Need Help Planning Electrical for House and Shop

[matthimself456]

I have a project starting soon that is going to require my main panel to be moved and a new electrical service installed. At the same time I would like to take the opportunity to setup an automatic transfer switch and replace the power feed to my detached shop building. My understanding of electrical is mostly internet-fueled but I'd say its better than the average homeowner. That said, I have zero experience with service-level stuff and really don't know all the lingo that goes along with that. I'm pretty comfortable with NM and THHN and general household stuff but I'm certainly no pro.

Right now I have a 200A service coming overhead into a meter on the front of my attached garage. There is a service disconnect inside the garage and a cable then runs above the garage ceiling to my main C-H 200A panel on the back wall. From there branch circuits go out to the rest of the house and some way-too-small cable runs underground about 130ft across my backyard to a 60A sub panel in the detached shop. I also have a 10kW backup generator that has never been installed.

The new service will run underground into the attached garage. The main panel will still be in the garage but to simplify the panel move I will probably end up with another sub panel in the basement. I'd like to upgrade to 100A panel in the detached shop and the easiest route to get there from the attached garage is through the basement, out the rim joist, underground for approximately 20 feet, and then up and into the shop. The 10kW gen should be plenty for backup. I have no need or expectation of being able to run air conditioning, electric stove, or shop equipment during a power outage. Its there primarily for sump pumps, furnace fans, fridge, freezer, and some lights. That said the simplest approach seems to be to put a 200A automatic transfer switch on the incoming service rather than the individual branch circuit-type and just manage load manually during an outage. Does that seem reasonable? Also is there some kind of residential equivalent to the switchgear commonly seen upstream of any breaker panels in industrial settings? Like have the service come into 3 large breakers which each feed a single panel instead of the normal residential main-panel / sub-panels setup? Not sure that would actually be of any advantage to me, just curious.

Also, how should the run to the detached shop go? I think SER(?) is what should be used through the basement and then transition to something else for the underground portion depending on direct bury or in conduit?

FYI, I will not be doing most of this work personally. I just like to understand options before hearing from the contractor so I can speak somewhat intelligently and know what the pros and cons are of any approach suggested to me by the contractor.

 

[ard]

Since you seem to be replacing the main home panel, it seems that a separate 'generator only' sub might be a more foolproof way to go.

I would identify the circuits you need to power and see if they are limited to only a few.

However, if the generator will need to power anything in the shop, you really need the 200A switch and manual load control. (Problem is that power can go off with nobody home....)

 

[wyliesdiesels]

I have a project starting soon that is going to require my main panel to be moved and a new electrical service installed. At the same time I would like to take the opportunity to setup an automatic transfer switch and replace the power feed to my detached shop building. My understanding of electrical is mostly internet-fueled but I'd say its better than the average homeowner. That said, I have zero experience with service-level stuff and really don't know all the lingo that goes along with that. I'm pretty comfortable with NM and THHN and general household stuff but I'm certainly no pro.

Right now I have a 200A service coming overhead into a meter on the front of my attached garage. There is a service disconnect inside the garage and a cable then runs above the garage ceiling to my main C-H 200A panel on the back wall. From there branch circuits go out to the rest of the house and some way-too-small cable runs underground about 130ft across my backyard to a 60A sub panel in the detached shop. I also have a 10kW backup generator that has never been installed.

The new service will run underground into the attached garage. The main panel will still be in the garage but to simplify the panel move I will probably end up with another sub panel in the basement. I'd like to upgrade to 100A panel in the detached shop and the easiest route to get there from the attached garage is through the basement, out the rim joist, underground for approximately 20 feet, and then up and into the shop. The 10kW gen should be plenty for backup. I have no need or expectation of being able to run air conditioning, electric stove, or shop equipment during a power outage. Its there primarily for sump pumps, furnace fans, fridge, freezer, and some lights. That said the simplest approach seems to be to put a 200A automatic transfer switch on the incoming service rather than the individual branch circuit-type and just manage load manually during an outage. Does that seem reasonable? Also is there some kind of residential equivalent to the switchgear commonly seen upstream of any breaker panels in industrial settings? Like have the service come into 3 large breakers which each feed a single panel instead of the normal residential main-panel / sub-panels setup? Not sure that would actually be of any advantage to me, just curious.

Also, how should the run to the detached shop go? I think SER(?) is what should be used through the basement and then transition to something else for the underground portion depending on direct bury or in conduit?

FYI, I will not be doing most of this work personally. I just like to understand options before hearing from the contractor so I can speak somewhat intelligently and know what the pros and cons are of any approach suggested to me by the contractor.

FYI when an ATS is used code requires the generator to be sized to handle the entire connected load or have load shedding capabilities.

So an ATS will NOT be the simplest approach.

