Super basic question- if I'm planning a sub panel for in the garage how do I know if my main can handle it?

[iadr]

So... when the ground is unfrozen, I plan to trench to the garage.
Right now, I have 15amps, total, in my 1952 22x23. that is: 1 x 15a 120v And that's on an arc fault breaker that is kind of trippy.

I want 50amps. Actually watts would make more sense to rate panels by, no? Watts = heat, right and I feel "heat/load" must have some relvence to the max a panel can take? I bring this up because 2 of the new circuits would be 240V.

I **** at electrical as its terminology is, more than most trades, super specific, and because my Dad who I didn't have a great relationship with in the 2nd half of his life, was an electrician, so I had less reason to learn. Might argue less opportunity, too, though that's b/c of the relationship, and could certainly be put "on me".

Anyway, the 240V circuits I am thinking of would be each ~25-30a@240v, namely supplemental heating/weld /possible electric car charger for future, as I hope to be in this house 20+y...and seems wise to future proof.

I have a brand new 150a panel and feed from municipal, in the house. Just passed inspection last fall after a full to the studs/redo the floor plan/redo all utilities gut and remodel, so thankfully, not dealing with old/inadequate stuff

House is 2100 Sq feet fully developed with 5 bedrooms (2 in rental suite.. so potentially 5- 6, even 7+ persons living here). Gas water heater. 2 stoves, electric clothes dryer.

There are 4 empty slots on the panel, which is great.

In the garage, if I utilize 2 of 3 of those new 240V options at any one time, I'm at 50-60amps- plus lighting @ ~8-10a, plus a 15a tool or vaccum. Welding would be only light-moderate automotive and homeowner stuff, so probably lowest of the three. Should I plan for more than 60Amp capable?

Aside from actually triggering the main panel breaker, is there a code question raised in devoting 60 or say even 75 amps out to the new garage subpanel? Esp considering that a lot of it is 240V (more watts)?

Properly made connections to the buss in the panel should produce no heat, but I'm trying to understand what I might run into in forming a by Code Maximum when asking for this, this summer.

I can see sub panels that would appear to work fine for the garage for just $117cdn at Home Depot.
#6 Aluminum was suggested as what I'd need to run. 38-40 ft of it in 3/4" non metallic tubing in a 22 inch down trench? Odds are good I have some detail wrong there.
I may have someone that will work with me and let me do the grunt work and parts purchasing, but I don't fully trust him... not 100% sure he's ticketed. Neighbor found him for me after I had a couple electricians bail on their appointments with me for something else- we're talking bailed out over half a dozen times, same day or without even a call, over over 8 weeks each. Seems just nuts to get someone locally at any price.

 

[billconner]

I assume not electric heat in house so probably fine at 150 in house but I think you want more than 50 in garage - for a future EV charger. I'm going with 90 amp for pipe and wire size. I won't do much work but could have 2 cars on chargers someday.

 

[Zeke]

Nothing to add per your request for info. But I will say go for it DIY. You can get all the help you need here and on other forums. You will probably hear that 60 amps is normally adequate for a one man shop. I hope your laundry isn't out there. And people will say that you can/should charge the car at night, late at night so you're not welding and heating as well.

 

[dave*99]

You probably can do 90A and meet your need to future proof.

You are in Canada - some advice from the US guys will apply, some will not, you need to keep an eye on that.

Some folks will recommend mobile home feeder for this application.
In any case you will need 4 conductors.

Your main panel should be able to supply this load. The way to check is look at the labels in the main panel and find the max allowable branch circuit size. If it's 90A or greater (it should be) then you are fine.

 

[wyliesdiesels]

60a would be fine for what you want EXCEPT for the EV charger which could use 50a or more. If you want an EV charger along with a welder and electric heat, I'd do at least 100a.

