how many wires to detached garage

[StupidFlanders]

I am going to install solar panels on my roof of my detached garage and put the battery and charge controller in the garage, but I am having trouble figuring out how many trenches I need.

Currently, the power to the garage comes from an overhead wiring running from the house main panel to the garage. The batteries and inverters and other guts of my solar panel system will be in the garage.

Do I need just these two trenches dug between the garage and house?

1. One from the inverter in the garage to the critical loads panel
2. One from the critical loads panel back to the garage to power the garage.

Or is there a wiring option that lets me use just a single trench? I use powertools in the garage, so I need probably 40Amps.

 

[snoobler]

Or...

1 trench from garage to house panel for critical loads
overhead lines powering garage to inverter.
Inverter to garage panel powering entire garage.

Grid ----> Inverter ----> Garage
Inverter ------> trench ---> Critical loads

You'll need a transfer switch for the critical loads to ensure the grid and inverter are never powering them at the same time.

You'll want an inverter with good surge to handle power tools.

 

[StupidFlanders]

I am trying to eliminate all overhead wires.

does transfer switch typically go in the house or the garage in this situation?

 

[Steve_S]

My suggestion is as follows, I have a separate Powerhouse from my home so it is similar in some senses.

1) Use ONE trench. Wire it with 8/3 (good to 240V/40A) or 6/3 to carry 240VAC from Garage to Home. All depends on what your pushing to home BUT also remember to future proof yourself, you do not want to dig up the trench again. You may likely want to upgrade later or when sold, the capacity should be there for future. Use Conduit & NMWU grade sheathed wire (Non Metalic, Wet, Underground) (FOLLOW YOUR CODE RULES !!!)
I ran 2, 4" Conduits from Powerhouse to Home, one for Water & Communications wires, one for AC Electrical, it's a bit unique.

2) You can run dual lines, 1- to house and 1- back to garage. I am assuming Grid Power goes to House, so you will want Grid Power ON till it fails then autoswitch to Inverter system and feed back to house from Inverter. Installing the ATS switch in this model would put it next to the inverter/charger. NOTE, You have to be certain that the ATS you are going to use is COMPATIBLE with your generator. If intending to use a Grid connected Standby Genset with ATS they have their own and many are quirky with Solar Systems, some even void warranty ! Not all Inverters can communicate with / trigger an ATS. This is a complex area depending on what your exact plan is.

ATS: for Genset & Battery banked Solar.
Have a look at these from Atkinson Electronic and look at the list of Compatible Generators. http://atkinsonelectronics.com/gscm-mini-60hz-usa-canada/
ATS for Grid AC is a bit different and should be matched to the Inverter System you have.

 

[newbostonconst]

What power tools are you trying to power at 40 amps?

In my mind, you are going to need to keep the solar separate from the power to the garage.

1. For garage power you can keep what you have...
2. Run a 20amp new cable for outlets from a breaker in the house to the garage...
3. If you want to have more then 20 amps in the garage I believe you are going to have to run 3 conductor cable of the right size with a ground and put in a sub panel and ground rod....

Solar....Depending on where you live, you will have a 240VAC cable from critical loads panel breaker box in the house to disconnect switch by your meter, from the meter to the garage to the inverter/hybrid inverter....with a ground rod...

All can be in one trench.

Why are you wanting a transfer switch?

What solar hardware are you planning to use?

 

[StupidFlanders]

What power tools are you trying to power at 40 amps?

In my mind, you are going to need to keep the solar separate from the power to the garage.

1. For garage power you can keep what you have...
2. Run a 20amp new cable for outlets from a breaker in the house to the garage...
3. If you want to have more then 20 amps in the garage I believe you are going to have to run 3 conductor cable of the right size with a ground and put in a sub panel and ground rod....

Solar....Depending on where you live, you will have a 240VAC cable from critical loads panel breaker box in the house to disconnect switch by your meter, from the meter to the garage to the inverter/hybrid inverter....with a ground rod...

All can be in one trench.

Why are you wanting a transfer switch?

What solar hardware are you planning to use?

I don't have any 40A power tools., so I am not sure where that number came from. But right now my detached 6 car garage is only powered by 20amps. Standard these days is at least 60A going to a detached garage, and if I can going to dig a trench and bust up my driveway to run conduit I am going to redo garage power so that I am not limited. My garage is about 100 feet from the house.

I intend on having both battery banked solar and a generator for extended outages, so a transfer switch is required. I am still studying my solar options. I am meeting with another contractor today. I will probably have a 9KW system on my garage roof, with 5KW battery.

 

[StupidFlanders]

My suggestion is as follows, I have a separate Powerhouse from my home so it is similar in some senses.

1) Use ONE trench. Wire it with 8/3 (good to 240V/40A) or 6/3 to carry 240VAC from Garage to Home. All depends on what your pushing to home BUT also remember to future proof yourself, you do not want to dig up the trench again. You may likely want to upgrade later or when sold, the capacity should be there for future. Use Conduit & NMWU grade sheathed wire (Non Metalic, Wet, Underground) (FOLLOW YOUR CODE RULES !!!)
I ran 2, 4" Conduits from Powerhouse to Home, one for Water & Communications wires, one for AC Electrical, it's a bit unique.

