# 6-Lamp T5 High Bays



## A Little Short

What is the amp draw on the 6-lamp T5 High Bays? Maybe 3A?

Does the current stay the same from start-up to continuous run, or is there an in rush current like on a motor?

What I'm leading up to is I have a potential customer who wants to add 1 more light to the same circuit. I think he has 6 on there now but I'm not sure since I didn't turn off the switch because they were working.

I was wondering if there was already 6, if one more would be too much?

I probably will just go back and measure the current to be sure, but thought some of you might know.


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## ponyboy

the voltage would help. 120, 277, 347?


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## Cletis

It's 5.41amp at 120V. You should be fine. A negligable surge and it last for such short a time it won't matter


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## ponyboy

FWIW all the T5 lamps i've dealt with have been 54 watts a lamp. from there you can do the math with whatever voltage system you're working with.


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## Vintage Sounds

I am currently installing some and they draw 339w. Whatever your voltage is, you can work it out from there.


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## Cletis

Vintage Sounds said:


> I am currently installing some and they draw 339w. Whatever your voltage is, you can work it out from there.


more like 363 watts :whistling2:


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## ponyboy

where are you pulling these numbers. you know just because you saw a 6 lamp t5 highbay while doing one of your big commercial jobs doesn't mean they're all the same ya know


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## ohiosparky99

Remember the ballast factor


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## A Little Short

ponyboy said:


> the voltage would help. 120, 277, 347?


I knew I left something out!

120V, so probably around 2.70A
7 would put it at 18.90A so maybe not a problem?


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## ohiosparky99

Number of lamps,x wattage, x voltage, x ballast factor, = amps


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## ponyboy

Little-Lectric said:


> I knew I left something out!
> 
> 120V, so probably around 2.70A
> 7 would put it at 18.90A so maybe not a problem?


your current will be higher than that for sure. and even if it was 18,9 i wouldn't do it. something about 80% and whatnot. lots of times i've switched the fixtures to a 208 volt supply to lower the current and avoid the whole switch/contactor thing.


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## A Little Short

ponyboy said:


> your current will be higher than that for sure. and even if it was 18,9 i wouldn't do it. something about 80% and whatnot. lots of times i've switched the fixtures to a 208 volt supply to lower the current and avoid the whole switch/contactor thing.


I will agree that 7 might put it over for the 80% thing.
But according to your statement of 54W per lamp, it wouldn't be any higher than that.

54Wx6=324W
324W/120V=2.70A
2.70A ea x 6=16.20A
2.70A ea x 7=18.90A

I looked up some T5 High Bays and most had a BF of 1 so the 18.90 would be correct.


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## A Little Short

ohiosparky99 said:


> Number of lamps,x wattage, x voltage, x ballast factor, = amps


shouldn't that be #lamps x wattage ÷ voltage x ballast factor?


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## ponyboy

Little-Lectric said:


> I will agree that 7 might put it over for the 80% thing.
> But according to your statement of 54W per lamp, it wouldn't be any higher than that.
> 
> 54Wx6=324W
> 324W/120V=2.70A
> 2.70A ea x 6=16.20A
> 2.70A ea x 7=18.90A
> 
> I looked up some T5 High Bays and most had a BF of 1 so the 18.90 would be correct.


The line is already being toed at 16.20. You need actual current readings on this circuit because even an amp or two will make or break it.


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## A Little Short

ponyboy said:


> The line is already being toed at 16.20. You need actual current readings on this circuit because even an amp or two will make or break it.


Yep, I plan on taking some readings before I do anything. I have to go back and check a few other things anyway.


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## Vintage Sounds

ponyboy said:


> where are you pulling these numbers. you know just because you saw a 6 lamp t5 highbay while doing one of your big commercial jobs doesn't mean they're all the same ya know


True, but the OP didn't have a specific model in mind either, so I just pulled the number from a light I've been hanging hundreds of for the past few weeks.


