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-   -   Service Load Calcs and Install (http://www.diychatroom.com/f18/service-load-calcs-install-52092/)

sstinman 08-31-2009 08:22 PM

Service Load Calcs and Install
 
2 Attachment(s)
He guys thought I would ask the question. I recently bought a house (after a full home inspection). A couple of problems have cropped up since I've moved in. The first was and A/C problem that stemmed from a really bad duct work install. Had most of that repaired by the last owner (I bought the builder's showcase home). Now that I'm starting to suspect the house is more show than go, I thought I would really do a much better second look at everything again.

What I have noticed is the electrical service is 200amps (main breaker) the sub-breaker (service and feeder lines) add up to 830amps total all in one panel.

The lines break down as follows:
Two-phase (240v)
A/C (5 ton) #1 2 x 60amps
Dryer 2 x 30amps
Double Oven 2 x 40amps
Cooktop 2 x 30amps
A/C (2.5 ton) #2 2 x30amps
Two-Phase total is 380amps

Single-Phase (120v)
9 x 20amps (three legs are GFI)
18 x 15amps
Single-Phase Total 450amps

In addition to the appliances mentioned above I have:
Washer (11amps max)
Frig (7 amps max)
Microwave (1800 watts max)
Dishwasher (11amps max)
whirl pool bath tub (1200 watts)

36 pot lights with 75 watt halogen bulbs
23 outdoor landscape lights (1000 watts max)

Plus a home office with about 3000 watts of stuff


I found an NEC article 220 load calculation in a professional forum that when I enter the data in a liberal manor (giving the builder the benefit) I get an answer of 260amps minimum service load which rounds-up to a 300amp main breaker. I could easily take the calculation much higher.

I want the forums opinion on the install and the calculations. My next step is to hire a real professional electrician and get his opinion. But before I spend the money I thought I would get some free advice.

Scuba_Dave 08-31-2009 08:32 PM

Do you have breakers kicking off?

Main breaker kicking off ?

EBFD6 08-31-2009 08:36 PM

Quote:

Originally Posted by sstinman (Post 322062)
What I have noticed is the electrical service is 200amps (main breaker) the sub-breaker (service and feeder lines) add up to 830amps total all in one panel.

The lines break down as follows:
Two-phase (240v)
A/C (5 ton) #1 2 x 60amps
Dryer 2 x 30amps
Double Oven 2 x 40amps
Cooktop 2 x 30amps
A/C (2.5 ton) #2 2 x30amps
Two-Phase total is 380amps

Single-Phase (120v)
9 x 20amps (three legs are GFI)
18 x 15amps
Single-Phase Total 450amps

In addition to the appliances mentioned above I have:
Washer (11amps max)
Frig (7 amps max)
Microwave (1800 watts max)
Dishwasher (11amps max)
whirl pool bath tub (1200 watts)

36 pot lights with 75 watt halogen bulbs
23 outdoor landscape lights (1000 watts max)

Plus a home office with about 3000 watts of stuff


Service calculations are not done this way. You can not just add up breaker values and get a total. Looking at the loads you have listed (without doing any actual math, because I'm lazy tonight) nothing really jumps out at me as exceptional, your 200 amp service should be sufficient. However, if you have concerns, contact a licensed electrician and have them do a proper load calc.

sstinman 08-31-2009 08:38 PM

No not yet, but we haven't really run the house yet. Meaning a big Thanksgiving Day family party with both ovens going and the cooktop. Where the A/C might have to come on to get rid of cooking heat and the many people in the house.

I've thought of doing a test run and try everything on at the same time but that may not prove the install is less than code or specifications since almost every home install has some level of over amperage. If plug-in enough you can get any house to trip the main.

sstinman 08-31-2009 08:42 PM

Quote:

Originally Posted by EBFD6 (Post 322072)
Service calculations are not done this way. You can not just add up breaker values and get a total. Looking at the loads you have listed (without doing any actual math, because I'm lazy tonight) nothing really jumps out at me as exceptional, your 200 amp service should be sufficient. However, if you have concerns, contact a licensed electrician and have them do a proper load calc.

Please look at the PDF file where I've done the NEC article 220 calculations. I realize that its not a straight sum of the breakers. But I'm not experienced to know if I plugged in the right values in the spread sheet.

My next step is to hire a pro but I don't want to waste his time with a potentially non-issue.

Yoyizit 08-31-2009 08:48 PM

It does look like your 240v loads add up to 190A [they should be 1x, not 2x] but I don't do this for a living.

Magnettica 08-31-2009 08:58 PM

Quote:

Originally Posted by sstinman (Post 322062)
He guys thought I would ask the question. I recently bought a house (after a full home inspection). A couple of problems have cropped up since I've moved in. The first was and A/C problem that stemmed from a really bad duct work install. Had most of that repaired by the last owner (I bought the builder's showcase home). Now that I'm starting to suspect the house is more show than go, I thought I would really do a much better second look at everything again.

