[OP]
Contributor
not sure if labeled wright but what looking for is tool that could measure amp draw for shop as use different tools. i have 200 amp meter that powers house and shop and not want to be running tools and have the misses turn on oven and lights dim.... looking for budget friendly option.
Member
Maybe like this ...?? https://shop.emporiaenergy.com/produ...SABEgK2wfD_BwE
No experience with it.
Contributor
Malcolm I believe that measures KW usage. A clamp meter can show you amp usage while the tool is running but you would need to clamp each hot lead that goes to any particular tool. If you have a sub panel this would be easier.
The easier thing to do is calculate all major draws in the house based on equipment rating for running amps and estimate the smaller stuff add that all up and figure out what worst case draw on the house would be and figure out from there what worst case in the shop would be(compressor/dust collector/table saw/lighting)
Adding those together you should be safe.
Worst case would be if you had electric (dryer/stove/electric heat).
Member
search for 'clamp on ammeter'. There are many choices, 15-$big, depending on your needs.
Caveat, for your intended use, the labeled specs on tools and motors will provide enough accuracy. Just allow for a current surge when motors start.
Member
You may be right; I should have looked closer. I saw the CTs 'Amp' ratings and just assumed.... silly me.Originally Posted by George Yetka
(Also seems silly the supplier would not give you a way to see the amps?)
Contributor
I think the idea of that device is to monitor your money going down the drain amp draw isnt as important in that regard
Member
You would use a clamping multimeter. You need to have access to the individual wires. For 120v you could use a splitter like this:
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
For 240v you could cut a length of heavy duty extension cord, attach male and female plugs on the ends, and split it partially along its length to have access to the individual wires, carefully clamping on one of them (before powering it up.)
That’s safer than opening up the panel.
I bought a donut CT & digital display for my DC that was shockingly inexpensive and quite accurate. You'd need 2, 1 for each line. I think it was from Amazon, or maybe ebay.
Moderator
I use a clamp-on amp meter. If not familiar, these are actually "clamp around" meters. I clamp around the individual conductors at the breaker. Don't clamp around a cable (such as Romex) with more than one conductor.
Since it is sometimes difficult to get the fat clamp around a conductor in a tight spot, Klein, Fluke and probably others sell a clamp meter with a flexible probe. I want one.
https://www.homedepot.com/p/Klein-To...L150/305221468
JKJ
Contributor
Unless you're running some really big stuff, a 200 amp service should be plenty. I have 50 amps to my shop (subpanel) and never tripped the breaker. I doubt if I ever get close to 50 amps.
I have the usual 240 volt tools - jointer, table saw, dust collection, bandsaw. The bandsaw requires a 30 amp circuit but I doubt if I ever draw close to that. All the other tools are on 20 amp circuits.
Mike
Go into the world and do well. But more importantly, go into the world and do good.
Contributor
I have a 70 amp sub panel in my shop. All the usual suspect tools, plus both a stick and MIG welder. Never lacked for power. Own a HF clamp on amp meter. Works for everything I need.
Contributor
I have a clamp on ammeter too. I made a special cable to make it easy to use without needing to open up the panel. The cable consists of a receptacle and a line cord where the individual conductors at the receptacle end are available to be individually clamped. So, if I want to measure the current that something is drawing, I just plug the cable in to the wall receptacle and plug the tool into the adapter cable.
Member
Adding a 50amp circuit to your sub panel so you can charge an electric car (as many of us will sometime over the next decade) really changes things. I would put a 100amp sub panel as the future proof minimum these days. Of course, if your cars never go anywhere near your “shop”, that might be different. ;^)
Contributor
If you use a clamp on meter around two wires, like a power cord, it will read zero amps ac or dc. This is because equal amps are flowing in opposite directions, so net zero flow. You have to make an extension cord that separate power wires are clamped individually. The old dumb power meter indicated power draw by the rpm of the spinning disk.
the new smart meters show nothing at all except total usage over time in units too large to be useful. Our utility dumbs down the meter so no information is shown. My mothers showed voltage hz etc. I guess it confused the local idiots so they dropped it.
BillD
Contributor
Just recently, I put in a second subpanel for electric car charging. That one is 100 amps. So I have a 50 amp subpanel for the shop and a 100 amp subpanel for EV charging.
Remember that an EV will only draw 80% of the circuit current - at max. So the most your car will draw on a 50 amp circuit is 40 amps. Some cars, such as the Tesla Model 3 and Y, will only draw 30 amps on a 50 amp circuit. That's because of a limitation on the charging circuit in the car.
When you plug an EV into a 15 amp 120 volt circuit, it will only draw 12 amps. Takes a loooong time to charge an EV at 12 amps, 120 volts. The Superchargers operate at 440 volts (if I remember correctly). They're planning for long haul trucks to be electric. Those will have to draw some really big power from the charger to charge up the batteries in a reasonable time.
Mike
[I checked and the voltage on the SuperCharger is 480 volts. See here.]
Last edited by Mike Henderson; 03-04-2021 at 1:08 PM.
Go into the world and do well. But more importantly, go into the world and do good.
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