Upgrading panel to detached garage

[tec508]

Hi all,

My detached shop garage was built before I purchased the house. They laid 2" pipe in the ground and ran what looks like either 6 or 8 gauge wire between the shop and house.

House has a 200A service panel with a 60A breaker for the shop. Shop has a small 6 circuit sub panel with a 60A main breaker.

I'd like to upgrade the shop to 100A if possible to run a larger panel and get some more circuits. I'd also like to do some light welding and run a small mill out there at some point so I don't want to tax the 60A to it's limit.

Can I simply pull 3 guage through the conduit replacing the existing wire, replaced the 60A breaker with a 100A, and drop in a new 100A sub panel?

Am I missing something?

 

[barbedwireleather]

Hi all,



My detached shop garage was built before I purchased the house. They laid 2" pipe in the ground and ran what looks like either 6 or 8 gauge wire between the shop and house.



House has a 200A service panel with a 60A breaker for the shop. Shop has a small 6 circuit sub panel with a 60A main breaker.



I'd like to upgrade the shop to 100A if possible to run a larger panel and get some more circuits. I'd also like to do some light welding and run a small mill out there at some point so I don't want to tax the 60A to it's limit.



Can I simply pull 3 guage through the conduit replacing the existing wire, replaced the 60A breaker with a 100A, and drop in a new 100A sub panel?



Am I missing something?

I don’t see anything missing


Sent from my iPhone using Tapatalk

 

[pattenp]

To make sure you understand, the feeder needs to be 4 wires. So three #3 Cu and one #8 CU or three #1 Al and one #6 Al for 100A. You may want to think about just putting in a 100A main breaker panel and leaving the feeder as 60A for now and see how it goes. If you do find you have a power shortage then pull new feeder wires. If the existing feeding breaker is 60A then the feeder needs to be #6 Cu.

 

[tec508]

To make sure you understand, the feeder needs to be 4 wires. So three #3 Cu and one #8 CU or three #1 Al and one #6 Al for 100A. You may want to think about just putting in a 100A main breaker panel and leaving the feeder as 60A for now and see how it goes. If you do find you have a power shortage then pull new feeder wires. If the existing feeding breaker is 60A then the feeder needs to be #6 Cu.

pattenp,

I do understand. I'm pretty experienced with electrical, I just wanted to make sure I'm not missing something crucial. A lot of time I over think stuff too.

I may pop in a larger sub panel first as you say and see how it goes load wise. I'm preparing to spray foam so I wanted to get all the wiring done before that happened. I'm adding some 220V circuits along my back wall for machines and a welder as well.

The wiring right now is probably 6, I didn't look at the print on it. I was just scoping out the run during the buying process and it looked like either 6 or 8.

 

[Bretny]

100a should fit in 2in conduit. It will be tight and if theres any 90* it wont fit. A sweeping 90 it will be fine. I would try and find out if theres any 90* in the conduit before i did anything.

 

[Norcal]

100a should fit in 2in conduit. It will be tight and if theres any 90* it wont fit. A sweeping 90 it will be fine. I would try and find out if theres any 90* in the conduit before i did anything.

Should fit????????? There will be no problems at all.

 

[tec508]

100a should fit in 2in conduit. It will be tight and if theres any 90* it wont fit. A sweeping 90 it will be fine. I would try and find out if theres any 90* in the conduit before i did anything.

Theres 2 hard 90s at the LBs but I've seen much thicker pulled through 2". Probably worth noting I planned on pulling individual conductors, not a SER cable.

 

[Norcal]

Theres 2 hard 90s at the LBs but I've seen much thicker pulled through 2". Probably worth noting I planned on pulling individual conductors, not a SER cable.

SER is not permitted underground.

 

[dave89iroc]

as long as it's 2" the entire way, and not just the risers, with direct burial in the dirt for the run

 

[tec508]

as long as it's 2" the entire way, and not just the risers, with direct burial in the dirt for the run

Eww, I never even thought of that. I'll stuff my conduit snake down one of the LBs when I get home. That would be awful.

 

[Bretny]

I have 2in for risers to my garage. 2in with DB and a hard 90 can give you some difficulty.

