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Upgrading lighting - who knows wiring and T5 high bay lights?

SRT Mike

Stainless
Joined
Feb 20, 2007
Location
Boston MA
My shop right now has four T8 fixtures with 2 bulbs each, 8 foot long bulbs. It's dim as hell. I want to upgrade to six T5 high-output fixtures with 6 bulbs each, to brighten it up a lot.

I am not going to re-use the existing wiring, I am gonna pull those lights out and put air circulation fans in their place.

Got a couple questions for those in the know...

1) The new fixtures are rated 360W each, 2160W total. Electrical supply house recommends not exceeding 80% of the circuit max (2400W on a 20-amp circuit, 1920W would be 80%). Is that correct not to exceed 80%? Running all 6 would be 90% utilization.

2) Electrical supplier says each of these T5HO fixtures has 2 ballasts... one runs 4 bulbs, one runs 2 bulbs. Can the ballasts be wired separately without having to break into the units? If so, I would run all the 4-bulb ballasts one one circuit, the 2's on the other... then I'd have two switches and I could turn on 2, 4 or all 6 bulbs.

3) These light fixtures are available in 208 version. As I understand, 208 is the voltage between two phases of a 3-phase setup. I have 3 phase... a 12 gauge wire will run 20-amps (16-amps at 80%). If I run 208v, it would be just under 11 amps, and I can run 12-ga wire. Is that right?

4) If I run these lights on 208, can I use 12/3 wire and have 2 hots and a ground, or do I need 2 hots, neutral and ground?


The fixtures are Philips and they don't give much info on their website. The electrical supply house doesn't have them in stock so they can't crack the box to let me take a look... and it's over a grand to order these so I wanna know how I am gonna do this and order all my cable and boxes before I start - so if anyone knows, it would help me out a lot!
 
According to the 2008 NEC (NFPA ) THHN wire 90C, not more than 3 conductors in a raceway, pg 70-148, 12 ga is rated 30 amps. I see nothing requiring derating of amp rating just because of the ballast, only that 90C or better wire must be used.

So according to the NEC, you can run 12 ga at 30 amps and be ok.
Tom
 
1) yes, 80% is the usual limit for continuous loads
2) don't know, sounds like a fixture-specific question
3) yes
4) yes, 208 does not use a neutral
 
1) yes, 80% is the usual limit for continuous loads
2) don't know, sounds like a fixture-specific question
3) yes
4) yes, 208 does not use a neutral

+1

2) One way or the other you are going to have to get inside the fixture to wire it up. Each ballast will have it's own set of wires for supplying power to it. One of the main reason's for having two ballast is exactly what you wish to do with it (being able to control the lighting with two seperate circuits).
 
...2400W on a 20-amp circuit, 1920W would be 80%). Is that correct not to exceed 80%?...

Careful. 80% is a calculation that is to be applied to the current draw, not wattage.

Since fluorescent ballasts don't have a power factor of 1.00, the current will be a tad higher than you expect. Look up the current drawn by the ballast...
 
One more question..... Does your shop have sufficient ceiling height for the T5HO's? On the 6 tube fixtures with polished reflectors, they'll usually state 14-16 ft minimum. I tried hanging one at 8 ft in an area where I wanted "lotsa light". Might as well have mounted a car headlight on my head, aimed at my eyes. Lots of light for sure, but way too much glare to be useful.
 
One more question..... Does your shop have sufficient ceiling height for the T5HO's? On the 6 tube fixtures with polished reflectors, they'll usually state 14-16 ft minimum. I tried hanging one at 8 ft in an area where I wanted "lotsa light". Might as well have mounted a car headlight on my head, aimed at my eyes. Lots of light for sure, but way too much glare to be useful.


Not to mention the reflective heat, T-5 HO's run quite warm.
 
According to the 2008 NEC (NFPA ) THHN wire 90C, not more than 3 conductors in a raceway, pg 70-148, 12 ga is rated 30 amps. I see nothing requiring derating of amp rating just because of the ballast, only that 90C or better wire must be used.

So according to the NEC, you can run 12 ga at 30 amps and be ok.
Tom

You may want to do some more checking as yes the 12ga is rated at 30 ampsl but 240.4(d) says you must look at over current protection limitations.

