After dealing with a persistent leak under my forward heat pump I figured the leak had to be coming from the lag bolts. I found the bolts wet and rusted, so I tried sealing the holes and relocating the bolts, but the leak always returned. Time to think outside the box. I envisioned a mount that would wedge into the roof and be water proof. Research found rubber well nuts. The largest available utilize a 3/8" 16 nut. They are specifically designed for sign mount, but also provide sound isolation, great! My approach was to drill out each screw hole and insert a 1,1/4"hardwood dowel to repair the plywood. Not good. My first hole found only wet rotten wood. Instead I drilled a 3/4" hole, inserted the well nuts and covered each well nut with 4" wide Eternabond tape. Directly over each nut i fashioned four 1/2" PVC spacers that the heat pump sat on. After tightening the bolts, the heat pump synched tight and the 1/2" PVC sealed into the Eternabond tape over the well nuts. BTW the heat pump is noticeably quieter as a bonus.
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After dealing with a persistent leak under my forward heat pump I figured the leak had to be coming from the lag bolts. I found the bolts wet and rusted, so I tried sealing the holes and relocating the bolts, but the leak always returned. Time to think outside the box. I envisioned a mount that would wedge into the roof and be water proof. Research found rubber well nuts. The largest available utilize a 3/8" 16 nut. They are specifically designed for sign mount, but also provide sound isolation, great! My approach was to drill out each screw hole and insert a 1,1/4"hardwood dowel to repair the plywood. Not good. My first hole found only wet rotten wood. Instead I drilled a 3/4" hole, inserted the well nuts and covered each well nut with 4" wide Eternabond tape. Directly over each nut i fashioned four 1/2" PVC spacers that the heat pump sat on. After tightening the bolts, the heat pump synched tight and the 1/2" PVC sealed into the Eternabond tape over the well nuts. BTW the heat pump is noticeably quieter as a bonus.
Jtcochran
What make model of heat pump do you have that is designed to be attached to the roof substrate?
(That method of fastening is unlike that of any heat pumps I have seen).
Mel
'96 Safari
Nor'easters Club Workhorse Chassis Owner iRV2 No Limits Club
Join Date: Oct 2004
Posts: 30,785
The bolts are usually screwed into the metal rafters that are 16" on center.
A 2002 coach may need new seals under the AC to prevent water from entering.
Fiberglass roof would have thin plywood glued to the rafters.
Here is instructions for remounting the AC's.
Here is wiring for AC system you may have. ----- Control repair=== 5 Button Install All Comfort Controls old and new can be found in QT's 1 & 2
All the links below in my signature have more info for your Newmar.
Newmar Owners Club Nor'easters Club Appalachian Campers Ford Super Duty Owner Coastal Campers
Join Date: Dec 2007
Posts: 2,463
Quote:
Originally Posted by mel s
Jtcochran
What make model of heat pump do you have that is designed to be attached to the roof substrate?
(That method of fastening is unlike that of any heat pumps I have seen).
Mel
'96 Safari
Newmar has mounted their A/C's and heat pumps this way for many years. This is because there is no central return directly under the A/C or heat pump, the return is a set of small vents like the supply. They've always used Dometics, both Brisk Airs and Penguins have been mounted this way over the years.
__________________
Stewart, Brenda and kids
2008 Newmar Canyon Star 3410, now at a new home
2006 Roadtrek Versatile 210
My compliments to the OP for his level of effort for securing the roof structure. But having spent the past month replacing my Penguin II A/C units with the newer Dometic Blizzard NXT, I have to agree with "007" on the Newmar roof construction.
Not knowing what model year RV he has, the Newmar information identifies the A/C mounting directly into an aluminum plenum which is secured to the coach roof rails and than covered with 9mm plywood. The technical drawing will actually show the mounting points for both Penguin and Brisk air.
Here's a snap shot of the adapter & tech. drawing.
