Dwelling demand load calculation questions

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  #1  
Old 05-27-02, 11:11 AM
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Dwelling demand load calculation questions

I have learned much from this forum since I found it almost a year ago and read archived post after archived post. I thank everyone for everything so far. But now I need to ask my own question(s).

From what I've learned and considering what needs to be done in my house, I have decided to start from (almost) scratch. So I visited Wg's site and printed out detailed instructions for calculating demand load (thanks Wg!). A couple of things are unclear to me:

1) I measured the outside dimensions of my house for the general lighting load calculation. Since my house (like many) is not an exact rectangle, I need to know which dimensions to use.

My house is shaped something like this:

..--.........................._______
...|..........................|.........|
...|..........__________|.........|____
...|.........|..................................|
...|.........|..................................|
...|.........|..................................|
...|.........|..................................|_
...|.........|_______..........................\
...A.....................|..........................|
...|.....................|..........................|
...|.....................|......................._ /
...|.....................|......................|
...|.....................|......................|
...|.....................|......................|
..--.....................|_____________.|

..............|-------------B--------------|

So do I use the longest of each measurement (AxB) for my square footage, or do I use the sf determined my my *exact* outside dimension measurements? (I have already measured and calculated both--all I have to do is 'plug' the number in [pun, unfortunately, intended].)

2) On Wg's list of fixed-in-place appliances (FIPA) I saw no washer. I know 1500 Va is required to be included in the calculation for a laundry. But since a dryer is included later I didn't know if I should include my washer in my FIPA calculation. So is a washer covered by the laundry requirement or should I include it in FIPA?


This is an indirect question:

I also have a whole house fan in the hall ceiling. I have yet to find a plate or any other indication on the motor of the amp load or wattage of the motor. The house was built in mid 50s and I do not know if the fan was original but the wiring looks consistent with the other original wiring. It seems to be 120V and the fan is 36" in diameter. Does anyone have an experienced educated guess as to the amp load of a fan such as this? I need to include this fan in my list of FIPA.

I am on my way to the store now for batteries for my flashlight and as soon as I get back I will go in the attic, clean the motor up really good and look for a plate or other info. But in case I *still* couldn't find something I wanted to go ahead and have the question out there.

Please forgive the long post but I wanted to include enough info initially so I would not have to clarify anything with more posts and thus play 'tag' with anyone willing to answer.

I hope everyone is having/has had an enjoyable Memorial Day. Please remember those who have given their lives so we might be able to live in a country where some of our biggest concerns are wondering the amperage of our ceiling fan motor.
 
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  #2  
Old 05-27-02, 03:00 PM
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Wgoodrich
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YOU SAID;
So do I use the longest of each measurement (AxB) for my square footage, or do I use the sf determined my my *exact* outside dimension measurements? (I have already measured and calculated both--all I have to do is 'plug' the number in [pun, unfortunately, intended].)

REPLY;
By looking at the design of your home you should cut off the offset part of your dwelling. Then calculate your dwelling as a square or rectangular home and find the square feet of that squared off part. Then perform a second calculation for the offset part of your house as a separate square foot calculation. Then add to two together. Remember that an attached garage or unfinished basement is omitted in your square foot calculation. Also remember that if you have a two story house then you have to calculate that second story living area also and add that to your total square foot calculation.

YOU SAID;
2) On Wg's list of fixed-in-place appliances (FIPA) I saw no washer. I know 1500 Va is required to be included in the calculation for a laundry. But since a dryer is included later I didn't know if I should include my washer in my FIPA calculation. So is a washer covered by the laundry requirement or should I include it in FIPA?

REPLY;
The washer and gas dryer is included in the 1500 va for the laundry. An electric dryer is added later as a separate calculation remembering that 5 kva is the minimum allowed for an electric dryer regardless how small the electric heat style dryer.

YOU SAID;
This is an indirect question:

I also have a whole house fan in the hall ceiling. I have yet to find a plate or any other indication on the motor of the amp load or wattage of the motor. The house was built in mid 50s and I do not know if the fan was original but the wiring looks consistent with the other original wiring. It seems to be 120V and the fan is 36" in diameter. Does anyone have an experienced educated guess as to the amp load of a fan such as this? I need to include this fan in my list of FIPA.

REPLY;

Most often a whole house fan uses a 1/2 horse power motor. A 1/2 horse power motor is rated in table 430.148 at a full load current of 9.8 amps. You should be pretty close if you used the 9.8 for that fastened in place appliance to be added to fastened in place appliances and using the 25% reduction allowed for fastened in place appliances if 4 or more fastened in place appliances.

