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Joined: Jun 2007
Posts: 301
J
Member
Simply start/energize the compressor with the one coil lead disconnected. Measure the voltage across the loose lead and the one still connected. If it's 240, find a neutral (if possible) in the circuit and connect it to one side of the coil. Then take one of the single wires left and reatach it. Let the neutral run through the overload relay. Tape up the remaining lead. Now you have 120 volt control for the coil. No need for XFMR unless there is no neutral available.
Or the easiest way is just to get the correct voltage coil for the starter.

ps....I bet you can find a neutral somewhere. Even if you have to pull it into the existing conduit.
Start switch and presure switch in series!!! Unless you want it to start automatically.
Check on the overload for single phase operation. Sometimes you must put in a jumper or the overload relay will not work. Look at the nameplate/paper tag.

Joined: Jun 2007
Posts: 301
J
Member
Sorry double post.

Ps....Again. Remove the coil and see if it is rated for 120/240. If so, there will be a metal jumper to select the voltage you have.

Joined: May 2002
Posts: 1,716
R
Member
What double post? wink

Roger

Joined: Nov 2005
Posts: 826
J
Member
I don't care much for 240VAC control ladders but if you must: Marc's drawing is lacking one or or two fuses for it to be warm and fuzzy with me. I would add two small fuses and holders to where you tap off of the line side of the contactor. I doubt that you would need more than 1 Amp slow-blows, depending on coil ratings and indications used. You will be much safer and your control wiring will far exceed your added protection instead of being far less than needed. My obvious assumption is that you aren't using #8 control wiring.

As you probably know, it takes less current to hold a contactor than to pick one. Many applications use a late-break aux contact to introduce resistance in series with the coil after it is energized to reduce coil dissapation and increase life.
Joe

Joined: Feb 2003
Posts: 939
F
Member
Joe ,

I know what you are talking about putting in the inline fuse holder for the contoller circuit. that drawing did not including the inline fuse holder in there so if it can be doable.

Merci, Marc



Pas de problme,il marche n'est-ce pas?"(No problem, it works doesn't it?)

Joined: Dec 2000
Posts: 4,288
Member
Quote
You will be much safer and your control wiring will far exceed your added protection instead of being far less than needed. My obvious assumption is that you aren't using #8 control wiring.


RDK's in Canada, but as far as the NEC, control wiring is permitted to be protected by a higher OCPD

Table 430.72(B) allows, where the control wires extend beyond the enclosure, as in this case:

45 Amps for #14
60 Amps for #12
90 Amps for #10
and 300% the value specified for 60° conductors (in 310.16) where over #10

Where they do not extend beyond the enclosure, the protection can be up to:

100 Amps for #14
120 Amps for #12
160 Amps for #10
and 400% the value specified for 60° conductors in 310.16 where over #10

Joined: Apr 2007
Posts: 33
R
RDK Offline OP
Member
More info plz?

Originally Posted by JValdes
Simply start/energize the compressor with the one coil lead disconnected. Measure the voltage across the loose lead and the one still connected. If it's 240, find a neutral (if possible) in the circuit and connect it to one side of the coil. Then take one of the single wires left and reatach it. Let the neutral run through the overload relay. Tape up the remaining lead. Now you have 120 volt control for the coil. No need for XFMR unless there is no neutral available.
Or the easiest way is just to get the correct voltage coil for the starter.

ps....I bet you can find a neutral somewhere. Even if you have to pull it into the existing conduit.
Start switch and presure switch in series!!! Unless you want it to start automatically.
Check on the overload for single phase operation. Sometimes you must put in a jumper or the overload relay will not work. Look at the nameplate/paper tag.

Joined: Nov 2005
Posts: 826
J
Member
Originally Posted by electure
Quote
You will be much safer and your control wiring will far exceed your added protection instead of being far less than needed. My obvious assumption is that you aren't using #8 control wiring.


RDK's in Canada, but as far as the NEC, control wiring is permitted to be protected by a higher OCPD

Table 430.72(B) allows, where the control wires extend beyond the enclosure, as in this case:

45 Amps for #14
60 Amps for #12
90 Amps for #10
and 300% the value specified for 60° conductors (in 310.16) where over #10

Where they do not extend beyond the enclosure, the protection can be up to:

100 Amps for #14
120 Amps for #12
160 Amps for #10
and 400% the value specified for 60° conductors in 310.16 where over #10


I never realized that the Code allowed me to do this. It could be fun arc welding here and there and blowing up stuff where i would normally just take out a control fuse or two. Thanks for the explosives training!
Joe

Joined: Jun 2007
Posts: 301
J
Member
RDK,
Quote "More info plz"?

What else can I try to help you with? Any particular statement I made in my post?
Just let me know and I will do my best to assist....John

Joined: Sep 2006
Posts: 6
H
Junior Member
I've been watching this topic with great interest. I really must admire the patience and restraint shown by the other posters.

I really don't think our original poster is clear as to how 240 works, or on the difference between single phase and three phase. The starter he's using is massive - much larger than what he needs for the motor - so I think we're dealing with some salvaged equipment here.
With used equipment, all bets are off!

A 240v single phase circuit won't have a neutral with it. If the job was done in pipe, bringing in a neutral is no big deal. If Romex, MC, or some other cable was used, he's screwed .... time to re-wire.

Coil fried? This suggests some confusion as to how a starter is wired.

Another possible contribution to the problem might be the way the thing is switched. We can't assume a proper start / stop push button station is being used .... and the use of a cheap toggle switch just might be behind the coil burning up. Many toggles will let a minor amount of current through, even in the 'off' position frown

At some point, a man has to say "I'm lost," and call in a local pro to sort things out.

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