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Forum topic by Trout121180 posted 02-14-2018 01:22 AM 1632 views 0 times favorited 67 replies Add to Favorites Watch
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Trout121180

44 posts in 104 days


02-14-2018 01:22 AM

So here’s my problem. I want to start off by saying I know very little about electrical so bear with me. My shop is a 24’x24’ detached garage. When I purchased the house power was already run to it. It has a sub panel with 30amp service. So far I have had zero issues running a 60 gallon compress, 1.75hp saw stop. A 1.5hp jointer. And a 3hp planer. Also with dust collection. Obviously not all at the same time. The problem is I am looking to possibly upgrade to a 5hp planer which requires a 30amp breaker. Also the conduit that is run under ground is only 3/4” conduit. Now my electrician is saying that conduit is too small to run bigger wire out to the garage. Basically he is saying I’m gojng to have to dig a trench and run new conduit all the way out to the garage. Is he right? Does anyone have any suggestions I could pass a long to him. Does everyone agree with him? What is the biggest wire you can run in 3/4” conduit. It’s about a100’ run under ground if that makes any difference. I am figuring at some point whether I get the 5hp planer or not I am going to need more that a 20amp breaker so I might as well do it now before sheetrock goes up in the spring. This is not a cost I was planning on and could really put a dent in my planer fund. We just can’t have that. I would be forever in your debt if someone could come to my rescue with a cost effective solution!!!!!

-- Luke “I thought I was wrong once, but I was mistaken.” “If you wait till the last minute it only takes a minute.”


67 replies so far

View MrUnix's profile (online now)

MrUnix

6705 posts in 2195 days


#1 posted 02-14-2018 01:27 AM

This may help:

Conduit Fill Table

Cheers,
Brad

-- Brad in FL - In Dog I trust... everything else is questionable

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Knockonit

375 posts in 198 days


#2 posted 02-14-2018 01:32 AM

you want to get an electrical company to do the work, problem with running a secondary service is the size of wire, the distance you are running and the size of conduit, it does heat up when pulling lots of power. 100 ft is quite a long run for some wire size, think of it as a long extention cord, so to speak, if you have experience small cords on over 25 ft plus runs, you can tell of the drop in power, and usually will pop a breaker,

My rule of thumb is to figure how much power i’d need if i used everything, then calculate a shade over half,
as you usually don’t use but a third of power at one time, unless you are a huge shop. Being bigger is always better, so if you have to run new secondary power, go big, and don’t look back, there may be some “gotta have, units which could add to load.
good luck
Rj in az

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Trout121180

44 posts in 104 days


#3 posted 02-14-2018 01:37 AM

I saw the table but unfortunately it might as well be in Chinese. also i would never dream of doing this myself. I just want to make sure my electrician isn’t missing anything. Or taking the more expensive route. I mean I trust him but only as much as I would trust any contractor.

-- Luke “I thought I was wrong once, but I was mistaken.” “If you wait till the last minute it only takes a minute.”

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Trout121180

44 posts in 104 days


#4 posted 02-14-2018 01:54 AM

Also being just a one man shop I am never running more than one piece of machinery at a time. All I really need is to be ale to have a 30amp breaker or two. At least for now. And according to him the only thing that is stopping me is the wire run to the garage is too small. So to be more specific my questions are

1. What size wire do I need to run from the main breaker to the sub panel to allow for a 30amp breaker.

2. Is 3/4” conduit big enough to fit that wire.

I understand my electrician will know this but as I stated above just trying to see if anyone can come up with a better idea than his. And by better I mean less expensive.

Maybe down the road I will break down and just pay for 100amp service out there. But for right now I am just hoping to be able to run the 5hp planer. I would love to just do both but i just don’t have the money.

-- Luke “I thought I was wrong once, but I was mistaken.” “If you wait till the last minute it only takes a minute.”

