Orton DIY - Portable Hot Water Tank

My 08 was purchased with the optional Espar water heater. The plan was to use the heater for space heating and to heat water for the shower. Thanks to Mercedes engineering there are several reasons why this was difficult to accomplish. I will still use the Espar for space heating but would not buy the Espar option again. Space heating would be done better with an aftermarket Espar air heater. My electrical system is different than most conversions. Since I wanted 3 stage battery charging and did not want to direct connect my house battery to the Sprinter battery, I have two inverters. The 1000 watt "house" inverter makes 120 volt pure sine power from the house 255 amp-hr. battery. The 600 watt "vehicle" inverter makes 120 volt pure sine power from the Sprinter 12 volt system. The Sprinter engine must be running before the vehicle inverter will operate. The vehicle inverter will be used for the power to heat the water.

The portable hot water tank will consist of 3 parts:

1. Tank - 5.16 gallon stainless beer keg that is 9 1/4" dia. x 23 1/4" tall and weighs 12 lbs. The beer outlet is a 1 3/4" dia. hole at the top of the keg. The SS pipe and check valve have been removed from the keg. Caution: even an empty keg has high pressure in the tank. This pressure must be relieved before the pipe and valve are removed. Be sure to manually press down the rubber ball check valve to be sure pressure is gone. After the pressure is released, the pipe and valve can be extracted by removing the spring retaining ring with two small screwdrivers. I acquired the tank for free.
2. Heating element - This is a "Hottrod" electric conversion 6 gallon water heater part # HR6. I purchased this from AdventureRV.net for $94.00 delivered. Kit was designed to replace the drain plug on Suburban and Atwood RV propane heaters so shore power can be used to heat water instead of propane. Kit includes the 450 watt Calrod heating element, a 90 deg. to 150 deg. adjustable thermostat and an electric cord. It will screw into a SS coupling added to the bottom of the keg. The thermostat will be attached to the keg side above the heating element.
3. Pump - This is a Rule "Charge N' Flow" pump part # RP280KR. I paid $71.24 from Amazon.com delivered. The kit includes a 1 1/2" dia. 12 volt 4.7 gpm pump, 8' of hose, spray nozzle, battery, battery charger and a 12 volt plug. Pump will be installed in tank by dropping it through the beer outlet.

Two SS couplings will be welded to the tank. The one on the side at the bottom of the tank will be for the heating element and the other will be a 3/4" coupling welded on the opposite side at the top. The top coupling will have a street ell installed with a reducer for a 3/8" NPT Norgren air cylinder valve exhaust muffler part # C/S3 to let air into tank as the water is pumped out. The muffler will be removed to fill the tank with water. I will have to figure out how to suspend the pump in the tank so it does not touch the heating element at the bottom. The completed tank will weigh about 60 lbs when full of water. The water can be heated several ways: put tank in the sun, 120 volt shore power or 120 volt power from the vehicle inverter when the engine is running. The pump can be run from the house battery or from its portable battery. The portable battery is supposed to be good to pump 100 gallons. So tank can be used inside or outside of van. The thermostat will be set for about 100 deg. and only the water in the tank will be used to shower. Cold water will not be mixed with the tank hot water. About 4 gallons of water will be available.

Thanks to "srsosbso" for starting the "12v. hot water heater" thread. The discussion led me to this solution. If this works as expected, it is simpler than tapping into the Sprinter's cooling water system. I will document the tank build as I put it together.

Did you actually try the espar water heater option? I'm wanting to try it on mine, its supposed to give 2.5kW of heating power.

It would be the perfect setup for dry camping and redundancy for the hot water system...

1. You could heat water by just running the engine.
2. Heat water just with the espar.
3. Use espar as a pre-heater to one of those Ozzy 12V/240V Duetto's when on 12V.
4. Just use the Duetto when on shore power.

The problem with the Sprinter Espar option is the piping has hot water when the engine is running with the Espar off. Anything you put inside the van connected to the piping will be hot. I do not want a lot of hot water piping inside the van in the middle of summer. By using the portable hot water heater idea, I can limit the hot water inside by fabricating a small heat exchanger just for space heating. The heat exchanger will be well insulated to keep heat out of van. The Espar piping will be inside the heat exchanger. I have a truck cab radiator/fan located in the back of the van with 5/8" heater hoses in the floor from the front to the back. I will buy a small solar water pump to circulate the hot water from the exchanger to the radiator/fan. I will not use the Espar to heat hot water for the shower water. I will use the vehicle inverter powering a Calrod heater for that purpose in the portable keg.