 

[matthimself456]

Hmm. That is good to know. How is the connected load calculated? Or is it measured? If no one is home the stove shouldn't be on and most ATS can cut off the AC at the thermostat level without a load shedding module. I'd guess that with the stove, AC, and compressor off my house almost never runs more than 10kW but I have no data to back that up.

I was thinking along the same lines as ard: with a generator-only sub I can't have anything in the shop run off the generator because then I'd have 2 separate feeds to that building. About the only thing I'd want to run off the generator out there is the heat but I might be able to live without that - just not ideal.

My setup is a fairly new Generac so I could do load-shedding modules on the stove and AC. Not sure if that would be enough. I guess I could do 2 panels in the shop and have the first panel run just the heater fan and put a load shedding module powering the second panel with all other shop circuits.

On the other hand I have a 16-circuit ATS that came with the generator and I probably only have 6 circuits that we'd actually need to run on backup power so that probably is the way to go. Definitely cheaper than buying a new ATS and a handful of load shedding modules. I just wish there was some clever way to do that and still be able to have heat in the shop...

 

[exranger06]

If you want the freedom/flexibility of having the generator power any circuit you choose, the easiest way to do it is to install an interlock kit on the main panel.

 

[MattT]

Also is there some kind of residential equivalent to the switchgear commonly seen upstream of any breaker panels in industrial settings? Like have the service come into 3 large breakers which each feed a single panel instead of the normal residential main-panel / sub-panels setup? Not sure that would actually be of any advantage to me, just curious.

A meter main can be used to do basically what you're asking about. I'm using one to feed the house sub panel with the feed thru' lugs and garage and shop sub panels with large breakers. Not sure you could get one that'd work safely with your proposed generator scheme though.

 

[matthimself456]

If you want the freedom/flexibility of having the generator power any circuit you choose, the easiest way to do it is to install an interlock kit on the main panel.

That would be more flexible but I need the cutover to be automatic. I lose power very rarely but if it goes out during certain times of the year I only have an hour or two before the sump crock is overflowing water onto the basement floor.

 

[mm08822]

What are the model/part #'s of the gen and xfer sw?

 

[matthimself456]

Its this package minus the wifi capability because mine is almost 2 years old:

https://apelectric.com/generac-7032-11kw-guardian-generator-with-100a-16-circuit-transfer-switch/

 

[matthimself456]

I'm still curious how the total load would be calculated or measured fr sizing a generator for a service-level ATS.

 

[yeldogt]

What is the reason for the change ? Is it all about getting the service underground?
Is the service entering at a different location?

What you have now is typical. I have the same at one of my places -- except the panel in the garage is the main with load center -- sub panels from there. The main disconnect has to be at the point where the service enters the building.

The load is the load .... they add up the house for the generator and the transfer switch. For my new build it was easier to get a larger generator and just do the whole house with load shedding.

My beach house has an older unit with a separate panel/ auto transfer for necessities. I'm not sure if you can have any other wires in a conduit w/ the feed to the sub panel. Forget how I did mine -- I have lighting circuits on and in the out building with switches and control from the main house

Do you need more then 60amp to the garage .... that's a lot of power unless you have something special.

 

[matthimself456]

What is the reason for the change ? Is it all about getting the service underground?
Is the service entering at a different location?

What you have now is typical. I have the same at one of my places -- except the panel in the garage is the main with load center -- sub panels from there. The main disconnect has to be at the point where the service enters the building.

The load is the load .... they add up the house for the generator and the transfer switch. For my new build it was easier to get a larger generator and just do the whole house with load shedding.

My beach house has an older unit with a separate panel/ auto transfer for necessities. I'm not sure if you can have any other wires in a conduit w/ the feed to the sub panel. Forget how I did mine -- I have lighting circuits on and in the out building with switches and control from the main house

Do you need more then 60amp to the garage .... that's a lot of power unless you have something special.

Service is moving location as part of this project:

https://www.garagejournal.com/forum/showthread.php?p=7921508#post7921508

The new service entrance location may be close enough to the main panel to not require a separate disconnect but I like the convenience of being able to shut off upstream of the panel. It makes working in that panel more comfortable.

Since everything is either moving or new installing the individual-circuit type ATS won't be too big of a deal, just less flexible.

So is the generator load calculated as if every load on the entire service is on?

 

[wyliesdiesels]

Service is moving location as part of this project:

https://www.garagejournal.com/forum/showthread.php?p=7921508#post7921508

The new service entrance location may be close enough to the main panel to not require a separate disconnect but I like the convenience of being able to shut off upstream of the panel. It makes working in that panel more comfortable.

Since everything is either moving or new installing the individual-circuit type ATS won't be too big of a deal, just less flexible.

So is the generator load calculated as if every load on the entire service is on?

I forgot to mention this earlier.

