Do I need to Upgrade Electrical Service?

[SRoberts006]

Alright so here's my question, I have calculated that my house uses about 80 amps as of now. I have a meter capable of 200 amps, BUT I believe I've only got 100 amps service to the house. I'm looking to add a large air compressor and a MIG welder that I was willed after my Uncles death. So do you think that I need to have my home updated to 200 amps? I seriously doubt the air compressor and welder will ever be running at the same time, but I guess you never know. Any suggestions from someone smarter than me would be greatly appreciated.

 

[pattenp]

If the main service panel breaker is a 100A then you do have 100A service. How did you come up with the 80A usage?

 

[SRoberts006]

Yea the main breaker is 100 amp. I came up with 80 by using an estimation that most home inspectors use.

 

[SRoberts006]

And remember the welder and compressor would be running at the same time as the A/C or Heat.

 

[pattenp]

If you are currently at 80A of load for things that would be running at the same time, I will say you are a good candidate for an upgrade. A large compressor or mig welder being used at the right moment will most likely trip the main breaker.

 

[SRoberts006]

Alright thanks for the information.

 

[usair]

You probably dont need an upgrade. Most houses have what we call demand factor. I doubt at any time you are actually pulling 80 amps.

 

[porschedude996TT]

Yea the main breaker is 100 amp. I came up with 80 by using an estimation that most home inspectors use.

Please explain. I sometimes wonder about home inspection services in general. They have always been ahh, how should I say this, "lacking in intelligence".

Bit that's my experience.

 

[wyliesdiesels]

Yea the main breaker is 100 amp. I came up with 80 by using an estimation that most home inspectors use.

I dunno what method you used but if it wasn't standard load calcs, then its probably way over factored. Most home inspectors are only good at visually seeing things that are wrong and very few understand electrical theory!

And please don't tell me that you just added up all the breakers of circuits that could be running at the same time!

Lets start off with this:

How big is your house?
Electric or gas for: heating, cooking, dryer, h20 heater?
What size A/C unit?

 

[sberry]

I have never seen one overloaded with a mig and a comp. How big is the AC and do you have electric hot water?

 

[SRoberts006]

Porschedude996tt - This is what I used to figure my amp load:

Here is how you can get an estimate of your load.

3 Watts per square foot for lighting and general outlets; say 7500 for a 2500 square foot house.

Now add electric dryer (5500), electric water heater (4500), electric stove or cooktop + oven (8500), two kitchen appliance outlets at 1500 (3000), laundry outlet (1500), two tons of air conditioning (3000 watts). Let's add 6000 watts for your shop (6000). You probably aren't running your welder and your saw at the same time.

Total is about 39,500 Watts or Volt-Amperes. We are going to round it up to 40,000 to make the calculations easier.

Now all of those things are not operating at one time, so the NEC lets you take 100% of the first 10,000 Volt-amperes, and 40% of the balance. So you have 10,000 + 0.4 x 30,000 = 10,000 + 12,000 = 22,000 Volt Amperes.

Now 22,000 VA/ 240 Volts = 91.7 Amps, say 92 Amps.

It is good practice to have 25% margin, and 125% of 92 Amps = 115 Amps. THAT IS YOUR LOAD, for the assumptions that we made. You may not have an electric water heater or electric dryer.

WyliesDiesels - 1. House is about 1000 sqft. 2. Electrical for everything (Heat/AC, Stove, Hot Water Heater, Dryer, Fridge and Extra Freezer, Dishwasher, Microwave)

sberry - Yes I have electric hot water. And its a big York model AC unit. I'd have to check the book. (the previous owner was an older lady and was talked into buying a larger unit than this house needed).

I also called and e-mailed the power company to see if they could tell me what service they were providing to me. But they haven't responded as of yet, its been 4 days.

 

[tylernt]

3 Watts per square foot for lighting and general outlets; say 7500 for a 2500 square foot house.

That's... a lot of power. Your power bill would be hundred$ with that kind of consumption. Ok, yeah, I understand you want a conservative estimate, but honestly I'd call 1 watt per square foot a conservative estimate.

Now add electric dryer (5500),

Dryers are typically 3,500W.

two tons of air conditioning (3000 watts).

2-tons is about 2,000W with modern high-SEER A/C units.

 

[SRoberts006]

I'm thinking I just need to go check the books and plates for all my "major" electrical equipment and see what the amps is.

 

[Rob_b]

Umm, have you ever taken a clamp meter and actually measured your amp draw at some given time or multiple readings throughout the day? I have...my normal draw is about 10-12 amps per line. The highest I've ever got a reading on it was 42 amps/37amps on each line with my wife cooking up a storm and the AC going at full tilt along with the normal stuff going. IMO, your estimates are a bit high.
Have you ever tripped your mains or random breakers? I do have a small compressor but no welder, gas water heater and dryer, electric stove in a 2400sq/ft home. My 100amp service works well for me. just my opinion...

 

[wyliesdiesels]

That's... a lot of power. Your power bill would be hundred$ with that kind of consumption. Ok, yeah, I understand you want a conservative estimate, but honestly I'd call 1 watt per square foot a conservative estimate.

Dryers are typically 3,500W.

2-tons is about 2,000W with modern high-SEER A/C units.

3,500w for a dryer? Wow! What model are U using? I wish my dryer pulled that small of a load! My 5yr old dryer pulls about 5,500w! And my not so old 3ton A/C condenser pulls about 6,000w.

I think u might be underestimating those average loads!