DC power question

[John Moorhead]

Folks -

My dust collector is a 1.5 hp Penn State DC-2, I also have a smaller collector, the DC1B-XL, a 1hp unit

The 1.5HP unit's label says it draws 18a at 110 or 9a at 220... It never tripped a breaker running on a 15a 100 circuit - in fact, I had been running it, and my Delta Drum Sander on the same circuit - I think I was lucky.

My question for the larger collector is this: If it draws 18a on 110, and the max that you are supposed to draw on a 15 or 20a circuit is 80%, then I shouldn't run anything over 12a on the 15 and 16a on the 20... how can they sell the 1.5hp unit to run on 110?

I would like to run the smaller collector as a dedicated unit for the tablesaw and rewire the larger unit to run on 220. The wierd thing is, is that the smaller unit (1HP) also says it draws 18/9 amps...

Would any of the electrical types on the rec be able to tell me how much current a 1 HP and a 1.5hp motor would use during steady operation? I am assuming that the amperage ratings on the data plates are for start up current, rather than continuous draw.

I'd sure appreciate it if someone could fill in the gaps/chasms in my knowledge. I'll be working on the rest of my electrical layout for the new shop and will likely have a number of other questions as things progress, so I'd suggest that you run like hell, or you may end up being my new best friend! Thanks in advance...

John Moorhead

[Wilson Lamb]

Who knows. They are all over the map. The best thing to do is get a cheap clamp on ammeter from HF and find out the truth. I use mine often and enjoy having it.

As stated here so many times, 1HP=746 Watts.

1.5 HP=1119 Watts. Since the motor has a power factor of about 0.8, you need more amps, say about 12, for 1.5 HP and 8 for 1 HP. But who knows how heavily the fan is loading the motor...depends on the rotor design.

Unless your DC is on for hours, I wouldn't worry about the load factor (the

80% you mentioned). House circuits are very conservatively designed and the breakers will trip long before you could possibly heat up any wire or connection in good condition.

Since all wire carries twice the HP at 240 as at 120, it's obvious that using 240 makes things cheaper to install and allows more stuff on the same circuit. It's a myth that the tools work better on 240, ASSUMING that the circuit is properly sized. Now if you need to run your TS 200 feet out in the yard, 240 is LOTS better, because your 200 ft cord probably won't be big enough to really supply 120V at heavy currents.

Rule 1. Put in lots of recepptacles

Rule 2. You can't have too many receptacles.

Rule 3. Don't put all plugs on a circuit next to each other. Hop around a bit so it's easy to plug adjacent loads into different circuits.

Rule 4. It takes a lot of lights to load a circuit, but it's nice to have two, just so you don't go plum dark all at once. There's no reason not to have a couple of lights on a tool circuit. The occasional blink won't hurt you.

Wilson

[Kent]

The current draw of the motor will depend on the load, which in a DC is proportional to the airflow.

I have a 2 HP Penn State DC. Nameplate amps are, surprise, 18/9 at

120/240V (hmmm... starting to wonder if Penn State uses the same label for all their motors).

The actual running current, with the 5" inlet wide open, is 6.5A at

240V. The only way I ever got it up to the full 9A was by running it with the impeller cover removed (maximum airflow, producing maxium current draw). Startup current is much higher - about 40A at 240V.

Scaling these numbers down will give you a ballpark estimate for 1 and

1.5 HP machines.

[Rob Dingnagian]

snip

John,

I don't know the answers to all of your questions. I am pondering some different wiring scenarios for my Dust collectors also. One of them is three phase.

However, I wanted to tell you that I overlooked your post several times thinking you were talking about battery operated tools. I also refer to dust collectors as DC but in the context of power, I think Direct Current. I wonder if you would get more hits spelling it out for us.

I would like to see more feedback to your question and am now following this thread.

Good luck,

Eric

[Doug Miller]

120V circuits are not limited to 20 amps, of course. There's no reason this unit could not be supplied with a circuit consisting of 10-gauge wire protected by a 30A breaker.

Also, the 80% standard refers to continuous loads, which is defined as "a load where the maximum current is expected to continue for three hours or more."

The 18A rating is most likely the startup current on the dust collector motor; while running it probably draws a good bit less than that. Even if it draws the full 18 amps while running, it still meets the definition of a non-continuous load unless you normally run it for three hours at a time.

-- Regards, Doug Miller (alphageek-at-milmac-dot-com)

Get a copy of my NEW AND IMPROVED TrollFilter for NewsProxy/Nfilter by sending email to autoresponder at filterinfo-at-milmac-dot-com You must use your REAL email address to get a response.