 

[wyliesdiesels]

Dont forget ground rods and isolated neutral bus.

 

[Crazyjake8493]

Lots of good advice here! First thing I'd do is check that the conduit is continuous, as mentioned. Again, you may not need a full 100 amps unless you plan to be running a mill, transformer welder, air compressor, etc. all at the same time. You can install a 100 amp sub panel fed by the 60 amp breaker just to give you more room in the sub panel.

You mentioned light welding, which I would assume would be a 120v MIG or 240v machine, which would require either a 20A or 30A circuit. Even then, that's only at max load and while it's being used. Smaller machines typically have lower duty cycles. I don't have a mill so I can't comment on that, but I've been TIG welding while another friend was running the table saw and my 30 gallon compressor kicked on, as well as 7 light fixtures, with no issue. Even that is rare to have that much going on at once.

LED lights keep the lighting load down, and also figure in what type of heat you use for winter time. If you heat with electric you may want to go to the 100 amp service just because of that.

 

[pattenp]

It the existing individual wires are not direct bury rated then the conduit better go the whole way. I'm assuming the existing feed is individual wires and not a cable such as UF.

 

[ard]

Eww, I never even thought of that. I'll stuff my conduit snake down one of the LBs WITH THE POWER OFF when I get home. That would be awful.

Fixed....

 

[Bert_]

It the existing individual wires are not direct bury rated then the conduit better go the whole way. I'm assuming the existing feed is individual wires and not a cable such as UF.

It SHOULD, but I've seen THHN run right in the dirt at least once. I would think it is done right but never underestimate the hack's that are out there.

 

[75gmck25]

Aluminum 2-2-2-4 MHF will pull through 2" conduit, although its only rated for 90 amps. I was able to pull it through two sweeping 90's underground, up to an LB at each end, then turn 90 degrees at each LB to go into the panel. Since its really 4 conductors weaved together, it makes it easier to bend to make that 90 degree turn at the LB.

Most MHF wiring is wet rated for underground, and in most cases the insulation is also fire rated for inside the dwelling. If it works to do a single pull, you can run it all the way from panel to panel in conduit.

Bruce

 

[sberry]

I seen a lot of stuff ran from 60A, done it myself. I have probably 8 panels fed with 2 alum and 60A breakers. Never ever tripped one. Have wired a couple dozen garages including a couple busy ones, never had a call for a trip, never had to upgrade a breaker.

 

[bczygan]

I seen a lot of stuff ran from 60A, done it myself. I have probably 8 panels fed with 2 alum and 60A breakers. Never ever tripped one. Have wired a couple dozen garages including a couple busy ones, never had a call for a trip, never had to upgrade a breaker.

Awww come on...................He needs a CT cabinet and 400 Amps!

Bill

 

[Bert_]

Awww come on...................He needs a CT cabinet and 400 Amps!

Bill

yup, better make it 480v 3 phase too. Put a few 120/240 step down transformers around the garage.

 

[rburke65]

Stop before you confuse him!

 

[tec508]

Looks like pipe goes all the way. Thinking more, i'll definitely be upgrading the panel. I test some high power amplifiers on my bench so I'd like to be able to plug one of my distros into the shop. Those are using 50A cali style plugs.

Amps are using a bunch of different plugs. Some are 220 at 20A, some 120 but 30A. So passing through the rack mounted distros makes life easier.

I'm adding a dual zone mini-split in the building too. I know it'll be rare for me to tax 60A at one time, but having the ability to flex is good. Adding the wiring before I spray foam it just makes the most sense to me.

 

[sberry]

Something to consider, not everything with a 50 plug uses 50.

 

[tec508]

I decided against individual conductors because my conduit isn't from panel to panel. Is there a 2-2-2-4 copper indoor/outdoor rated cable?

 

[Bert_]

I decided against individual conductors because my conduit isn't from panel to panel. Is there a 2-2-2-4 copper indoor/outdoor rated cable?

Nothing readily available, aluminum rated for direct burial can be had everywhere though.

