3hp @ 220v vs. 3hp @ 110v ??

[Longrider]

Hello everyone;

Is there a power difference between a 3hp Cabinet TS running at 220v and a 3hp TS running at 110v.?? or is 3hp a 3hp a 3hp.....

I am thinking of upgrading from a 3hp benchtop ts to a 3hp cabinet ts.

All of your help is greatly appreciated.

Thank You.

Longrider

[Peter in Wainfleet]

As long as the wiring is of adequate size, the power should be the same. You would probably need #8 wire and a 30amp plug if you want to run a 3hp motor @ 110v. At 220v, only #14 wire is needed and a double 15amp breaker

[Denis Chénard in Ottawa]

There is a big difference: the cabinet saw is a real 3 HP while the 3 HP is "maximum developed" HP, in practice that amounts to about 1 1/2 HP.

Other thing, the benchtop saw probably uses a universal motor, which are not that durable, while the cabinet saw uses a motor that can run all day.

These saws are two very different animals.

DC

[Frank Pellow]

There is a big difference: the cabinet saw is a real 3 HP while the 3 HP is "maximum developed" HP, in practice that amounts to about 1 1/2 HP.

Other thing, the benchtop saw probably uses a universal motor, which are not that durable, while the cabinet saw uses a motor that can run all day.

These saws are two very different animals.

DC
What Denis said!

I was in the middle of typing something along the same lines, when I saw the reply by Denis.

[matt in golden]

Longrider,

I just wanted to try and clarify what Pete said. He is talking about how some induction motors, like those found on a cabinet saw, can be wired to be run effectively at both 110v and 220v if the circuits are properly designed. I thought that was what you were asking as well the first time I read your post, and missed the words "bench top".

Now, I don't want to knock your getting a cabinet saw, but you would probably find that a 2hp contractors saw (induction motor), at half the price of a cabinet saw, would be a big step up from a bench saw (universal motor). Of course, I've only used contractors saws so I'm ignorant of the joys of a big cabinet saw.

Matt

[Ivan in Nova Scotia]

Besides their looks what is the difference in a contractors saw and a cabinet saw?

[billh]

Besides their looks what is the difference in a contractors saw and a cabinet saw?

The main difference is that the motor, blade arbour, tilting mechanism is mounted all within the base of the saw and not attached to the table. This makes adjusting the table mitre slot to the blade a lot easier since you only have to move the table top rather than fool with the rod assembly which can be a PITA. Overall, the blade moving/tilting mechanism is a better design.

The motor weight isn't hanging off the belt which means the belts don't get a bump in them if they aren't used for a while. Because of the enclosed base dust collection is better and you can get more powerful motors in a cabinet saw than you generally can in a contractor saw.

This doesn't mean contractor saws are no good just that the cabinet saws are a better design.

Now days they have hybrid saws which look like a cabinet saw but have the guts of a contractor saw inside a cabinet. I haven't looked carefully at one but AFAIK they have the disadvantages of the contractor saw - just hidden away.

billh

[OttawaP]

Don't underestimate the power of a real 3 hp motor in a cabinet saw, there is substantial difference in performance. Having said that a quality contractor saw with a good fence can last a lifetime worth of projects with no difference in quality of the cuts.
Buy it once and enjoy it for decades.

Paul

[danpower]

Mr. Longrider,
Assuming all things being equal, horsepower is horsepower. The rule of thumb for the electrical side of things is that if the voltage goes up, the current will go down as far as motors, transformers and the like. The thing I watch on motors is the current rating on the motor and ''not'' the HP. For example, I saw a picture of a vacuum cleaner that was rated at 6 Peak HP, at 120 volts. Now, Power=voltage X Current (we'll leave it at that to make it simple). If you take 120 volts X 15 amps (that's the rating of the wall socket), you get 1800 watts. 1 horsepower= 746 watts. So, 1800 watts divided by 746 = 2.4 HP. That's assuming 100% efficiency of the motor, which they're not. Remember the motor heats up when running, so you're losing energy in the form of heat. Also, ever look into a drill, for example, and see the blue sparks(for want of a better term) on the commutator? That's more energy dissipated. Let's assume then 70% efficiency of the motor, 2.4 HP X 0.7 = 1.68 HP. So, it's better to go with the current rating than the HP. I hope this was helpful to you.

