Monday, December 5, 2016

300 watt Solar Panel Upgrade and AC/DC Compressor Fridge Upgrade


I recently replaced our 3-way Dometic fridge to an AC/DC compressor fridge which I should have done long time ago, no more scrambling for a leveled parking spot with the new fridge. The compressor type fridge is also consistent in keeping the set temperature and cools way faster than the Dometic 3-way fridge. The only thing I like about the 3-way fridge is it uses minuscule amount of DC power when operating on propane, a big plus when boondocking.

I went with Norcold DE0788 as it was locally available, saving me shipping fees and long wait. At first, I was contemplating of getting the Nova-Kool with the proven Danfoss compressor, but I really did not like the mounting location of its compressor and electronics. The Nova-Kool compressor/ electronics are mounted on the bottom rear of the fridge; this location is prone to getting wet from water/rain intrusion through the open side vents. I plan of leaving the old fridge outside vents open for the new compressor fridge venting and ease of access to the condenser for cleaning.

The Norcold DE0788 has Sawafuji compressor (a swing type motor) and is mounted high up along with the power inverter and electronics. The fridge AC/DC power inverter is covered and tucked towards the rear left uppermost corner of the fridge and facing the front of the vehicle which should be an ideal location to prevent it from getting wet.

The Norcold fridge draws about 3 amps when running, about 50-65% duty cycle (estimate) at thermostat setting #3 (middle setting)  that keeps the fridge temp below 40ºF and freezer at 20ºF. If you want to freeze ice creams, you need to set the thermostat dial to setting #5 (highest setting) but that obviously will consume more power. With the fridge compressor cycling 24/7, our 200 watt solar panel is able to slowly bring the battery to full charge the next day.

I decided to add a third 100-watt panel (Renogy Eclipse) to our existing 200 watt panel (from this post) for a total of 300 watt panel system. The Renogy Eclipse has same small footprint and specs but cost a cheaper than the AM Solar sells (SP100 or the older GS-100), it also uses same SunPower back-contact PV cells. With our average power use and with the fridge running 24/7, our 300-watt PV system is already float charging our batteries right before 1 PM. I'm sure we'll get more PV charge current during the summer months.

The new PV panel is mounted in front of the Fantastic ventilation fan and will also cover the crank-up TV antenna.  I was able to keep the TV antenna, but it will be on a fixed flat position under the PV panel. It still works good, but obviously not as good when it is up on its rotatable mast.

I first remove the TV antenna crank by loosening the small allen set screw located at the base of the crank handle. The hex elevating shaft/ worm gear that connects the crank to the plastic elevating gear is easily removed from the top of the gear housing. Next is to remove the antenna head, the antenna mast, and the rotating gear housing.

With the gear housing removed. The middle hole for the elevating shaft was sealed by filling it with Sikaflex sealant.

The gear housing is just held in place with a nylon retaining nut, a 15/16 deep socket is used to remove it.

The Rayzr antenna head is mounted under the PV panel using two aluminum angle bars. The antenna head is bolted into the aluminum bars using the existing well-nuts located towards the bottom of the antenna.

Since the antenna is now mounted facing upside down, a new drain holes was drilled on the bottom, the existing drains holes which is now on the top of the antenna was sealed closed.

The PV panel mount is fabricated from aluminum angle bars, the top bracket is a 2" x 2" x 20.8" while the bottom bracket is a 1" x 2" x 20.8" aluminum angle bar. A small wedge is needed between the top bracket and PV panel to compensate for the slight curvature of the sprinter roof.

The bottom PV panel bracket is attached to the roof using 3M VHB tape then sealed with Sikaflex 221 adhesive/sealant. Three evenly spaced stainless steel rivet-nuts were installed on the bottom brackets and Nylon plastic hand knob with stainless steel threaded stud is used to secure the panel in place.

With the PV panel secured. A 1-inch wide 3M VHB 5952 tape is used to secure the bottom bracket to the roof, it is applied to the entire length of the bottom bracket. A good prep of the area for superior VHB tape adhesion is extremely important; follow the recommended prep procedure by 3M (found here).

Wiring the new panel to the existing combiner box is straight forward. Since all 3 panels are wired in parallel, it is advised to fuse each panel for safety, I did not. There is not enough space in the combiner box for fuses, besides my wiring is well sized and protected and the PV panels are diode protected so the risk is very minimal in my opinion, your opinion may defer though. An inline fuse would be a solution, but that creates more connections and creates more resistance, so I left it at that.

 With the TV antenna.

TV antenna clearance to RV roof. The TV antenna base plate also clears the solar panel glass by just over a quarter of an inch.

Angled shot of the (3) 100-watt solar panels. I wasn't really comfortable using same AM solar mounting feet to the front panel as it is subjected to strong frontal wind when vehicle is underway, so I decided to fabricate a stronger aluminum mount.
Top view of the panels.
A view from the front. I was able to test the strength of the PV mount during our recent trip to Death Valley, I drove the RV for many hours at 70-75 mph with strong gusty headwind and the panel held up pretty well.

At first, I installed a DIY wind deflector/fairing in front of the panel but found it to cause severe air turbulence resulting to severe flapping/shaking of the Fantastic fan cover while driving at highway speed. I tried to adjust the angle of the fairing but with similar results, so decide to ditch that idea.

The new Norcold DE0788 AC/DC fridge fits nicely where the old fridge was. I added a thin rubber weather seal around the fridge for an airtight fit. The fridge sits atop an existing 3/4" high aluminum platform with its 4 metal pancake legs hanging, so the legs were removed. The elevated platform acts as a dam to prevent any water intrusion into the RV flooring via the outside vents. The fridge is then secured with couple of screws through the side of the cabinet enclosure.

Added a wood trim on top of the fridge, this is where the old 3-way fridge control eyebrow was located. The wood trim was stained using combination of cherry/gunstock/ antique maple stains. 3-layers of protective coats of Minwax Wipe-On Poly Satin was applied. I let the Polyurethane coating cured for several days before buffing it with 0000 grade steel wool to remove any sheen and match the existing cabinet. The stain finish is not a perfect match, but the difference is barely discernible and only at certain angles. A pair of drawer catches behind the trim was used to hold it in place. The wood trim can easily be removed to facilitate easy access to the fridge if it needs service or removal.

Fridge latch. Note the rubber weather seal around the fridge.

Inside of the Norcold DEO788 fridge.

Outside bottom vent. I added a thermal insulation mat on the back (lower half) of the fridge.

Outside top vent.

Fridge AC/DC power inverter located on the uppermost left and the compressor on the uppermost right of the fridge. 

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