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## ponyboy

Vintage Sounds said:


> True, but the OP didn't have a specific model in mind either, so I just pulled the number from a light I've been hanging hundreds of for the past few weeks.


sorry vintage i was directing that at cletis. your info was helpful


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## drumnut08

Little-Lectric said:


> What is the amp draw on the 6-lamp T5 High Bays? Maybe 3A?
> 
> Does the current stay the same from start-up to continuous run, or is there an in rush current like on a motor?
> 
> What I'm leading up to is I have a potential customer who wants to add 1 more light to the same circuit. I think he has 6 on there now but I'm not sure since I didn't turn off the switch because they were working.
> 
> I was wondering if there was already 6, if one more would be too much?
> 
> I probably will just go back and measure the current to be sure, but thought some of you might know.


I just put a bunch if these in for a customer . At 120 volts they're drawing 3 amps give or take . I put 8 of these on a 240 volt circuit with no problems at all . I wouldn't add another one at 120 v to an already maxed out circuit . If they're 120-277 ballasts and don't need several switching locations , change the breaker , put in a double pole switch and call it a day . Obviously , making sure the neutral isn't going anywhere else and re identify it as well as the fixtures .


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## A Little Short

drumnut08 said:


> I just put a bunch if these in for a customer . At 120 volts they're drawing 3 amps give or take . I put 8 of these on a 240 volt circuit with no problems at all . I wouldn't add another one at 120 v to an already maxed out circuit . If they're 120-277 ballasts and don't need several switching locations , change the breaker , put in a double pole switch and call it a day . Obviously , making sure the neutral isn't going anywhere else and re identify it as well as the fixtures .



You would need to change the wiring at the ballast too wouldn't you?


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## drumnut08

Little-Lectric said:


> You would need to change the wiring at the ballast too wouldn't you?


No , the multivolt ballasts only have two power leads . They adjust to the voltage applied , whether it's 120 . 208 , 240 or 277 . The ballast has to say 120-277 though . If its 120 or 277 then there is no in between . Ideally , you wouldn't be using a white wire as your other hot , and if it's not a big deal , replace with proper phase color , but as long as fixture and current neutral wire are identified as no longer being 120 volt . You should have no issues . The right smart ballast is key to making this work . If the existing light aren't that old , I'm sure you'll be able to do this .


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## drumnut08

drumnut08 said:


> No , the multivolt ballasts only have two power leads . They adjust to the voltage applied , whether it's 120 . 208 , 240 or 277 . The ballast has to say 120-277 though . If its 120 or 277 then there is no in between . Ideally , you wouldn't be using a white wire as your other hot , and if it's not a big deal , replace with proper phase color , but as long as fixture and current neutral wire are identified as no longer being 120 volt . You should have no issues . The right smart ballast is key to making this work . If the existing light aren't that old , I'm sure you'll be able to do this .


The older ballasts were an either or for voltage and still needed a neutral . They've improved on that tremendously and went the one shoe fits all approach to voltages now , which makes things a lot easier for us . The old wives tale used to be if you powered these ballasts with 120 v and down the line , wanted to run them at a higher voltage , you couldn't because the ballast would lock in to the lower voltage . I don't think that was ever true and have disproved it several times.


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## drumnut08

drumnut08 said:


> No , the multivolt ballasts only have two power leads . They adjust to the voltage applied , whether it's 120 . 208 , 240 or 277 . The ballast has to say 120-277 though . If its 120 or 277 then there is no in between . Ideally , you wouldn't be using a white wire as your other hot , and if it's not a big deal , replace with proper phase color , but as long as fixture and current neutral wire are identified as no longer being 120 volt . You should have no issues . The right smart ballast is key to making this work . If the existing light aren't that old , I'm sure you'll be able to do this .


If you're unsure of this , a call to the ballast manufacturer will either out you at ease or make you happy you called them before you did anything with changing voltages . That's what I did as step one , lol ! I don't always believe what I read on a label .


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## A Little Short

drumnut08 said:


> No , the multivolt ballasts only have two power leads . They adjust to the voltage applied , whether it's 120 . 208 , 240 or 277 . The ballast has to say 120-277 though . If its 120 or 277 then there is no in between . Ideally , you wouldn't be using a white wire as your other hot , and if it's not a big deal , replace with proper phase color , but as long as fixture and current neutral wire are identified as no longer being 120 volt . You should have no issues . The right smart ballast is key to making this work . If the existing light aren't that old , I'm sure you'll be able to do this .