 

[iadr]

Doing some research as the posts have been coming in here. I'll quote some and comment, but have a link and a thought I want to post in.
Sounds like 4 ga in 1 inch would be minimum for even 60:

Wire Size For 60 Amp Breaker: Which AWG Wire To Use? (NEC CODE)

Correct wire sizing is very important. Especially safety-wise. One of the most common questions we get about wiring is ‘what is the wire size for a 60 amp breaker?’. A lot of homeowners make this very common mistake: They use 6 AWG wire for a 60 amp breaker because 6 AWG gauge wire has 65A ...

learnmetrics.com

So 60amps divide out the .80 safety allowance and I am at 75, and do the 10 percent for going 50 ft (including verticals, thats safe, probably) and I'm at 82.5, or 83.333 on an 85amp rated wire.
Which will need 1".
If I understand correctly, code requires me to completely disable the 15a 115v feed? Can someone comment on that?

 

[dave*99]

If I understand correctly, code requires me to completely disable the 15a 115v feed? Can someone comment on that?

Code questions are answered best by your local AHJ.
For example, currently in my jurisdiction, I would be required to have only 1 feed to a detached garage. But in some newer codes, it is permitted.

 

[dave*99]

Doing some research as the posts have been coming in here. I'll quote some and comment, but have a link and a thought I want to post in.
Sounds like 4 ga in 1 inch would be minimum for even 60:

Wire Size For 60 Amp Breaker: Which AWG Wire To Use? (NEC CODE)

Correct wire sizing is very important. Especially safety-wise. One of the most common questions we get about wiring is ‘what is the wire size for a 60 amp breaker?’. A lot of homeowners make this very common mistake: They use 6 AWG wire for a 60 amp breaker because 6 AWG gauge wire has 65A ...

learnmetrics.com

This link is jibberish.

Listen to Wylie, he does this stuff every day.

 

[Zeke]

In the U.S. two feeds to a detached building are not allowed. But there is an exception for certain emergency equipment. You probably won't get that far. One feed.

I plan on using my old conduit for CAT 5.

 

[iadr]

I assume not electric heat in house so probably fine at 150 in house but I think you want more than 50 in garage - for a future EV charger. I'm going with 90 amp for pipe and wire size. I won't do much work but could have 2 cars on chargers someday.

Yes, nat gas heat.
Well.. I'm somewhere between late adopter and total crank. I don't have a cell phone, never bought a music CD. Never owned a TV.
I've made a lifetime of being last to adopt new stuff. So the perceived need is .. idk resale of the house (which I hope is unlikely) and a bit of covering my bases. I'd think chances of my ever having two cars on plug would round to zero. Single and do not have more than one daily driver veh, and odds of it staying gas powered for the 20 years I'll be driving, maybe 25, remain close to 50/50.
IMO, you can spend a lot of money trying to guess the future.
An aspect of my approach to future proofing is being kind of stuck on not using direct burial cable, and running an oversize conduit.

Nothing to add per your request for info. But I will say go for it DIY. You can get all the help you need here and on other forums. You will probably hear that 60 amps is normally adequate for a one man shop. I hope your laundry isn't out there. And people will say that you can/should charge the car at night, late at night so you're not welding and heating as well.

Ha, well I don't lack for length on my posts. Tried to get everything in there.
Yes, I believe that my use-case is: this OR that. But you can't have hardwired 3 30amp plugs and have them fed off a 60amp panel or off a 60amp/85amp-rated cable.
So at some point it comes down to a case of having terminated the cables on my three high load devices to the same 240v/30amp plug style (is that NEMA?), and having only one, or two at most wall outlets of that type. I can 100% accept two, and comfortably make do with one as I see it.

You probably can do 90A and meet your need to future proof.

You are in Canada - some advice from the US guys will apply, some will not, you need to keep an eye on that.

Some folks will recommend mobile home feeder for this application.
In any case you will need 4 conductors.

Your main panel should be able to supply this load. The way to check is look at the labels in the main panel and find the max allowable branch circuit size. If it's 90A or greater (it should be) then you are fine.

Well oddly one of the things that does seem to be different in Canada is that mobile home feeder simply doesn't exist. Neither does 3/8" gas pipe, but that's another story.

So, I've gone over to the panel. There's nothing visible. I take off the cover?
It's one of these: https://new.siemens.com/ca/en/products/energy/low-voltage/components/loadcentres.html 30 breakers, 15 in 2 columns, plus the main ones up top.
For that matter what is the difference between lug load center and breaker load center? Two tabs there...