 

[RCornell]

The biggest problem I have seen is underestimating the future. If you are considering a new panel in the shop, don't short yourself on breaker space. You didn't say what brand panel you have in the house, but you can buy a 200A feed thru breaker and safely and legally feed a second 200A panel in the garage. You will need 4/0 wire for the lines and can use a reduced neutral (#2) along with a #6 ground wire. This way you can install a 200Amp 42 space panel in the garage. Square D QO breakers are switch rated whereas many other brands and the homeline are not.

As I said, capacity is rarely the issue, breaker space is.

 

[Crazyjake8493]

I decided against individual conductors because my conduit isn't from panel to panel. Is there a 2-2-2-4 copper indoor/outdoor rated cable?

If 90 amps is sufficient, you could run 2-2-2-4 AL MHF from panel to panel, but it has to be in conduit indoors. Otherwise, you could transition to 2-2-2-4 SER if you didn’t want conduit indoors.

 

[tec508]

I was hoping to simply upgrade what I had which is 6/3 indoor/outdoor rated cable with something like 2-2-2-4 which would also be indoor/outdoor rated.

What I'm finding is cable like MHF which must be in conduit, direct burial which isn't rated for indoor use, or indoor cable which can't go in the conduit underground.

I gather from this that what I'd like to buy doesn't really exist.

 

[pattenp]

AlumaFlex type MC PVC jacketed cable. $$$. Or Armorlite MC PVC jacketed (copper) $$$$.

 

[tec508]

I hope no one minds that I resurrect my old thread. This took a back burner for a little and now I'm getting ready to order cable and do this.

Can I run this through the conduit underground to replace the 6/3 I have now? I know I'd need to drive a ground anode for the garage because one doesn't exist. Am I missing something else?

https://www.wireandcableyourway.com...und/2-3c-thhn-pvc-tray-cable-with-ground.html

 

[wyliesdiesels]

how long is the run?

at $5/ft thats gonna cost an arm and a leg or 2.

Also, you need 2 ground rods 8' min in the ground spaced 6' min apart

dont forget to isolate the neutral bus

 

[brewchief]

I ran across some tray cable feeding an A/C unit a few years back, IIRC I couldn't find it listed as an acceptable wire for residential use.

For some years tray cable was sold to connect the indoor and outdoor sections of minisplits, for whatever reason that has changed to a jacketed mc type cable.

Verify that you can use it before you buy.

Sent from my SM-G965U using Tapatalk

 

[bergheger3]

Sounds like your on the right path. Good info here posted already.

2" conduit is good for (4) 2/0 with a #4 service ground so you are plenty good to pull (3) #3 and a #8 equipment ground.

My question would be how far are you from breaker to breaker, if over 75 feet you need to look at voltage drop. The 3#3 is good for 90Amps at full load and still maintain a 3% VD. If you wanted a full 100Amps with VD factored in you would need to pull (3)#1 and a #8 ground.

No need for a ground rod as this is not a separately derived system. Actually I would not recommend installing one because if you do you will need to connect the new ground rod to the old existing ground rod or you will have an unequal ground potential.

Also by code you don't need to have a main breaker in the garage panel if you are fed from a breaker in the main panel. It would save you some money to get a MLO panel, run it off the 60A breaker and if you trip the breaker then look at running new wire and replacing the breaker.

my 2 cents

 

[wyliesdiesels]

Sounds like your on the right path. Good info here posted already.

2" conduit is good for (4) 2/0 with a #4 service ground so you are plenty good to pull (3) #3 and a #8 equipment ground.

My question would be how far are you from breaker to breaker, if over 75 feet you need to look at voltage drop. The 3#3 is good for 90Amps at full load and still maintain a 3% VD. If you wanted a full 100Amps with VD factored in you would need to pull (3)#1 and a #8 ground.

How did you come up with this?

I did the calcs and #3 cu @ 100' is only 2% voltage drop.

your numbers are way off.

No need for a ground rod as this is not a separately derived system. Actually I would not recommend installing one because if you do you will need to connect the new ground rod to the old existing ground rod or you will have an unequal ground potential.

2 ground rods are required by code unless one can prove 25 ohms or less resistance to earth.

Also by code you don't need to have a main breaker in the garage panel if you are fed from a breaker in the main panel. It would save you some money to get a MLO panel, run it off the 60A breaker and if you trip the breaker then look at running new wire and replacing the breaker.

my 2 cents

This is incorrect if there are more than 6 handles in the subpanel. Code requires a disconnect.

