Garage/office, shop wiring

[floatinghat]

I am building a 36'x25' garage with a 2 story office, the shop area is 25'x25'. I will be feeding garage from the homes 200a panel with a 2 1/2" pvc sch40 conduit through the yard into a subpanel with 30 spaces. I am thinking 125a on the sub panel and #2 copper feeder. I am going 2 1/2" if the need changes in the future (not my lifetime). I am thinking 2 spaces for 40a electric car charger ( city required), 2 spaces 30a welder ( don't have) 2 spaces 20a HVAC, 5 spaces 20a (120v receptacles) garage, 2 spaces, 30a hot water, 1 20a dedicated for future car 4 post lift, 1 space 20a dedicated for 9x16' garage door. For the office spaces 2 spaces 20a (120v) kitchenette, 1 space lighting (120v) and 2 (120v) receptacles, and 1 20a for the bathroom. So that leave about 9 spare spaces.

The shop floor slopes 2.75in front to back. For the receptacles I was going to go 48" from the bottom of the box and lazer level to where are receptacles are level with each other and not the floor, is this the right tactic?

I wanted to keep the lighting and wiring threads separated to topic.

 

[mm08822]

Go with 40 space panel, 2" conduit is plenty, use aluminum conductors.

Do a load calc.

Recept ht doesn't matter...either way.

 

[dcg9381]

I'd set outlets with a laser, just like you're suggesting. Ignore distance from the floor on a slope.

EVSEs (EV chargers) are of two varieties, 60A (hardwired) or 50A (14-50R). If you put it on a receptacle, get one that is "EV rated".

For a 60A EVSE circuit, you get a max charge of 48A continuous. (80%)
For a 50A EVSE circuit, you get a max charge current of 40A continuous. (80%)

Pick your HVAC now. Some of the Mr.Cool systems, I've seen with higher amp requirements than 20A. If you are up north, definitely investigate how their efficiency curve changes when it's cold. Not all of them are worth a darn in the cold.

I use my 14-50Rs for welding all the time.

Small shop hot water, you probably can get away with less than 30A.. Just a sink point of use 3-6 gallon system, 120V @ 20A. Shower would be different, but I'm not sure I want to heat a full 50-100 gallons of water for a shop.

Bathroom may need a fan so remember that.

I think the guys like 240V lifts a lot better than 120V lifts, but I don't own one.

 

[floatinghat]

dcg9381​

Thanks for the reply, I'll do the 60A for the car charger it will only be about 20ft from the panel and I will blank it off.

The HVAC, I can just run a flex from the panel to the location of the outdoor unit and disconnect. I have a bid from a HVAC contractor but think I will DIY. Although, I might check out his Daikin recommendation and see about doing a dyi and have a professional vacuum and charge? I was going to cross shop MRcool

Hot water will be for office, which will have full bath so guess i'll get something in the 40gal range.

does the bathroom fan require a dedicated circuit?

good idea, it's only 1 wire.

mm08822​

40 space panel is a good idea

 

[mm08822]

Oversized conduit and copper is just wasted $$$ thrown in a hole.

Do your load calc. Copper is not needed.

 

[PackagingSea]

You’ve thought this out really well. Oversizing the conduit is a smart move for future-proofing. As for leveling the outlets to each other rather than the sloped floor, yes, that’s definitely the right approach.

Visually and functionally, having everything aligned to a laser level line looks much better and avoids headaches down the road

 

[dave*99]

• Perhaps a circuit for your IT equipment / IT closet?
• Maybe another conduit run to garage for fiber for network from the house / WiFi hotspot etc. / security cameras?
• Surge protector in the sub panel? 2 spaces.
• Check your main panel and confirm you can have a 125A branch circuit. Some are limited to 100A.
• 2" conduit is plenty big for the run to garage, how long is the run?
• A typical bathroom fan draws less than an amp and does not require a separate circuit.
• Bathroom fan with an electric heater built in, that's a different story.

 

[BoostAddiction]

dcg9381​

Hot water will be for office, which will have full bath so guess i'll get something in the 40gal range.

mm08822​

40 space panel is a good idea

My new garage has a small electric tankless water heater. Normally that would be the very last choice for domestic HW, but the use case for a garage is (at least mine is) infrequent hot water demand, and with very low quantities. Mine was very cheap (<$200) from HomeDepot, and has been perfectly adequate for sink and other miscellaneous use. I'd put in a conventional heater if there was a shower or tub involved, but for infrequent, low-volume demand, an electric tankless is the cheapest to acquire, and cheapest to run (assuming you can handle the spikes).

 

[floatinghat]

• Perhaps a circuit for your IT equipment / IT closet?
• Maybe another conduit run to garage for fiber for network from the house / WiFi hotspot etc. / security cameras?
• Surge protector in the sub panel? 2 spaces.
• Check your main panel and confirm you can have a 125A branch circuit. Some are limited to 100A.
• 2" conduit is plenty big for the run to garage, how long is the run?
• A typical bathroom fan draws less than an amp and does not require a separate circuit.
• Bathroom fan with an electric heater built in, that's a different story.

