starter switch
- Thread starter tommy
- Start date
- Status
Power Tech
Senior Member
- Location
- Lebec, California
I don't understand you.
You have a 230 volt motor that requires thermal protection do you protect both ungrounded conductors or one. I have done 120 volt single phase and three phase and I recall using a 3 pole starter switch for a two pole, but can you use a single pole starter switch for a two pole motor?
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
You may do this, break one pole, for motor starting purposes only. Your required disconnecting means must open both line conductors.
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
NEC article 430 (can't remember the exact paragraph) has required overload protection in all ungrounded legs ever since around 1978. The old 3 phase starters with only 2 overload devices have been illegal* since then.
*Illegal is, I know, not the appropraite word, but I use it in the context of a code violation for new installations of course. There are no "Overload Police"... yet.
*Illegal is, I know, not the appropraite word, but I use it in the context of a code violation for new installations of course. There are no "Overload Police"... yet.
A not so subtle reminder of my age. I installed bunches of 2 overload 3 phase starters in my life. 1978 ? really ? WOW!
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
Me too. It sucks when you can remember things that are now considered history...
I was listening to a "Golden Oldies" radio station this weekend and enjoying the songs of the 60's I used to hear my older brother and sister playing. Then they played some 70's music and I at first thought "Wait, that's not "oldies", that's MY music!"
Then it hit me...
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
My oops.
I was thinking of toggle style manual motor starters, like Square D's 2510 FG2, which only have 1 thermal unit, but both poles open when 'tripped'.
One in EACH conductor.
Really, A couple of the young guys asked me, 'why were you using RMC underground in
that story' , because PVC was not in use yet !! Huh ??
- Location
- Illinois
- Occupation
- retired electrician
I think it was about 10 years earlier. The main part of the plant that I normally work at was built in 65-66 and has starters with 2 overloads. They expanded in 70-71 and those starters have 3 overloads.
You could also run TWW conductors of any size in cable tray when they built the original buildings. They ran conduit from the field to the MCC room and then dropped into tray to get the the starters. By the time of the expansion, you had to use tray cable for the smaller conductors so they piped directly to the starters.
benaround said:
Jreaf said:
I'm reading 430.37, table 430.37, and 430.38 and each says that a sufficent number of conductors need to be opened by TOL's. Table 37 says for the OP (single phase 230) that only one in either ungrounded conductor is required. For 3-phase one in each is required. Where are you required to put one in each?
Rick
weressl
Esteemed Member
He was asking about a 2 wire system.
Just for gigles, would somebody explain to me why would you need overload in both legs for overload protection? Would an overload current flow anywhere else but through the 'other' conductor? Unless it is a short to ground, in which case we are not talking about overload protection.
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