starbright28
Senior Member
- Location
- Minnesota
I went to that page, but there is so many ballasts to choose from. How do you determine which ballast you are using?
Lighting Calcs for indiv. branch circuits
- Thread starter starbright28
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jtester
Senior Member
- Location
- Las Cruces N.M.
starbright28 said:
Amanda
Most data sheets for ballasts do list wattage by number of lamps. If you look in the Columbia catalog for example, it will list input watts by # of lamps. Also, for Columbia, watts and volt-amps are the same. Columbia defines input amps as input watts/volts.
You must use the correct # of lamps in determining the fixture wattage.
Jim T
Bob NH
Senior Member
- Location
- The "Live Free or Die" State
220.14(D) Shall be based on maximum V-A rating of equipment and lamps for which luminaire is rated.
220.18 Total load shall not exceed rating of the branch circuit.
220.18(B) Inductive lighting loads - Shall be based on total ampere rating of ballasts, transformers, . . . Not on total watts of lamps.
220.42 Lighting demand factors (Probably 100%; see table 220.42)
220.18 Total load shall not exceed rating of the branch circuit.
220.18(B) Inductive lighting loads - Shall be based on total ampere rating of ballasts, transformers, . . . Not on total watts of lamps.
220.42 Lighting demand factors (Probably 100%; see table 220.42)
starbright28
Senior Member
- Location
- Minnesota
I found the sheet with the input watts for columbia lighting. That will help out. And those code dealings - my engineer apparantly is not going by code then, when he is just "adding up wattage".
That I want to change - or would like to change.
Aside from Columbia Lighting - we also do specify other lighting for our projects. How do I go about finding out the input watts for these lights. Examples would be Recessed Can lights, track lighting, surface compact fluorscent cylinder lights, etc. Should each company on the websites have input information for there lights?
If the light uses incandscent lamps - then what do you use for input wattage? There would be no ballast in that case.
Just trying to understand all these calculations, and do thing properly.
That I want to change - or would like to change.
Aside from Columbia Lighting - we also do specify other lighting for our projects. How do I go about finding out the input watts for these lights. Examples would be Recessed Can lights, track lighting, surface compact fluorscent cylinder lights, etc. Should each company on the websites have input information for there lights?
If the light uses incandscent lamps - then what do you use for input wattage? There would be no ballast in that case.
Just trying to understand all these calculations, and do thing properly.
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jtester
Senior Member
- Location
- Las Cruces N.M.
Ballast information for each different type of lighting, linear fluorescent, recessed fluorescent, HID, etc., is available and should be used. You could get typical values for each type of fixture and that would be sufficient, you don't need to go light fixture manufacturer by manufacturer.
Incancescent lighting is figured at the bulb wattage since there is no ballast.
Jim T
Incancescent lighting is figured at the bulb wattage since there is no ballast.
Jim T
starbright28
Senior Member
- Location
- Minnesota
i just did the calculations in regards to how much wattage difference is betweent using the input wattage and the lamp wattage only.
shocker.
15060 watts total using ballast input
14547 using just the lamp wattage
total difference: 513 watts.
i think i may be doing some panelboard lighting calcs in the future.
shocker.
15060 watts total using ballast input
14547 using just the lamp wattage
total difference: 513 watts.
i think i may be doing some panelboard lighting calcs in the future.
starbright28 said:
Here's another shocker:
Given your data-
Lamp wattage: 14547
Ballast input watts: 15060 (assuming this is watts, not VA)
Actual VA load on schedule: 15853 minimum, based on a ballast power factor of 0.95 Actual power factor may be less. (Watts/VA = power factor)
Difference: 1306
You need to stop thinking watts and use VA because your panelboard has to supply VA to the load, not just watts. Thats why the load column says (or should say) "VA." You can use watts for energy code calculations only.
How do you choose a ballast? That would be a long discussion on lighting 101 but basically you have to decide what your goals are, considering tradeoffs between cost, light output, efficiency, harmonic level, switching requirements (determines # of ballasts per fixture), lamp life, warranty, and in some cases dimming requirements. Add to that any code requirements such as a limit of 1.1 watts per sq ft for an office here in CA for example.
If you have the luxury of no energy code and a client that thinks cheapest is best, then you can use standard generic ballasts that the fixture mfr will supply. They are not the best in terms of efficiency, but are not the worst either.