Basically you will only be allowed 20amps on 12 gage.

"you can use the ampacities listed in table 310.16 to apply any derating factors you may have (over 3 CCC, temp, etc) but 240.4(D) gives you maximum overcurrent protection allowed." quoted from internet, but is worded correctly.
 
You may want to do some more checking as yes the 12ga is rated at 30 ampsl but 240.4(d) says you must look at over current protection limitations.

Basically you will only be allowed 20amps on 12 gage.

"you can use the ampacities listed in table 310.16 to apply any derating factors you may have (over 3 CCC, temp, etc) but 240.4(D) gives you maximum overcurrent protection allowed." quoted from internet, but is worded correctly.

As far as I can determine, csharp is correct. 240.4 (D)(5) specifically limits 12 ga copper wire to 20 amps.
Tom
 
... 4) If I run these lights on 208, can I use 12/3 wire and have 2 hots and a ground, or do I need 2 hots, neutral and ground? ...

208 Volts, here, is a three phase source. If you measure between two legs you get 208 Volts single phase. The Neutral is only used with one of the phases to get 110 Volts. Therefore if you want 208 Volts you do not use the Neutral. The ground is also used.
 
You may also want to consider holophane high bay metal halides. Holophane is a manufacturer but the high bay HID metal halides seen in a lot buildings is referred to as holophane lighting.

If you do want to go to HID, metal halides are better for indoor lighting than high pressure sodium. HPS is best used in roadway and parking lot lighting. Most consider it be too yellow for comfort.

Among other things to check for ask for the lumens/watt rating of the complete fixture. This takes into account the lamp, the ballast factor and the reflector, or to say it another way, how much usable light do you get out of the complete assembly.

A last item would be to have a lighting designer do a simulation using computer software. This will tell you what ft-candles of light intensity at the work surface. Typically, you should have at least 50 ft-candles and for detailed work closer to 100.
Tom
 
According to the 2008 NEC (NFPA ) THHN wire 90C, not more than 3 conductors in a raceway, pg 70-148, 12 ga is rated 30 amps. I see nothing requiring derating of amp rating just because of the ballast, only that 90C or better wire must be used.

So according to the NEC, you can run 12 ga at 30 amps and be ok.
Tom

It's a common mistake to interpret the ampacity rating of wire as the allowable ampacity of the circuit. There are multiple reasons why they are rarely the same. One is 240.4(D), which simply sets a fixed ceiling on 12,14, and 16 ga wire. But another factor, which usually prevents running a circuit at 90C wire rating, is that everything in the circuit has to have the same minimum temperature rating. So if your circuit breaker is 75C rated, you can't use the 90C wire rating. Same goes for everything, panelboards, etc. Virtually everything has at least 75C rating these days, so you can always assume that, but there's lots of components that don't have 90C rating, so to use 90C rating on a circuit you'd have to specifically verify all the components are so rated.

In the real, practical world, the 90C conductor ampacity rating is only used as the start point for conductor de-rating (per temp and number of wires in raceway)
 
Got a couple questions for those in the know...

1) The new fixtures are rated 360W each, 2160W total. Electrical supply house recommends not exceeding 80% of the circuit max (2400W on a 20-amp circuit, 1920W would be 80%). Is that correct not to exceed 80%? Running all 6 would be 90% utilization.

And that's too high. As someone else mentioned, you can't exceed the breaker rating, and most breakers are only rated to continuously carry 80% of their trip rating.

3) These light fixtures are available in 208 version. As I understand, 208 is the voltage between two phases of a 3-phase setup. I have 3 phase... a 12 gauge wire will run 20-amps (16-amps at 80%). If I run 208v, it would be just under 11 amps, and I can run 12-ga wire. Is that right?

Six of one, half dozen of the other. On 208V, you have one circuit, but it requires two breaker positions in the panel, as each "hot" needs protection. So, you don't gain anything there.

If it 'twas me, I'd go with two circuits @ 120V. The fixtures are more common, they'll be easier to move and use elsewhere, and you can always add an emergency outlet off the circuit if you need one at some point in the future.