2) You can run dual lines, 1- to house and 1- back to garage. I am assuming Grid Power goes to House, so you will want Grid Power ON till it fails then autoswitch to Inverter system and feed back to house from Inverter. Installing the ATS switch in this model would put it next to the inverter/charger. NOTE, You have to be certain that the ATS you are going to use is COMPATIBLE with your generator. If intending to use a Grid connected Standby Genset with ATS they have their own and many are quirky with Solar Systems, some even void warranty ! Not all Inverters can communicate with / trigger an ATS. This is a complex area depending on what your exact plan is.

ATS: for Genset & Battery banked Solar.
Have a look at these from Atkinson Electronic and look at the list of Compatible Generators. http://atkinsonelectronics.com/gscm-mini-60hz-usa-canada/
ATS for Grid AC is a bit different and should be matched to the Inverter System you have.

I like this idea of using one trench. I had no idea that ATS were quirky. Do the hybrid inverters not handle this? One contractor was pushing me toward the Schneider Conext, and I just assumed that since it knew when to fire up the generator that it also knew to cut power from the grid. I need to research further.

 

[RickP]

I’d encourage you to install cabling that will cover the greatest loads you anticipate would ever go there, and not to cable for current capacity only. Any construction project should be capable of growing into, or you‘re very likely to grow out of it in short order. The relative difference in cost becomes very inconsequential at that point. Do it right, do it once.

 

[Steve_S]

I like this idea of using one trench. I had no idea that ATS were quirky. Do the hybrid inverters not handle this? One contractor was pushing me toward the Schneider Conext, and I just assumed that since it knew when to fire up the generator that it also knew to cut power from the grid. I need to research further.

Well asking if a Hybrid Inverter will do it or not is generic. Depends on Make & Model really. Some do and some don't and everything in between. ATS' are specific for the application intended, quirky I suppose is accurate. Schneider Conext is Tier-1 Grade A product and will do everything you need with the bits. So will Victron (I am a huge fan of Victron). If you are having a contractor install it and are going with permits etc to feed into grid, then stick with UL/CSA etc certified grade equipment - also your insurance co won't balk and you know they do at every opportunity.

Hey, I put a deposit on a 8.5kw Champion Standby Genset with 50A ATS only to discover I cannot use it because A) I am offgrid, no grid power so that voids warranty and B) their ATS system is not compatible with my gear and would require even more gear in between.

BTW: Just to be a PITA, you really should check out what Tesla Solar is offering, they have some sweet deals for their solar setup.

 

[John Frum]

I ran 2, 4" Conduits from Powerhouse to Home, one for Water & Communications wires, one for AC Electrical, it's a bit unique.

Pex and communication wire in the same conduit?

 

[Steve_S]

Pex and communication wire in the same conduit?

Yes, 3/4" PEX for water and comms (Cat.6 Ethernet) is in 1/2" pex within the 4" conduit. The conduits are also 6' deep and within 4" thick XPS "boxes"/

Picture of my conduit run. All the foam is glued together with Lepage LP Polyurathnce construction adhesive.

 

[StupidFlanders]

Well asking if a Hybrid Inverter will do it or not is generic. Depends on Make & Model really. Some do and some don't and everything in between. ATS' are specific for the application intended, quirky I suppose is accurate. Schneider Conext is Tier-1 Grade A product and will do everything you need with the bits. So will Victron (I am a huge fan of Victron). If you are having a contractor install it and are going with permits etc to feed into grid, then stick with UL/CSA etc certified grade equipment - also your insurance co won't balk and you know they do at every opportunity.

Hey, I put a deposit on a 8.5kw Champion Standby Genset with 50A ATS only to discover I cannot use it because A) I am offgrid, no grid power so that voids warranty and B) their ATS system is not compatible with my gear and would require even more gear in between.

BTW: Just to be a PITA, you really should check out what Tesla Solar is offering, they have some sweet deals for their solar setup.

Yeah, I am very interested in Tesla Solar right now. I thought fancy name brand would be expensive, but it actually looks quite reasonable. As soon as their architectural shingle roof is available in my area, I am jumping on that.

 

[Ampster]

The cost of conduit is minor compared to the cost and effort of trenching and backfilling. It is easier the throw another conduit in the trench when it is open. That way you don't have to worry if technology changes your design in five years.

 

[Steve_S]

Hence the main reason I used 4" conduit, easy to pull stuff through it. I got a deal I could not pass up, so when I wired Powerhouse to home, I put in #6/3 & #8/3 NMWU so regardless of what will be wanted in the future it's there, the #6/3 is coiled up and dead headed on both ends just in case it's needed later. "Future Proofing". Now if the cost would have been retail then NO but I got my wire for a heck of a deal so (70% off msrp).