Wiring 8' two lamp HO's in series

[Zrxpilot]

I recently purchased 3-8' H0 fluorescent strip lights and want to hook them up to one switch. Ie, flip one switch and all 3 come on at the same time.

Garage application on its own isolated circuit. All wiring will be encased in EMT.

Couple questions:

1 - Capacity - Bulbs are 110w each or 220w for each fixture. 660 total w not including the 6 ordinary fixtures that currently have standard 75w bulbs. Max draw with every light on is well under 1200 w if I am doing this right. Should not be a problem running all this on one 20 amp circuit. I think a 10 amp would have sufficed and am considering changing out the 20 amp breaker for a 10 amp.


2 - Can I simply jumper from one light to the next? Ie, I have the most convenient location for the switch and origination of the wiring in the general location of the first light. I actually have that one hooked up already (which brought me to the realization I needed two more of them). My plan is to simply tap into the first light and run to the second and repeat to the 3rd light.


3 - Can I match the wire diameter and type that is supplied with the light throughout the system? The wire that comes out of the ballast is single strand of what appears to be 16g. Maybe not but definitely not as big as 14g.

What I have so far is 12g wire to the first box I tapped into, and ran 14g to the first light light. My plan if acceptable was to run smaller wire to the next two lights as there is a no-splice/push in connector supplied by the factory off the ballast. No way is 14g going to fit in it. I can easily cut it and attach bigger wire but this doesn't make sense when you compare to the existing wire supplied by the factory.

Total length of wiring downstream of the first light is going to be less than 30'

 

[Alchymist]

Any wire you run between fixtures needs to be the same size as your initial run, and sized according to the breaker used. Forget the 10 amp breaker, use a 15 or 20. Your initial post said the first leg was 12 gauge, so keep that size throughout. You can't mix wire sizes on a circuit. Throw a 20 amp breaker in there and be done with it.

 

[pattenp]

You can mix the wire size but the breaker has to be sized to the smallest wire use. So if the first part of the run is #12 and then you switch to #14 for the remainder of the circuit then the breaker needs to be 15A. To get the accurate amps needed to power the HO fixtures you need to get the line/input amps from the ballast label. The lamp wattage will get you close but is not exact.

 

[Gary S]

Even more important. You can't wire the lamps in series. They need to be wired in parallel to work.

 

[Zrxpilot]

I buy into that but what's hanging me up here is the size of the wires inside the fixture. Wire size between 19 and 20 g. at 0.036 (or so). Single strand.

This size wire runs full length of this 8' fixture fixture several times to operate the lamps and is the size wire of the pigtail at the ballast (power-in connection)

It would seem that this size wire would be suitable throughout the system.

Not trying to be argumentative. Just trying to understand.

You can mix the wire size but the breaker has to be sized to the smallest wire use. So if the first part of the run is #12 and then you switch to #14 for the remainder of the circuit then the breaker needs to be 15A. To get the accurate amps needed to power the HO fixtures you need to get the line/input amps from the ballast label. The lamp wattage will get you close but is not exact.

 

[Milton Shaw]

That fixture wire is loaded to the max with just the one ballast and pair of bulbs. Each fixture should be wired by 14 or 12 gauge to other fixture and to switches. That fixture wire is also high temp rated to operate next to the ballast, so your wire should be high temp also. Don't know the code on them but should be about 105C wire used in that fixture type.

 

[ishiboo]

I buy into that but what's hanging me up here is the size of the wires inside the fixture. Wire size between 19 and 20 g. at 0.036 (or so). Single strand.

This size wire runs full length of this 8' fixture fixture several times to operate the lamps and is the size wire of the pigtail at the ballast (power-in connection)

It would seem that this size wire would be suitable throughout the system.

Not trying to be argumentative. Just trying to understand.

The fixture is a very short run of equipment wire in a controlled environment, with a known load (only the maximum rating of the bulbs.) So it is up to the manufacturer to properly size the wire.

The feed needs to be sized knowing that at any point, it could be shorted, added on to or otherwise modified, be in adverse conditions such as insulation with poor heat dissipation, etc.

The minimum wire to the fixture you can have is 14ga for a permanent installation. (You could use a lighter gauge extension cord.)

You cannot have 14ga breakered to 20A, as has been said.

 

[Norcal]

One quick note, you cannot go by the lamp wattage the ballast loss has to added. Read the ballast label for the correct info.

 

[OccupantRJ]

The small wires in the fixture are only feeding that fixture. Your circuit wires will be feeding ALL the fixtures.

 

[Alchymist]

You can mix the wire size but the breaker has to be sized to the smallest wire use. So if the first part of the run is #12 and then you switch to #14 for the remainder of the circuit then the breaker needs to be 15A. To get the accurate amps needed to power the HO fixtures you need to get the line/input amps from the ballast label. The lamp wattage will get you close but is not exact.