Dennis
 
One more question..... Does your shop have sufficient ceiling height for the T5HO's? On the 6 tube fixtures with polished reflectors, they'll usually state 14-16 ft minimum. I tried hanging one at 8 ft in an area where I wanted "lotsa light". Might as well have mounted a car headlight on my head, aimed at my eyes. Lots of light for sure, but way too much glare to be useful.

+1 absolutely. T5HO are way too intense in 8' ceiling.

There are some lighting calculators on the web. They let you model a room, by width, length, height; set reflective values for wall, floor, ceiling; set fixture layout output; etc. Then they tell you how many footcandles you'll get at 36" off the ground. You'll find these tools on the manufacturers websites, amongst other places. I think Cooper has one.
 
If your ceiling height is in the 13' - 16' range the T5s should be perfect. If your height is 18' or higher you might want to consider high-bays like Thermite mentioned. High Pressure Sodium is OK but it gives off an orangish light. Around here the hot setup for this application is now Metal Halide which produces a very natural light that I much prefer to the HPS output but I think it's probably a judgement call as to which you prefer. Our local electrical supplier tells us that the Metal Halides are more efficient but I don't think the difference can be huge.

They're best for higher ceilings but we found that by cutting a couple inches off the bottom of the reflector they work well in the 18' - 20' range. At that height they are a bit too much like a spotlight but removing some of the reflector spreads the light quite nicely. The "working" area of our shop is about 1600 sq. ft. and 4 x 400W fixtures provide adequate lighting. As my brother and I have gotten older we find that more light is an advantage so we're planning to add two more fixtures which will make it quite bright in our working area...
 
I'd just do 2 circuits as well, I've got one that runs 5 sets of 4 t8's, and one circuit that runs just 2 of them in the middle for when I go in for other stuff and don't want them all on. Other possibility is get a 30amp wall switch and use #10 wire and a 30amp breaker if you want just 1 circuit.

By code you have to go with the lowest temp rating which is usually at the breaker/connector. Often 60°C, sometimes 40°C.

Breakers are only meant to run at 80% of their stamped rating for continuous duty.
Kind of like a 200amp service is really only rated at 160amp/continuous.
Resistive loads have their own exception as you can oversize the breaker 25% for those so long as the wire matches the max load of the unit. Actually here they wouldn't pass a 60amp breaker on a 55amp max load with 55amp wire, had to put a 70amp.
 
Much more water having passed under the bridge by now ....

Mike,

If you can be bothered to provide the LxWxH dimensions of the space, better yet a computerish sketch with machine locations, doors and clearways.....

I'll have a go at a specific recommendation that will give you the increased lighting AND the fans, with same or LOWER total load - on the existing wiring - plus a very modest bit of tap-off wiring for the fans.

Neither what you have now, nor what you propose to use, make very good use of the energy input for the light output, so gains can be had rather economically.

Now - if you rely on them to HEAT the shop thru the sort of Boston Winter I remember from Hosmer Elementary 1951, well... even that has more comfortable and economic solutions!

Radiant cove units to name one....

Bill


Hey that is really generous of you, thanks!

I have attached a basic sketch of the shop. It's basically a 65' x 55' rectangle give or take a few feet. In the sketch, the black bars on the edges are drive-in rollup doors. I have the 5 fluorescent fixtures now that are just dim as all get out. I don't know exactly their light output, but they are 8' twin-bulb fixtures, so I have 8 bulbs total. Most of those 8' bulbs are around 5,000 lumens, so that would only be 40,000 lumens total.

The fixtures I am looking at are like these:

Philips TBW654EB4-8 6-Light T5HO Fluorescent High Bay 120-277V Lamps Included - ProLighting.com

These are 30,000 lumens each, which would give me 180,000 lumens total. I would be going from about 10 foot-candles to about 50 foot-candles, which would be a HUGE improvement.

I have 25 foot ceilings in my shop... actually it's a pitched roof. I have 1/4 of the whole building, so towards the doors the ceiling is more like 23' and more like 28' at the office end of my shop. The T8 fixtures are hanging down on chains, about 12' off the ground.

My plan is to take out the existing fixtures out and re-use the wires and put four 60" fans up on the ceiling to circulate the heat. Right now the heat (forced hot air) runs half the day keeping it at 65 degrees. I have storage on top of the offices (since they are just a 12' high rectangle built out into the shop space) and when I am up there, I notice it's hot as hell. Then when I come down it's cool on the floor. So I want the fans to help circulate the hot air and save the heating running all day heating up top just to make the lower area "kinda warmish".

