remote switching a motor

ready961

Member
Join Date
Jan 2003
Posts
78
So I'm looking to switch on a shopvac remotely, so my first thought was to get a motor contactor from automation direct that fit the horsepower rating. But the hp on this vac is like 5.5hp. How the heck can this be a 5hp motor? And how can they be switching this on with a tiny toggle switch that it is supplied with if that is the case? Someone please straighten me out.
 
Get a clamp meter and a test cord and measure the running current of the vac. Size your contactor based on your measurements.

cheers
 
Rdrast
You're right, it does say peak horse power. Not really sure what that means.

ctw3
dont i need the switch or contact to have a hp rating?
 
I am not a sparky, and I am sure there are a lot better qualified people visiting this forum, but I will try.

Getting HP from amps or vice-versa with a motor can be tricky if all the details are not known. The reason why the HP rating on the vac is 5.5Hp I believe is to "cover all bases" by the manufacturer. A rdrast said. If the power factor is unknown, then I don't believe you can get a decent calc to find the HP of a motor.

Thats why I said earlier, measure the current of the vac, and size accordingly.

cheers
 
A couple of things. First, when you measure the amps with a clamp on ammeter you need to split the cord so you only measure line and not both line and neutral.

Second, I'm skeptical about the data - are you absolutely positive that it isn't amps?

A = hp x 746 / (V x eff x p.f.)

Let's assume: 120 VAC, 0.9 efficiency, and 0.7 power factor

Then you get 54 amps! Even for inrush that's a lot of current.

The nameplate on the vacuum should show someplace the volts and amps. That is more likely to be good data.
 
Just a thought...

Is this shop vac being used as a dust collector when some other piece of equipment switches on?

Check with your local distributor of woodworking tools. Lots of small mom & pop shops, as well as weekend hobbyists like myself use shop vacs for dust collection so there are several companies that make different kinds of remote switches for shop vacs. Some use a remote control so you can start it from across the room (provided you didn't set the remote down somewhere), some use a current relay on the machine tool to start the vac as soon as you turn on the machine. I've seen them advertised and at one woodworking machine supplier here - sorry I can't give you a brand, I still walk across my shop to turn on the shop vac before starting up the table saw or planer, but since my shop is one half of the garage, its not that far.


As far as sizing a contactor goes, use the rated amps of the motor, not the HP rating. Its a single phase motor and you simply cannot rely on anything the motor tells you except its amperage.
 
Last edited:
So I'm looking to switch on a shopvac remotely, so my first thought was to get a motor contactor from automation direct that fit the horsepower rating. But the hp on this vac is like 5.5hp. How the heck can this be a 5hp motor? And how can they be switching this on with a tiny toggle switch that it is supplied with if that is the case? Someone please straighten me out.

Give us all nameplate data please. I would trust the motor nameplate more than anything. However to avoid teardown the specs in the manual should suffice. If that is really a 5HP it could be a 220 single phase or maybe even three phase.

Single phase 120 V motors generally stop at 2 HP or less, then you go into single phase 220 to about 5 HP then you go into 3 phase for larger.

The Peak HP claim on a lot of consumer stuff is Madison Ave at work trying to impress Americans with power. Just like they do with automotive HP.

Dan Bentler
 
I have a "6.5 hp" Ridgid wet/dry vacuum. It runs on 110V and has never tripped any of my 15 amp breakers.... might blow your ear drums without ear protection, but never the breaker.
 
Give us all nameplate data please. I would trust the motor nameplate more than anything.
Dan, You might trust it for most industrial motors, but these newer "consumer retail" appliance and shop motors may not even have the horsepower on the motor. Instead it is painted somewhere on the tool (typically air compressors, shop vacuums, saws, drills, and so forth). It is used as a big sales pitch to the consumer, but anyone who knows about electrical devices can quickly look at the plug (NEMA 5-15R in most cases) and know that the advertisements are false. There is no way that you could get more than 2 real Horsepower out of a 15-amp 120 volt circuit.

If they will lie about this, who or what can we trust?
 
Last edited:

Similar Topics

Got any pointers or rules if I have system that has a Local HMI and is also is able to be controlled by a network. Should the person locally only...
Replies
3
Views
2,216
Hello, I work at a large canning factory, We have many can tracks from our processing area to the warehouse. To be flexible it is required that...
Replies
3
Views
3,481
I have to provide remote access and control to a touch screen. I was thinking about using Weintek and the Weincloud. Does anyone know if this is...
Replies
2
Views
132
Folks, I have a client with an old ABB Advant / MOD300 system (v14.4). Around y2k I installed the ABB Industrial IT MOD300 OPC Server 1.1/2...
Replies
0
Views
66
Hello, I presently have a Allen Bradley PanelView 5310 at a client site and i can access to the PLC/HMI local network with a remote module...
Replies
4
Views
89
Back
Top Bottom