60a would be fine for what you want EXCEPT for the EV charger which could use 50a or more. If you want an EV charger along with a welder and electric heat, I'd do at least 100a.

I accept your point, but see my above background statements. I actually wanted to re-sort the quotes so the two EV-specific ones were together and I answered them together, but don't see the software allowing me to do that.

 

[dcg9381]

60a would be fine for what you want EXCEPT for the EV charger which could use 50a or more. If you want an EV charger along with a welder and electric heat, I'd do at least 100a.

Having just bought two EVSE's what I'm finding is that almost all are going to peak out at 48A continuous. And I think I've only seen that peak once. Most are under. The charger that came with our Ford is 40A. Actual demand draw has been 70% of that at peak.

You can set the charge rate on a Tesla (on the car) - that's a Telsa feature. Other brands, you'll depend on the EVSE (charger) being configurable - many of them are. 28A @ 240V is a lot of power over 10 hours or so.. I can charge at 120V @ 12A if I know the EV is going to sit for a while.

Can your main panel handle it? The electrician answer to that will be to do a "load calculation". Or many generator company websites can estimate it for you. I don't like that answer. For under $100, stick a monitor in your main panel and actually figure out what your peaks are.

This is an emporiaenergy monitor, under $100. Took me about 15 minutes to install on my 320A service. I've done the load calcs, if I factor in the shop and other things, it's gonna tell me I need 400A service. The reality is we don't use near that much power.



If you've got solar, you'll see cool things like this:

 

[dave*99]

So, I've gone over to the panel. There's nothing visible. I take off the cover?
It's one of these: https://new.siemens.com/ca/en/products/energy/low-voltage/components/loadcentres.html 30 breakers, 15 in 2 columns, plus the main ones up top.
For that matter what is the difference between lug load center and breaker load center? Two tabs there...

The sticker will be on the inside of the door or inside the panel.

A breaker load center has a main breaker. A lug load center just has lugs to accept the incoming power.

I would use a breaker load center for your detached garage. The breaker in your house main panel then determines the ampacity of the sub panel and the main breaker in the sub panel serves as a convenient local disconnect.

 

[Zeke]

Sure, you're not supposed to have breaker values that add up to more than 120% of the main, or in the case of a sub, the feeder breaker. But that's what the main is there for. If you get inspection and then want 3) 30 A circuits, why not?

OK, I'm ducking for cover now.

 

[billconner]

I believe the 80% derating applies only to continuous loads, not the panel nor many of the receptacles. For instance, your plug in welder would not be a factor - not continuous (3 hour). EV chargers would be I believe. Most lighting is.

And pretty sure you can have as many 30 amp receptacles as you want on as many 30 amp breakers as you want.

IMO, you can spend a lot of money trying to guess the future.

I agree but you croak and your heirs have to sell it, just not that much more to up from 50 to 90. (I pick 90 because that's what I'm doing - no. 2 - iirc - in 1" rigid conduit.) But close call - and I wouldn't criticize at all if you stick with 50 amp.

 

[Norcal]

Sure, you're not supposed to have breaker values that add up to more than 120% of the main, or in the case of a sub, the feeder breaker. But that's what the main is there for. If you get inspection and then want 3) 30 A circuits, why not?

OK, I'm ducking for cover now.

Huh???? The only way to determine the load is load calc's, not adding up the sum of the branch breakers.

 

[rancherbill]

When you are buying wire, look around for "end of the roll" deals at Home Depot. I am pretty sure they will be too short, BUT, get the HD guy to write out the price on the little quote things they have in their apron pockets. Take it down to Rona and they will price match plus give you 10%.

It works.

 

[mike93lx]

Being in Canada, most of the advice here won't apply

 

[Noltz]

Also Canadian and a good deal of what's said here is just plain good advice though.

I'd be looking at 90A feed to your garage. It's pretty standard and it's plenty for a single Level 2 EV "charger" along with single-person workshop. Yes disconnect the single 120v line to the garage and recycle the conduit for network cables if you'd like. Consider pulling 2 network cables; One for your router and a separate one back to the house for a security camera.

 

[alfredeneuman]

This link if jibberish.

