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Forum topic by Plain posted 06-30-2016 06:39 PM 649 views 0 times favorited 15 replies Add to Favorites Watch
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Plain

157 posts in 166 days


06-30-2016 06:39 PM

I had a 2HP table saw and 2HP Harbor Freight dust collector. Both 110V. Unfortunately only 15A outlets in the garage. The table saw never gave me problems, however the dust collector would pop up the breakers 1 times out of 3, maybe because the impeller is much heavier than a saw blade so motor has to work harder on start.
I’ve been postponing the circuit upgrade for a while because I did not want to mess with the permits.

Now a new 3HP 220V/13A saw is on the way so I have no choice but to upgrade the wiring. I have one empty slot in the breaker panel and all smaller breakers are doubled, so no choice but to install a subpanel. Of course I would like to use all 120A the subpanel I bought is designed for but the convoluted city permit process makes me pay twice more of already hefty fee if I have a circuit over 45A.
So I plan to feed the subpanel via a 45A breaker. The panel will only serve ( for now) the table saw 220A 13A and the dust collector 110V 20A). I am not going to be starting both machines simultaneously, but still is 45A is enough for this ?


15 replies so far

View joey502's profile

joey502

487 posts in 985 days


#1 posted 06-30-2016 06:53 PM

It will be enough. 13 a saw plus 20 a DC= 33 amp. 80% of you 45 amp main would be 36 amps.

The problem with the dc tripping the 15 amp breaker before is because the start up draw is much higher than the running draw. The same goes for your saw.

Your saw and dc were not on the same 15 amp breaker were they? If so then your problem was an overloaded circuit.

View MikesProjects's profile

MikesProjects

163 posts in 1369 days


#2 posted 06-30-2016 06:54 PM

Use 10 gauge solid core wire or 8 to wire up the outlets., I have both those machines running on a 30a circuit, Sparky wired it up for me & hes licensed. Imo you should be good if you use 10 gauge wire. I used the (romex) southwest orange 10 gauge to wire up my shop, its thicker than the yellow 12 gauge & sure works good.
If you are pulling permits are you also hiring an electrician ? If so the electrician will know better than most.

-- -Mike, Southern California, YouTube User ( Give & Take )

View Rentvent's profile (online now)

Rentvent

148 posts in 316 days


#3 posted 06-30-2016 07:38 PM

Same situation here. I’m in process of running a subpanel to add 220v capability to my garage.

I’ve been using this calculator:

http://www.paigewire.com/pumpWireCalc.aspx?AspxAutoDetectCookieSupport=1

Interesting that if I ran just 1 cable for the 13A 240v saw, I would only need 16GA
but if I were to run just 1 cable for a 15A 120V dc I would need 12 ga.

In my case, I’m rewiring the DC to 240V.

The cost difference between 8 and 10 ga wire is about $20 for a 50 foot run so I’m going with 8GA, but only putting a 30A breaker.

View Plain's profile

Plain

157 posts in 166 days


#4 posted 06-30-2016 08:03 PM


Use 10 gauge solid core wire or 8 to wire up the outlets., I have both those machines running on a 30a circuit, Sparky wired it up for me & hes licensed. Imo you should be good if you use 10 gauge wire. I used the (romex) southwest orange 10 gauge to wire up my shop, its thicker than the yellow 12 gauge & sure works good.
If you are pulling permits are you also hiring an electrician ? If so the electrician will know better than most.
- MikesProjects

I am actually going to use much thicker wire, enough for 100A for later upgrade. It is only 2 ft or so so price-wise it does not matter. It is only the breaker that will be 45A. I will probably going to do it myself, electricians in my area charge more than brain surgeons.

View JBrow's profile

JBrow

819 posts in 387 days


#5 posted 07-01-2016 02:48 AM

Plain,

Since you plan to use a 120A panel and heavy wire, with a 45A breaker, I can foresee the electrical inspector believing that after he leaves, you will swap out the 45A breaker with a 100A breaker and thus have a problem getting that green tag. Therefore, when pulling the permit, discussing your plans with the Chief Inspector could avoid this potential headache. Alternatively, spending the extra permit money now could save money since when you do upgrade the subpanel to 100A, the higher cost permit will then be required.

View Plain's profile

Plain

157 posts in 166 days


#6 posted 07-01-2016 06:31 PM


Plain,

Since you plan to use a 120A panel and heavy wire, with a 45A breaker, I can foresee the electrical inspector believing that after he leaves, you will swap out the 45A breaker with a 100A breaker and thus have a problem getting that green tag. Therefore, when pulling the permit, discussing your plans with the Chief Inspector could avoid this potential headache. Alternatively, spending the extra permit money now could save money since when you do upgrade the subpanel to 100A, the higher cost permit will then be required.

- JBrow


I would argue that the inspector has not legal standing to not allow thicker than needed wire, solely based on his assumption that I can mess with it later without his approval. I would counter it that I would have not pulled a permit if I was not seeking his approval in the first place.
However quick look in the internet suggest that such instances did take place.

The fee schedule here besides administrative fees is the following.
first 5 circuits up to 45A – $135 then $35 for the next 5 circuits.
each 3 circuits 50A-200A – $174

I assume that the feed from the main panel to the subpanel is considered to be a separate circuit in which case it would require additional $174, bringing the price for the permit to $410 in my case. Even though I only need to add one 240V and two 110V outlets.
$174 might not seem like a huge lot but I already spent much more than I planned on the saw so I am trying to trim unneeded expenses.

