Compressor "On" light

[sands35]

Laying in the boxes and planning runs for wiring in garage.

I'd like to have what amounts to a pilot light for the compressor.

I'll lay in 8 guage THHN wire through a conduit from the main panel to the compressor location, but I'd rather not run 8 to the light (I doubt it will even fit under the screw clamps). Am I allowed to run 8 through the motor disconnect switch and have a light leg with 14-2 coming off that? (my understanding is that mixing wire gauge on a single breaker is a no-no)

Or do I need to get a three pole disconnect switch and use one of them for the light and pull power for the light from another circuit?

 

[nehog]

Where will the light be located? In the box where the compressor disconnect is? A separate but dedicated box? If the light is the only thing on the circuit with the smaller gauge wire you should be OK. IOW, you don't need 8 AWG to the light. What kind of light are you going to use, btw?

 

[sands35]

I was planning on mounting it a few feet above the disconnect switch. Just a screw base Edison bulb. Blue or something. Blue is the ANSI color for compressed air, so probably use that.

Logically, I know the bulb only pulls 0.5 amps, but there is the electrical code..... Sort of wondering if I put it all in conduit I can sidestep the issue of having a 14 gauge wire tapped into a 50 amp circuit.

Checked ebay too, and there are three pole safety switches for ~$50 or so. Running the hot leg of the light circuit through the 3rd pole would solve that problem too.

 

[Mr onetwo]

Use the correct RIB relay for what you are doing.If you can't do business with a wholesaler, try these guys...http://ribrelays.com/

 

[sands35]

Use the correct RIB relay for what you are doing.If you can't do business with a wholesaler, try these guys...http://ribrelays.com/

Very cool and reasonable price too.

The coil side is in parallel with the compressor after the disconnect switch and the light pulls from another source?

 

[sands35]

So, asked my AHJ about this. He directed me to the "NEC Tap Rule"

(1) Taps Not over 3 m (10 ft) Long. Where the length of the tap conductors does not exceed 3 m (10 ft) and the tap conductors comply with all of the following:

(1) The ampacity of the tap conductors is
a. Not less than the combined calculated loads on the circuits supplied by the tap conductors, and
b. Not less than the rating of the device supplied by the tap conductors or not less than the rating of the overcurrent protective device at the termination of the tap conductors.
(2) The tap conductors do not extend beyond the switchboard, panelboard, disconnecting means, or control devices they supply.
(3) Except at the point of connection to the feeder, the tap conductors are enclosed in a raceway, which shall extend from the tap to the enclosure of an enclosed switchboard, panelboard, or control devices, or to the back of an open switchboard.
(4) For field installations where the tap conductors leave the enclosure or vault in which the tap is made, the rating of the overcurrent device on the line side of the tap conductors shall not exceed 10 times the ampacity of the tap conductor.

BUT - lighting still requires over-current protection at the end of the tap.

So either I need to:
Isolate the "On Light" with a relay
or
run it through the 3rd pole of a 3 Pole disconnect and pull power from another source
or
provide a breaker or fuse sized to the tap wire right at the light

 

[metal4130]

Does your compressor have a magnetic motor starter? On my compressor, which has a magnetic motor starter, you are able to buy an add on contactor for use with lights or other auxiliary functions.

 

[sands35]

I haven't bought a compressor yet. So I need to get the basic stuff into the walls before I sheet rock.

3 pole new/used disconnects are in the ~$40-60 range, so I might just do that then run conduit for the compressor supply and put in a 14-2 feed from a light circuit. As far as I can tell, that covers 99% of the compressor options.

I did think of pulling from the motor starter...

 

[Ryf]

if you pull from motor will it be lit when then compressor is at pressure? I'd think the idea of this is to not leave the compressor switched on when at pressure so if it bleeds down it wont restart.

lost the first part, oops... run a 30/60 amp disconnect to a 4 circuit subpanel and have a breaker for lights and a breaker for the compressor.

