Passing Solar MC4 cable through concrete block wall.

KnowledgeSponge · May 2013

I need to run my MC4 cables through my outer wall through stucco and concrete cinder block.

What's the best way to bore the hole and also the best way to run the cable through?

My initial thoughts are to bore a 1 inc diameter hole, line it with PVC or some type of protective pipe, then mount my combiner box on the inlet side.
But getting the cable through the outer opening and making it water tight and bug proof is of concern.

Maybe theres a box specifically for this?

solarix · May 2013

Re: Passing Solar MC4 cable through concrete block wall.

Generally, what is done is to put a junction box near or under the array and transition to regular THHN wire there If there is not far to go, then may be cheaper to just run the PV wire all the way - but go ahead and run conduit all the way to the array. By the way, USE-2 wire is great wire but is not rated for interior use as it is not smoke rated. USE-2 wire is single insulated, while PV wire is double insulated. Either can be used for exposed wiring. Bore the hole with a masonry hole saw and then seal the conduit in it with foam sealer or RTV. I only use PVC conduit below ground, and EMT above ground. Remember, you are trying to make this last 25+ years.

vtmaps · May 2013

Re: Passing Solar MC4 cable through concrete block wall.

solarix wrote: »

Generally, what is done is to put a junction box near or under the array and transition to regular THHN wire

That box is usually called a combiner box (if you have two or more strings of panels). It is good to have a combiner box outside the house with a lightning arrester.... then bring the wires (without the lightning) from the combiner into the house. Make the cable (combiner to controller) thicker than you need, to allow for future expansion.

--vtMaps

mike95490 · May 2013

Re: Passing Solar MC4 cable through concrete block wall.

Bore the hole at an upward angle, - just a couple of degrees is all that's needed. Keeps water from getting inside the house from running/wicking along the conduit you line the hole with. If it's solid masonry - drill a small hole first, and then step up the hole sizes.

KnowledgeSponge · May 2013

Re: Passing Solar MC4 cable through concrete block wall.

Ok,

Great suggestions guys !

Mike, boring at a slight up angle is a great tip. thx.

the local Home Depot ONLY has a 4 inch bit...and it's broken.

I have a 1" concrete bit that is 15 inches so I can easily bore a 1 inch hole clean through.

But 1 inch isn't big enough. I think I need a 2 inch opening.

Guess I'll have to check other local mom and pop rental places.

KnowledgeSponge · May 2013

Re: Passing Solar MC4 cable through concrete block wall.

Local tool rental calls itself "DISCOUNT TOOL RENTAL" and their low low price to rent a 2 inch core bit for one hour?.....$70

Bass-tids

Man, it sure is EASY to find more and more ways to spend money on this hobby.

KnowledgeSponge · May 2013

Re: Passing Solar MC4 cable through concrete block wall.

Made up my mind.

I will NOT spend another hundred bucks for something that I'll use for 5 minutes then probably not again for a decade or more.

Here's my plan.....

I already have all the masonry bits mentioned here....so...

I'm going to take a 1/4 concrete bit that is 14 inches long and drill at an uphill angle of about 15 deg into the outside wall of the block
then through the inside wall. There will then be a 1/4 "pilot" hole going from outside to inside, in an uphill angle..

Next, I'll mark a 2-1/4 inch circle around those two holes inside and out.

Next, I'll use a 6 inch 1/4 diameter masonry drill bit to drill a series of holes on the marked circles inside and out (also at an angle) until I can "knock out" the plug
on each side.

I'll then run a section of plastic electrical conduit pipe through the hole and using silicone, seal it to on both ends so there is no way for insects or
water to get past it and enter the wall.

Finally, I'll mount my combinerbox on the outside wall and elbow it into the combinerbox.
I may have to warm the elbow with my heat gun to soften it just enough to get it to accommodate the slight angle.

Haven't figured out how to make the inside entry nice and finished yet....but I will.

How does that sound?

NorthGuy · May 2013

Re: Passing Solar MC4 cable through concrete block wall.

KnowledgeSponge wrote: »

Finally, I'll mount my combinerbox on the outside wall and elbow it into the combinerbox.

It will look much nicer if you mount the combiner box so that it covers the hole in the wall and then mount the conduit through the back of the box. Of course you will need to attach the conduit to the box first then stick it through the wall.

Why would you need 2" conduit? You can easily put three #6 wires through 3/4" EMT conduit, which will go through 1" hole without any problems. #4 wires may fit in as well.

mike95490 · May 2013

Re: Passing Solar MC4 cable through concrete block wall.

KnowledgeSponge wrote: »

Next, I'll use a 6 inch 1/4 diameter masonry drill bit to drill a series of holes on the marked circles inside and out (also at an angle) until I can "knock out" the plug
on each side.

Sounds like fun. I don't think it will work very well though. Even just a little web of material will hold things up, and with the aggregate in the concrete, the origination of the 30 perimeter holes will wobble a bit, and duplicating the 15 degree angle for each one will be tough too.

The drill bits are pricey, but you need the right tool for the job
http://www.mcmaster.com/#masonry-drill-bits

Slow spiral bits are better than fast spiral bits for drilling concrete.
Fast spiral bits are for more brittle, soft to medium materials such as block and brick.

mike95490 · May 2013

Re: Passing Solar MC4 cable through concrete block wall.

figure out what size conduit you need for the # of wires (use a table for the fill ratio) you need to install. 2" is pretty big, combine the wires outside, and just bring the 2 DC wires through. 1" hole should fit 3/4 " conduit OD.