As soon as the link said "220Volt" I knew it was BS. Disinformation galore

 

[dave*99]

Huh???? The only way to determine the load is load calc's, not adding up the sum of the branch breakers.

I don’t think I can add all these up in my head. Probably more than the 100A main I would guess.

 

[mike93lx]

Sure, you're not supposed to have breaker values that add up to more than 120% of the main, or in the case of a sub, the feeder breaker. But that's what the main is there for. If you get inspection and then want 3) 30 A circuits, why not?

OK, I'm ducking for cover now.

That's not true. You can load it up way past that

 

[mike93lx]

I don’t think I can add all these up in my head. Probably more than the 100A main I would guess.

That's a lot more than would be on most 100a services, but nothing wrong with it. Likely a lot of wasted wire on dedicated circuits and breakers though

 

[dave*99]

That's a lot more than would be on most 100a services, but nothing wrong with it. Likely a lot of wasted wire on dedicated circuits and breakers though

It’s a commercial location and I’m told they load the panel with unused breakers. Multiple theories on exactly why. But I bet it was expensive……

 

[mike93lx]

It’s a commercial location and I’m told they load the panel with unused breakers. Multiple theories on exactly why. But I bet it was expensive……

If they need to add a circuit, no one has to go shopping for a breaker. Likely saves a lot of time and single pole breakers are pretty cheap

 

[Norcal]

It’s a commercial location and I’m told they load the panel with unused breakers. Multiple theories on exactly why. But I bet it was expensive……

It's cheaper when ordering the panelboard to fill it, then buying them later.

 

[iadr]

This link [is] jibberish.

Listen to Wylie, he does this stuff every day.

Glad to, when we get there. He's not posted specifics yet because I'm not "there" yet. hah

I didn't find it gibberish. It was written to be very incremental and informal teaching from scratch. So they should have said 240? I see lots of references to "110V, 115V, 120V, 125V" I've just figured there is some background and not everyone is misinformed...? I can be cocky, even abrasive in my own field, but this is not it!

So they say X-amps divided by 0.8
Then multiple 1.2 per 100ft span
I have 50, roughly, and I quibble why it's not divide by point eight again. Or in my case point 9 for 50ft.
So 4awg, copper, 3 conductor. 85a rating.
But/though that may be a good size to use, the safety margin they speak of may not even apply. Likely doesn't, per BillConner's post

So... What is the conduit size if I want to upsize by one size in my one nod to future proofing?
(Can I pull in an additional say 10-12 ga? is mixed legal? I assume so... hoping I wouldn't waste the 4ga wire. I'm thinking like, say, run the bench outlets and the coming furnace off the supplement if I got too close. Shame about having to disconnect the existing 15a.)
Using Southwires calculator I could use 1 1/4 PVC for up to 2 ga. One inch even is a little too tight- 3ga works in 1" even, not recommended for 2. Sounds like my sweet spot. That sounds huge but in grey it could go along the bottom of the grey vinyl siding and look OK.

As a car dealership parts manager, I tend to focus first on BOL (bill of material, aka shopping) issues first.

Surprisingly wire isn't easily found at HomeDepot.ca in any quantity. 4 or 6a 3 conductor, one ground. Romex/Looomex? all the terms confuse me.

 

[iadr]

Sure, you're not supposed to have breaker values that add up to more than 120% of the main, or in the case of a sub, the feeder breaker. But that's what the main is there for. If you get inspection and then want 3) 30 A circuits, why not?

OK, I'm ducking for cover now.

I believe the 80% derating applies only to continuous loads, not the panel nor many of the receptacles. For instance, your plug in welder would not be a factor - not continuous (3 hour). EV chargers would be I believe. Most lighting is.

And pretty sure you can have as many 30 amp receptacles as you want on as many 30 amp breakers as you want.



I agree but you croak and your heirs have to sell it, just not that much more to up from 50 to 90. (I pick 90 because that's what I'm doing - no. 2 - iirc - in 1" rigid conduit.) But close call - and I wouldn't criticize at all if you stick with 50 amp.

Also Canadian and a good deal of what's said here is just plain good advice though.

