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To upgarde from 100 amp service based upon Probable load calcultion

To upgarde from 100 amp service based upon Probable load calcultion

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  #1  
Old 01-12-06, 06:48 AM
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To upgarde from 100 amp service based upon Probable load calcultion

I currently have a 100 amp servise. Based on the below calculation should I upgrade?
I have no plans on adding any major loads, like central air, spa, whrilpool. But may add another window A/C in the summer. Did I miss anything?

From "Wiring Simplifed" 40th edition p 77.

Calculating total Probable load in Volt-Amps:
5883 - Area of house 1961 * 3VA
3000 - Two appliance circuits
1500 - Laundry circuit
8000 - Range
0 - Water Heater

Other permanently connected appliances (I ramdomly broke these up based upon how many hours/day I think they will be on):
2184 - On for 12 hours or more / day: 5.0 Refrigerator, 5.7 dehumidifier, 7.5 Window A/C = 18.2 * 120 = 2184
4440 - On for 2 to 12 hours / day: 2.7 Dishwaser, 4.5 Kitchen vent, 6.6 Computers, 8.3 Bathroom vents, 5.4 cieling fans, 2.0 Stereos, 3.75 TVs, 3.75 Furnance motor. = 37 * 120 = 4440
4680 - On for 2 hours or less / day: 12.5 Microwave, 6.0 Garage door opener, 6.5 sump pump, 14.0 Hair dryer = 39 amps * 120 = 4680
11304 - Sub Total of Other

29867 - Grand Total
24000 - 100 amp service

5867 VA - Over
 
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  #2  
Old 01-12-06, 08:40 AM
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If you do not have any problems now with the main breaker tripping or overheating and you do not plan to do any major home upgrades like a kitchen remodel, central A/C, spa, basement finish or addition, and your existing service equipment is in good shape, then I do not see the need for a service upgrade. Keep it as-is until such time as you (or a future owner) want to do a major modification to the home or appliances.

There is one little flaw in your load calculation; you counted both the furnace and the A/C when they would never be on at the same time. Standard practice is to count only the larger of the two. Moreover you counted some items that are not usually counted or would never all be on like the hair dryer and garage door opener. The microwave may be plugged into one of those small appliance circuits that has already been accounted for.
 
  #3  
Old 01-12-06, 09:49 AM
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Ben he also doesnt show if he has electric dryer so assuming he doesnt and has gas I'm calculating the below taking into cosideration what you have already metioned. If he has electric dryer we would need to add minimum 5000 VA to the below.

19,174 VA......80 amps

Minimum Service 100 amps
 
  #4  
Old 01-13-06, 05:19 AM
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Yes, I missed my Electric Dryer at 5600 VA. So, removing the Furnace, Microwave, Hair dryer and door opener (4350 VA total). And adding in the cloth dryer the total is:

31117 VA

Roger, I still must be adding in too much, because our numbers are off by ~6000 VA.
 
  #5  
Old 01-13-06, 06:15 AM
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Yes, I missed my Electric Dryer at 5600 VA. So, removing the Furnace, Microwave, Hair dryer and door opener (4350 VA total). And adding in the cloth dryer the total is:

31117 VA

Roger, I still must be adding in too much, because our numbers are off by ~6000 VA
Probably no two people are going to come out exactly the same but we should be closer than 6000 VA.


Your house square footage should be calcualted at its outside dimensions of all habitable minus any unihabitable space. so your garage (if attached) square footage would not be counted. Unfinished basements arent counted.

On your list I threw out the below items because they are part of the general lighting and receptacle load (your house square footage x 3 VA).

Computers, baths*,Stereos,TV's, GDO's, Sump pump, Hair dryer's, Ceiling fans, Kitchen vents.

furnace*.

* Your Baths have no continuous load to be considered such as wall heaters.
* Furnace is not considered it is smaller than the window air.

I also used a standard wattage chart for items you didnt list such as garbage disposal and I changed your dishwasher as it isnt including the heater.

So with out going into detail if it isnt a fastened in place type appliance generally speaking it is included as part of the general lighting and receptacel load. The dehumidifyer is a toss up but you can count it if you like.

Anyway not considering the dehumidifier I threw out 7296 watts.

The differences in our calculations would take a bit to get down to the exact reasons. I dont think it is necessary to try to figure it all out.

Remember demand load is what would be considered (a diversity average) to be operating at any given time.

So if we consider the dryer your are real close to having a demand of 100 amps more or less but not by very much.

You do have to consider special loads like hot tubs, pools, fixed electric heat,
welders, and things like that.

Does this make sense......

Roger
 
  #6  
Old 01-13-06, 06:43 AM
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Roger, Thanks, that does make sense. Using the outside dimensions, my house's sq feet is 2050, adding another 267 VA. My 100 amp service should be fine as long as I do not add a hot tub etc.
Thanks.
 
  #7  
Old 01-13-06, 07:06 AM
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I did notice your running another thread and that you have a split bus Adams panel. If I remember correctly and maybe this is analagous with all split bus panels that the lower bus (secondary) is fed by one breaker in the top bus.
So that breaker lets say is 50 amps, then your lower buss that contains all your 120 volt loads would trip the 50 amp out if the loads in the lower portion demand more than 50 amps. Split bus panels are generally considered poor to unsafe design so if you can possibly swing the cost of a panel change I would do it regardless of my demand load. If your service isnt for anything more than 100 amps lots of times, though it is getting more rare, the utility will bring a bigger service in a no charge. Its money in the long run for them if your going to be needing more electric. Then you could put in a modern panel
with the advantages of todays designs even if you had to stay with a 100 amp panel.
I doubt your going to find tandem (twin) single pole breakers to fit an old split bus panel that you mentioned in another thread.

Good luck
 
  #8  
Old 01-13-06, 12:58 PM
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Ok, the safest/best thing to do is get a new panel. I looked at the cable coming into my house, (the meter is in the basement, just 4" above my panel box). Although hard to read (over 43 years old) printed on the service cable is something like "Narragansett 2-2-4 AL TYPE SE STYLE ??? 5C." Any ideas on what this mean? If it means 2 AWG Aluminum 75 degrees Celsicus then according to "Wiring Simplified" p. 27, I may only have a 90 amp service. So, I really should quickly upgrade the panel and service to the house. I might as well get 150 amp service to be on the safest side of safe. Woud $800ish be reasonable for the western upstate NY area?
 
  #9  
Old 01-13-06, 01:17 PM
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Originally Posted by b4u8cake
If it means 2 AWG Aluminum 75 degrees Celsicus then according to "Wiring Simplified" p. 27, I may only have a 90 amp service. So, I really should quickly upgrade the panel and service to the house. I might as well get 150 amp service to be on the safest side of safe. Woud $800ish be reasonable for the western upstate NY area?
There is a special rule which allows #2 aluminum for a 100A service to dwellings. Table 310.15(B)(6).

Get three estimates; probably $1,000 plus or minus is what to expect.
 
  #10  
Old 01-13-06, 01:25 PM
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I agree with your asessment.

You probably have Type SEU Service Entrance Cable. Its kinda "U" shaped.

Where it comes into your panel the neutral is a bare bunch of stranded wires.

You are going to be changing it so no need to worry about it.
 
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