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starbright28
Senior Member
- Location
- Minnesota
How I came up with the information in regards to the input watts was by using the following formula:
input watts x # of fixtures = watts. then Divide by 120 to get Amps.
I did this for every room. 120 volts, 20 Amp circuit.
So, are you saying the VA I still need to calculate? Also - The formula I am using up above, I calcualte 125% load into effect. But that only affects the Amps. So I take the Amps that I get then, and multiply by 120 and I should get my VA which should be different that of watts listed on the panelboard.
Because on the engineer's panelboard schedule is shows the headings like so:
Circuit Name --- VA --- PF --- Watts --(circuit #'s)
MN does have an energy code, and for the energy code we base it off the lamp wattage for worse case scenerio. The engineer in house just used that number and sorted it per phase on the panel, and I told him some are much higher than regular lamp wattage so really you can't do this. Plus in the code it also says not to do this.
input watts x # of fixtures = watts. then Divide by 120 to get Amps.
I did this for every room. 120 volts, 20 Amp circuit.
So, are you saying the VA I still need to calculate? Also - The formula I am using up above, I calcualte 125% load into effect. But that only affects the Amps. So I take the Amps that I get then, and multiply by 120 and I should get my VA which should be different that of watts listed on the panelboard.
Because on the engineer's panelboard schedule is shows the headings like so:
Circuit Name --- VA --- PF --- Watts --(circuit #'s)
MN does have an energy code, and for the energy code we base it off the lamp wattage for worse case scenerio. The engineer in house just used that number and sorted it per phase on the panel, and I told him some are much higher than regular lamp wattage so really you can't do this. Plus in the code it also says not to do this.
kingpb
Senior Member
- Location
- SE USA as far as you can go
- Occupation
- Engineer, Registered
Amanda,
Here are a couple of formulas that need to become your friend's:
View attachment 191
Where pf will be less then or equal to 1.0, and efficiency will always be less then 1.0. Therefore your VA will be greater then or equal to Watts, and input VA will be greater then output VA.
If you don't know, or can't find these values a good rule of thumb is:
pf = 85%
eff = 92%
They will get you close, and usually on the conservative side.
Here are a couple of formulas that need to become your friend's:
View attachment 191
Where pf will be less then or equal to 1.0, and efficiency will always be less then 1.0. Therefore your VA will be greater then or equal to Watts, and input VA will be greater then output VA.
If you don't know, or can't find these values a good rule of thumb is:
pf = 85%
eff = 92%
They will get you close, and usually on the conservative side.
starbright28
Senior Member
- Location
- Minnesota
on the panelboards he always shows the power factor as 1.0
so will that mean my VA and watts being equal?
so will that mean my VA and watts being equal?
kingpb
Senior Member
- Location
- SE USA as far as you can go
- Occupation
- Engineer, Registered
starbright28 said:
Yes it will! For many loads that are considered, for all intensive purposes, resistive only, the pf=1. But, motors, many types of lighting, etc. uisng pf=1 is not realistic.
Review what Sparkie001 calculated, the effect could be somewhat significant depending on the type of equipment.
starbright28
Senior Member
- Location
- Minnesota
Alright
Since I am getting different formulas, different ways to do all this, let me make it concise and clear what I am doing.
All I want to know how to do is calculate the lighting loads for a commerical building. I used the formulas like I have mentioned before instead of the method only using lamp wattage.
as far as power factor is concerned, for lighting it most the time would be one. I am not calculating the whole panelboard at this moment in time, just for the lighting loads. the motors have already been taking care of and shown on a different panelboard.
does everyone now understand what i was looking at and trying to accomplish?
EDIT: I'm not trying to sound picky - but I need to learn how to understand these calculations, especially when I haven't done them before, ever.
I appreciate all the comments/remarks and help that i have gotten, at least it has gotten me much farther than where I was in the beginning, and that was clueless on what the engineer did, and what you are supposed to do.
Since I am getting different formulas, different ways to do all this, let me make it concise and clear what I am doing.
All I want to know how to do is calculate the lighting loads for a commerical building. I used the formulas like I have mentioned before instead of the method only using lamp wattage.
as far as power factor is concerned, for lighting it most the time would be one. I am not calculating the whole panelboard at this moment in time, just for the lighting loads. the motors have already been taking care of and shown on a different panelboard.
does everyone now understand what i was looking at and trying to accomplish?
EDIT: I'm not trying to sound picky - but I need to learn how to understand these calculations, especially when I haven't done them before, ever.
