wyliesdiesels
Well-known member
Max ocpd for #4 is 85a not 70a. But i would use #2 al MHF. It will be cheaper and have more ampacity.
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Running a sub panel to the garage/shop
- Thread starter Don1357
- Start date
Max ocpd for #4 is 85a not 70a. But i would use #2 al MHF. It will be cheaper and have more ampacity.
Max ocpd for #4 is 85a not 70a. But i would use #2 al MHF. It will be cheaper and have more ampacity.
I ended up settling for 2-2-2-4 URD ran from the meter box to its own breaker box. The electrician that will do the actual connection said that run from the meter box it can be used at its full 100amp capacity, as opposed to down rated to 90amps when run off a main breaker box. I found a Square D 24 slot 100-amp main breaker panel on sale at Lowes that I'm using.
wyliesdiesels
Well-known member
I ended up settling for 2-2-2-4 URD ran from the meter box to its own breaker box. The electrician that will do the actual connection said that run from the meter box it can be used at its full 100amp capacity, as opposed to down rated to 90amps when run off a main breaker box. I found a Square D 24 slot 100-amp main breaker panel on sale at Lowes that I'm using.
URD is not permitted to go inside the structure and when used as a feeder, it must be breakered at 90a.
The electrician is wrong.
It can be breakered at 100a only when it feeds the entire load of a dwelling.
Also, not a good idea to run unfused wire on the property like you did straight off the meter. You have no protection on it. The cutouts on the transformer will not open upon a short or fault on that line. So you will have thousands of amps flowing throw it upon a fault
mike93lx
ALLIANCE MEMBER
Sweet baby Jesus! $72 for 50 feet of 10/2 wire... On top of that the only plug they had in 30amp/240v was the turnlock so that was $20 for the plug and $20 for the outlet...
What does the SPL means?
Special
It means the HP rating they list is ********
URD is not permitted to go inside the structure and when used as a feeder, it must be breakered at 90a.
The electrician is wrong.
It can be breakered at 100a only when it feeds the entire load of a dwelling.
Also, not a good idea to run unfused wire on the property like you did straight off the meter. You have no protection on it. The cutouts on the transformer will not open upon a short or fault on that line. So you will have thousands of amps flowing throw it upon a fault
I think it is meant to split right after the house 200 amp outside breaker, and go straight into the detached garage breaker panel.
I'll ask him about it but the way I see it if that wall catches fire it makes zero difference whether the cable is terminated on the inside or outside of the wall, the end result would be the same.
JeepJohn62
Well-known member
My 2 cents. Install a larger wire for 100A service. You may not use the rated ampacity, but the voltage drop will be less and your equipment will be happier. The extra one time cost will make your trenching and installation more worthwhile.
Sent from my SM-A102U using The Garage Journal mobile app
Sent from my SM-A102U using The Garage Journal mobile app
JeepJohn62
Well-known member
The main electrical service panel is configured to bond the neutral to ground. Look closely at the panels and you will notice a special screw or plate for this. When you run a feeder panel, the 4 wire run includes a ground. You do not bond the ground to neutral at the feeder. The intention is to have one bond at the main panel. This prevents odd current loops in the system.That question was not about the sub panel but about circuit wiring. How some 240 circuits require the extra wire and how while I can't think of anything I'll be running needing it, whether it makes sense to wire with the extra cable just in case. Again, extra cable meaning to the outlets.
Exception. If you are running a longer cable , such as a detached garage, for 100 feet or longer. Run a 3 wire to a feeder panel. But you must establish a separate earth ground at the new panel in the garage. Ground rods, bare copper, etc... Then you bond ground and neutral here for a separate ground system.
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JeepJohn62
Well-known member
Sounds like your electrician is on the right path. I'm sure he will connect to a protected point at the main panel or service.I think it is meant to split right after the house 200 amp outside breaker, and go straight into the detached garage breaker panel.
I'll ask him about it but the way I see it if that wall catches fire it makes zero difference whether the cable is terminated on the inside or outside of the wall, the end result would be the same.
Sent from my SM-A102U using The Garage Journal mobile app
My 2 cents. Install a larger wire for 100A service. You may not use the rated ampacity, but the voltage drop will be less and your equipment will be happier. The extra one time cost will make your trenching and installation more worthwhile.
Sent from my SM-A102U using The Garage Journal mobile app
The distance itself is 35 feet from meter to new breaker box so the drop would be negligible. Maximum load on the system at any one time should not top 60~65 amps (lights on, air compressor went off while planning a board with the dust collector running) so I figure a hundred amps is just to have excess capacity and get the extra circuits that come with the larger box.
pattenp
Well-known member
The main electrical service panel is configured to bond the neutral to ground. Look closely at the panels and you will notice a special screw or plate for this. When you run a feeder panel, the 4 wire run includes a ground. You do not bond the ground to neutral at the feeder. The intention is to have one bond at the main panel. This prevents odd current loops in the system.
Exception. If you are running a longer cable , such as a detached garage, for 100 feet or longer. Run a 3 wire to a feeder panel. But you must establish a separate earth ground at the new panel in the garage. Ground rods, bare copper, etc... Then you bond ground and neutral here for a separate ground system.