 

[bergheger3]

This is the engineering rule of practice. There is a fudge factor in there. We use 3% VD which comes out to 90A. Our rule of thumb is anything over 75' we up the wire size.

I agree but they have to bound together. The out building doesn't need a ground rod as the equipment ground will suffice.

I agree with you. But you cannot have an automatic breaker feeding an automatic breaker, they will fight each other and is not a good practice. If you do this you should use a non automatic breaker for the main in the sub panel.

 

[mm08822]

This is the engineering rule of practice. There is a fudge factor in there. We use 3% VD which comes out to 90A. Our rule of thumb is anything over 75' we up the wire size.

I agree but they have to bound together. The out building doesn't need a ground rod as the equipment ground will suffice.

I agree with you. But you cannot have an automatic breaker feeding an automatic breaker, they will fight each other and is not a good practice. If you do this you should use a non automatic breaker for the main in the sub panel.

I’m all for upsizing for proper voltage levels delivered. While it may be your practice to upsize >75’, I would not say 75’ is a magic trigger point. In this case 150’ distance is where 3% VD occurs assuming OP ever gets to 100A actual load. (135’ @90a for AL.)

Detached buildings require a grounding electrode system in addition to the equipment grounding conductor run with the feeder. The use of two 8’ grd rods spaced >=6’ apart eliminates the need for testing to verify if <=25 ohms or less to ground.

While a single disconnect would suffice to meet the <=6 throws of hand disconnect rule, it is a much simpler and cleaner installation to provide a panel with a factory installed main cb. A cb at the sub panel can be of any value as its purpose is only for disconnecting means. When the sub panel cb is the same value as the feeder protective ocd, then there might be some coordination issues, but I would expect it rare at best due to not reaching full load and each cb has mfg tolerances. This is not a multifunction facility where unnecessary cb trips have downtime costs.

A 200a cb in the sub panel and 100a cb in main panel would not cause any issue.

 

[grounded-b]

This is the engineering rule of practice. There is a fudge factor in there. We use 3% VD which comes out to 90A. Our rule of thumb is anything over 75' we up the wire size.

Good practice but not required.

I agree but they have to bound together. The out building doesn't need a ground rod as the equipment ground will suffice.

WRONG. All remote buildings need an equipment ground conductor AND made ground electrodes.

I agree with you. But you cannot have an automatic breaker feeding an automatic breaker, they will fight each other and is not a good practice. If you do this you should use a non automatic breaker for the main in the sub panel.

FIGHT each other? You most certainly can have an "automatic (your words)" breaker feeding another "automatic" breaker. Done all the time. they will NOT "fight" each other. Which one will trip during a fault is unknown, if they are equal ratings. If it's not an "automatic" breaker, we call it a "switch"

Steve

 

[tec508]

Thanks for the responses guys. Everything I'm finding says TC-ER is fine for this purpose.

The cable I'm looking at is 3x #2s, 1x #6. Run is just over 100ft panel to panel. I see this as proper for 100A. Am I wrong?

Price of the wire is steep but I havent found anything cheaper to accomplish this. Definitely taking suggestions. I cant fit AL through the pipe at a size that can do 100A.

 

[75gmck25]

2-2-2-4 AL is rated at 90 amps, and readily available at a good price in either MHF or SER. Do you really need that additional 10 amps? You can use a 100 amp sub-panel and a 90 amp breaker in the main panel.

I ran 2-2-2-4 AL SER inside the house and then transitioned to 2-2-2-4 AL MHF and buried conduit for the run to the garage. I had to use a large junction box and some relatively expensive wire connectors (Polaris?) to make the connections, but other than that it was relatively simple.

Bruce

 

[Bert_]

Price of the wire is steep but I havent found anything cheaper to accomplish this. Definitely taking suggestions. I cant fit AL through the pipe at a size that can do 100A.

I thought you had 2" pipe? You could pull 4/0 through pipe that size if you needed to, 2/0 or less will fit easily. Need #1 Al for 100a. That will fly into 2 inch pipe.