I appreciate all the comments/remarks and help that i have gotten, at least it has gotten me much farther than where I was in the beginning, and that was clueless on what the engineer did, and what you are supposed to do.
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The power factor is never 1 for any lighting with a ballast, i.e. fluorescent, metal halide, high pressure sodium etc. It is CLOSE to one but more like 0.95, meaning that all of your calcs will be about 5 percent low.
A quick look at the Advance ballast catalog reveals power factors of 0.5 to 0.99. Most modern electronic ballasts are 0.95 or higher. I'd assume 0.95 unless you know the exact ballast power factor, or even better, the amps.
A quick look at the Advance ballast catalog reveals power factors of 0.5 to 0.99. Most modern electronic ballasts are 0.95 or higher. I'd assume 0.95 unless you know the exact ballast power factor, or even better, the amps.
starbright28
Senior Member
- Location
- Minnesota
okay - so when do you factor in the power factor in the equation?
when calculating VA?
when Calculating watts?
That's the 2 main things we use to show on the panelboards. If you can see the picture below, then you know what I am talking about.
View attachment 193
when calculating VA?
when Calculating watts?
That's the 2 main things we use to show on the panelboards. If you can see the picture below, then you know what I am talking about.
View attachment 193
jtester
Senior Member
- Location
- Las Cruces N.M.
sparkie001 said:
Many manyfacturers, Columbia as in the example used or Lithonia in their charts, define input amps as watts/volts. There is no concern for pf in that calculation. The manufacturer is not technically correct in his equation, but there's no need to include a pf adjustment based on his equation as shown in the table.
Jim T
starbright28
Senior Member
- Location
- Minnesota
study materials
study materials
the study material that I currently have:
anything from my 1 year at college (construction electrician)
Mike Holt's Electrical Formula's book
some books from a local inspector doing seminar's
codebook
journeyman exam prep guide bought from internet
this forum
I just got very curious to know how to calculate the lighting loads in order to figure out
1) # of circuits that I need
2) the VA and watss to assign them to circuits and how to group them together.
The examples I gave are not examples, they are actual things that I have been using for projects.
Put yourself in my shoes - and bring it to an equation that I use everytime when figuring this out.
study materials
the study material that I currently have:
anything from my 1 year at college (construction electrician)
Mike Holt's Electrical Formula's book
some books from a local inspector doing seminar's
codebook
journeyman exam prep guide bought from internet
this forum
I just got very curious to know how to calculate the lighting loads in order to figure out
1) # of circuits that I need
2) the VA and watss to assign them to circuits and how to group them together.
The examples I gave are not examples, they are actual things that I have been using for projects.
Put yourself in my shoes - and bring it to an equation that I use everytime when figuring this out.
scott thompson
Senior Member
- Location
- Anaheim, California
As mentioned, the load on each Branch Circuit used for lighting should be calculated as Volt-Amps, rather than Lamp Wattage / System Voltage - _When Luminaires use Transformers or Ballasts to drive Lamp(s)_.
When "Pure Resistance" lighting loads are used, Lamp Wattage is equal to Luminaire Volt-Amps, and the True Power (Wattage) value may be inserted into the "Volt-Amps Cell" of a Panel Schedule Spreadsheet.
These "Pure Resistance" lighting loads include:
* Line Voltage Incandescent Lamps,
* Line Voltage Quartz-Halogen Lamps.
Low Voltage Incandescent Lamps - like "MR-16s", use a Transformer, so Lamp Wattage is not accurate.
All other types of Lighting, use the load Volt-Amps value per fixture, add up all loads per circuit and enter this value in the corresponding Cell(s) of a Panel Schedule.
To find the Volt-Amp rating of a given fixture, either locate the nameplate Line Input Ampere rating, and multiply this by the System rated Voltage,
- or -
Verify the ratings from fixture cut sheets, per fixture type (either submittals or on-line documents).
"Common" Fluorescent Lamp Ballasts' input VA ratings may be obtained from Manufactureres like Advance, etc.
The reason to use the rated line Amperes / Volt-Amps values on Lighting circuitry is due to _Actual Values_ during operation.
Typically, 32 Watt F32T8 Lamps are driven lower than 32 watts, and the Ballast may have a Power Factor less than 99% - which increases the Line Input Volt-Amps, without increasing the nominal Wattage drawn from the Supply.
