Starting Current - Router Forums
Old 03-21-2011, 11:04 AM Thread Starter
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Starting Current

Hi,

I will be buying a Bosch POF 1400 ACE router soon. I want to make sure the electrical circuit that will serve it is sized properly. At 220V the normal operating current will be 6-7 amps. Frequently, these types of machines have a high starting current but this is not mentioned in the manual. This high current, if it exists, could cause a trip if it is not designed for. Any thoughts? Thanks

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Old 03-21-2011, 11:12 AM
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The surge starting current on a non-soft-start motor can be in the range of 150% to almost 200% of the running current. It is, however, quite brief. Here in the U.S., anyway, the surge is over before the typical circuit breaker can react. I have no idea what the electrical standards are there, however.

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Old 03-21-2011, 07:21 PM
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Bob:

When we electrical engineers calculate the needed circuit breaker, a technique is to total the running currents of the loads on that circuit and add 1/4 of highest motor current on the circuit. This usually keeps one out of trouble with nuisance tripping of the circuit breaker.

For example, if you have router with a running current of 7 amps and a dust collector with a running current of 5 amps, the minimum circuit breaker rating is 7 + 5 + (7/4) amps. That's a load of 13.75 amps. So, a 15 amp breaker should be adequate, especially since the total running current is 12 amps, or 80 percent of a 15 amp breaker's rating.

A router with a soft-start takes less current during starting than a router with no soft-start. The calculations just given can still be applied, resulting in a greater margin from nuisance tripping.

Cassandra

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Old 03-21-2011, 08:48 PM
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Hi Cassandra

I have a question for you ,I know you are sharp with this type of stuff. I have a vac. system 2HP (15 amp. pull )on a 20 amp.breaker and the 3 1/4 HP router (15amp) on the same breaker, on 10 ga. copper wire running from the panel to the outlet boxes, I just about always I fire up the Vac.system 1st.but not always and than the router and never pop the breaker, how can that be ?

=========

Quote:
Originally Posted by Cassandra View Post
Bob:

When we electrical engineers calculate the needed circuit breaker, a technique is to total the running currents of the loads on that circuit and add 1/4 of highest motor current on the circuit. This usually keeps one out of trouble with nuisance tripping of the circuit breaker.

For example, if you have router with a running current of 7 amps and a dust collector with a running current of 5 amps, the minimum circuit breaker rating is 7 + 5 + (7/4) amps. That's a load of 13.75 amps. So, a 15 amp breaker should be adequate, especially since the total running current is 12 amps, or 80 percent of a 15 amp breaker's rating.

A router with a soft-start takes less current during starting than a router with no soft-start. The calculations just given can still be applied, resulting in a greater margin from nuisance tripping.

Cassandra

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Find all threads started by bobj3
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Last edited by bobj3; 03-21-2011 at 08:56 PM.
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Old 03-21-2011, 10:30 PM
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Quote:
Originally Posted by bobj3 View Post
Hi Cassandra

I have a question for you ,I know you are sharp with this type of stuff. I have a vac. system 2HP (15 amp. pull )on a 20 amp.breaker and the 3 1/4 HP router (15amp) on the same breaker, on 10 ga. copper wire running from the panel to the outlet boxes, I just about always I fire up the Vac.system 1st.but not always and than the router and never pop the breaker, how can that be ?

=========
Hi Bob:

It all comes down to what the numbers mean. If one throws an ammeter on the line to each piece of equipment, one is likely to see that neither the vacuum nor the router is actually drawing the amperage indicated on the label. Why?

Let's look at that 3-1/4 HP router. Routers tend to be rated in peak power or current. Peak is the operative word here. One would not normally push the router hard enough to sustain the peak current. Peak means one can push the router to this value without damage to the router. However, in most work, one wouldn't achieve peak.

Similarly, the vacuum will draw the 2 HP only under certain conditions. Most of the time, these conditions don't exist and the vacuum draws less power and current.