Consider a Zodi outback type heater,,,

http://www.zodi.com/Consumer/zodihottaptravelshower.html

icarus

Graphite Dave said:

The problem with the Sprinter Espar option is the piping has hot water when the engine is running with the Espar off. Anything you put inside the van connected to the piping will be hot.

Click to expand...

Yes good point. Hmmm. There are manual valve taps you can get inline in your hoses, but isn't the espar plumbed in with the dash heater hoses? My understanding was that you had to turn the dash ac/heater dial to hot before the espar would work, no?

I haven't gotten my espar working yet, my MB star diag is telling me its giving a blower motor fault, and the circ pump isn't working even with direct 12V on it. So I've got a bit of work to do before I can even evaluate its potential.

But I really like the idea of using it, because it is already there so no extra weight/space, and it gives a lot of options/redundancy/backup when things go wrong or circumstances change.

So first I'd get the espar working lol.

Then I'd get/make a small heat exchanger like this which would sit in the engine bay and plumbed into the dash heater hoses...
http://www.ebay.com.au/itm/380158515655

The house hot water pipes would be run outside under the van and would enter and go straight to the duoetto...
http://www.ebay.com.au/itm/DUOETTO-12v-240v-Hot-Water-System-Caravan-RV-/250620419118

So I'm hoping the engine/espar will only heat the exchanger when the dash heater circuit is on, but obviously with the fan off and air vents closed.

Then the engine or espar can be used to pre-heat the water for the duoetto when its on 12V to save the stress on my battery bank, or I can just run it on shore power without the espar/engine pre-heat.

In order for Espar to start in my 08 without the engine running, the dash temperature control must be above ambient and fuel tank over 1/4 full. I was going to install a 3 way valve just above the floor so I could bypass the piping inside the van. I believe the Espar is controlled by the Sprinter inside thermostat. When inside temperature reaches the set point then the Espar stops producing heat. The other choice is to run the Espar with the engine running. In that mode I believe the Espar is controlled by the engine water temperature. Espar continues to run until engine coolant reaches its operating temperature.
My new design will use the portable hot water tank for shower hot water. I am building a small heat exchanger to provide space heating. The two systems are completely separate systems. For space heating I will pump the hot (warm?) water from the heat exchanger located just behind the driver seat back to a radiator/fan at the back of the van through 5/8" rubber heater hoses. So heating will be both warm air from the radiator and the lost heat from the hoses. Since I am so far along with this system I will complete it to learn how well it works. As I said, if there is a next time, I would not buy the Espar water heater but would buy the Espar air heater for space heating. I have also tried a 12 volt heating pad under my sleeping bag. That works very well but uses about 9% of my 255 amp-hr battery capacity per night. The idea of the heating pad is to only heat me instead of the whole inside of the van.
In an 08 valving must be installed to prevent the hot water from continuously flowing inside the van at engine coolant temperature.

Progress report. Have all the parts to complete tank. Two SS half couplings are being welded to tank. A 1/4" NPT coupling will be on bottom of tank for the heating element. It will be located off center halfway between tank centerline and outside edge of tank. Needed to be offset so pump and element were not in the same real estate. A 3/4" NPT half coupling will be welded to the top of the tank again halfway between tank centerline and outside edge. A 3/4" to 1/4" bushing will be installed in the coupling. A 1/4" NPT pneumatic valve exhaust muffler will be installed in the bushing to allow air to enter tank as water is pumped out. Both bushing and muffler will be removed to fill tank.

Finally got back my beer keg with a 3/4" NPT half coupling welded to the top for the fill opening/air vent, a 1/4" NPT half coupling welded to the bottom for the heating element and a plate on the bottom to mount the thermostat. Decided to put heating element into bottom instead of the side. The 3/4" NPT half coupling is welded to the top for a fill hole and a place to install an air vent. The air vent is a Norgren CS/3 3/8" plastic exhaust muffler for a pneumatic valve. (I also used the muffler as an air vent for the fresh water tank.) A 3/4" to 3/8" bronze bushing will be added to the top fill opening.

The tank is a SS 5.16 gallon beer keg. It weighs 12 lbs empty and 55 lbs full.

Pictures are of the top and bottom of the tank. Third picture shows parts you remove from the beer keg. You must release the pressure in the tank by pushing on the ball check valve before removing snap ring. The submersible pump will drop down thru the beer opening.