 

[sands35]

Yeah - though about the sub after the disconnect too. Honestly, there are too many ways to do it. The hard part is finding the way that is simplest and cheap (and to code)! Simple or Cheep is easy. Simple AND Cheep isn't.

 

[mayday0017]

Out of curiousity what is the purpose of the light? Sounds like you only want it to be on when the circuit is live, and that you plan on killing the circuit when not in use... is that correct? If so why not just wire a relay into the setup and run a wire to your light switch for the shop... Then when you turn the lights off in the shop the compressor won't run, and when you are in the shop the lights will be on and the compressor will be available for use....

 

[Ryf]

Yeah - though about the sub after the disconnect too. Honestly, there are too many ways to do it. The hard part is finding the way that is simplest and cheap (and to code)! Simple or Cheep is easy. Simple AND Cheep isn't.

$25 for a switched disconnect at menards or lowes and $20 for a 6 or 8 circuit box, add $20-30 for 3 breakers and your only at $60-80 bucks and you KNOW its safe and to code (not always the same thing ya know) not saying there aren't other ways, not saying you couldn't do it with less and not burn the building down, but it has to pass inspection.. nowww.. if you could fit a bigger wire in the light socket, you wouldn't have all these problems lol.

PattenP will know what you can get away with as I'm sure its been asked before.. just make sure whatever you do you don't draw your power through the bulb, you want parallel not series. if I was doing it (which I might) I would do it the way I said it, mostly so I know its right and safe if anyone decides to use that bulb as an outlet for something stupid (been known to happen around here) not saying I couldn't think of a shortcut, but just don't want the liability..... now that said, if you want a "fer instance" you could put in a double box after the switch and run you comp circuit through it, cut one leg in and neutral, and splice them back together adding in 12 gauge wire to the wire nuts, hook that 12 gauge to your bulb on that box and IMO its as safe as having 12 gauge wire spliced the same way to a light that has 14gauge for its hookup. make any sense?

 

[lametec]

I'd just use an inline fuse.

 

[RickP]

Yeah - though about the sub after the disconnect too. Honestly, there are too many ways to do it. The hard part is finding the way that is simplest and cheap (and to code)! Simple or Cheep is easy. Simple AND Cheep isn't.

What about using a 220v bulb? Wire it up with the same gauge wire and use crimp terminals to get the wire to fit on the light socket terminals. Should be a couple of bucks plus shipping?

There's plenty of small European bulbs available:
www.bulbtown.com

Then you'd just have to find an E12 candleabra socket for it, or get an adapter to fit into a standard keyless ceramic base (which are rated for 250v).

 

[RickP]

What about 220v LED bulbs? I don't have any experience with them, but google found this:
eBay LED 110V/220V

That one's a lot brighter than you want, but you might be able to find something else.

 

[sands35]

Am I allowed to add stuff to the inside of a safety switch box (inline fuse holder)? I've seen it done on main breaker panels (door bell transformers..)

Ryf - yes, that is a solid idea (sub after disconnect). I might just end up there due to the "idiot factor" that does matter. I'm trying to stay with Square D stuff since that's what my house is and what the main panel is in the garage. Not a big issue, but it would be nice. Haven't seen a simple 4 place sub panel from Square D yet.

Mayday0017 - because I can! It's really because I've been known to leave the compressor on - only to get woken up at 3am with the sucker running. I know, soap check all connections, etc. Leaks still happen. The compressor will be in a detached garage, so it could be weeks between uses of the garage - and me not knowing it's running. It's not a HUGE issue, but something that is an annoyance that is relative easy to get right given that I have bare stud walls and have just started to put in electrical. Worst case, a line lets go and the compressor runs continuously. Rare, but if it's easy to fix now, might as well.

 

[mayday0017]

Soo... did you read the rest of my post or just the why question?

The rest of the post gives another option that won't have a light you have to look at and manually turn off. It will turn off every time you walk out of the shop. Hell if you wanted to go even further with it you could buy a motion switch to connect to the relay. If you did this, the compressor wouldn't come on unless someone has been moving around in the shop recently....

 

[sands35]

Soo... did you read the rest of my post or just the why question?

