Finally, the start of my 25kw Ground Mount grid-tie system

[wattmatters]

10 degrees to either the east or west of south will make 2/5ths of bugger all difference. Line them up with the property and at least make the array aesthetically pleasing.

 

[live4soccer7]

Here are some pics of the bluesun solar mount system. It comes in at about half the price of sunmodo, unirac, or iron ridge. Wind rating of just under 100mph and snow load of 30lbs/sqft.

One of the concerns I see with it is that the brackets are held into the concrete by bolts instead of a post being set into concrete. This is a 30kw system from blue sun in Cincinnati. Seems like the arrays should be farther apart based on what we talked about already in this post, but that not really the point. Any input on this mounting system? I think the ironridge with 3" pipe is the best option, but I am trying to keep costs down where possible without compromising the system.

 

[live4soccer7]

100 yards =(2/1)^2*PI()*6*36/27
You're not kidding! That's 10 truckloads.

Is 2' diameter necessary? 1' would be 1/4 the concrete.

We saw another design with gravel or something spread over a precast footing.
What if you did a 3' diameter hole with 1' or 8" sonotube, and rebar spread out at the bottom? Kind of a deep "T" footing. Backfilled dirt to provide hold down weight.

I think your calculation there is wrong.

Area of a circle should be PI*r^2

PI*1^2 = 3.14
(3.14 * 6 * 36)/27 = 25.12

 

[Hedges]

I think your calculation there is wrong.

Area of a circle should be PI*r^2

PI*1^2 = 3.14
(3.14 * 6 * 36)/27 = 25.12

You're correct.
I wrote (2/1)^2 where 2 was D.
Should have been (2/2)^2.

25 yards of concrete isn't nearly so bad.

For footings like these, where size and mass is the goal, if a cheap source of rock was available an alternative could be to drop large rocks in the holes as they are being filled with concrete. Something like up to 8". If getting a concrete delivery that might be too much distraction and would make amount of concrete difficult to plan for. But if mixing on-site in smaller batches, could provide savings.

 

[live4soccer7]

You're correct.
I wrote (2/1)^2 where 2 was D.
Should have been (2/2)^2.

25 yards of concrete isn't nearly so bad.

For footings like these, where size and mass is the goal, if a cheap source of rock was available an alternative could be to drop large rocks in the holes as they are being filled with concrete. Something like up to 8". If getting a concrete delivery that might be too much distraction and would make amount of concrete difficult to plan for. But if mixing on-site in smaller batches, could provide savings.

I think truck would be the only way. 25 yards would be a heck of a lot of labor. I think I had calculated that out to be roughly 600 bags of 80lb. I could be remembering wrong, but I think I'll pass on self mixing. haha.

 

[rhino]

I think truck would be the only way. 25 yards would be a heck of a lot of labor. I think I had calculated that out to be roughly 600 bags of 80lb. I could be remembering wrong, but I think I'll pass on self mixing. haha.

There was mention of using ground screws earlier in thread, what happened to that idea? I'm going to expand my system further from the 4 top of pole mounts to a ground mount system like iron ridge with ground screws and not having to dig all those holes and add concrete seemed like a really nice option for me at least. I've not been able to get pricing yet.

 

[Hedges]

If multiple legs, not single-pole mount that requires torsional strength, then 2" galvanized pipe.
Thread a flange on the end to prevent pull-out from concrete.
Place a bit of rebar across that at bottom of hole, and pour maybe 1' of concrete. Then backfill hole with rocks and gravel.

This should give similar same hold-down weight to 2' diameter & 6' deep concrete footing. The rocks wouldn't provide same torsional resistance as the concrete would have, but a mount with multiple 2" legs doesn't need that.
The galvanized pipe would be more subject to corrosion exposed to water/dirt rather than concrete, so suitable paint might be good.

Some but not all the legs of my mounts are simply 2" pipe driven by hand using a larger pipe with plate welded over the end. I put them in ~ 17 years ago.

 

[live4soccer7]

There was mention of using ground screws earlier in thread, what happened to that idea? I'm going to expand my system further from the 4 top of pole mounts to a ground mount system like iron ridge with ground screws and not having to dig all those holes and add concrete seemed like a really nice option for me at least. I've not been able to get pricing yet.

None of us were really saying the ground screws were bad, but more that they probably won't last as long because they are in direct contact with the dirt/ground where they will be more susceptible to rusting out. This definitely won't happen over night, but I think a lot of us are building these systems for places we will be for a LONG time. I may very well end up going with the ground screws as well. I'm still waiting on pricing from CEDgreentech.