I'd be looking at 90A feed to your garage. It's pretty standard and it's plenty for a single Level 2 EV "charger" along with single-person workshop. Yes disconnect the single 120v line to the garage and recycle the conduit for network cables if you'd like. Consider pulling 2 network cables; One for your router and a separate one back to the house for a security camera.

More just acknowledging these posts.
90AMP requires what gauge feed from the house? (~50ft)
Seems like continuous demands would be lighting, the possibility of an electric radiant heat tube to assist the direct vent furnace (I have planned) in bringing it up from well below freezing. Or a car brought in from outside where it was well below freezing. I used an unvented 60KBTU to work in the garage this winter, so a 20-24K direct vent wall unit and a 7200W heat tube seems like a nice combo. Worst case continue to use the unvented as supplement, depending on my budget to equip the space in the remainder of 2023.
If I made the 30a 240v plug with possibility of re-facing it as needed for an EV charger, I might be risking lack of capacity on that, so OK, that's data for my decision I'd have had to do hours of research to find.
But in doing so I might pass code requirements with all the outlets I want. Determine that plan/menu for the box soon enough.
Oversize the wire going to the plug on the wall closest to the breaker box so as to put a 40/50 amp breaker on that one if/when I reface it into an charger down the road. I see EV charger ports all over the car, depending on manufacturer. Out of curiosity, is there any growing consensus where on the car they will be located? Forward third, versus rear third as was used for gas fillernecks, for instance? Just so I could choose the outlet to upgage the feed to.

https://www.homedepot.ca/product/sq...with-12-spaces-24-circuits-maximum/1001717504 looks like a sub panel that would cover all needs, fits the budget and is at big Orange just over walking distance from me. Comments? (That's ~$90US)

Humour me and point me to where an appropriate 4ga wire can be bought? Or is that Canada-code specific?
Is it 4-4-4-6 I want from the house to the sub panel in conduit?

​

 

[iadr]

Grrr. Reading (elsewhere) that I can only do 360* in a run of conduit? Nope, can't do this this run with less than 480*, though also being told, if I have a junction block in which I don't actually break the wire, but use it to break up the pull into two legs, I could- placed in the feed just where it heads down to the ground I could put 180* in the first leg. and leave 300 for the rest.
Or I could be pushed to use direct burial and lose my future proofing concept.

 

[u2slow]

Check your main panel label for the maximum subfeed breaker.

The cheapest way to run power is ACWU cable (looks like a Teck, but lighter-duty and aluminum conductor.) It is direct-burial.

I believe I caught 40' earlier, so don't need to oversize for voltage drop.

HTH.

 

[mike93lx]

Grrr. Reading (elsewhere) that I can only do 360* in a run of conduit? Nope, can't do this this run with less than 480*, though also being told, if I have a junction block in which I don't actually break the wire, but use it to break up the pull into two legs, I could- placed in the feed just where it heads down to the ground I could put 180* in the first leg. and leave 300 for the rest.
Or I could be pushed to use direct burial and lose my future proofing concept.

It can be hard for an amateur to plan out complex conduit runs. In many cases, a bend can be eliminated by flexing pvc conduit or just slightly tweaking the run/widening the trench.

That said, 360 is a hard limit in the US. You need a pull box in the run if you want to exceed. No idea on what Canada's rules are

 

[dave*99]

Do realize that the typical LB conduit fitting often used on the side of the buildings where conduit penetrates is a 90 degree fitting. But it does not "count" in the 360 total.

Is the most simplistic run from a house to a garage, you would exit the house with an LB, go down into the ground, hit a 90, run to the garage, hit a 90, come up into another LB and go into the garage.

There would only be an effective bend of 180 due to the (2) 90s in the ground. The LBs do not count and the wire is unbroken inside them. There is a total bend of 360.

Does the buried section of your run require more than 360?

 

[acer66]

Do realize that the typical LB conduit fitting often used on the side of the buildings where conduit penetrates is a 90 degree fitting. But it does not "count" in the 360 total.

Is the most simplistic run from a house to a garage, you would exit the house with an LB, go down into the ground, hit a 90, run to the garage, hit a 90, come up into another LB and go into the garage.