KnowledgeSponge · May 2013

Re: Passing Solar MC4 cable through concrete block wall.

NorthGuy wrote: »

It will look much nicer if you mount the combiner box so that it covers the hole in the wall and then mount the conduit through the back of the box. Of course you will need to attach the conduit to the box first then stick it through the wall.

Why would you need 2" conduit? You can easily put three #6 wires through 3/4" EMT conduit, which will go through 1" hole without any problems. #4 wires may fit in as well.

Good suggestions. Maybe I'll go with a 1.5 inch hole. and use 1-1/4 conduit.
Mounting the combiner box over the hole won't work with the combiner box I have unfortunately.

KnowledgeSponge · May 2013

Re: Passing Solar MC4 cable through concrete block wall.

mike95490 wrote: »

Sounds like fun. I don't think it will work very well though. Even just a little web of material will hold things up, and with the aggregate in the concrete, the origination of the 30 perimeter holes will wobble a bit, and duplicating the 15 degree angle for each one will be tough too.

The drill bits are pricey, but you need the right tool for the job
http://www.mcmaster.com/#masonry-drill-bits

Slow spiral bits are better than fast spiral bits for drilling concrete.
Fast spiral bits are for more brittle, soft to medium materials such as block and brick.

You know what they say, where there's a hammer...there's a way.
I'll use a grinding wheel to smooth up the hole a bit but if it's just going to be covered it doesn't need to be perfect.
I think the more pilot holes I drill, the smoother the finished hole will be.
I could spend that $100 on a charge controller or something more beneficial than a one use drill bit.
When cash was flowing like water it was no problem....taint so now unfortunately.

solarvic · May 2013

Re: Passing Solar MC4 cable through concrete block wall.

I used a star pointed chissle to put the hole thru my cement block and it worked just fine. Then used the ballprne end of a balpene hammer to get the hole the size dia, I needed. Just be sure t0 put the hole thru a place in the cement block wall between the ribs. Also punch the hole from the outside. I did the outside first and just a small hole to know where to go from the otherside of the wall. I was afraid to do this at first but my friend that is a union carpenter said they do this all the time. Also he had the chissels to loan me. He thinks they are antiques and bought them at a farm auction. :Dsolarvic:D

KnowledgeSponge · May 2013

Re: Passing Solar MC4 cable through concrete block wall.

solarvic wrote: »

I used a star pointed chissle to put the hole thru my cement block and it worked just fine. Then used the ballprne end of a balpene hammer to get the hole the size dia, I needed. Just be sure t0 put the hole thru a place in the cement block wall between the ribs. Also punch the hole from the outside. I did the outside first and just a small hole to know where to go from the otherside of the wall. I was afraid to do this at first but my friend that is a union carpenter said they do this all the time. Also he had the chissels to loan me. He thinks they are antiques and bought them at a farm auction. :Dsolarvic:D

Cool beans. Thanks

niel · May 2013

Re: Passing Solar MC4 cable through concrete block wall.

i'm not sure if they still make those chisels, but i had one laying around here somewhere and i don't recall seeing it for many years now. they work, but are tediously slow compared to power tools. key to using the chisel is to constantly rotate it 45 degrees with each hit.

Blackcherry04 · May 2013

Re: Passing Solar MC4 cable through concrete block wall.

Harbor Freight has a couple different set's of these bits ( 12 " & 16 " up to one inch ) , with a hammer drill they would make quick work of concrete block. Core bits are fine , if you need that kind and size holes. Yeah HF, use once and pitch in the garbage, thats about all I buy from them.

http://www.harborfreight.com/5-piece-12-inch-sds-masonry-bit-set-46754.html

Here is a diamond bit set, but it's short and would be hard to line up, depends how close you want to be.

http://www.amazon.com/gp/product/B000TYIWUW/ref=pd_lpo_k2_dp_sr_1/191-0881034-2584155?pf_rd_m=ATVPDKIKX0DER&pf_rd_s=lpo-top-stripe-1&pf_rd_r=0BDQKBDSBWKDMSH6XSB7&pf_rd_t=201&pf_rd_p=1535523722&pf_rd_i=B00460W760

KnowledgeSponge · May 2013

Re: Passing Solar MC4 cable through concrete block wall.

Harbor Freight Masonry Chisel set....

http://www.harborfreight.com/3-piece-sds-max-type-masonry-chisel-bit-set-60377.html

If you don't mind dropping $100 - $400 for a tool to bore a hole, then by all means it's faster and more efficient and makes a cleaner hole.

I figure I can get a reasonably good clean hole done in under 30 minutes and I don't make $50 - $200 / hr.....so the math is easy.

solarvic · May 2013

Re: Passing Solar MC4 cable through concrete block wall.

eBAY LINK TO AN ANTIQUE STARPOINTED CHISLE LIKE i USED. http://www.ebay.com/sch/i.html?_nkw=star+chisel I just bought a set of 6 from another seller. :DSolarvic:D

BB. · May 2013

Re: Passing Solar MC4 cable through concrete block wall.

Get some concrete block similar to your place and practice first?

The little I had worked with CC Block, it was usually too easy to punch a hole through rather than too difficult (unless the space was filled with concrete and re-bar).

-Bill

Passing Solar MC4 cable through concrete block wall.

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