PDA

View Full Version : Measuring electric load requirement



Clarence Martinn
10-26-2017, 11:38 AM
Electricians: Need help figuring this one out!!

Trying to estimate total amperage used by these appliances in sizing an electric panel box.
This is what I have: Not all would be running at the same time, so the total electric use at a given time will vary.


1. Well Pump
2. Sump Pump
40 Gallon Electric Water Heater

Clothes Dryer 4500 Watts

Dishwasher

Washing Machine

1100 watt Microwave
Gas stove
Refrigerator
Porch motion sensor light.
Desk Top Computer

TV

Desk top Lamps and hall lights

Got 100 Amps now. Is this enough ?

Roger Nair
10-26-2017, 2:05 PM
Clarence, sorry I will not do the estimate, not my field, however you failed to mention AC and heating needs and .circuits for a home shop. What I did when I fixed up my old house with a minimal fuse box and knob and tube wiring is I just had a 200 amp service put in and declared myself ready for the future. So if you need to replace the service for any reason moving up from 100 amp to 200 amp will give you likely all the needed head room. The larger box will also allow for dedicated circuits for all larger appliances and a branch to a workshop sub-panel.

Lee Schierer
10-26-2017, 2:22 PM
You can run all of those from one 100 amp pane. However, unless you plan on running them simultaneously 100 amp should allow you to operate some of them. Figure out the wattage for each and divide by the operating voltage to get your current draw. Your 4500 watt dryer operates on 240 volts and draws about 19 amps (4500/240=18.7) when drying on high. Probably the same for the water heater. Your gas stove and motion light don't draw much current at all nor does your computer.

All of the devices should have a nameplate with current draw or wattage on them or look up similar models on the internet to get ratings.

Matt Day
10-26-2017, 3:43 PM
Funny you mention a single porch light but not the rest of your lighting!

As mentioned already, any AC windows units or anything? What kind of heat do you have? Gas, electric?

Any other big draw appliances? No hot tub or jetted tubs?

And youíre on a Woodworking forum - haw about your shop machines?

The answer is likely yes, itíll work, but donít plan on running lots at the same time. My house had a sketchy full 100A panel when we moved in which which breakers that didnít fit right and a panel manufacture that went out of business decades ago. I also wanted to add a couple lighting circuits and add a couple to the shop. So I replaced the panel with a 200A one, well with it.

Iím not an electrician, and you probabaly should have one check it out if youíre unsure.

Ken Fitzgerald
10-26-2017, 4:24 PM
Contact an electrical contractor and ask them to give you an estimate. I'd think they'd give you a breakdown on what would be required and what they were installing.

Kev Williams
10-27-2017, 1:01 PM
This is just for reference, may help may not, this is a list of what's electrical in our house:

Business: 3-C02 lasers, air pump, water chiller, 1-fiber laser, 1-vinyl cutter, 10-cnc engravers, 2-drill presses, 1-bench grinder, 1-table saw, 1-safety saw, 1-radial arm saw, 1-cutoff bandsaw, 2-tool grinders, 1-beveller, 1-belt/disk sander, 5-dust collection blowers, 1-mini lathe, 1-80 gallon air compressor, 1-5 gallon compressor, 6 computers, 71 fluorescent tubes lighting up the place--

"Home": Central air, hot tub, oven, washer/dryer, 2-refrigerators, 1-upright freezer, 2-coffee makers (refers and coffee always on :) ), 2-microwaves, 2-flat screens, theater sound, Playstation 4, wii, various indoor and outdoor lighting, battery chargers, induction cooktops various appliances... --water heater and stove are gas--

We have 200 amp service. And in 40+ years, tripped a breaker twice: once when the first big compressor motor seized up, and once when I hooked a second blower up to the one laser engraver circuit.

John K Jordan
10-27-2017, 7:12 PM
Electricians: Need help figuring this one out!!
Trying to estimate total amperage used by these appliances in sizing an electric panel box.


Curious - you don't explain why you want to know. If what you have now works fine with your 100A box and doesn't trip the main breaker then it should be enough. Are you planning some modification or upgrade and want to consider more capacity? If so, a box larger in amperage and/or breaker spaces is cheap compared to the upgrade job (as long as the wire feeding it is sufficient)

However, if you really want to know just go to each device and write down what the label says, either the # of amps or # of watts. For lights, add up the wattage. Convert all watt values to amps: Amps=Watts/Volts. Add up all the amps. Take a wild guess at any electrical users you might add in the next 10 years and add those (like a shop???). If the total is less than 100 amps it will work. Whether it is enough or not depends on what you actually add in the future. If you are SURE that two things will not run at once, you can make an adjustment but for my money I just add them all then add a good margin on top of that. As long as the wiring is sufficient to feed for amps I'd personally err on the side of too much, maybe twice what I was using now.