I replaced the foam dam a month ago. When I bored through the roof there was no aluminum plate. I assumed the factory would not mount directly to the aluminum substrate in order to reduce noise propagation. The expanding nuts hold to the roof extremely tightly, but I think I will replace the PVC spacers with rubber or vinyl to further isolate. It is incredible just how quiet the unit is now.
Newmar has mounted their A/C's and heat pumps this way for many years. This is because there is no central return directly under the A/C or heat pump, the return is a set of small vents like the supply. They've always used Dometics, both Brisk Airs and Penguins have been mounted this way over the years.
Luv2go
Thanks for the that courteous and informative reply.
Mel
I replaced the foam dam a month ago. When I bored through the roof there was no aluminum plate. I assumed the factory would not mount directly to the aluminum substrate in order to reduce noise propagation. The expanding nuts hold to the roof extremely tightly, but I think I will replace the PVC spacers with rubber or vinyl to further isolate. It is incredible just how quiet the unit is now.
Don't know what to say ... it is precisely as shown (Lass' picture) on my Essex. If the Universal Plenum (the black plastic liner) is removed you can see it. The flat plates extend out from the square opening as shown and the plywood substrate rests on the plates. The fiberglass rests on the plywood. As long as you drill where the plates are located, the lags will go into fiberglass, then plywood, then aluminum. You will not be drilling into structural crossmembers ... it's a special frame that matches "certain" holes in a Dometic base. You need to be careful when drilling or bolting ... the ductwork is under a portion of the frame and can be pierced.
BTW, the engineering drawing is correctly oriented .... the photo is flipped left/right (it's face down when photographed). The extra square piece is on driver's side rear to match a hole location in the Dometic.
Well, I didn't attempt to bore completely through the roof. As an engineer I am surprised that ANY factory would mount an AC unit directly into a frame member. It's akin to mounting an engine to the frame of a car. I assumed they mounted to wood; I was wrong. I would have mounted them to rubber encapsulated mounts onto an aluminum substructure. I suppose they just don't care. My mount, although not as strong, will stand up to everything except an overpass or tornado. I'll take my chances. I am enjoying the silence. I must alter the bedroom unit next.
Well, I didn't attempt to bore completely through the roof. As an engineer I am surprised that ANY factory would mount an AC unit directly into a frame member. It's akin to mounting an engine to the frame of a car. I assumed they mounted to wood; I was wrong. I would have mounted them to rubber encapsulated mounts onto an aluminum substructure. I suppose they just don't care. My mount, although not as strong, will stand up to everything except an overpass or tornado. I'll take my chances. I am enjoying the silence. I must alter the bedroom unit next.
Not sure what you mean ... the aluminum A/C mounting frame is flush with the underside of the plywood. The fiberglass, plywood, and aluminum frame is about 3/4" thick.
Well, I didn't attempt to bore completely through the roof. As an engineer I am surprised that ANY factory would mount an AC unit directly into a frame member. It's akin to mounting an engine to the frame of a car. I assumed they mounted to wood; I was wrong. I would have mounted them to rubber encapsulated mounts onto an aluminum substructure. I suppose they just don't care. My mount, although not as strong, will stand up to everything except an overpass or tornado. I'll take my chances. I am enjoying the silence. I must alter the bedroom unit next.
I agree the mounting system leaves lots to be desired. Seems like 4 threaded holes in the aluminum plate and 4 stud type rubber isolators would have been an improvement. Initial adjustment would be a bit of a nuisance (stacked rubber washers on the studs) but only required at install or replacement.
The water damage mūst have swelled the plywood because the well nuts are 1" deep and I felt I could have drilled deeper. I did, however, predrill a 3/8" hole through the roof to clear out any wood that would interfere with the machine bolts, but I didn't notice, nor was I looking for, any aluminum substrate. The well nuts as installed have turned out to be the best mounting method I could have dreamed. I will remount the rear unit this spring in the same manner with the exception of rubber spacers rather than PVC. As I write this the unit just turned on above my head, yet I can really only hear the air and a faint hum.