If you install a disconnect or TS(manual or automatic) ahead of you main service panel, then it becomes the main service panel where neutral needs to be bonded. This means the main service panel will become a subpanel and thus the neutral to ground bond will need to be removed. This can be a challenge on some types of panels such as meter mains because the neutral bar is bolted to the enclosure and would require plastic standoffs which may not be available.

Also, the GEC going to the grounding electrodes, as well as the bonding wire going to water lines, gas line, etc would need to be moved over to the TS.

 

[matthimself456]

Thanks, wyliesdiesels. I did have some general awareness of that but its a good reminder. My current setup was not done this way but it is approximately 20 years old and may have pre-dated that rule. I'll make sure the new setup follows that for all subpanels.

I also just realized I forgot to answer one of yeldogt's questions:

100A is probably more power than I'll ever need in the shop. The existing 60A subpanel was wired to the main panel with about 125 feet of... #10 wire. The previous owner of my place had some pretty third-world standards when it came to electrical work. Luckily he hired my neighbor (who is an electrician and does very professional work) most of the time but when he did something himself he took some pretty crazy shortcuts. So all that to say my existing 60A panel in the shop is not actually capable of safely supplying anywhere near 60A and since it has to be redone anyway its not much extra work/cost to pull the larger wire for a 90A or 100A panel out there. I plan to have a decent wood shop out there someday as well as the normal mechanical stuff: compressor, welder, lift, maybe a future bridgeport. Since I can really only run one machine at a time I'll never draw a lot of power but again, it provides flexibility.

 

[b-boy]

That would be more flexible but I need the cutover to be automatic. I lose power very rarely but if it goes out during certain times of the year I only have an hour or two before the sump crock is overflowing water onto the basement floor.

I recommend a water-powered backup pump for that. I had the same problem in my old house. It saved me several times.

I'd get one even if you get a generator. It's good insurance.

I've heard multiple stories of automatic generators failing to start during a power loss.

 

[wyliesdiesels]

Thanks, wyliesdiesels. I did have some general awareness of that but its a good reminder. My current setup was not done this way but it is approximately 20 years old and may have pre-dated that rule. I'll make sure the new setup follows that for all subpanels.

I also just realized I forgot to answer one of yeldogt's questions:

100A is probably more power than I'll ever need in the shop. The existing 60A subpanel was wired to the main panel with about 125 feet of... #10 wire. The previous owner of my place had some pretty third-world standards when it came to electrical work. Luckily he hired my neighbor (who is an electrician and does very professional work) most of the time but when he did something himself he took some pretty crazy shortcuts. So all that to say my existing 60A panel in the shop is not actually capable of safely supplying anywhere near 60A and since it has to be redone anyway its not much extra work/cost to pull the larger wire for a 90A or 100A panel out there. I plan to have a decent wood shop out there someday as well as the normal mechanical stuff: compressor, welder, lift, maybe a future bridgeport. Since I can really only run one machine at a time I'll never draw a lot of power but again, it provides flexibility.

pre-dated what rule? no bonded neutrals in subpanels?

Thats always been required, long before 20yrs ago, in subpanels in attached structures.

For detached structures, the code was adopted in 2008.

And for good reason. A bonded neutral anywhere but the main is a potential shock hazard.

 

[matthimself456]

pre-dated what rule? no bonded neutrals in subpanels?

Thats always been required, long before 20yrs ago, in subpanels in attached structures.

For detached structures, the code was adopted in 2008.

And for good reason. A bonded neutral anywhere but the main is a potential shock hazard.

To clarify, I'm not sure if the neutral / ground bond is broken in the sub panel. If that has always been the rule then I'm sure it is since it was done by a very good electrician. I do know that the sub-panel is where the wire to the water pipe is terminated and that the wire to the ground rods terminates at the service shutoff.

 

[matthimself456]

I recommend a water-powered backup pump for that. I had the same problem in my old house. It saved me several times.

I'd get one even if you get a generator. It's good insurance.

I've heard multiple stories of automatic generators failing to start during a power loss.

I already have 1 of those in each sump pit which I will leave in place. The issue I have with them is they use like 2 gallons for every gallon they pump. When they kick on they FLOOD the yard real fast. The other problem is I have enough water pressure / flow to run each of them but if they both come on at the same time their efficiency goes way way down. Then the ratio goes to like 7 gallons used for every gallon pumped.

Once the backup power is in place my plan is to stack a second electric pump in each pit, each on a different circuit and also leave the water-powered siphons. My luck will have to be really bad for everything to fail at once. I'm also working on a way to remotely monitor the power status and sump level that does not rely on grid power or hard-wired internet service.

I'm probably making it sound worse than it actually is, We've only flooded once in 8 years and the damage was very minor. But the backup power and pumps are relatively cheap peace of mind and the backup power also provides a whole bunch of other conveniences in an outage.