Then I was going to put 6 of those T5HO fixtures spaced evenly across the ceiling and run new wires for those.

I would be running either 2 circuits with 2 wires going to each light and 2 wall switches, so I could turn on 2 or 4 or all 6 lamps. OR, I would run a 30A circuit and 10/3 wire and put them all together, OR I would get the 208V model of the lights and run them on 208V.

12/3 armored cable is cheap so I would probably just run the two circuits since it gives me flexibility in turning on 2 or 4 or 6 bulbs on each fixture.


I will be doing the work myself... gonna borrow the scissor lift of the guy across the way and I am reasonably well versed in electronics (wired up the whole rest of the shop myself). I do want to stick to code though.

I am not 100% intent on only using those T5HO fixtures, but I have to be honest, I am pretty sure that's what I'd like to use. I've seen them in 3 other shops in this park and I really like the light they throw out. Someone else has HID's (the big round things) and I don't like that light nearly as much - but I am open to suggestions.

We do machining, electronics assembly, pack/ship and that sort of stuff. I would like high-CRI lights and hopefully once I do this, I don't wanna be messing with it, since I have no way to get up to the ceiling easily myself :)

Oh, and also - I'm on a budget with this. Local supplier has the 6-bulb T5 lights with bulbs at $165/ea. 500' of armored 12/3 wire is enough for all my wiring $250. Breakers, distribution boxes, and other misc parts maybe $200. Then the fans $130/ea from the same local supplier and I am looking at around $2k for everything doing the work myself.

That's about as much as I wanted to spend on this, ideally.

EDIT: Forgot to mention - the lights I am looking at are specifically called "high bay" lights, for mounting 20' and above. Also, efficiency is important... but I'm not trying to chase pennies on my monthly electric bill. Power is cheap here - my bill is rarely over $120/mo aside from running the A/C in summer. And I don't need to do the fans and new lights together - if there is a better kind of light to get, I can spend more on the lights and do the fans next month or something.
 

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Got enough to go on.

Just about enough light at present to not trip - I feel your pain.

But a far bigger issue is the heating bill for the bloody aviary yer sponsoring. Fans are just a band-aid for heat you want to not go up there in the first place.

Should be able to improve on the wintertime situation enough for a substantial saving, even with half-measures short of a dropped ceiling or mezzanine deck.

Summertime's another story altogether - that space can work FOR you then.

What is the present heat input source again?
And from units located where?

And do you own or rent?

Feel free to PM or direct to [email protected]

Bill

I rent - just moved into this new space and have just about 5 years left on the lease. The heating is overhead forced hot air (one giant duct running down the center of the shop with vents coming off each side). It's plumbed into the city gas supply and the actual burner unit is mounted on the roof. But, I may be overstating the heating issue... if I set the thermostat at 70 degrees, it will run for 4-5 hours to get to that temperature, then it will kick in every several minutes to maintain it. That leads to $400/mo gas bills.

So what I do instead is run it at 62 degrees or so... which is fine with a sweater, especially when you're going back and forth between the machines. That leads to $150/mo heat bills, but I don't even turn the heat on until maybe mid-November and I don't really use it after April or thereabouts, so we're not talking huge money. The guy in the shop next door installed four 60" fans and said his heating bill dropped by 40%. I'd be more than happy with that result... not looking to do major upgrades on the building owners heating system :)

The bigger problem is that now that I've seen the other shops around, I realize how bad our light is - it's terrible. I also realize my workers all have lights running on their desks so they can see... but I'd really rather have the whole place a lot brighter rather than trying to put light in specific places we work in often - truth be told, we really need a lot more light everywhere.
 
The 80% derate is about the heat generated in a "lighting panel" where all breakers are loaded, and heating the load center.

If your lighting breakers are sandwiched between breakers for machines or receptacles that aren't constantly loaded, I suggest you won't have a problem.

And if you have access to 277 volts (and the fixtures are what? 12 foot above the floor?), you can run 277 volt fixtures.

Ask about "intellivolt" ballasts that can run on 120-240-277 volts.
 








 
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