Few starters have 3 overload contacts in the control circuit.
Don(resqcapt19)

In the old days, there were only 2 heaters, and therefore only 2 sets of NC contacts in series in the control circuit. As long as I've been at it, however,(18 yrs.) there have been 3. I think in the 60s & 70s, three became the norm.

Redsy,
Redsy,
You are correct that there are three heaters and there has been three heaters since the '68 code. In the early 70's there were three overload relays with a heater in each relay. This type of starter is correctly shown with 3 overload contacts. Current starter design uses 3 heaters with mechanical operation of a single overload relay contact. It should only be shown on the electrical drawings as a single contact because that is all that is in the overload relay.
Don(resqcapt19)

How about we run those control circuits via #12, extend them in romex @ 480V , assume the motor's OCPD is 60A ???