 

[MattT]

I'm also working on a way to remotely monitor the power status and sump level that does not rely on grid power or hard-wired internet service.

You might be able to get text and/or email outage alerts from your light company. Anything more than that is gonna require some kind of internet connection. Or you might could do it with SMS text messaging but everything I've seen that'll do SMS notifications is industrial and not cheap or easy to set up. And anything you do will need it to be on some kind of battery back-up to cover the lights going out and the generator not cranking.

 

[matthimself456]

Working on an arduino-based solution using a GSM cell network shield. I think I should be able to use a Google Fi data-only SIM card. The whole deal should be able to run for weeks on a small UPS in a power outage. It will also give the ability to run all kinds of I/O. For starters I want to monitor power status, air temperature, and water level but tons of possibilities to expand. I think it should be able to be setup to push data to a website or a google sheet and I can setup alerts for alarm conditions from there. Another alternative would be to have it send text messages to several phone numbers in an alarm condition.

The problem is I'm smart enough to figure out that this should be theoretically possible but I kind of doubt I'm smart enough to implement it. I'm going to have to recruit help that know what they're doing with programming.

 

[matthimself456]

Back to the electrical topic what is everyone's favorite panel/breaker manufacturer/series? My 200A panel is Eaton type CH which I have read has some really nice features. Should I keep it?

Since stuff is being moved I am told I may need AFCI breakers. So that may be a factor. Those things are crazy expensive.

 

[wyliesdiesels]

To clarify, I'm not sure if the neutral / ground bond is broken in the sub panel. If that has always been the rule then I'm sure it is since it was done by a very good electrician. I do know that the sub-panel is where the wire to the water pipe is terminated and that the wire to the ground rods terminates at the service shutoff.

you should check to make sure. youd be surprised at how much screwed up work Ive seen done by licensed certified electricians.

Back to the electrical topic what is everyone's favorite panel/breaker manufacturer/series? My 200A panel is Eaton type CH which I have read has some really nice features. Should I keep it?

Since stuff is being moved I am told I may need AFCI breakers. So that may be a factor. Those things are crazy expensive.

i like the Eaton CH stuff.

 

[matthimself456]

FYI when an ATS is used code requires the generator to be sized to handle the entire connected load or have load shedding capabilities.

So an ATS will NOT be the simplest approach.

Wyliesdiesels, do you know specifically where this is in the code? The reason I ask is I just spoke with the electrical inspector and presented him this question. He thought it was permissible to use an "under-sized" generator on a service-level ATS. Obviously if the load exceeded the capacity of the generator the ATS would cut off emergency power when the Hz falls as the generator bogs. But is there anything else about this approach that is inherently unsafe?

Now I know that inspectors are human beings too and he could be wrong about this. My goal is do things correctly, not to take advantage of an area of the code that my inspector may just not be super familiar with. If I go this route I would incorporate load shedding for AC, electric stove, and most loads in my shop.

 

[mm08822]

For automatic xfer, a generator has to be sized for the connected load or load management (load shedding) has to be used. You'll find this in NEC 702.4(2).

Your inspector should know this and require a load calc/shedding plan if gen cant support full load.

The xfer panel you have is rated for only 100a so you can not transfer over a 200a service with it. It can transfer up to 16 ckts (100a max) which could include the feeder to a sub panel. The typical installation for this xfer switch requires pulling ckts out of a main panel and putting them onto new cb's within the xfer panel. Pretty simple when every circuit you want is in the main panel.

You could plan your rewiring of main panel/service to move the needed backup ckts to the xfer panel. What I have found is some people change their mind what they want backed up later. This could be a problem for you to change later if some ckts originate in different panels.

To give you the most flexibility, change the xfer switch to a 200A. Sell the 100a 16 ckt xfer switch. Then you can run anything within the load limits of the generator. 10KW is only going to provide 40a @240v. Then you need load shedding for ac, elect stove, elect dryer, elect hot water, elect heat. If these are gas then those can be ignored - just the ac interlocked.


Load calcs are required to be submitted for generators. You do not just add up the loads in the house. There are diversity factors for certain portions of the load and some loads are mutually exclusive.

 

[matthimself456]

Thanks, mm08822. I'm going to have to look more into how to do those load calcs. My water heater, dryer, and heat are all gas so if I can lockout AC, mini split, elec. stove, and air compressor with load shedding and get the remaining calculated load below the capacity of my generator then I'll likely get rid of the ATS I have and get the 200A Service Entry one.

 

[mm08822]

For load calcs, start by gathering this data:

Dwelling sq ft
Following nameplate data (pics are best):
• a/c
• mini split
• stove
• air comp
• dishwater
• sump pump
• sewage lift pump(?)
• any other large elect loads