Dan P.

[matt in golden]

So, it's better to go with the current rating than the HP.

Thanks Dan,

So you're talking amps then?

Matt

[danpower]

Thanks Dan,

So you're talking amps then?

Matt
Hello Matt,
I'm always looking at horsepower but I also check the current against the HP rating. I'm starting my shop soon (brand new to the woodworking field), and any major tool I can run on 220 volts, I will.

Dan

[Michael in Port Alberni]

Dan has a valid point when he says that the circuit will deliver 1800 watts (120v x 15amps), however there is one other factor to consider in all of this. Circuit breakers are designed to trip when the rated load exceeds 80% of the rating of the breaker for more than a set peroid of time, which I believe has been pegged at 2 minutes. As a result, the circuit (120v @ 15amps) will actually trip at 1440 watts. 1440/746= 1.93hp. This is why you will find so many appliances rated not at 1800 watts, but at 1400, or more commonly 1500. Check things like your toaster, hair dryers and other appliances and I doubt you'll find anything rated at 1800 watts with a 5-15r style plug on it. (standard household cord end) If you find anything rated higher than 1500 watts, somebody is playing with the numbers - the capacity of electrical equipment is set by the electrical safety branch, what a company puts on a sticker on the equipment is much less rigorously regulated.

Cheers

Michael

[billh]

... Circuit breakers are designed to trip when the rated load exceeds 80% of the rating of the breaker for more than a set peroid of time, which I believe has been pegged at 2 minutes. ...
Michael


According to Square-D, breakers are designed to run at their handle rating continuously at a 40C ambient temperature, a UL requirement. NEC says they should be derated according to load particularly continuous loads or loads that will be on for 3hrs or more. In this case, the 80% of rating is applied and appears to be a fudge-factor in case the breaker is installed in a warmer than 40C piece of equipment.

billh

[Michael in Port Alberni]

In all of my years as an electrician I have never installed a breaker that is rated at 100% of the nameplate. We haven't become part of the United states yet, so the NEC doesn't apply north of the border...yet. The CEC states that a circuit can be loaded to 80% of the nameplate rating UNLESS it is marked for 100% duty on the case and other rules in chapter 8 and 10 of the Canadian Electrical Code are satisfied..

Any equipment wiring must be derated when run in an ambient environment over 40C, that is not where the 80% rule comes from.

The breaker is not there to protect your connected equipment, it is there to protect the wiring in your house.

Cheers

Michael

[Marty S]

The main difference is that the motor, blade arbour, tilting mechanism is mounted all within the base of the saw and not attached to the table. This makes adjusting the table mitre slot to the blade a lot easier since you only have to move the table top rather than fool with the rod assembly which can be a PITA. Overall, the blade moving/tilting mechanism is a better design.

The motor weight isn't hanging off the belt which means the belts don't get a bump in them if they aren't used for a while. Because of the enclosed base dust collection is better and you can get more powerful motors in a cabinet saw than you generally can in a contractor saw.

This doesn't mean contractor saws are no good just that the cabinet saws are a better design.

Now days they have hybrid saws which look like a cabinet saw but have the guts of a contractor saw inside a cabinet. I haven't looked carefully at one but AFAIK they have the disadvantages of the contractor saw - just hidden away.

billh

Bill,

You're correct when you stated that cabinet saws' main workings are suspended from the cabinet and not the top. However... I would suggest that the major differences in the two types of saws lays in the heavier, more finely machined castings and bearing sets. In the case of Delta's Unisaw, for instance, there are 3 drive belts and the arbor is dynamically machined, meaning that it is machined after it's been assembled. These features and more result in less runout and therfore smoother, more accurate cutting... and of course higher costs. Like many things in life, you get what you pay for.

