Thread: Power Consumption, FWIW

Interesting exercise, some sure draw some cerrent on start up don't they?
thank goodness they dont draw mutch working.

By my basic calculations, total energy = power x time = voltage x current x time.

Even if the dusty draws 15 amps for a whole second at startup, leaving it on for just 5 seconds uses the same amount of energy. (240x15x1=240x3x5).

So unless the machine will be off for less than 5 seconds, it is much more efficient to turn it off and on.

This same concept applies to the other machines.

(and yes, the maths isn't exact because the current draw is not linear etc etc, but the general principle still applies)

(and wow - 34amps for the table saw - crikey!)

Originally Posted by Rookie

My BIL brought his clamp tester over last night and we ran some numbers off on the various bits of equipment I have in the workshop. I was curious as to how much it costs to run things, and he wanted to get away from my sister's sewing night with the girls. Easy done.

We measured current draw at startup, under load, and with no load and the results are below.

I must stress that these are rough order of magnitude figures. Not too rough but it was by no means a tightly controlled experiment, it was purely an exersize to see what the rough numbers would be.

For what it's worth, this is what we came up with. All numbers are Amps. The results for the dusty are with it completely free of connections as I still wheel it around when I need it. If I had ducting installed the numbers would probably be a bit higher due to the drag.

1HP C'tec Dusty
Startup 15
No Load 3
Load 3

H&F 2325 3HP Table saw
Startup 34
No Load 3
Load 7.5

I have a 2 HP dusty and it occasionally pops a 16A fuse on startup, even when it's the only thing on the circuit. It's enormous start current was the reason I discovered one of my "power" circuits is actually an 8A lighting circuit :eek:. The figures you give are also the reason I want everything of any significant size 3 phase. I wouldn't be able to run my table saw on single phase - it has a 3.5kW motor that slows for NOTHING, even with a full 105mm rip, but I'd hate to think what the start-up would be on 1 phase.

Originally Posted by Rookie

The results for the dusty are with it completely free of connections as I still wheel it around when I need it. If I had ducting installed the numbers would probably be a bit higher due to the drag.

The start up and no load figures are very similar to the values I have measured for my gear.

In terms of your load figures - because load can be anything from a whisker to a whatnot, it should be pointed out that most devices will draw considerably more if you place an bigger load on them. This particularly the case for something like a TS. See my post at http://www.woodworkforums.ubeaut.com...ad.php?t=37692

If you have standard bags on your dusty you'll find the biggest load is the effort required of the motor/fan to push the air through these bags, Unless you use really constricted pipe, adding ducting doesn't do much to the electrical load. I have 2 x 3.5 m long branches of ducting on my 1 HP and cannot detect a change in the current draw greater than 0.1 A whether the ducting is connected or not. Even if you block the fan altogether the the current does not seem to change. Cleaning the bags makes 0.1 - 0.2 A difference to current draw.

Just getting back to this, and the reason I made these measurements in the first place.

I was curious as to how much it cost on the power bill to use the equipment in my workshop. Now this isn't going to be an exact thing by any means, but I wanted an order of magnitude on how much I was spending. Was it dollars, or cents.

Turns out, not much. One question which John G referred to, was the dusty. I wasn't interested so much in where the cut off point was in terms of power consumption, but whether or not I was spending lots of dollars by leaving it running for a couple of hours. Seems I'm not.

The dusty, at 720 Watts, costs about 9.5 cents per hour to run. In fact, with the mix of everything I use in an evening in the shop, I'd be surprised if I spend more than about $2. So ignoring things like how quickly the dusty, and other gear, wears out if it's running all the time (what we call MTBF or mean time between failures), I know SWMBO won't scream about the power bill because of what I do in the workshop.

I can still say with all certainty that it is the kids racking up the big power bills.

Originally Posted by Rookie

The dusty, at 720 Watts, costs about 9.5 cents per hour to run. In fact, with the mix of everything I use in an evening in the shop, I'd be surprised if I spend more than about $2. So ignoring things like how quickly the dusty, and other gear, wears out if it's running all the time (what we call MTBF or mean time between failures), I know SWMBO won't scream about the power bill because of what I do in the workshop.

Worthy little exercise - handy info - thanks Rookie!

Originally Posted by Rookie

I can still say with all certainty that it is the kids racking up the big power bills.

I just kicked my last one out - who am I gonna blame :eek:

Originally Posted by TTIT

I just kicked my last one out - who am I gonna blame :eek:

Any hobby your wife has that remotely uses electricity. And if she doesn't believe you, tell her to find a mate with a tong tester to prove you wrong.