 

[rhino]

None of us were really saying the ground screws were bad, but more that they probably won't last as long because they are in direct contact with the dirt/ground where they will be more susceptible to rusting out. This definitely won't happen over night, but I think a lot of us are building these systems for places we will be for a LONG time. I may very well end up going with the ground screws as well. I'm still waiting on pricing from CEDgreentech.

I don't think that is a valid concern. Numerous permanent structures including houses are built on similar anchors/screws. I think the issue is many areas are used to just using concrete.

As a side note, if you use concrete you should not use anything in the hole between the concrete and walls of hole. It is common for people to mistakenly use sonotubes or other cylinder type items below ground level to pour concrete in which then results in severely weakened upward force resistance since the sonotube rots away eventually. You literally have just an air gap around the entire hole you dug and results in it being able to wobble. With multiple poles in ground for same structure not as big of deal but is a waste of time and money and you simply weaken the structure by doing that.

 

[live4soccer7]

I don't think that is a valid concern. Numerous permanent structures including houses are built on similar anchors/screws. I think the issue is many areas are used to just using concrete.

As a side note, if you use concrete you should not use anything in the hole between the concrete and walls of hole. It is common for people to mistakenly use sonotubes or other cylinder type items below ground level to pour concrete in which then results in severely weakened upward force resistance since the sonotube rots away eventually. You literally have just an air gap around the entire hole you dug and results in it being able to wobble. With multiple poles in ground for same structure not as big of deal but is a waste of time and money and you simply weaken the structure by doing that.

I'm sure it would be fine. On the other side of the argument with the sono tubes and soil is that when the cardboard degrades it will be fill with surrounding dirt from moisture entering the ground and vibrations. If you were installing it into another hard/fixed structure then I would 100% agree with that statement. In fact, we did just what you said with sonotubes (not using them against another hard structured hole).

 

[Hedges]

Drilled (and driven) piers get their support (and pull-out resistance) from friction with dirt on the sidewalls. Not pressure on the bottom.
(Leaning Tower of San Francisco excepted.)

But with enough mass, gravity alone will hold the footings down.

 

[MarkSolar]

One of the concerns I see with it is that the brackets are held into the concrete by bolts instead of a post being set into concrete.

I'd prefer the J bolts, they have greater resistance to failure from corrosion and rust. A 3" schedule 40 pipe wall is only 0.216" thick. It looks like those brackets are held on with 4 bolts, probably each 1/2". The corrosion problem occurs right at the surface of the concrete, so the more steel area you can put there, the longer it will last. If you look at the posts for stop lights, street lights, store signs, etc they are set using bolts embedded in the concrete and then a flat plate is attached to the bolts.

 

[live4soccer7]

I'd prefer the J bolts, they have greater resistance to failure from corrosion and rust. A 3" schedule 40 pipe wall is only 0.216" thick. It looks like those brackets are held on with 4 bolts, probably each 1/2". The corrosion problem occurs right at the surface of the concrete, so the more steel area you can put there, the longer it will last. If you look at the posts for stop lights, street lights, store signs, etc they are set using bolts embedded in the concrete and then a flat plate is attached to the bolts.

That's a very good point. I need to give the county a call and see what they really require to give me a permit for the framework and panel install (aside from electrical). I would have to set the pillars a little higher than in photo to get off the ground more for snow. Their paperwork makes it sound like I will HAVE to have an engineered stamped plan, which kinda sucks if that is the case.

 

[live4soccer7]

Anyone have any experience with this company/individual?

Seems like they have a great price for the solis inverters and wire seems to be cheapest there that I can find.

Solis 10kW Single Phase Solar Inverter 4 MPPT 208/240VAC with internal Sunspec MLRSD transmitter (SKU Part Number Solis-1P10K-4G-US-SPRT)

Solis 10kW Single Phase Solar Inverter 4 MPPT 208/240VAC with internal Sunspec MLRSD transmitter (SKU Part Number Solis-1P10K-4G-US-SPRT)

thepowerstore.com

Wire:

PowerStore | Wholesale Solar Inverters, Grid-Tied Solar

PowerStore provides a one-stop shop for wholesale solar products, including grid-tied solar, off-grid solar, and solar storage solutions. Same-day shipping. Shop now!

thepowerstore.com

My run from the panels to the inverters will be about 200'. I would have about 5 "strings", so 10 wires. 2000' ft total + a little buffer. I'm sure I will need a few hundred feet more for the paneling. Are the connectors on the back of the panels traditionally long enough to be able to connect to the panel next to it without extending them? I would THINK so, but I hate to assume anything.

I could grab the inverters and wire from that "thepowerstore"

Ground mount and connectors from bluesun solar

Panels from local company (Hyundai Bifacial) unless I decide to go with bluesun on that panels. I'd probably pay about $2k extra for the panels locally as opposed to through bluesun. I just don't know that I trust their panels.