Sent from my SM-A102U using The Garage Journal mobile app
Your exception is incorrect. Any branch feeder from a main service panel after the first main disconnect serving a detached structure is to be a four wire feeder with the neutral being isolated at the detached structure. Distance has nothing to do with it. Any detached structure is to have its own earth grounding electrode system when fed power from a primary structure. The grounding conductor that runs with the feed is the equipment grounding conductor and is for clearing fault current to trip breakers. The earth grounding system is to divert lighting strikes.
wyliesdiesels
Well-known member
I think it is meant to split right after the house 200 amp outside breaker, and go straight into the detached garage breaker panel.
I'll ask him about it but the way I see it if that wall catches fire it makes zero difference whether the cable is terminated on the inside or outside of the wall, the end result would be the same.
200a breaker is too big for #2 AL....
200a breaker is too big for #2 AL....
But not for the thousands of amps you mentioned on your scenario. Anything between 101 and 200 amps can be tripped by the garage breaker.
I'll double check with the electrician to make sure. This is why I wanted to subcontract this part, so I could have a sanity check on the setup.
mike93lx
ALLIANCE MEMBER
But not for the thousands of amps you mentioned on your scenario. Anything between 101 and 200 amps can be tripped by the garage breaker.
I'll double check with the electrician to make sure. This is why I wanted to subcontract this part, so I could have a sanity check on the setup.
Either trust him or the electricians here. You can't have both, apparently
JeepJohn62
Well-known member
Ok thanks for the info. Do you tie the grounds together at the detached structure?Your exception is incorrect. Any branch feeder from a main service panel after the first main disconnect serving a detached structure is to be a four wire feeder with the neutral being isolated at the detached structure. Distance has nothing to do with it. Any detached structure is to have its own earth grounding electrode system when fed power from a primary structure. The grounding conductor that runs with the feed is the equipment grounding conductor and is for clearing fault current to trip breakers. The earth grounding system is to divert lighting strikes.
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wyliesdiesels
Well-known member
But not for the thousands of amps you mentioned on your scenario. Anything between 101 and 200 amps can be tripped by the garage breaker.
I'll double check with the electrician to make sure. This is why I wanted to subcontract this part, so I could have a sanity check on the setup.
Incorrect. This is why the wire should be fused.
Even if youll have a main disconnect in the garage, it will NOT trip upon a short or ground fault on the line side of the breaker.... so your logic is not correct.
wyliesdiesels
Well-known member
Ok thanks for the info. Do you tie the grounds together at the detached structure?
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Tie what grounds together? The EGC and the GEC from the rods? Yes. All grounds land on the same bar. The key in a subpanel si that the neutral is isolated.
Incorrect. This is why the wire should be fused.
Even if youll have a main disconnect in the garage, it will NOT trip upon a short or ground fault on the line side of the breaker.... so your logic is not correct.
Trying to learn here...
So what's protecting the current setup right now?
Incorrect. This is why the wire should be fused.
Even if youll have a main disconnect in the garage, it will NOT trip upon a short or ground fault on the line side of the breaker.... so your logic is not correct.
I just checked again and besides the outside disconnect breaker and the inside main breaker there isn't anything on my house service. Should something be there?
JeepJohn62
Well-known member
I'll have to review my NEC or Mike Holt codebook. I thought there was an option for 3 wire sub panel service with a separate ground rod system. In this case, you bond the neutral at the panel. I could be wrong.Tie what grounds together? The EGC and the GEC from the rods? Yes. All grounds land on the same bar. The key in a subpanel si that the neutral is isolated.
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wyliesdiesels
Well-known member
I just checked again and besides the outside disconnect breaker and the inside main breaker there isn't anything on my house service. Should something be there?
dont quite understand your question....
I'll have to review my NEC or Mike Holt codebook. I thought there was an option for 3 wire sub panel service with a separate ground rod system. In this case, you bond the neutral at the panel. I could be wrong.
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youre a bit outdated. that has not been allowed since 2008... all subpanels are now required to be 4-wire with isolated neutral and 2 ground rods. BTW ground rods are not the same thing as a low impedance fault current pathway aka equipment grounding conductor
dont quite understand your question....
When you say this:
Incorrect. This is why the wire should be fused.
Even if youll have a main disconnect in the garage, it will NOT trip upon a short or ground fault on the line side of the breaker.... so your logic is not correct.
I ask: what is stopping this from happening on what is there already going to the house?
rayra
Well-known member
Planning for minimums re electricity is planning to fail. Go larger capacity, slots, ESPECIALLY if you can't imagine any reason to do so. Future-proof it. Go up in amp and circuit/fuse capacity.
Planning for minimums re electricity is planning to fail. Go larger capacity, slots, ESPECIALLY if you can't imagine any reason to do so. Future-proof it. Go up in amp and circuit/fuse capacity.
I did that already. I don't see me using more than 65 amps at a time, I'm doing 100 amp panel. I need about 17 breaker slots, I got a 24 slot box.