combined PV and hot water

[dreadlocks]

how are yeh gonna prime it? the pump wont do it, climb up on the roof and fill it up there? or some other pump to start the cycle and let the low power one take over? Gonna leave it always primed and deal with that weight up high and just hope prime is never lost?

Just make one of these:

 

[Alloy]

On a closed loop with the air bled out it wouldn't matter...gravity assist on the downleg.

Bleading the air out to start needs valves and a way to fill both sides of the loop.

Once the loop is running air becomes trapped at the top of the loop if there is not enough flow to force the air down the loop.

 

[Alloy]

Our first shower system was a 25' black garden hose laid on the ground so the sun would heat it. For circulation the hose was connected to 400gph 12v Rule bilge pump that sat on the bottom of a 5gal pail.

Once the water was warm we used the pump and hose to shower with.

 

[tanuki.himself]

OK, can't quote everyone but to answer some of the questions and points raised:

building a slide-on hardside camper to go on a Ford Ranger - similar dimensions to a Lance 865 but to fit the narrower tub and should come in lighter as a shell. I want to make the camper self sufficient so that everything works when it is off the truck, so engine and exhaust systems are out. Ditto charging from the truck, so I want to put enough PV on to make it capable of supporting lights, roof vent fans, compressor fridge(s), water pump, entertainment system, power jacks, etc. I don't want to add any weight to the cab-over so by the time i allow for a couple of roof vents (maybe one day one will swap for an aircon unit) roof space is limited, so dedicated solar heating is probably not going to make the cut.

Hadn't thought as far ahead as pump flow rates or pressure/head. I'd figured something like a windscreen washer pump, maybe linked to a temp sensor on the panel so it only kicks in when the water on the roof is hot and needs refreshing.....

as we are building shower and sinks into the camper I want any system to be built in so it works with those - don't want to mess with external systems and having to decant water back and forth. Also we tend to do long travel days when we are on the road, so a system that works throughout the day while we are driving is preferable to something that we may only get to set up at dusk

 

[dreadlocks]

it sounds like your already going to have issues fitting enough solar in that limited area, if you want hot water.. you should go with a passive or LP system that adds no additional electrical loads.

 

[luthj]

With that type of camper, I would consider making/finding a small vessel (say 2-3 gallons?). Insulate it very well, then run a small coolant line from your engine to a coil inside the vessel/tank. Whenever you drive the tank will be heated to coolant temp (180F or so). Put a thermostatic mixing valve on the output. It will stay warm for 24 hours with good insulation, and 2 gallons of 180F water will make 5+ gallons of shower temp water.