The rest of the post gives another option that won't have a light you have to look at and manually turn off. It will turn off every time you walk out of the shop. Hell if you wanted to go even further with it you could buy a motion switch to connect to the relay. If you did this, the compressor wouldn't come on unless someone has been moving around in the shop recently....

Yes I did, and putting a relay on the light circuit is starting to get more complicated than I want. The whole point of my thinking through this question is to provide a solution that is simple and cheep (will pass inspection and is safe too). I'm happy to think hard about a problem to make it simple to do.

I'd like to have everything contained in one area and, ideally, inside one box.

I did a quick google and there are 5hp 3phase rated contactors, but I didn't see any split phase 5hp ones... 5hp is the biggest compressor I can see buying.

 

[Imcrazy]

You might want to look at this thread I think it is what you are looking for:

http://garagejournal.com/forum/showthread.php?t=140209

I used the switch that was recommended and ran the light off of one leg of the 220 at the switch. Pics on post #24 I think.

My compressor is 220V single phase 5hp

 

[Ryf]

I have thought more about this today, if you did contain the whole setup in one box (junction to bulb as in my "fer instance") it certainly would be safe enough, I think the big issue to me is leaving said box and routing light wire elsewhere. this IMO opens you up to wiring/breaker size issues. hopefully someone will chime in, I really can't see how this would be any different code wise than any light circuit in the house run on a 20 amp circuit, and your lighting device having smaller built in wiring.

I found two wire size calcs and both said 30 amps at a distance of .6 ft can be done on 14 gauge (thats one way length so 7 inches per wire to hook up light give or take)

 

[Ryf]

wanted to add, square d doesn't make a homeline 4 circuit thats not really a 2 space box, you'd need a 12 circuit 6 space to do it cheaply.

http://www.lowes.com/pd_162577-296-...uctId=3127883&Ns=p_product_qty_sales_dollar|1

good luck whatever you decide, its a tough decision.

 

[sands35]

QO (or is it QD?) is the rest of my house and will be my garage. The Square D 4 spot panel is around ~$60 or so. More than the "generic" stuff at HD.

 

[RickP]

I might add one of these lights also -- do we really need to add a spot panel just for a light bulb?

Could we use a 240v bulb if we were able to wire it with 8 gauge (or a very short length of 14 gauge as Ryf suggested)? It looks like these bulbs are available in a standard medium base for a few dollars.

 

[Ryf]

I might add one of these lights also -- do we really need to add a spot panel just for a light bulb?

Could we use a 240v bulb if we were able to wire it with 8 gauge (or a very short length of 14 gauge as Ryf suggested)? It looks like these bulbs are available in a standard medium base for a few dollars.

I would say as long as any runs of cable were rated for the amps of the breaker used you can do it easily.. so 8 gauge to a light would work, the issue I see someone having is a 14 gauge run off a 30/50 amp run that leaves a box, as "the breaker protects the wire" and the wire will have issues before the breaker trips if its rewired for say an outlet at some point.

 

[RAYJAY]

i just did this use one leg form the 220 and ground

 

[Mr onetwo]

Keep in mind that if your compressor motor does not have integral thermal protection, you must use a magnetic motor starter.Just search around for a used one of the correct amperage rating and then get a pilot light kit for it.simple and code worthy.

 

[sparky36000]

This should work if you follow these two code sections. I'd pull a #12 white neutral with your #8's, tap the load side of your motor disconnect with a piece of #12 and set a box above your disconnect to mount your lampholder and 120v blue lamp. Anybody see why this wouldn't meet code and accomplish what the OP wants?