What I have noticed is the electrical service is 200amps (main breaker) the sub-breaker (service and feeder lines) add up to 830amps total all in one panel.

The lines break down as follows:
Two-phase (240v)
A/C (5 ton) #1 2 x 60amps
Dryer 2 x 30amps
Double Oven 2 x 40amps
Cooktop 2 x 30amps
A/C (2.5 ton) #2 2 x30amps
Two-Phase total is 380amps

Single-Phase (120v)
9 x 20amps (three legs are GFI)
18 x 15amps
Single-Phase Total 450amps

In addition to the appliances mentioned above I have:
Washer (11amps max)
Frig (7 amps max)
Microwave (1800 watts max)
Dishwasher (11amps max)
whirl pool bath tub (1200 watts)

36 pot lights with 75 watt halogen bulbs
23 outdoor landscape lights (1000 watts max)

Plus a home office with about 3000 watts of stuff


I found an NEC article 220 load calculation in a professional forum that when I enter the data in a liberal manor (giving the builder the benefit) I get an answer of 260amps minimum service load which rounds-up to a 300amp main breaker. I could easily take the calculation much higher.

I want the forums opinion on the install and the calculations. My next step is to hire a real professional electrician and get his opinion. But before I spend the money I thought I would get some free advice.

The first part of the calculation is to know the square footage of the living space of the house.

Then add 3,000 Volt-Amps (VA) for both small appliance kitchen circuits.
Next, 1500 VA for the laundry receptacle.
Electric Dryer is rated at 5,000 VA unless it is higher than 5,000 VA and then it's calculated at the name plate rating.
Both A/C's get rated at their name plate rating too.
Got any small motors like a garbage disposal?
Apply the largest motor VA rating at 125% of the FLA and simply add the rest of the motors at their name plate ratings.


etc, etc....

Your 200 amp main breaker I'll bet is sufficiently sized.

I'll let the other licensed guys take it from here.

spark plug 08-31-2009 09:01 PM

Concern about overload!
 
Quote:

Originally Posted by sstinman (Post 322073)
No not yet, but we haven't really run the house yet. Meaning a big Thanksgiving Day family party with both ovens going and the cooktop. Where the A/C might have to come on to get rid of cooking heat and the many people in the house.

I've thought of doing a test run and try everything on at the same time but that may not prove the install is less than code or specifications since almost every home install has some level of over amperage. If plug-in enough you can get any house to trip the main.

As the previous poster said; You've got the calculations wrong. But the basic idea behind having a 200Amp. @ 220v. main is, that you (and no one else in their right mind) will not use all the loads to the max at the same time. At any rate, the loads do not add up the way you calculated them! Without knowing the particular loads, (just from your list) I'd venture to say that you may be using 150-160 Amps (@220v) at peak usage!(Now more than ever) :yes::no::drink:Don't Drink and Drive!!!

300zx 08-31-2009 09:03 PM

Try This Free NEC Standard Method Single Family Residential - Electric Service Entrance Load Calculator http://zenfixit.com/electrical-wirin...ad-calculator/

Magnettica 08-31-2009 09:12 PM

Remember...

Current = Volt-Amps/ Volts (I=P/E)

sstinman 08-31-2009 09:13 PM

Guys I have used the residential calc and get a 260amp service load.

Please look at the PDF file found under the picture.

[IMG]file:///C:/DOCUME%7E1/SPASEN%7E1/LOCALS%7E1/Temp/moz-screenshot.png[/IMG]

Magnettica 08-31-2009 09:18 PM

Quote:

Originally Posted by sstinman (Post 322101)
Guys I have used the residential calc and get a 260amp service load.

Please look at the PDF file found under the picture.

[IMG]file:///C:/DOCUME%7E1/SPASEN%7E1/LOCALS%7E1/Temp/moz-screenshot.png[/IMG]


Well then you need to hire an electrician to install you a new 300 amp service, updated grounding and bonding. You're looking at probably close to $3 grand.

sstinman 08-31-2009 09:22 PM

Quote:

Originally Posted by Magnettica (Post 322108)
Well then you need to hire an electrician to install you a new 300 amp service, updated grounding and bonding. You're looking at probably close to $3 grand.

Assuming I did the calculations correctly then I'm in for a fight with the builder.

Magnettica 08-31-2009 09:24 PM

You're wasting your time fighting the builder or electrician.

Has the main breaker ever tripped?

Does it even get warm?

Trust me, I am an electrician and I own and operate my own business, you're 200 amp main breaker panel is fine the way it is.

sstinman 08-31-2009 09:32 PM

But what about the builder, electrical contractor, the city inspector, the home inspector who all promised me the electrical was installed correctly for the load and meets minimum code requirements as outlined in NEC article 220? I haven't installed any extra appliance or equipment (other than the home office equipment). The builder installed all the appliances.


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