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How hot is too hot? #166166 07/14/07 03:32 PM
Joined: Jul 2007
Posts: 6
K
ksensen Offline OP
New Member
Hey, new to the forum, been an avid reader for awhile but this is my first post. Here's my question I recently had to replace a starter for a 3phase pump in a garden center. (I do mostly resi work) replaced existing Square D starter with same make a model. One small difference the old starter coil was rated 240V the new starter coil is rated 120V (same make and model) wired the new starter exactly the same as the old one. Turned it on everything works.- So here's my question how hot should the starter get?- I know it will get warmer but it gets too hot to touch and smells. I double checked all my amp reading on the lines in and on lines out- All were well within bounds and balanced across all three phases. Everything seemed to check out ok, but not having a lot of experience with motors and starters I am a little concerned with how hot it is getting, am I concerned over nothing or is there a problem?

Work Gear for Electricians and the Trades
Re: How hot is too hot? [Re: ksensen] #166167 07/14/07 03:40 PM
Joined: Jan 2003
Posts: 4,391
I
iwire Offline
Moderator
Originally Posted by ksensen
One small difference the old starter coil was rated 240V the new starter coil is rated 120V (same make and model) wired the new starter exactly the same as the old one.


Did you change the wiring so the 120 volt coil gets 120 or did you leave it as it was with 240 volts supplying a 120 volt coil.

If you have 240 supplying a 120 volt coil you bet it will..

Get Hot.

Smell bad.

Let smoke out.

Stop working.


Bob Badger
Construction & Maintenance Electrician
Massachusetts
Re: How hot is too hot? [Re: iwire] #166168 07/14/07 03:47 PM
Joined: Jul 2007
Posts: 6
K
ksensen Offline OP
New Member
No- I thought about that- coil is only getting 120. Any other thoughts?

Re: How hot is too hot? [Re: ksensen] #166173 07/14/07 04:35 PM
Joined: Nov 2000
Posts: 2,148
R
resqcapt19 Offline
Member
Quote
No- I thought about that- coil is only getting 120. Any other thoughts?

How is it getting 120 volts? It would be rare for there to be a grounded conductor in that starter.
Don


Don(resqcapt19)
Re: How hot is too hot? [Re: resqcapt19] #166193 07/15/07 01:50 AM
Joined: Oct 2006
Posts: 745
E
EV607797 Offline
Member
I agree. A typical three-phase starter isn't going to have a grounded conductor ("neutral") for a motor load. Was the coil in the old starter bad? If not, I'd swap them since my guess is that you are sending 208 volts into a 120 volt coil.

The starter that you replaced may have the same part number, but someone could have changed out the coil in the field for a standard three-phase 120/208 installation. I can't begin to imagine how many times that I have done this at gas stations and car washes.


---Ed---

"But the guy at Home Depot said it would work."
Re: How hot is too hot? [Re: EV607797] #166200 07/15/07 10:10 AM
Joined: Mar 2004
Posts: 251
W
WESTUPLACE Offline
Member
I think he is measuring voltage from ground to the coil not across the coil. A common problem for people who do not understand 3 phase. Robert

Re: How hot is too hot? [Re: WESTUPLACE] #166207 07/15/07 06:09 PM
Joined: May 2001
Posts: 376
F
frank Offline
Member
Ahh the smell of burnt windings.A 240v coil can be bought if need be.So you wont have to replace the entire starter again.It will last about a day at 2x the rated voltage.You are probably smelling the varnish burning off the coil windings.Short answer is that if it stinks you got a problem.I would check it right away as a hot coil can distort the body of the starter causing it binde when pulling in and out manking the whole assembly junk.the original coil should fit if the numbers match and it's still good
cheers

Re: How hot is too hot? [Re: frank] #166254 07/16/07 05:59 PM
Joined: Jul 2007
Posts: 6
K
ksensen Offline OP
New Member
Update- thanks for the information- you guys were right the coil was getting 240V- and I was measuring voltage on the coil to ground. Switched out the 120V coil and replaced it with 240V seems to be running fine. Only thing that puzzles me- how would you get a 120V coil to work in a 3phase starter? And why do they make/sell them that way?

Re: How hot is too hot? [Re: ksensen] #166255 07/16/07 06:17 PM
Joined: Jan 2006
Posts: 558
R
Rewired Offline
Member
You may want a 120V coil in a starter if say its controlled from another source. A common occurance of this would be where a regular every-day 120V photoelectric eye used to control outdoor lighting, is used to drive a contactor with a 120V coil which in turn can control a 3 phase lighting circuit..
Also it could be used where its preferred the control wiring is at a " safer" voltage.. safer as in being as low as possible.
I have a single phase starter controlling my pool pump, it has a 24V COIL,the reason for that the controls are outside in a sometimes damp shed, and sometimes are operated by people standing on barefoot on concrete..

A.D

Last edited by Rewired; 07/16/07 06:18 PM.

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