Thanks, no "IT" closet just WIFI extender
Extra conduit is always a good idea
Surge protector in panel not something I had considered, I will look into that
Will check max breaker size
agree 2 1/2 larger than I need but the trench was open
Will be standard bathroom fan

All receptacles will be 20a all lighting 15a

 

[dcg9381]

Thanks for the reply, I'll do the 60A for the car charger it will only be about 20ft from the panel and I will blank it off.

Make sure you put it in a big enough "box" with enough pig tail. Often the wiring for 50A and 60A is the same copper (ask your electrician). Pragmatically, there isn't much difference between being able to charge at 40A or 48A, it's all about which EVSE you get and how you want to install it. For me, I'd just put it on an EV-rated 14-50R plug. Most EV owners will have their own charger.

The HVAC, I can just run a flex from the panel to the location of the outdoor unit and disconnect. I have a bid from a HVAC contractor but think I will DIY. Although, I might check out his Daikin recommendation and see about doing a dyi and have a professional vacuum and charge? I was going to cross shop MRcool

Just have him put in 10/2 to the disconnect. This will cover you on all <24k units so you're good for up to a 30A breaker. Daikin is what I installed (they've been great), but I do have a vacuum pump. The unit was pre-charged, so I just did leak down / pressure test on it.

My "low end" Daikin won't heat worth a darn below 25 degrees though, so again, in a cold climate, watch that. Mitsu and others make "hyperheat" units that are better designed for cold.

One thing I wish I could change about my garage is I wish I had included wiring for 2 x EVSEs. And as these double for my welding outlets and can be used for RV hookups, 14-50Rs are my go-to. You can "schedule charging" or charge at lower rates (Tesla) - lots of ways to make 2 x EVSE's work with a 90A-125A feed.

 

[dan1554]

Just going through this now. I went with #2 aluminum for 100amp service to a 40 space panel in my shop/office combo. 1.5 inch conduit. Other than that, your plan looks very similar. I have a few circuits ran already and so far, so good.

I pulled a piece of twine through the conduit by tying a piece of plastic bag to the end and sucking it through with a vacuum. Then I used it to pull some legit pull tape, which was absolutely necessary. I was right a 360 degrees and the 3 #2's plus the ground meant I was having to use my full weight and some leverage to get it through, especially since it was a one-man crew.

Aside from this forum, I spent a lot of time using the AI (grok) to plan out my electrical, and its been very helpful for understanding wire sizing and code.

I second adding another conduit for low voltage.

 

[Norcal]

Just going through this now. I went with #2 aluminum for 100amp service to a 40 space panel in my shop/office combo. 1.5 inch conduit. Other than that, your plan looks very similar. I have a few circuits ran already and so far, so good.

I pulled a piece of twine through the conduit by tying a piece of plastic bag to the end and sucking it through with a vacuum. Then I used it to pull some legit pull tape, which was absolutely necessary. I was right a 360 degrees and the 3 #2's plus the ground meant I was having to use my full weight and some leverage to get it through, especially since it was a one-man crew.

Aside from this forum, I spent a lot of time using the AI (grok) to plan out my electrical, and its been very helpful for understanding wire sizing and code.

I second adding another conduit for low voltage.

2 AWG is only allowed to be used up to 90A unless certain conditions are met and that does not apply to the OP’s situation.

 

[dan1554]

Just conveying what I ended up with, not meant to be explicitly applied to the OP. I should have made that clear.

Edit - Looked closer in to the 2023 NEC and I might be buying a 90A breaker before inspection. Thanks @Norcal. Looks like #2 was sufficient for 100A at some time in the past, lots of interesting discussions between electricians out there as to why it changed.

 

[Gutman]

2 spaces for 40a electric car charger ( city required)

Would you expound on that requirement, and if you don't object, what city?

 

[floatinghat]

My new garage has a small electric tankless water heater. Normally that would be the very last choice for domestic HW, but the use case for a garage is (at least mine is) infrequent hot water demand, and with very low quantities. Mine was very cheap (<$200) from HomeDepot, and has been perfectly adequate for sink and other miscellaneous use. I'd put in a conventional heater if there was a shower or tub involved, but for infrequent, low-volume demand, an electric tankless is the cheapest to acquire, and cheapest to run (assuming you can handle the spik

We will have a full bath with a shower

 

[floatinghat]

2 spaces for 40a electric car charger ( city required)

Would you expound on that requirement, and if you don't object, what city?



Bainbridge Island WA, Actually GC said it was required and laughed. I wiring the space myself as was going to install anyway. My wife sells real estate and shocking how many times that is a major issue.

 

[dcg9381]

We will have a full bath with a shower

With how much use? A bad-*** RV has a 10-gallon water heater @ 120V. A nice RV to me has a 6-gallon water heater. I dislike the thought of having to heat 50-80 gallons of water for a shower that doesn't get used much. Not to mention the space it takes up.

On a sub-panel, you don't do tankless, they pull too much power.