There would only be an effective bend of 180 due to the (2) 90s in the ground. The LBs do not count and the wire is unbroken inside them. There is a total bend of 360.

Does the buried section of your run require more than 360?

Do LB‘s also allow for another 360?

 

[dave*99]

Do LB‘s also allow for another 360?

YES
National Electrical Code or NEC limits the total number of bends in one continuous run to 360 degrees or four 90 degree bends. It specifically states, “There shall not be more than the equivalent of four quarter bends (360 degrees total) between pull points, for example, conduit bodies and boxes.”

 

[mike93lx]

Do LB‘s also allow for another 360?

More specifically, a pull box, which includes an LB, resets the bend counter.

 

[mrhemi426]

I will offer this as a suggestion, as I am located in Ontario and have this setup for my own house and shop. It may or may not work in your situation. Look into having your meter base changed to one that provides two output feeds. I have a meter base which incorporates a manual transfer switch for a generator. However, in addition it provides two outputs (fed from a 200 amp breaker). One feeds the house 200 amp panel and the other feeds the shop 100 amp panel. Each is routed underground to the respective panel. Since you mention trenching, it may be more direct to get to your shop from the meter base location in your particular application.
Just an alternative suggestion to your dilemma.
Yes this all meets Canadian code and was inspected (new build).

 

[billconner]

On LBs, I discovered that some LBs are limited capacity, less than the conduit they are sized for. I'm using 2 AWG for a 90 amp feed in 1" rigid, and the LB is listed for just 2 no. 2. Just check or oversize. (I had planned on 50 amp then decided to up it to 90 - at inspectors suggestion - after conduit was in.) An LB would have been simpler but I made it without (and still only about 210+/- degrees.)

 

[Zeke]

I'm sure load calcs have been used since electricity was 110v. But what a breaker feeds can change daily. Especially with plug strips. I'm sure the average house in my 100 YO neighborhood has a dozen. I have half a dozen with a total rewire. I'll go with load calcs where equipment is hard wired and not likely to change.

 

[Noltz]

Grrr. Reading (elsewhere) that I can only do 360* in a run of conduit? Nope, can't do this this run with less than 480*, though also being told, if I have a junction block in which I don't actually break the wire, but use it to break up the pull into two legs, I could- placed in the feed just where it heads down to the ground I could put 180* in the first leg. and leave 300 for the rest.
Or I could be pushed to use direct burial and lose my future proofing concept.

Between pull points. You just need to put a pull box inline to "reset" your 360°. I had to do this too when I pulled #6 for an EV charger in my own home. It was useless as a pull box but the inspector said it had to be there. I had made the entire run and never broke the conductor from my panel to my garage. So pull it all apart, put in the box, and reassemble.

 

[iadr]

OK, yeah I looked into LR LL and LLR's. Got that. I think.

So 60-70amps, what wire do I use? Not doing 90, have given my reasons. 50 seems light.
I need to split out the 115 from the 240v so minumum 3 conductor and one ground. Aluminum is slightly cheaper, but bulkier. I recall family friends having problem with aluminum wiring in their home almost 40y ago. So for the extra few (I think) dollars copper for peace of mind, I think. NOT direct burial. Not that I suppose the pipe would ahev been big enough, but I'm digging because direct burial was used here.
I know I seem pretty opinionated on that for someone with no clue. Maybe I''ll soften when I see the price breakdown to go each way?
Looking on Homedepot.ca, I don't see 4 or 6ga 3 conductor+grnd listed unless I have terms wrong.
We seem to use terminology like 12/3 up until you get to the big stuff.
Then I see the terminology switch to, 4+4+4+6, (what I think I may want, subject to correction here)
If in fact I am going to have to get wire from a specialist supplier, I want to avoid the dear in headlights look at their counter.
1 1/4 grey PVC is in stock at big orange, so that part's a no brainer.

 

[dave*99]

The problems you heard about with aluminum wire in 15 and 20 amp branch circuits from 40 years ago are real.

But they are completely irrelevant to the larger aluminum wire that would be used in your project.

Of course you can use Copper.
You can also buy individual conductors rated for wet use. In the US they are designated THWN or TWN. This is the insulation type.