You are correct in that NEC allows mixed wire sizes as you described; however I warn against it for the simple reason if it's to be inspected, it may not pass. There are jurisdictions that don't allow it. One job I did I remember vividly- wire size was not mixed, but I used a piece of old stock 12-2 NMB with black insulation instead of yellow. Had to change it to pass. Just illustrates what the local AHJ can do.

Guess I should have said "shouldn't" instead of "can't".

 

[Zrxpilot]

Looking again at it last night I think I found my solution. Probably some poor explanation on my part. I was not intending to install these in a "series" per seasoned electrician lingo. I should have said "in a row". All the wiring is black to black and white to white.

Ended up going with two lights. Tapped into my nearest receptacle (an existing box that fed the lighting circuit) using 12 g wire to the first light.

Inside the light fixture itself I have 12g wire going to the light attached to the 20g factory wires inside the light. From that point I attached another run of 12g wire exiting the fixture to power light 2. Again...whites to whites and blacks to blacks.

So now I have a total of 6-75 watt standard light bulbs and two 8-strip lights for a total of 930 watts max draw on this circuit. Everything from the sub box to any light is in 12g.

Seems legit with the exception of perhaps an oversized breaker currently at 20 amps. I gather from the comments above that I should drop to a 15 amp breaker.

 

[pattenp]

As long as the circuit wiring is all #12 then the 20A breaker is okay. The circuit wiring does not include the fixture wires that came on the fixtures.

 

[Zeke]

The fixture is a very short run of equipment wire in a controlled environment, with a known load (only the maximum rating of the bulbs.) So it is up to the manufacturer to properly size the wire.

The feed needs to be sized knowing that at any point, it could be shorted, added on to or otherwise modified, be in adverse conditions such as insulation with poor heat dissipation, etc.

The minimum wire to the fixture you can have is 14ga for a permanent installation. (You could use a lighter gauge extension cord.)

You cannot have 14ga breakered to 20A, as has been said.

That's not what was said.

Zrxpilot, if you have 12ga through out, use a 20A breaker. Don't bother to change it. I think I see what you are thinking. You're considering the wires INSIDE the fixture as part of the wiring circuit. They're not. Your 12 ga is not interrupted, it's a continuous circuit pigtailed at each device and run to the next until termination. The wires inside the fixture to the ballast and from the ballast to the lamp sockets are not considered part of the circuit AFA the house wiring size and appropriate breaker size. It really is not possible to use the lighter gauge wires inside the fixtures as a bridge to the next fixture as there are only 2 leads inside many times long enough for a connection near either end of the fixture. And that connection is where the next leg of the house wiring begins.

As mentioned, you could also do this connection in a separate box outside the fixture and run a leg to inside the fixture. I believe the code allows for a hardwired extension cord or one plugged into a receptacle within 6 feet. No weight is allowed on the extension cord unless the cord and connections are specifically designed to carry the weight of the fixture. You could also use MC from the remote box to the fixture and for that I don't know the sizing code. If it were me, I'd size it the same as the house wiring.

 

[Zrxpilot]

^ Were getting closer to resolving this.

So if I am understanding this correctly, there should only be one set of wires entering this fixture. I can go into it (obviously), but under no circumstances can another set of wires come out of it.

I can however install a receptacle box next to the fixture (or between the two fixtures somewhere) and pigtail over to each light. There are many options.

If this is accurate, this is the area of my confusion. You are joining wires in a box. Weather you are joining them inside the fixture or in the separate box, the end result is still exactly the same. Using this philosophy, you could meet the intent by installing a receptacle box inside the fixture and ganging the 3 wires (in from the source to the light/out to the next light).. im not advocating doing this...just making a point. I think the point is to NOT have the 3 wires (or 6 depending on your perspective) ganged inside the fixture.

Again, not trying to be argumentative, just trying to understand.

 

[Zeke]

You are over-thinking this. I did not nor did anyone else say only one pair of wires (with ground) could enter the fixture housing. The FH is rated as a connection location. Therefore, you can go from one end of a fixture to another and pigtail the switched power to the ballast black the black, white to white and with the grounds attached to the frame. You would have 3 wires in each wire nut — 2 house wire cables and the ballast feed.

You can do the identical wiring outside the fixture housing, as I said, in a remote box. How you do this is dependent on the conditions of the garage, e.g., open framing or finished ceiling; flush or surface mount fixtures. For example, if you have a finished ceiling and surface mount fixtures, you cannot run Romex cable on the surface from one fixture to the next. You could use an extension cord to a box or use conduit and/or MC from fixture to fixture.

In this image nevermind the disconnect. You see 2 wires in each nut:

You see the house wire coming in from the top on the left. This would be how the last fixture looks on the bank. The others in line would have a 2nd house cable either in the same connector, of if more convenient, out of the other end and 3 wires in each nut. There are knock outs on the ends, sides and top for different wiring plans.

 

[kenfath]

Don't forget the ground wire. (Haven't seen it mentioned except in the above illustration/diagram.)

 

[Norcal]

If receptacles are used, then they need GFCI protection.