As regards hybrid saws, my son owns one - the Delta - and I was quite impressed with its performance and features. I looked carefully inside the cabinet and felt that it had more resemblance to a cabinet saw than a contractor's saw.

Marty S,

[billh]

In all of my years as an electrician I have never installed a breaker that is rated at 100% of the nameplate. We haven't become part of the United states yet, so the NEC doesn't apply north of the border...yet. The CEC states that a circuit can be loaded to 80% of the nameplate rating UNLESS it is marked for 100% duty on the case and other rules in chapter 8 and 10 of the Canadian Electrical Code are satisfied..

Any equipment wiring must be derated when run in an ambient environment over 40C, that is not where the 80% rule comes from.

The breaker is not there to protect your connected equipment, it is there to protect the wiring in your house.

Cheers

Michael

Hi Michael,
I realize the breaker is there to protect the house and not the equipment but it appears that the breaker is derated to 80% of its 40C free-air rating because if it is in a panel with a lot of other breakers generating heat, it may operating in an environment higher than 40C.

My point is that breakers are not designed to deliberately trip after a designed in delay of 2 minutes or whatever if run over 80% of the handle rating. It seems the de-rating of the breaker is actually dependent on the type of load and if it is handling a continuous load (which seems to mean on continuously for 3hrs or more) then the continuous load cannot be higher than 80% of the breaker rating. If the load is not continuous or has a much smaller continuous load then this 80% rule for the breaker doesn't apply.

I agree we are not under the jurisdiction of NEC but the codes do tend to be fairly well-aligned in general concept, aren't they?

This link describes what I am getting at and yes, it does refer to NEC but is the CEC different in this area?.

http://ecmweb.com/mag/electric_sizing_circuit_breaker/

There seems to be a lot of "80%"s kicking around in electrical ratings and I'm trying to get a better understanding of it.

Thanks,
billh

[billh]

...
As regards hybrid saws, my son owns one - the Delta - and I was quite impressed with its performance and features. I looked carefully inside the cabinet and felt that it had more resemblance to a cabinet saw than a contractor's saw.

Marty S,

Hi Marty,
That is interesting because I had the impression it was the other way around. I have been taken to task for saying this before because it is possible to do good work on a "cheap" saw but if I were to do it all over again I would if at all possible buy a good cabinet saw. It is the workhorse of the workshop and having a good machine can make any stock preparation straight-forward and pleasant.

billh

[Mike C.]

As long as the wiring is of adequate size, the power should be the same. You would probably need #8 wire and a 30amp plug if you want to run a 3hp motor @ 110v. At 220v, only #14 wire is needed and a double 15amp breaker


Peter you are correct. I run no.12 qauge wire for my 3hp General.. which is more than enough. I took an amp reading while the motor was running and it pulled 7 amps under no load..on each leg..then I ripped 2 inch thick maple while my son was holding the amp probe on the wire and it went to 12 amps ..which means I could have gotten away with regular 14 gauge wire if the run wasn't too long.


http://img.photobucket.com/albums/v260/canaris/LEESON.jpg

[danpower]

Peter you are correct. I run no.12 qauge wire for my 3hp General.. which is more than enough. I took an amp reading while the motor was running and it pulled 7 amps under no load..on each leg..then I ripped 2 inch thick maple while my son was holding the amp probe on the wire and it went to 12 amps ..which means I could have gotten away with regular 14 gauge wire if the run wasn't too long.


http://img.photobucket.com/albums/v260/canaris/LEESON.jpg
Hello Mike,
I see your saw is rated 230 volts @ 12.5 amps. That's all you need really, size the wire to the full load amps rating of the saw. No. 14 wire is rated for 15 amps. Horsepower as Peter mentioned, has nothing to do with (to a point) with sizing wire for a motor. As long as the wire's current rating matches the FLA of the motor (generally speaking) that's what matters.
Sincerest Regards,
Dan P.

