Formula For Changing Lights To Recessed Bulbs? - Electrical - DIY Chatroom Home Improvement Forum

 DIY Chatroom Home Improvement Forum Formula for changing lights to recessed bulbs?
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01-19-2007, 09:59 AM   #1
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## Formula for changing lights to recessed bulbs?

In our kitchen we have a one light similar to this:

http://www.lowes.com/lowes/lkn?actio...2RC&lpage=none

I'd like to get rid of the fluorescent light and add recessed lights and a couple of pendant lights like this: http://www.lampsplus.com/products/42...r-_-NA-_-42522

How do I figure out if the existing wiring going to the fluorescent light will support the pendant lights and recessed lights? What is the max # of recessed lights that I can install?

Jeff

01-19-2007, 10:12 AM   #2
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Start by mapping the circuit to see what all is on it now. To do this turn off all your breakers one at a time till the kictchn lights go out. Next turn on every breaker but the kitchen light circuit. Next go around the house and make a note of everything that is not working. Include all light fixtures and recepticles.

You need to add up the wattage of everything. If you have recepticles on the circuit, the code says that you do not need to count them, but common sence says to add a value for what may be plugged into it.. TV, Vacume, etc.

If any of your kitchen or dining room recpticles are on this circuit, you have a code issue and you should pull a new circuit to start.

Next deduct the light fixture that you plan to remove from the total, and add the wattages for all the things you want to add.

Now do the math. 120v is the nominal number we use for this. So multiply 120 times the amperage associated for the wire size. number 14 is for a 15 amp breaker. number 12 wire is for a 20 amp breaker.

never load a circuit beyond 80 percent of its capacity.

So: 120 volts x 15 amps = 1800 watts x .80 factor = 1440 watts.
......120 volts x 20 amps = 2400 watts x .80 factor = 1920 watts.

Do not load the circuit beyond this value.

Lighiting in a home is not considered to be continous load the way it would be in an office or other building. If it were you would need to muliply the lighting load times 1.25 in the middle of your calculations.

Last edited by jwhite; 01-19-2007 at 10:16 AM.

 01-19-2007, 10:38 AM #3 Newbie   Join Date: Dec 2006 Posts: 28 Rewards Points: 25 Thanks so much for the quick reply. Let me see if I have this right: If the existing light has (4) 40 watt bulbs, I would subtract 160 watts. The two pendant lights are 35W each = 70 W Typical recessed lights (approx. 50-75W each) x 6 = 300-450 W Total = approx. 370 - 520 W Maybe there are some low voltage recessed lights that I can find? Otherwise, this probably isn't a DIY project? Jeff

 01-19-2007, 10:43 AM #4 Newbie   Join Date: Dec 2006 Posts: 28 Rewards Points: 25 ooops, sorry JWhite. I didn't scroll down all the way and see the end of the message where you made the sample calculations. Once I determine which breaker the kitchen lights are on, could I see the value for the breaker (15A or 20A) and use that for the calculation? I see now though that I need to find out everything that is on that circuit and add it all up. Looks like I might have enough wiggle room. If I determine that there are 5 receptacles on that circuit, how do I estimate the wattage for the receptacles? I don't think anything more than a coffee pot, blender, etc would be used on those plugs. How many watts do those types of appliances require? Sorry for all the questions. Jeff
 01-19-2007, 11:12 AM #5 Member   Join Date: Mar 2006 Posts: 682 Rewards Points: 500 For flourcent lights, read the ballast. The wattages may not work out the way you would expect. If the coffee pot or blender is on that circuit, then go back and read what I posted above. Unless you use these in some room other than the kitchen or dininng room you have a code violation. Kitchen and dining room recepticles are supposed to be on a small appliance circuit. Nothing else can be on this circuit. The lights being on that circuit would be a violation. You can generally speaking use 180 VA or watts for all other recepticles. That is unless you know something larger is on the circuit, for example an entertainment center, or freezer on the back porch. If that is the case look on the appliance and find the actual load.
01-25-2007, 08:33 AM   #6
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Quote:
 Originally Posted by jwhite You can generally speaking use 180 VA or watts for all other recepticles.
I agree. For non continuous loads that is the number. For continuous loads use the rating of the equipment connected.

Quote:
 Originally Posted by Jemo Typical recessed lights (approx. 50-75W each) x 6 = 300-450 W
I cant seem to find it in the code, but someone told me before that interior lights are typically 65watts max and exterior are typically 75 watts max, that doesnt cover special fixures just a rule of thumb.

