Electrical panel/load calculation

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Old 02-10-16, 09:13 PM
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Electrical panel/load calculation

I have recently moved into a home with a 100 amp panel. I'm considering upgrading some appliances and I'd like to add an additional refrigerator in the kitchen. I've been reading about load calculations, but I don't feel comfortable enough with my knowledge of the subject.

The house is approximately 1300 sq ft. Appliances include electric stove/oven, microwave, electric dryer, washer, refrigerator, electric water heater, 3 ton AC unit with heat pump. Since I've been here I've not experienced any issues with breakers tripping or anything of the sort, but I don't want to add any additional appliances if I am already very close to capacity.

I would greatly appreciate any help determining the load calculations. When I attempted, ?I got somewhere between high 80s and low 90s. What should I be looking for with a panel of this size? Thank you.
 
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Old 02-11-16, 04:07 AM
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When I attempted, ?I got somewhere between high 80s and low 90s.
With everything that you listed I think that would be about right. It also means that you are right at the top of your allowable load if you have a 100 ampere service. An additional refrigerator will likely not be a problem unless it is a super large commercial model but if you plan on adding any other "power hungry" items to your home you will need to upgrade the electrical service.

that stated, your calculation (or more properly, the software or guide you used) could be significantly overestimating the load. Depending on how many other people live with you, what kind of lighting is used (incandescents, fluorescent, LED, etc.) lifestyle, especially turning off lights and other appliances when no one is using them can result in a real-life load significantly lower than the guesstimate of a demand load calculation.
 
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Old 02-11-16, 03:35 PM
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3 ton AC unit with heat pump.
What kind of heat backs up the heat pump, gas or electric? If electric, I can easily see an extra 10 KW to 15 KW occasional load you probably have not included. Where are you located?
 
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Old 02-11-16, 04:21 PM
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The heat pump is backed up by electric heat strips. I'm in South Carolina, so aux heat rarely kicks on. I'm the only one in the house so there are few instances in which I would actually be using appliances at once. I use the oven maybe a few times a month--generally cook in a crockpot.

Can you look at this panel and tell me if it is 100 amp?

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Old 02-11-16, 05:03 PM
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Photo

Take a photo from a little farther away so we can see the main breaker.

Or can you tell us the amps listed on the main breaker?
 
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Old 02-11-16, 05:09 PM
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From the bottom-- 50, 30-30, 30-30, 100-100

20-20, 20-20, 20-20, 20-20

At the very bottom there is a single pole with 20
 
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Old 02-11-16, 05:36 PM
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If that is the only circuit breaker or fuse panel you have I'm going to go out on the limb and state that the upper left hand two-pole circuit breaker is your main circuit breaker. That would make it a 100 ampere service.
 
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Old 02-12-16, 04:38 PM
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That would make it a 100 ampere service
I would agree.

Sherri Lee


From the bottom-- 50, 30-30, 30-30, 100-100

20-20, 20-20, 20-20, 20-20

At the very bottom there is a single pole with 20
All those breakers on the right side are single pole 20s. The bottom left breaker with the red handle looks like it shouldn't be in that Siemens panel.

The heat pump is backed up by electric heat strips. I'm in South Carolina, so aux heat rarely kicks on.
What is the KW of the heat strips?

I see the 2-pole 30A breakers for the dryer and water heater and the 2-pole 50A breaker for the range, but see no breakers for the heat strips unless they are all 120 volt strips.
 
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Old 02-12-16, 07:22 PM
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I'm pretty sure the heat strips are 5KW but that's just going from memory when they installed the unit. Would it say that on the machine somewhere?
 
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Old 02-12-16, 07:30 PM
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Sherri, is this the ONLY circuit breaker (or fuse) panel in the home? Do you maybe have another at the meter?
 
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Old 02-12-16, 07:42 PM
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As far as I know, this is the only panel. The meter outside doesn't have anything that I could identify as a panel.

Now that I think about it, there is a gray locked box underneath the meter. I assumed it was something with the power company. Perhaps that's an additional breaker?
 
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Old 02-12-16, 08:22 PM
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Please post a picture of the box.
 
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Old 02-13-16, 06:30 AM
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Pretty sure it is just the meter--when I actually looked at it, the box surrounds the meter

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Old 02-13-16, 06:46 AM
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That is only the meter socket. The 100 amp 2 pole breaker is your main breaker.
 
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Old 02-13-16, 07:04 AM
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Thanks. I've seen the aux heat come on a couple of times since I've been here and I've never had any issues. I called the woman who lived here before and she said in her three years she never had any breakers trip. I don't know if that means anything but, if I understand correctly, shouldn't the breakers trip if the are overloaded?
 
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Old 02-13-16, 07:07 AM
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The breakers should trip on overload. If properly sized circuits and service are installed you should not have tripping.
 
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Old 02-13-16, 07:33 AM
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Adding an additional refrigerator is not a significant load. Replacing existing appliances with new ones will likely reduce energy usage as newer ones will be more efficient. IMO I do not see any issues with your plan with your existing electric service.
 
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Old 02-13-16, 07:31 PM
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I'm pretty sure the heat strips are 5KW but that's just going from memory when they installed the unit.
How many heat strips are there? My guess is at least 2 or possibly 3, considering you have 1300 square feet and 3 tons of cooling. Now, where are the circuit breakers for the heat strips and the heat pump? The three 2-pole breakers in the panel are probably for the water heater, dryer and range, but there are no more 2-pole breakers. Is there another panel somewhere in the house?
 
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Old 02-13-16, 08:51 PM
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No. There are no other panels. There has always been a 3 ton unit here with electric heat strip kit. The unit was replaced shortly before I moved in. As the breakers have never tripped, I've never been concerned about the configuration.

I know the dryer is on a 30 amp and I know the range was a 50. For some reason, I thought the water heater was on a 20, but I could be wrong.
 
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Old 02-13-16, 09:38 PM
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Could you give us a close up of the alien breaker left bottom. You didn't list it in your list of breakers. Do you know what it controls?
From the bottom-- 50, 30-30, 30-30, 100-100
 
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Old 02-13-16, 09:45 PM
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It says test on the red part.
 
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Old 02-13-16, 09:47 PM
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So either GFCI or AFCI. Maybe a 20a for the bath. Can you find the breaker for the water heater.
 
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Old 02-13-16, 10:17 PM
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I will test in the morning, but it would make sense that it could be on a 20. I'm the only one in the home and there are times I can run out of hot water if I take a longer shower. If it's on one of the single pole 20 breakers, that would mean it is only 120v instead of the 240v it could be, right?
 
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Old 02-13-16, 10:35 PM
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Look at the data plate on the water heater. However we are probably getting a bit off track of your original question. Your choice on how much further to go.
 
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Old 02-14-16, 06:36 AM
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A 120 volt WH is a very small unit or is miswired and will not provide the recovery of a 240 unit.
 
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Old 02-14-16, 07:54 AM
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Assuming you have a 120 volt water heater, that would leave one 2-pole 30A breaker for the 3 ton A-C that might be also used to power one 5 KW heat strip. 5 KW wouldn't really be enough to heat 1300 square feet, but that might be what it is. I have seen small 2 bedroom all electric apartments with 10 KW heat before and I know their 100 amp services were maxxed out.
 
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