How to Measure Whole-House Amp Usage?

[Marty Tippin]

I've got 200 amp service at my house with a 100 amp feeder to my shop. As I contemplate adding a 3hp cyclone dust collector and 2-ton air conditioner to the shop, I find myself unsure as to how much excess capacity I presently have on the main 200 amp service.

The house is mostly electric - the heat pump (with gas backup), water heater, stove and dryer are the major current users. Out in the shop, I have several 3hp or less 240V tools but would only ever run one at a time, plus the cyclone dust collector and A/C. The 5hp air compressor may kick on from time to time as well.

Is there a way to accurately measure - with all the major current drawing appliances running - the actual, total real-time amperage draw at the main breaker box?

I have a clamp-style ammeter and I've checked both legs of the incoming feed, but I'm not sure what to do with the numbers I get, given that there is a mix of 240 and 120 circuits on each leg.

I'm sure there are spreadsheets to calculate total household load on a theoretical basis, but I'm more interested in the actual usage.

[John Lanciani]

I have a clamp-style ammeter and I've checked both legs of the incoming feed, but I'm not sure what to do with the numbers I get, given that there is a mix of 240 and 120 circuits on each leg.

There is no more to it than what you're doing. If you have a 200 amp service you have 200 amps per hot leg available.

[Marty Tippin]

There is no more to it than what you're doing. If you have a 200 amp service you have 200 amps per hot leg available.

Really? That sounds too simple!

So will the main breaker trip if either leg goes over 200 amps or when both of them go over 200 amps?

[Mike Henderson]

Normally, if either leg exceeds the rated amps, it will trip the circuit.

Mike

[Steve Rozmiarek]

You'll probably be surprised how low the actual amp reading is on your clamp meter. I had to log the usage to prove to the power company that their meter was defective once.

[Carl Weber]

I have a TED 5000 connected to my main. I can trend all usage (main incoming only) with my setup. There are kits available that will allow individual circuits. I have the remote that allows me to see what I am using at any given time. Or I can open a web page and see my usage.

[John Lifer]

Agreed, I wouldn't worry about it. You have plenty available in a one man shop

[Robert Delhommer Sr]

Yes that is how it works.