YOU SAID;
I am on my way to the store now for batteries for my flashlight and as soon as I get back I will go in the attic, clean the motor up really good and look for a plate or other info. But in case I *still* couldn't find something I wanted to go ahead and have the question out there.

REPLY;
If you can use the nameplate rating of your whole house fan if you have no tag to use then use the 9.8 amps which should be close.

YOU SAID;
Please forgive the long post but I wanted to include enough info initially so I would not have to clarify anything with more posts and thus play 'tag' with anyone willing to answer.

REPLY;
Sounds like you have been doing your homework. I am glad to see that you did your research and are making informed decisions for your safety. Congrats

YOU SAID;
I hope everyone is having/has had an enjoyable Memorial Day. Please remember those who have given their lives so we might be able to live in a country where some of our biggest concerns are wondering the amperage of our ceiling fan motor.

REPLY;
I agree with remembering those who have sacrificed for our freedom of choice and freedom to express opinions. I suspect that for a long time we are going to have a much more worrisome concern. Trying to protect ourselves from an enemy that is not strong enough to fight face to face yet can cause much misery due to there hide and seek hit and run tactics. Shame we will have to sacrifice some of what all those that fought for our freedoms becuase of hit in the night enemies.

Good luck

Wg
 
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Old 05-28-02, 07:41 AM
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Wg - thanks for the response. I was hoping the required laundry 1500 Va included the washer.

After getting in the attic with a flashlight and Formula409, I cleaned off the outside of the fan motor. I got all the grease and dust off until I could see all of the turquoise housing and made it look almost new. Still no plate. So of course I had to remove the 4 mounting bolts and turn the motor over to see the bottom. Voila! A plate. It is 6.4 amps.

(It worked out for the best, though, because the belt on the fan broke awhile back and when I replaced it with an extra one the previous owner had left behind, it was slipping. I had never taken the time to figure out how to tighten the belt on it, but in removing the motor to find the nameplate I figured out how.)

Now for an additional question regarding the calculation:

My refrigerator manufacturer states I should have a separate 15A circuit dedicated to the fridge and I have 2 bathrooms that are supposed to each have dedicated 20A circuits. Are these requirements included in the calculations? Or should I recalculate and leave out the fridge, get a total amp load and then add 55A to that?

(I hope not recalculate b/c sometime in the past the previous owner updated the service to 150A. My calculation came up with 121A minimum. If I recalculate w/o the fridge and add 55A at the end I end up with more than 150A.)

I have a few more questions regarding the service box and the breakers and amperages but I will stop here for now and ask those later.
 
  #4  
Old 05-28-02, 12:17 PM
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Wgoodrich
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The 20 amp circuit for bathroom receptacles are a design concern for that branch circuit ensuring that circuit can carry the load in that bathroom without irritating trips of that branch circuit breaker. No additional load should be added to your demand load calculation. Concerning demand load calculations the bathroom receptacles are counted in with your general lighting with no additional load added for these bathroom receptacle circuits.

Normal household Refrigerators and freezers are included in the demand load calculation in the 3000 Va included for the small appliance branch circuit loads. These refrigerators and freezers are considers as intermittent loads included with the small appliance branch circuit loads in that demand load calculation with no additional load added beyond the small appliance branch circuit 3000 Va loads already added in that demand load calculation.

Wg
 
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Old 05-28-02, 12:55 PM
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So I don't have to include my fridge in my list of FIPA? Wow, my demand load keeps falling and falling--I like that since I didn't want to have to replace my service.

Thanks again for your responses.
 
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Old 05-28-02, 05:01 PM
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Wgoodrich
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You refridgerator is not considered as a fastened in place appliance. You refrigerator is included in the 3000 Va you already entered as your small appliance branch circuit.

You receptacles in your bathroom is included in the general lighting load same as any other convenience receptacle per the 3 Va per square foot.

Glad you found good news.

Good Luck

Wg
 
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Old 05-29-02, 06:19 AM
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I don't want to waste TOO much bandwidth to say the same thing, but I will say it one more time to end this thread: Thanks! I appreciate your assistance and patience.

That was 'Step 1' and it is complete. My demand load is calculated at 115 amps. I have a 150A service. All is well there.

Now on to 'Step 2' which is addressed in the Service Panel thread.
 
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