 

[MurphyGuy]

As a side note, if you use concrete you should not use anything in the hole between the concrete and walls of hole. It is common for people to mistakenly use sonotubes or other cylinder type items below ground level to pour concrete in which then results in severely weakened upward force resistance since the sonotube rots away eventually. You literally have just an air gap around the entire hole you dug and results in it being able to wobble. With multiple poles in ground for same structure not as big of deal but is a waste of time and money and you simply weaken the structure by doing that.

Here in Michigan, you absolutely do want to use a sonotube or something similar. I can't speak for all areas, but in Michigan, where the frost line goes down 42 inches, most of our uplift is caused by freezing ground.

What happens is that the ice finds a lip or some other indentation or protrusion in the concrete, and uses that as leverage to lift the column.. then, when the ice melts, the soil fills in the gap and the column remains lifted.. only to be repeated the next winter.

The two biggest mistakes people in Michigan make are: 1) Not going well below frost line and 2) Uneven and rough sides on the columns.

 

[live4soccer7]

Here in Michigan, you absolutely do want to use a sonotube or something similar. I can't speak for all areas, but in Michigan, where the frost line goes down 42 inches, most of our uplift is caused by freezing ground.

What happens is that the ice finds a lip or some other indentation or protrusion in the concrete, and uses that as leverage to lift the column.. then, when the ice melts, the soil fills in the gap and the column remains lifted.. only to be repeated the next winter.

The two biggest mistakes people in Michigan make are: 1) Not going well below frost line and 2) Uneven and rough sides on the columns.

Great info. Is there a site online that I can find what my frost line is in this area? I THINK it is only 18", but could be wrong.

 

[MurphyGuy]

Anyone have any experience with this company/individual?

Seems like they have a great price for the solis inverters and wire seems to be cheapest there that I can find.

Solis 10kW Single Phase Solar Inverter 4 MPPT 208/240VAC with internal Sunspec MLRSD transmitter (SKU Part Number Solis-1P10K-4G-US-SPRT)

Solis 10kW Single Phase Solar Inverter 4 MPPT 208/240VAC with internal Sunspec MLRSD transmitter (SKU Part Number Solis-1P10K-4G-US-SPRT)

thepowerstore.com

Wire:

PowerStore | Wholesale Solar Inverters, Grid-Tied Solar

PowerStore provides a one-stop shop for wholesale solar products, including grid-tied solar, off-grid solar, and solar storage solutions. Same-day shipping. Shop now!

thepowerstore.com

My run from the panels to the inverters will be about 200'. I would have about 5 "strings", so 10 wires. 2000' ft total + a little buffer. I'm sure I will need a few hundred feet more for the paneling. Are the connectors on the back of the panels traditionally long enough to be able to connect to the panel next to it without extending them? I would THINK so, but I hate to assume anything.

200 feet is significant but not troublesome. You're better off mounting the inverters right to the solar array and run a single large gauge 240 volt 4-wire line back to the house.

If you mount the inverters to the home, you need to install rapid shutdown stuff, which can get really expensive fast.

25kw / 240volts = 104 amps, of which you will probably never actually see that much current.. 1 ga copper would do it.

My personal opinion is to stick with SMA inverters, but that's just my opinion. Each inverter has 3 "strings" and the biggest they make is the 7.7kW so you'd need 3 of them.

 

[live4soccer7]

200 feet is significant but not troublesome. You're better off mounting the inverters right to the solar array and run a single large gauge 240 volt 4-wire line back to the house.

If you mount the inverters to the home, you need to install rapid shutdown stuff, which can get really expensive fast.

25kw / 240volts = 104 amps, of which you will probably never actually see that much current.. 1 ga copper would do it.

My personal opinion is to stick with SMA inverters, but that's just my opinion. Each inverter has 3 "strings" and the biggest they make is the 7.7kW so you'd need 3 of them.

I've actually upped the array size to 36-40kw (can't change the thread title).

 

[MurphyGuy]

I've actually upped the array size to 36-40kw (can't change the thread title).

That's 166 amps at 240 volts.. What the heck do you need that much juice for? Do you own a Delorean or something?

Are you sure you need that kind of power?

 

[live4soccer7]

That's 166 amps at 240 volts.. What the heck do you need that much juice for? Do you own a Delorean or something?

Are you sure you need that kind of power?

I used almost 5000kw/h last month. I run a lot of stuff. I'll likely be adding to that consumption as the years go by. Hot tub, so my worn body and relax and electrical vehicles as well. 36-40 is over what I need right now. If I were to even zero out then I'd need low 30s at this very moment. I figure I'll over build right now with the tax credit available.