How to mount solar panels - main concern is no roof leaks

belfert · February 12, 2017, 02:19:16 PM

I will probably have four solar panels leftover from doing solar for my house. I would like to put one or more panels on the bus. How do I mount these to the roof without ending up with leaks down the road?

I wouldn't even consider this if I wasn't getting the panels essentially for "free". I am doing 30 panels for the house, but it was cheaper to get a pallet of 34 panels. I will still have about $300 into putting solar on the bus for controller, mounts, wire, and such.

chessie4905 · February 12, 2017, 02:25:28 PM

Something here oughta work

http://www.afsrhuck.net/us/en/Products/Fasteners/HuckBolts.html

PP · February 12, 2017, 03:19:16 PM

When we first bought our bus it had 4 different TV antenna's mounted on the roof and holes with paper towels stuffed in them for I don't know what purpose. The bus was stored in a large warehouse out of the weather so it never leaked inside, thank goodness. I removed the old TV antenna's and mounted a satellite dome. Then I picked the most logical hole and ran my cables through it (power and leads). I then cut some old road signs and predrilled them before laying down a heavy bead of adhesive and screwing the sign material down. the signs were aluminum and I used SS screws. The adhesive I used is the same stuff that is used to seal 2 piece concrete exterior toilet buildings together. It's impervious to everything including sun and temp changes and yet remains semi-flexible. I found a tube left behind on a construction site when we were doing the landscaping. It's not available to the general public. I also used this stuff in the holes that I anchored the dome down with. That was 8 years ago and not a leak to date. I coat the roof every other year with mobile home roof sealer (white) just to keep it looking good. I don't like leaks!
If you're interested, I will find out what the product was. But I have no idea where it can be had.

luvrbus · February 12, 2017, 05:01:25 PM

I see the installers using 3M VHB tape to attach the panels to the roof and the 7000000 series Ancor or Blue Sea Cable Clam for the roof penetration for the wire

Iceni John · February 12, 2017, 06:27:45 PM

I would be very nervous if my panels were stuck on the roof with tape, even VHB tape! Adhesives are only as good as the substrate to which they are attached - what happens if the paint lifts off the metal?

I attached my eight grid-tie panels by first making a walkway between my two roof hatches, then hinging the panels to that. The walkway is bolted to a roof rib every 19 inches using pairs of 3/8" stainless socket-head bolts coming through from underneath, and the sealing is by two EPDM washers per bolt that are compressed against the roof by a stainless washer under the walkway's vertical supports. There are also some EPDM washers under the Nylok nuts on the top of the bolts to prevent water wicking down the bolts inside the hollow vertical supports. I repeated the same system for the longitudinal rails bolted to the same roof ribs but just above the rain gutter - these rails are for each panel's telescoping/sliding/pivoting support struts. Doing all this, I've made 72 holes through the roof, but not a single drip or leak has happened even during the very heavy rains here recently. My panels are now completely secured on the roof, regardless of how strong the wind may be. I have absolutely no concerns whatsoever about them ever blowing off! I don't need any mastic or caulk doing it this way, so that's one less thing to be renewed every few years.

For getting the power down from the roof, I use a pair of Bell aluminum junction boxes bolted to the roof that cover openings through the roof skin that access the insides of the hollow roof rib underneath. Each bank of four panels has its own 4 AWG feed cable running down the kerb-side of the rib, and the two grounds run down the driver-side of the same rib - the cables then run down to one of the storage bays where the breakers and charge controllers are located. I also have PEX water lines to the roof for some eventual solar water heating panels and for the panels' washdown hose outlets (easier than lugging buckets of water up onto the roof!), and these PEX lines also run through roof ribs similarly to the PV downfeeds.

It's certainly not easy or quick doing it this way, but I'm happy with the results so far.

John

luvrbus · February 13, 2017, 04:30:21 AM

I would have a few reservations about the tape and old paint to, but it is good stuff I don't see the siding blowing off these new buses and it a bitch to remove a panel where it was used

belfert · February 13, 2017, 10:45:38 AM

The tape sounds great, but is it really going to keep a 63 pound solar panel attached with air blowing underneath the panel at 75 MPH when going down the road? That seems like a lot of uplift force to me.

eagle19952 · February 13, 2017, 11:15:50 AM

Quote from: PP on February 12, 2017, 03:19:16 PM
When we first bought our bus it had 4 different TV antenna's mounted on the roof and holes with paper towels stuffed in them for I don't know what purpose. The bus was stored in a large warehouse out of the weather so it never leaked inside, thank goodness. I removed the old TV antenna's and mounted a satellite dome. Then I picked the most logical hole and ran my cables through it (power and leads). I then cut some old road signs and predrilled them before laying down a heavy bead of adhesive and screwing the sign material down. the signs were aluminum and I used SS screws. The adhesive I used is the same stuff that is used to seal 2 piece concrete exterior toilet buildings together. It's impervious to everything including sun and temp changes and yet remains semi-flexible. I found a tube left behind on a construction site when we were doing the landscaping. It's not available to the general public. I also used this stuff in the holes that I anchored the dome down with. That was 8 years ago and not a leak to date. I coat the roof every other year with mobile home roof sealer (white) just to keep it looking good. I don't like leaks!
If you're interested, I will find out what the product was. But I have no idea where it can be had.

do you recall the name of the stuff >?

PP · February 13, 2017, 03:16:58 PM

Quote from: eagle19952 on February 13, 2017, 11:15:50 AM
do you recall the name of the stuff >?

Eagle-it's 3M product 760 Hybrid. I googled it and was surprised how popular it is even though it states on the containers that it is not for consumer use or sale. Damned good stuff. You can seal almost anything with it. It's used in forest settings for sealing CXT toilet buildings together because they're placed on site in 3 pieces due to weight.

HTH

ol713 · February 13, 2017, 04:58:50 PM

Hi;
I have two panels for a 24 volt system. I mounted them with "L" brackets
from Home Depot. Forgot what I sealed them with, but I was cautious
to attach the brackets to the roof frames for solid support. Then I routed
the wiring to the roof vent for the refrigerator. Even the wire came form
Home Depot. That was about 20 yrs ago and no problems yet. You will
be happy with solar power. Just a side note, get a regulator that can
charge two batteries/banks separately. Mine has a switch to select bat #1 or
bat #2.
Good luck, Merle.