210.10 Ungrounded Conductors Tapped from Grounded
Systems. Two-wire dc circuits and ac circuits of two or
more ungrounded conductors shall be permitted to be
tapped from the ungrounded conductors of circuits that
have a grounded neutral conductor. Switching devices in
each tapped circuit shall have a pole in each ungrounded
conductor. All poles of multipole switching devices shall
manually switch together where such switching devices
also serve as a disconnecting means as required by the
following:
(1) 410.93 for double-pole switched lampholders
(2) 410.104(B) for electric-discharge lamp auxiliary equipment
switching devices
(3) 422.31(B) for an appliance
(4) 424.20 for a fixed electric space-heating unit
(5) 426.51 for electric deicing and snow-melting equipment
(6) 430.85 for a motor controller
(7) 430.103 for a motor

210.19(A)(4)
(4) Other Loads. Branch-circuit conductors that supply
loads other than those specified in 210.2 and other than
cooking appliances as covered in 210.19(A)(3) shall have
an ampacity sufficient for the loads served and shall not be
smaller than 14 AWG.
Exception No. 1: Tap conductors shall have an ampacity
suffıcient for the load served. In addition, they shall have an
ampacity of not less than 15 for circuits rated less than
40 amperes and not less than 20 for circuits rated at 40 or
50 amperes and only where these tap conductors supply
any of the following loads:
(a) Individual lampholders or luminaires with taps extending
not longer than 450 mm (18 in.) beyond any portion
of the lampholder or luminaire.
(b) A luminaire having tap conductors as provided in
410.117.
(c) Individual outlets, other than receptacle outlets,
with taps not over 450 mm (18 in.) long.
(d) Infrared lamp industrial heating appliances.
(e) Nonheating leads of deicing and snow-melting
cables and mats.
Exception No. 2: Fixture wires and flexible cords shall be
permitted to be smaller than 14 AWG as permitted by
240.5.

 

[sands35]

Option #1
I've purchased a 3 pole 60 amp safety switch. I will use the 3rd pole to switch the light.

Three #8 THHN to the switch for the 240 VAC compressor (two hots, one ground). (in conduit - I'll probably wait to pull the wire until I buy a compressor.)
One 12-2 NM from an outlet run into the switch box.

I'll take power for the light from a 120vac 20 amp outlet and feed the hot through the 3rd pole. Wire nut the neutral and ground separately for the light. Safety switch will be grounded back to the main panel with #8 THHN. Keeps the outlet circuit and the compressor circuit electrically separate, but let's me switch the light with the 3rd pole.

If the inspector doesn't like that then I'll:
Install a 20 amp fuse after the safety switch
Run 8 THHN to the fuse from the safety switch (which is protected by the main panel breaker)
Then 12 NM to the light and abandon the 12-2 from the outlet run (which is protected by the fuse).
Pull a #12 THHN from the main panel for the light neutral (I suppose that the breaker panel becomes a "sub panel" at this point so I need to keep ground and neutral separate.)

Fuses / breakers are to protect the wiring, so I need something to protect 12 NM that will go to the lamp. My assumption is that I can't run 8 THHN directly to the lamp - just won't fit.

 

[willf650]

So, asked my AHJ about this. He directed me to the "NEC Tap Rule"



BUT - lighting still requires over-current protection at the end of the tap.

So either I need to:
Isolate the "On Light" with a relay
or
run it through the 3rd pole of a 3 Pole disconnect and pull power from another source
or
provide a breaker or fuse sized to the tap wire right at the light

What your are trying to do doesn't go by the tap rule. The tap rules are for powering multiple lower powered circuits of a larger feed.

There is a specific section of the code for motor controls that is exactly for this situation your only issue it the fact you are trying to use a regular light bulb and not a "standard" pilot light. Chances are you could get away with 14-12 awg with this rule. I don't have my code book in front of me so don't quote me on the gauges but its fairly lenient. Amazingly lenient if you don't leave the enclosure. The Necc doesn't require overcurrent protection for motor control circuits. The only require short circuit/ground fault protection.

Edit
Here's the table for motor control circuits
Table 430.72(B) Maximum Rating of Overcurrent Protective Device in Amperes

It states you can tap a #12 into a 60 amp circuit and #14 into a 45 amp circuit for motor controls and you indicator should qualify.

 

[sands35]

As i read it, the pilot light needs to be less than 12" and i need to mount the light on the disconect. Otherwise, it will work. I'll check with my inspector and see if he will accept it.