Im no electrician but that seems to apply to every fixture Ive worked on.

01-25-2007, 06:46 PM   #7
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Quote:
 Originally Posted by JoulesWinfield I agree. For non continuous loads that is the number. For continuous loads use the rating of the equipment connected.
Please tell me how you know what will be a continous load for a convience recepticle. Do you have ESP so you know what someone will plug in there in the future?

Quote:
 I cant seem to find it in the code, but someone told me before that interior lights are typically 65watts max and exterior are typically 75 watts max, that doesnt cover special fixures just a rule of thumb. Im no electrician but that seems to apply to every fixture Ive worked on.
Why would that even be in the code. Most lights are 60 bulb max. Not all. The OP was just making an estimate.

01-25-2007, 07:33 PM   #8
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Quote:
 Originally Posted by jwhite If the coffee pot or blender is on that circuit, then go back and read what I posted above. You can generally speaking use 180 VA or watts for all other recepticles. That is unless you know something larger is on the circuit, for example an entertainment center, or freezer on the back porch. If that is the case look on the appliance and find the actual load.
Quote:
 Originally Posted by jwhite Please tell me how you know what will be a continous load for a convience recepticle. Do you have ESP so you know what someone will plug in there in the future? Why would that even be in the code. Most lights are 60 bulb max. Not all. The OP was just making an estimate.
I was agreeing with what you said. A continous load would be something like a freezer as you mentioned. The code says 180va is to be used for determing the general load for a receptacle. If I had my book here at home I would site it.

The actual load calculation for lighting is the rating of the device that is used. I was tring to help the op in determing his load calculation.

 01-25-2007, 08:02 PM #9 Member     Join Date: Mar 2005 Location: Welland, Ontario Posts: 12,584 Rewards Points: 11,960 Blog Entries: 11 A freezer would not be a continuous load. It turns off and on.
01-25-2007, 08:12 PM   #10

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Quote:
 Originally Posted by JoulesWinfield I cant seem to find it in the code, but someone told me
Joules, with statements like this, and several others I've seen here, do you really feel you should be giving critical electrical advice on these forums?
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01-25-2007, 08:39 PM   #11

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Quote:
 Originally Posted by JoulesWinfield A continous load would be something like a freezer as you mentioned.
VERY few items in a residence would be considered a continuous load.

Quote:
 Originally Posted by JoulesWinfield The code says 180va is to be used for determing the general load for a receptacle. If I had my book here at home I would site it.
Not for a residence it doesn't.
I'll quote it for you:

220.14(I) Receptacle Outlets Except as covered in 220.14(J) and (K), receptacle outlets shall be calculated at not less than 180 volt-amperes for each single or for each multiple receptacle on one yoke. A single piece of equipment consisting of a multiple receptacle comprised of four or more receptacles shall be calculated at not less than 90 volt-amperes per receptacle. This provision shall not be applicable to the receptacle outlets specified in 210.11(C)(1) and (C)(2).

(J) Dwelling Occupancies In one-family, two-family, and multifamily dwellings and in guest rooms or guest suites of hotels and motels, the outlets specified in (J)(1), (J)(2), and (J)(3) are included in the general lighting load calculations of 220.12. No additional load calculations shall be required for such outlets.
(1) All general-use receptacle outlets of 20-ampere rating or less, including receptacles connected to the circuits in 210.11(C)(3)
(2) The receptacle outlets specified in 210.52(E) and (G)
(3) The lighting outlets specified in 210.70(A) and (B)
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 01-26-2007, 07:33 AM #12 Newbie     Join Date: Dec 2006 Location: Michigan Posts: 24 Rewards Points: 10 Youre right, a freezer would not be a continuous load. I was just trying to say for the op to use the rating of whatever is currently connected plus the 180va per convience recepticle. Last edited by JoulesWinfield; 01-26-2007 at 08:28 AM.
01-26-2007, 06:02 PM   #13
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Joules,
I have to agree with Pete. In this thread and others you have shown that you need to back away from giving too much advice.

The OP asked about a specific install that did not require dedicated recepticles, and you inserted a comment that does not apply, in a way the was misunderstood by me, and possibly others.

I am not trying to be too harsh on you, but it is important to be as accurate as we can when giving advice.

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