In my first (old) house I ripped out a 60 amp fuse box and put in a 200 amp breaker box. I had to run bigger wiring from the utility drop. (All this was a good education - it was my first rodeo.)

This house has a 200 amp breaker box. I put another box between the meter and the house to send 200 amps to the house and 100 amps to feed my shop. It was a long run so I ran big copper undergound to my shop, sized to less than 1% voltage drop at full 100 amps. I put a 100 amp box in the shop and all has been fine.

JKJ

Lee Schierer
10-27-2017, 7:33 PM
I had a discussion with my son a while back regarding his electrical panel. He wanted to add a circuit in his kitchen to give more diversity to the load from the kitchen. He had several open spaces in his panel. He had added up the value stamped on each breaker and it already was a larger number than the rating of the panel so he was concerned that the box was over loaded. I told him that as long as there were spaces in the box he could add circuits. It is expected that no one will operate every circuit at capacity all at the same time. Unless he was tripping the main breaker he was never exceeding the load that the panel was designed for.

The same is true in this instance. If the 100 amp main breaker or fuses are not tripping the load is not exceeding the capability of the panel. If the OP is considering adding additional load in the form of power tools, then he may in fact need a larger panel. In which case he needs to consult a local electrical contractor to determine what he needs.

Rollie Meyers
11-18-2017, 11:42 PM
I've seen all electric homes w/ 100A service, but a modest sized home w/ a electric dryer, range, & A/C, gas heat, & water heater, would be fine w/ a 100A service. Adding the sum of all the branch circuit breakers in a panel is a very poor & inaccurate way to calculate the load.

Jim Koepke
11-19-2017, 2:35 AM
Not all would be running at the same time, so the total electric use at a given time will vary.

1. Well Pump
2. Sump Pump
40 Gallon Electric Water Heater
Clothes Dryer 4500 Watts
Dishwasher
Washing Machine
1100 watt Microwave
Gas stove
Refrigerator
Porch motion sensor light.
Desk Top Computer

If the washing machine is on, so is the well pump and water heater. Then when the first load is out of the washing machine the dryer is also running. The refrigerator kicks in when it feels like it, like when someone pulls out some left overs to heat in the microwave after taking care of the laundry and loading the dishwasher. Believe me, it isn't a stretch to find all of those things running at the same time.

This is a job for a professional.

jtk

Jerome Stanek
11-19-2017, 8:13 AM
Electricians: Need help figuring this one out!!

Trying to estimate total amperage used by these appliances in sizing an electric panel box.
This is what I have: Not all would be running at the same time, so the total electric use at a given time will vary.

I have all that and AC and electric range running off a 125 Amp panel that was installed in 1970


1. Well Pump
2. Sump Pump
40 Gallon Electric Water Heater

Clothes Dryer 4500 Watts

Dishwasher

Washing Machine

1100 watt Microwave
Gas stove
Refrigerator
Porch motion sensor light.
Desk Top Computer

TV

Desk top Lamps and hall lights

Got 100 Amps now. Is this enough ?

I had all that and AC and electric range running off a 125 Amp panel that was installed in 1970. Now I have a gas range and water heater so it is plenty

Mike Cutler
11-19-2017, 8:49 AM
Electricians: Need help figuring this one out!!

Trying to estimate total amperage used by these appliances in sizing an electric panel box.
This is what I have: Not all would be running at the same time, so the total electric use at a given time will vary.


1. Well Pump 500-700 watts. 3x surge.
2. Sump Pump. 250-500 watts. 3x surge.
40 Gallon Electric Water Heater4500 watts

Clothes Dryer 4500 Watts. This would be high for a dryer. 3500 would be closer. If it's 4500, it's 4500.

Dishwasher 500 watts

Washing Machine700 watts.3X surge

1100 watt Microwave
Gas stove 200 watts
Refrigerator 700 watts
Porch motion sensor light. 100 watts
Desk Top Computer100-250 watts

TV

Desk top Lamps and hall lights. would have to count bulb ratings. Changing to compact fluorescents would cut this number significantly.

Got 100 Amps now. Is this enough ? 100 amps is a small panel by todays standards.


Clarence
What is it you are trying to accomplish?
If everything is functioning now with no issues, there would be no reason to incur the expense of a 200 amp panel.