With Reactor-Based (Core and Coil) HID Lighting, there will be a Power factor of anywhere between 90% (for High Power Factor listed fixtures), and 50% (for Normal Power Factor listed fixtures).
The load Volt-Amps versus the Lamp Wattage is between 25% and 100% increase in Line Amperes for each fixture - depending on the Power Factor.
Another thing to be considered is an LCL adder (+ 25% of the fixtures' Load Volt-Amps, added to the fixtures' rated Volt-Amps, when a fixture is to be run for 3 hours or more).
Doesn't look like the EE included LCL values for lighting, but the fixtures might be controlled by Occupancy Detectors - which may limit the total "On" time to 30 minutes maximum, then the lights go off for a few minutes.... repeated over time.
*Exception to this: Occupancy Detection in large, open areas will almost always be kept on for at least 4 hours at a time. LCL should be figured in for these areas.
Good luck on this quest!
Scott
When "Pure Resistance" lighting loads are used, Lamp Wattage is equal to Luminaire Volt-Amps, and the True Power (Wattage) value may be inserted into the "Volt-Amps Cell" of a Panel Schedule Spreadsheet.
These "Pure Resistance" lighting loads include:
* Line Voltage Incandescent Lamps,
* Line Voltage Quartz-Halogen Lamps.
Low Voltage Incandescent Lamps - like "MR-16s", use a Transformer, so Lamp Wattage is not accurate.
All other types of Lighting, use the load Volt-Amps value per fixture, add up all loads per circuit and enter this value in the corresponding Cell(s) of a Panel Schedule.
To find the Volt-Amp rating of a given fixture, either locate the nameplate Line Input Ampere rating, and multiply this by the System rated Voltage,
- or -
Verify the ratings from fixture cut sheets, per fixture type (either submittals or on-line documents).
"Common" Fluorescent Lamp Ballasts' input VA ratings may be obtained from Manufactureres like Advance, etc.
The reason to use the rated line Amperes / Volt-Amps values on Lighting circuitry is due to _Actual Values_ during operation.
Typically, 32 Watt F32T8 Lamps are driven lower than 32 watts, and the Ballast may have a Power Factor less than 99% - which increases the Line Input Volt-Amps, without increasing the nominal Wattage drawn from the Supply.
With Reactor-Based (Core and Coil) HID Lighting, there will be a Power factor of anywhere between 90% (for High Power Factor listed fixtures), and 50% (for Normal Power Factor listed fixtures).
The load Volt-Amps versus the Lamp Wattage is between 25% and 100% increase in Line Amperes for each fixture - depending on the Power Factor.
Another thing to be considered is an LCL adder (+ 25% of the fixtures' Load Volt-Amps, added to the fixtures' rated Volt-Amps, when a fixture is to be run for 3 hours or more).
Doesn't look like the EE included LCL values for lighting, but the fixtures might be controlled by Occupancy Detectors - which may limit the total "On" time to 30 minutes maximum, then the lights go off for a few minutes.... repeated over time.
*Exception to this: Occupancy Detection in large, open areas will almost always be kept on for at least 4 hours at a time. LCL should be figured in for these areas.
Good luck on this quest!
Scott
starbright28
Senior Member
- Location
- Minnesota
Scott:
I am looking at all the information that I have gathered in the past week or so, and I've been told to find the input watts. and that number I can put into the "watts" area of my panel schedule.
but as far as VA, sounds like I need to do some more digging to find the VA of the ballast, and go from there, if I am reading your post correctly.
This quest has sure been a long and drawn out process. Is it true that the electrical engineer here is doing these calculations all wrong and showing them on the panelboard wrong? Or is he okay with showing the the way that I have described in this tread?
I am looking at all the information that I have gathered in the past week or so, and I've been told to find the input watts. and that number I can put into the "watts" area of my panel schedule.
but as far as VA, sounds like I need to do some more digging to find the VA of the ballast, and go from there, if I am reading your post correctly.
This quest has sure been a long and drawn out process. Is it true that the electrical engineer here is doing these calculations all wrong and showing them on the panelboard wrong? Or is he okay with showing the the way that I have described in this tread?
starbright28 said:
You won't find the VA published but you will find the amps, on the ballast label and in the ballast catalogs. To get VA just multiply amps by voltage.
starbright28 said:
He's not wrong, he's just showing more info than most people do. I've never seen anyone show watts in a schedule. I've only seen VA, because its technically the more important value when sizing a panelboard.
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