-----------------

So, let's say you have a 1/4" double-flute spiral bit in the router, and you're proceeding with making a groove in oak, at normal feed speed. What power is being taken? Definitely not the 3-1/4 HP. Probably below 1 HP.

Being the diligent worker, you don't allow the vacuum to struggle against a clogged bag and you empty the vacuum before it fills more than half way. Probably less than 1 HP draw.

Together you have less than 2 HP, which is less than the 20 amp breaker rating.

--------------------------

Another issue is that your router may have a soft-start, which limits the current on start-up. So, it's smart for one to start the vacuum before the router. The vacuum probably has the greater starting current.

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Old 03-21-2011, 10:44 PM
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Hi

Thanks,,I have in the pass played with it by blocking off the hose on the Vac. to make it draw more at full load and push a Big panel bit at full cut and it did not pop the breaker.. just lucky I guess .. thanks

======

Quote:
Originally Posted by Cassandra View Post
Hi Bob:

It all comes down to what the numbers mean. If one throws an ammeter on the line to each piece of equipment, one is likely to see that neither the vacuum nor the router is actually drawing the amperage indicated on the label. Why?

Let's look at that 3-1/4 HP router. Routers tend to be rated in peak power or current. Peak is the operative word here. One would not normally push the router hard enough to sustain the peak current. Peak means one can push the router to this value without damage to the router. However, in most work, one wouldn't achieve peak.

Similarly, the vacuum will draw the 2 HP only under certain conditions. Most of the time, these conditions don't exist and the vacuum draws less power and current.

-----------------

So, let's say you have a 1/4" double-flute spiral bit in the router, and you're proceeding with making a groove in oak, at normal feed speed. What power is being taken? Definitely not the 3-1/4 HP. Probably below 1 HP.

Being the diligent worker, you don't allow the vacuum to struggle against a clogged bag and you empty the vacuum before it fills more than half way. Probably less than 1 HP draw.

Together you have less than 2 HP, which is less than the 20 amp breaker rating.

--------------------------

Another issue is that your router may have a soft-start, which limits the current on start-up. So, it's smart for one to start the vacuum before the router. The vacuum probably has the greater starting current.

"It's fine to disagree with other members as long as you respect their opinions"

Marc Sommerfeld Tools ,Videos

Find all threads started by bobj3
http://www.routerforums.com/search.php?searchid=944097

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Old 03-22-2011, 05:38 AM
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You're welcome, Bob!

Sometimes it's annoying. One might go months using a set-up and nothing happens. Then one day, one does the same thing and the breaker pops. "But I've doing this for months, what happened this time?" Nothing really, just one has been playing too close to the edge and went over this time.

Cassandra

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Last edited by Cassandra; 03-22-2011 at 05:41 AM.
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Old 03-22-2011, 09:39 AM
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Quote:
Originally Posted by Engine44 View Post
Hi,

I will be buying a Bosch POF 1400 ACE router soon. I want to make sure the electrical circuit that will serve it is sized properly. At 220V the normal operating current will be 6-7 amps. Frequently, these types of machines have a high starting current but this is not mentioned in the manual. This high current, if it exists, could cause a trip if it is not designed for. Any thoughts? Thanks
Seeing as I have that exact router, I can safely say you won't have a problem as it has 'soft start'.
As an example, in the basement of my building there is a wall plug that is wired up to the lighting circuit. I have run my router off of it many times without the breaker tripping.
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Old 03-22-2011, 01:59 PM
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Hi Gavin:

It is a good idea to keep power tools off the lighting circuits. If anything goes wrong with the tool and one is working late in the evening, one could easily be left in the dark.

My father's workshop had lights and receptacles on the same circuits. I re-wired the shop, using one circuit for the lights and two circuits for receptacles. No need to worry about a faulty tool leaving us in the dark.

Cassandra

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Old 03-22-2011, 02:20 PM
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I know Cassandra, but at the time I didn't have a choice. The building I live in is quite old and the wiring leaves a lot to be desired. Even some of the plugs in my apartment are on a lighting circuit.
I now have a workshop with proper wiring, even 3 phase, which I have no need for as yet.
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