I might not need to expand in the future and if I need I would have to apply for a new permit anyway so why to pay now?

View WhyMe's profile

WhyMe

617 posts in 1028 days


#7 posted 07-01-2016 10:09 PM


Use 10 gauge solid core wire or 8 to wire up the outlets., I have both those machines running on a 30a circuit, Sparky wired it up for me & hes licensed. Imo you should be good if you use 10 gauge wire. I used the (romex) southwest orange 10 gauge to wire up my shop, its thicker than the yellow 12 gauge & sure works good.
If you are pulling permits are you also hiring an electrician ? If so the electrician will know better than most.

- MikesProjects

This is so wrong to do if you are using 15A/20A duplex outlets on a 30A circuit with the stock cords that came on the equipment. You would need to use 30A plugs and outlets.

View WhyMe's profile

WhyMe

617 posts in 1028 days


#8 posted 07-01-2016 10:36 PM



Same situation here. I m in process of running a subpanel to add 220v capability to my garage.

I ve been using this calculator:

http://www.paigewire.com/pumpWireCalc.aspx?AspxAutoDetectCookieSupport=1

Interesting that if I ran just 1 cable for the 13A 240v saw, I would only need 16GA
but if I were to run just 1 cable for a 15A 120V dc I would need 12 ga.

In my case, I m rewiring the DC to 240V.

The cost difference between 8 and 10 ga wire is about $20 for a 50 foot run so I m going with 8GA, but only putting a 30A breaker.

- Rentvent

That’s a piss poor calculator. 16GA is wrong for 13A @ 240V. The wire size needed is #12 to meet NEC. This calculator is much more accurate. http://www.electrician2.com/calculators/wireocpd_ver_1.html

View TheFridge's profile

TheFridge

5765 posts in 953 days


#9 posted 07-01-2016 11:05 PM

Size your wire up and your breaker down. If the inspector has a problem Ask him what the code violation is. If he still had a problem then bring it up with his supervisor.

-- Shooting down the walls of heartache. Bang bang. I am. The warrior.

View mrg's profile

mrg

659 posts in 2467 days


#10 posted 07-02-2016 12:18 PM

Wouldn’t it be more cost effective to just upgrade your service?. I payed 1800 for a 200 amp service. Split some circuits so if I killed a breaker it wouldn’t kill 2 rooms. Have more slots for future needs. That price included everything. Glad I did that when I did for the shop because 2 years later I did a kitchen remodel and needed 2 more circuits to be run for lights etc.

-- mrg

View EEngineer's profile

EEngineer

1061 posts in 3081 days


#11 posted 07-02-2016 02:16 PM

Ah, there is so much misinformation here…
The recommended wire sizes represent a minimum wire thickness for specified current. Larger wire sizes are allowed and should not be a reason to deny permit.
Any calculator that you use that says you can use 16AWG for a 13A circuit is useless! Quit using it!
14 AWG is the minimum allowed => 15A
12 AWG => 20A
10 AWG => 30A
Yes, motor circuits should be sized to 80% of rated breaker trip.
Find out what year NEC your area bases its code on and get a copy. Pay attention to subpanel grounding and sizing requirements. They have an entire chapter on garage wiring and there are many other things you need to be aware of if you want to meet code.
I put a subpanel in and rewired my garage shop a few years ago.

-- "Find out what you cannot do and then go do it!"

View WhyMe's profile

WhyMe

617 posts in 1028 days


#12 posted 07-02-2016 03:30 PM



Ah, there is so much misinformation here…
The recommended wire sizes represent a minimum wire thickness for specified current. Larger wire sizes are allowed and should not be a reason to deny permit.
Any calculator that you use that says you can use 16AWG for a 13A circuit is useless! Quit using it!
14 AWG is the minimum allowed => 15A
12 AWG => 20A
10 AWG => 30A Yes, motor circuits should be sized to 80% of rated breaker trip. Find out what year NEC your area bases its code on and get a copy. Pay attention to subpanel grounding and sizing requirements. They have an entire chapter on garage wiring and there are many other things you need to be aware of if you want to meet code.
I put a subpanel in and rewired my garage shop a few years ago.

- EEngineer

Conductors are to be sized at 125% of motor amp rating based on the NEC HP/Amp table. Breaker size can be up to 250% of amp rating to handle startup load. Breaker serves as short circuit protection, overload protection should be at/on the motor. Speaking of misinformation, your 80% comment in its current context is not correct. Circuits are to be sized at 125% for continuous loads so that makes the load amount to be 80%, not the circuit size to be 80%.

View EEngineer's profile

EEngineer

1061 posts in 3081 days


#13 posted 07-03-2016 01:53 AM

Sorry – yes, that was phrased poorly. WhyMe has it right!

-- "Find out what you cannot do and then go do it!"

View daddywoofdawg's profile

daddywoofdawg

1010 posts in 1042 days


#14 posted 07-03-2016 04:22 AM

Why not just get a bigger panel and add 220/240V to it?seems you could save $410.

View WhyMe's profile

WhyMe

617 posts in 1028 days


#15 posted 07-03-2016 01:10 PM

A side note to what I said earlier about upsizing a breaker as much as 250% to handle motor startup loads. That only applies to dedicated hardwired motor circuits. If you have a general purpose multi-outlet circuit with plug connected tools such as a table saw and a dust collector on the same circuit and the breaker trips intermittingly you are not to increase the breaker size without increasing the circuit conductor size to match.

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