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Hermit

186 posts in 1321 days


#5 posted 02-14-2018 02:10 AM

Check with another electrician but I believe you can go 3 #8s and a #10 ground in 3/4 pipe. Which would allow you to go twin 50amp breakers. That way you could run more than just your 30 amp planer at a time. Otherwise 4-#10’s for 30 amp which is designed to trip at 24 amps. If you’re pulling wire, might as well go 3-#8s with #10 ground and plenty of soap. Secondly, how many bends/90’s do you have? More than 4 and you may have trouble pulling.

-- I'm like the farmer's duck. If it don't rain, I'll walk.

View Rayne's profile

Rayne

860 posts in 1536 days


#6 posted 02-14-2018 02:20 AM



Check with another electrician but I believe you can go 3 #8s and a #10 ground in 3/4 pipe. Which would allow you to go twin 50amp breakers. That way you could run more than just your 30 amp planer at a time. Otherwise 4-#10 s for 30 amp which is designed to trip at 24 amps. If you re pulling wire, might as well go 3-#8s with #10 ground and plenty of soap. Secondly, how many bends/90 s do you have? More than 4 and you may have trouble pulling.

- Hermit

For a 100’ run underground, is that really sufficient? I looked around and it looks like he needs 3-#4’s and a #8 ground at the very least for a twin 60 amp breaker. I’m nowhere near an expert, but I’d be worried if it’s anything under that due to the run. The electrician will definitely be able to tell him. If going with #4’s, the 3/4” conduit is indeed too small.

View Rick's profile

Rick

9593 posts in 3029 days


#7 posted 02-14-2018 02:26 AM

Get a Licensed Electrician to do the work! INSURANCE!!!! If something goes wrong and they find out YOU did the wiring, You’re NOT COVERED!

-- LIFE is what happens when you're planning on doing Other Things!

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Hermit

186 posts in 1321 days


#8 posted 02-14-2018 02:31 AM

I’m no expert but do know he can at least go to a 30 amp in 3/4 pipe. Again, contact another licensed electrician. It costs you nothing.

-- I'm like the farmer's duck. If it don't rain, I'll walk.

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Rayne

860 posts in 1536 days


#9 posted 02-14-2018 02:32 AM



Get a Licensed Electrician to do the work! INSURANCE!!!! If something goes wrong and they find out YOU did the wiring, You re NOT COVERED!

- Rick

He’s not doing it. He just wants second opinions from us to see if his electrician is correct about the 3/4” conduit size being too small; you know, to help from being swindled. .

View Trout121180's profile

Trout121180

44 posts in 104 days


#10 posted 02-14-2018 02:36 AM

The only problem with checking with another electrician is trying to get one out in a reasonable amount of time with out him charging you an arm and a leg. I have used this guy before and have some what of a report with him. I guess I was looking for some miracle answer that doesn’t exist.

Hermit,
I am going to propose what you gave me to him. Thank you for spending the time to break things down for me.

I may just end up biting the bullet and burying new conduit. What a waste. I can’t believe the previous home owner wouldn’t spring for bigger conduit. What a waste. This really put a damper on things. Now it looks like holding off on a planer or not getting what I wanted to get. And since I really had my heart set on it I can’t imagine settling for something else.

-- Luke “I thought I was wrong once, but I was mistaken.” “If you wait till the last minute it only takes a minute.”

View Rayne's profile

Rayne

860 posts in 1536 days


#11 posted 02-14-2018 02:45 AM



The only problem with checking with another electrician is trying to get one out in a reasonable amount of time with out him charging you an arm and a leg. I have used this guy before and have some what of a report with him. I guess I was looking for some miracle answer that doesn’t exist.

Hermit,
I am going to propose what you gave me to him. Thank you for spending the time to break things down for me.

I may just end up biting the bullet and burying new conduit. What a waste. I can’t believe the previous home owner wouldn’t spring for bigger conduit. What a waste. This really put a damper on things. Now it looks like holding off on a planer or not getting what I wanted to get. And since I really had my heart set on it I can’t imagine settling for something else.