I guess I knew that, but I was probably thinking of MH ballast that have different leads for various voltages.


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## drumnut08

Little-Lectric said:


> I guess I knew that, but I was probably thinking of MH ballast that have different leads for various voltages.


No problem . Hope it works out for you !


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## A Little Short

*Update*

I went back to the building today to do some further measuring and voltage/current checks.

I did what I could since there was no way to get to the lights as they had cars on all the racks. I wanted to get to the lights to see how they were wired, 120V or 240V.

What I did do was find the circuit that fed them. It is already on a 2-pole 20A breaker.

On one leg I measured between 18A and 19.5A and on the other it fluctuated between about 2A all the way to 18A.

If these lights are wired 240V, I don't understand the huge difference in the current in the two legs.

Only thing I can think of is somewhere they have tapped into one of the legs to feed something else.

They may not be wired 240V since I did see two neutral (white) wires in the conduit from this light circuit.

The wires run to j boxes then a whip to the lights. They either are 120V or they just ran neutrals to the j boxes for possible other uses.

Either way, it doesn't look like I can add another light to the circuit. 
The one leg stays low for a while then goes up to 18 or so amps, so I don't think it would be a good idea to tap that leg for 120V to another light.


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## drumnut08

Little-Lectric said:


> I went back to the building today to do some further measuring and voltage/current checks.
> 
> I did what I could since there was no way to get to the lights as they had cars on all the racks. I wanted to get to the lights to see how they were wired, 120V or 240V.
> 
> What I did do was find the circuit that fed them. It is already on a 2-pole 20A breaker.
> 
> On one leg I measured between 18A and 19.5A and on the other it fluctuated between about 2A all the way to 18A.
> 
> If these lights are wired 240V, I don't understand the huge difference in the current in the two legs.
> 
> Only thing I can think of is somewhere they have tapped into one of the legs to feed something else.
> 
> They may not be wired 240V since I did see two neutral (white) wires in the conduit from this light circuit.
> 
> The wires run to j boxes then a whip to the lights. They either are 120V or they just ran neutrals to the j boxes for possible other uses.
> 
> Either way, it doesn't look like I can add another light to the circuit.
> The one leg stays low for a while then goes up to 18 or so amps, so I don't think it would be a good idea to tap that leg for 120V to another light.


Something sounds weird there ? If you had six of these fixtures running on 240 , you should be seeing around 9 amps per leg . It definitely sounds like everything is on one circ. at 120 volts . They may have just put it on a two pole breaker and who knows why the other legs amperage is fluctuating ? Is this a 20 amp circuit ? If so , I bet that wire Is toasty , lol ? If you want to keep these at 120 V you can split the circ . Up and add a lighting contactor if they only want one switch to control this . If the branch is in # 10 wire , install 30 amp breaker and a 30 amp toggle switch ? Lots of options all hinging on what the owner wants to spend . I'm sure you'll see what's up once you gain access to the JB's . Keep me posted man . You'll get er !


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## A Little Short

drumnut08 said:


> Something sounds weird there ? If you had six of these fixtures running on 240 , you should be seeing around 9 amps per leg . It definitely sounds like everything is on one circ. at 120 volts . They may have just put it on a two pole breaker and who knows why the other legs amperage is fluctuating ? Is this a 20 amp circuit ? If so , I bet that wire Is toasty , lol ? If you want to keep these at 120 V you can split the circ . Up and add a lighting contactor if they only want one switch to control this . If the branch is in # 10 wire , install 30 amp breaker and a 30 amp toggle switch ? Lots of options all hinging on what the owner wants to spend . I'm sure you'll see what's up once you gain access to the JB's . Keep me posted man . You'll get er !


Yep it's a 20A 2-pole breaker with #12 wire.
I'll probably just quote him on either running a new circuit or tapping from another circuit close by, that isn't overloaded, and adding a switch for the new light. Then if I get the job, I'll get into the lights to see what's going on with the wiring for my own curiosity.


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