[danpower]

Dan has a valid point when he says that the circuit will deliver 1800 watts (120v x 15amps), however there is one other factor to consider in all of this. Circuit breakers are designed to trip when the rated load exceeds 80% of the rating of the breaker for more than a set peroid of time, which I believe has been pegged at 2 minutes. As a result, the circuit (120v @ 15amps) will actually trip at 1440 watts. 1440/746= 1.93hp. This is why you will find so many appliances rated not at 1800 watts, but at 1400, or more commonly 1500. Check things like your toaster, hair dryers and other appliances and I doubt you'll find anything rated at 1800 watts with a 5-15r style plug on it. (standard household cord end) If you find anything rated higher than 1500 watts, somebody is playing with the numbers - the capacity of electrical equipment is set by the electrical safety branch, what a company puts on a sticker on the equipment is much less rigorously regulated.

Cheers

Michael
Michael,
Breakers are designed to run at rated nameplate rating. A 15 amp breaker will handle 15 amps. Breakers are sometimes rated as thermal, magnetic, or both(thermal-magnetic). The thermal rating on breakers is for, say (for arguments sake) if you have a motor load that is rated 12 amps protected by a 15 amp breaker and its bearings start to wear. Then, the current will gradually rise as the motor tries to maintain rated speed. The thermal mechanism in the breaker which detects the heat from the overcurrent condition (over a period of time) will cause the breaker to trip. Which was how the old toasters popped up when your toast was done. Now I know that most of these motors have their own thermal protection. The magnetic rating on breakers is the protection provided for during a short circuit conditions when the current skyrockets; it's instantaneous. The reason you don't see many appliances rated at 1800 watts (1800 divided by 120 volts = 15amps) is, there's something in the Canadian Electrical Code that states that heating loads are to run at no more than 80% of the circuit breaker's rating. Which makes sense, why have a load running at 15 amps on a circuit that's rated for 15 amps? It's to close to the edge. Bill stated a very valid point as well.
Most Respectfully,
Dan P.:)

[billh]

... The reason you don't see many appliances rated at 1800 watts (1800 divided by 120 volts = 15amps) is, there's something in the Canadian Electrical Code that states that heating loads are to run at no more than 80% of the circuit breaker's rating. Which makes sense, why have a load running at 15 amps on a circuit that's rated for 15 amps? It's to close to the edge. Bill stated a very valid point as well.
Most Respectfully,
Dan P.:)

I think the heating load in that context is defined as residential heating as opposed to appliances like toasters but I think it is valid to say that it is running "on the edge" and if a breaker was a bit weak it could trip. Also, if you have a 1800W hairdryer there would be no slack on the circuit for a lamp or light when the dryer is running.

I think the heating (fixed, like base-board and elec furnace) rating aligns with the breaker being rated for only 80% of rating for a load that might be considered continous (>3hrs on) in the link I provided.

[Chris in Saskatoon]

Hello Mike,
I see your saw is rated 230 volts @ 12.5 amps. That's all you need really, size the wire to the full load amps rating of the saw. No. 14 wire is rated for 15 amps. Horsepower as Peter mentioned, has nothing to do with (to a point) with sizing wire for a motor. As long as the wire's current rating matches the FLA of the motor (generally speaking) that's what matters.

Motors have a whole separate section in the code. The conductor is supposed to be sized for 125% of FLA, then the breaker can be oversized to allow for inrush current. The max amount of oversize depends on protection type.

However, on a residential circuit that could be used for general applications (ie a regular receptacle) it is probably safest to not oversize the breaker beyond the rated ampacity of the conductor, otherwise the next owner could run into problems.