- Trout121180

Maybe you could reduce the cost of the new conduit install if you rent a small excavator and dig the trench yourself. Maybe get the details from your electrician to see what you could do to reduce it. I can’t imagine it costing too much more for running the conduit if the ends are easy to access and reroute it to the new one. (well, that’s what I would do if I was in your position).

View JBrow's profile

JBrow

1354 posts in 916 days


#12 posted 02-14-2018 02:56 AM

Trout121180,

It may be worth a phone call to your county/city electrical inspector. They should be able to tell you what upgrade can be achieved without replacing the ¾” conduit.

Since I am not an electrician, I could well be wrong, but is seems that #6 copper conductors can handle 50 amps up to a distance of 115 feet. From Mr. Unix’s table, it looks like # 6 may be allowed in ¾” pipe. But, as Hermit points out, pulling those conductors 100’ in ¾” pipe may be impractical.

Another option if trenching is required may be direct buried service entrance cable. However I am not knowledgeable of current code or rules in your area. If allowed, it may save some money. From what I recall, it requires no conduit and aluminum direct buried cable may be cheaper than copper conductors. However, the new trench may need to be deeper, adding to labor costs.

View WhyMe's profile (online now)

WhyMe

1013 posts in 1557 days


#13 posted 02-14-2018 03:11 AM

3/4” conduit can handle four #6 Cu THHN/THWN. Run three #6 and one #10. This can be fed by up to a 70A breaker. A 100ft is of no issue.

View msinc's profile

msinc

382 posts in 500 days


#14 posted 02-14-2018 03:42 AM


Check with another electrician but I believe you can go 3 #8s and a #10 ground in 3/4 pipe. Which would allow you to go twin 50amp breakers. That way you could run more than just your 30 amp planer at a time. Otherwise 4-#10 s for 30 amp which is designed to trip at 24 amps. If you re pulling wire, might as well go 3-#8s with #10 ground and plenty of soap. Secondly, how many bends/90 s do you have? More than 4 and you may have trouble pulling.

- Hermit

For a 100 run underground, is that really sufficient? I looked around and it looks like he needs 3-#4 s and a #8 ground at the very least for a twin 60 amp breaker. I m nowhere near an expert, but I d be worried if it s anything under that due to the run. The electrician will definitely be able to tell him. If going with #4 s, the 3/4” conduit is indeed too small.

- Rayne

You are correct sir, it is not enough. For a 100 ft run he should have #4 wire {minimum} and he could use a 50 amp breaker for a main in the sub panel. Then he would have whatever various breakers less than 50 he needs. That voltage drop is what will get you…the very first thing to look at is how many volts he currently has in the main panel he intends to feed from. I just had separate 200 amp service ran to what is going to be my new shop. It was 125 feet away. You get to a point where the run is too long to simply sub feed. I get that nobody wants to spend the money for another service, but it really is the best way to go when you get a run that is over 50 feet or so.
Zero chance that 3/4 conduit is going to do much good.

View B4B's profile

B4B

162 posts in 1354 days


#15 posted 02-14-2018 03:47 AM

Without knowing your workflow, I’ll say this.

If you are upgrading your sub panel, go worth a 100amp service, at a minimum.

That’s either 1/0 aluminum, or #1 copper. That will keep voltage drop under 3% for the entire run (150 feet from panel to panel).

That most definitely means a larger conduit.

At this size, 1/0 aluminum is perfectly safe, most feeders for your utility drop to your panel are aluminum.

Option two is to stuff the existing conduit to it’s max fill. Just keep in mind if you add a dust collector to your shop, that’ll be at least two pieces of 240v equipment drawwing power at the same time.

-- There's two routers in my vocab, one that moves data and one that removes wood, the latter being more relevant on this forum.

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