Actually GC said it was required and laughed. I wiring the space myself as was going to install anyway

Assuming EV is pretty modern code. Again, just throw a 14-50R up there and call it done.

 

[wyliesdiesels]

Just conveying what I ended up with, not meant to be explicitly applied to the OP. I should have made that clear.

Edit - Looked closer in to the 2023 NEC and I might be buying a 90A breaker before inspection. Thanks @Norcal. Looks like #2 was sufficient for 100A at some time in the past, lots of interesting discussions between electricians out there as to why it changed.

#2 was never allowed for 100a for anything but the entire load of a dwelling

 

[dscheidt]

Would you expound on that requirement, and if you don't object, what city?

The 2024 IECC has requirements for EV charging, so it will be required in most civilized places pretty quickly. For single family houses, the requirement is for a single EVSE 'capable' space, which means the load (7.2 kW, per the code) is included in load calculations, there is a panel space for the required breaker, and conduit run to a junction box where the EVSE would go. (no requirement for an EVSE, or even the wire). Multiple occupancy structures have different requirements, and some will require EVSE spaces at construction time; there are also some rules about how the load per space can be reduced with active energy management systems.

 

[manwithtools]

On a sub-panel, you don't do tankless, they pull too much power.

Sure you can, some are as low as 50-60 amps - perfect for a single full bath. I'm doing just that in my shop to include shower, clothes washer, hand sink and utility sink. Planing on somewhere near 2.5 GPM.

 

[dcg9381]

Sure you can, some are as low as 50-60 amps

That's too high for a 90-120A circuit with an EV on it. At least IMHO.
If I'm going to to showering in the garage, that's fine. Everyone else gets a small water heater.

 

[manwithtools]

That's too high for a 90-120A circuit with an EV on it. At least IMHO.
If I'm going to to showering in the garage, that's fine. Everyone else gets a small water heater.

You shower in the middle of the night while the EV is charging? Not sure I follow that logic.

 

[dan1554]

#2 was never allowed for 100a for anything but the entire load of a dwelling

You're right the discussion was in the Mike Holt forum around changes to the chart in article 310 and did not include the amperage for #2. Im going to disappear from this thread, but will buy my 90A breaker and am grateful you guys probably saved me a return visit for my final.

 

[Gutman]

Bainbridge Island WA, Actually GC said it was required and laughed. I wiring the space myself as was going to install anyway. My wife sells real estate and shocking how many times that is a major issue

The 2024 IECC has requirements for EV charging, so it will be required in most civilized places pretty quickly. For single family houses, the requirement is for a single EVSE 'capable' space, which means the load (7.2 kW, per the code) is included in load calculations, there is a panel space for the required breaker, and conduit run to a junction box where the EVSE would go. (no requirement for an EVSE, or even the wire). Multiple occupancy structures have different requirements, and some will require EVSE spaces at construction time; there are also some rules about how the load per space can be reduced with active energy management systems.

Thanks. Not doubting the 'requirement' but I sort of have an issue having a requirement for a specific future electrical load to be accomodated up front, regardless of current need or desire.
Understand it's always cheapest to do anything upfront, however IMO, that seems like overreach.

 

[dcg9381]

You shower in the middle of the night while the EV is charging? Not sure I follow that logic.

Fair point. What I find is that most people don't "schedule" their EV charging unless they are on time-of-use rates.. You can make it work with 90-120A and a 60A tankless, it's possible.. Might require a little management.

And likely the tankless isn't running "flat out" at 60A all the time. Depends on temp of the incoming water and GPM flow.

 

[grounded-b]

Just conveying what I ended up with, not meant to be explicitly applied to the OP. I should have made that clear.

Edit - Looked closer in to the 2023 NEC and I might be buying a 90A breaker before inspection. Thanks @Norcal. Looks like #2 was sufficient for 100A at some time in the past, lots of interesting discussions between electricians out there as to why it changed.

edited:
#2 AWG aluminum is allowed for a 100A "service" conductors in a dwelling unit, NOT to a 100A sub-panel

 

[kngelv]

#2 AWG aluminum is allowed for a 100A "service" conductors in a dwelling unit, NOT to a sub-panel

It's fine as long as you use a 90 amp breaker to feed the sub-panel.

James

 

[nadogail]

Workshop water heaters are not intended for “Hollywood Showers”.

 

[Norcal]

Workshop water heaters are not intended for “Hollywood Showers”.

Many eons ago I had the pleasure of a 10 gallon water heater, no way to install a low flow shower head & I learned to shower quick.

 

[75gmck25]

You may want to pre-wire your EVSE circuits and just cap them off for now until you buy the EVSE. If you install 240 volt receptacles they will probably want you to include GFCI breakers, but most EVSE manufacturers don't recommend using a GFCI breaker for an EVSE. However, if you hardwire the EVSE, it should have a built-in GFCI, so you don't need to use a GFCI breaker.

Also remember that the charging amps for an EVSE are controlled by the car. If the car supports a max 32 amp circuit (usually a 40 amp breaker at 80% load), it won't charge the car any faster on a 50 or 60 amp circuit.