The electric heater is a "Hott Rod" 120 volt heating element designed to add 120 volt water heating to an RV Suburban or Atwood propane heater. Instead of using propane when plugged into shore power, the conversion allows you to heat with 120 volt power. The kit consists of heating element, a thermostat and the power cord. The thermostat is adjustable between 90 degrees and 150 degrees.

The pump is a Rule "Charge N' Flow" model # RP280KR. It is a submersible 12 volt pump. The kit includes the pump, a case with a built in battery, a charger, a hose, a spray nozzle, a cigaret lighter plug and battery clips plug. Pump can be run from the case battery or 12 volts from Sprinter.

I will be building an assembly that drops down thru the beer opening in the keg to support the pump at the bottom of the tank.

Attached are pictures of the two kits and a PDF drawing giving details of the tank and the pump assembly.

So far I have tested the ability of the tank to heat water by just placing it in the sun. Below are the results:

Time / Ambient temperature / Water in tank temperature

8:00 / 64 / 65
9:00 / 68 / 69
10:00 /73 / 69
11:00 /78 / 73
12:00 /79 / 81
1:00 / 80 / 83
2:00 / 76 / 84
3:00 / 74 / 85
4:00 / 78 / 86
5:00 / 73 / 88
6:00 / 70 / 87

I checked the shower water temperature I use in the house and it was 92 degrees. So tank will work just putting it in the sun. I will be painting the tank with solar panel flat black Thermolox paint to increase the heating. The ambient temperatures were from the Sprinter and the tank temperatures by a pool thermometer dropped in the top opening.

Painting the tank black with any flat black paint will greatly improve that heat rise in the sun. Please post the numbers once you paint it and do the sun experiment again. I'm guessing you can get to 120+ with a black tank.

Chris

Next I tested heating the water with the HottRod heating element. Filled tank with hose that was in sun so starting temperature was 78 degrees.

Time / Water temperature / Gain

3:00 / 78
3:10 / 82 / 4
3:20 / 87 / 5
3:30 / 92 / 5
3:40 / 97 /5
3:50 / 103 / 6

So in 50 minutes the water gained 25 degrees so that is 30 degrees/hr. Heater draws 3.78 amps or 454 watts. The thermostat was set for 90 degrees but it did not turn off heater. I had it temporarily attached to bottom plate on tank so expected it to turn off at a higher temperature than 90. Will install it correctly and hit the reset button to see if I can make it work tomorrow. Bottom line this is a viable method of heating shower water. My electrical system has two inverters. One connected to the house battery and one connected to the Sprinter 12 volt system. I would not connect heater to the house inverter. I would connect it to the vehicle inverter to heat water while driving. Vehicle inverter only produces 120 volt power when the engine is running. So this idea works for heating shower water with the sun, powered by the Sprinter 12 volt system's inverter or shore power.

The submersible pump assembly is supported by a small flange at the top which is part of the tank. The 1 1/4" PVC coupling sits on the flange. The assembly has a 14 3/8" long 1/2" sched. 40 PVC pipe and the 1/2" rubber hose at the pump is 2" long. (The PDF drawing had the wrong PVC pipe length) The 1/2" pipe is glued to the bottom 1/2" coupling and the top 1/2" coupling. The 1 1/4" PVC caps with the holes for the pipe and the pump cord are not glued so I can remove cord without cutting cord. Assembly is just dropped in through the beer hole.

A bit more progress. Changed top PVC coupler to a female 1/2" sched. 40 PVC pipe to female 3/4" NPT threads. Added a brass 3/4" male NPT to male garden hose adapter to the coupler. The thin rubber tubing supplied with the "Charge n Flow" pump kit kinked at the tank outlet and prevented water flow. Decided to use a standard garden hose instead. A 10' hose will go up to the ceiling hang from a hook and drop into shower enclosure. A plain lever type garden spray nozzle will be used. With 10' I can run hose out the sliding door to shower outside. Also can put hot water in sink. I am adding another 12 volt switched plug behind the drivers seat for the pump power outlet. The switch will be located at top of shower enclosure so I can turn pump on/off while in the shower. Turn pump on,wet down,turn pump off, soap, turn pump back on to rinse. Waiting for 10' white sanitary hose, air vent muffler and special solar panel black paint for tank.

Graphite Dave said:

A bit more progress. Changed top PVC coupler to a female 1/2" sched. 40 PVC pipe to female 3/4" NPT threads. Added a brass 3/4" male NPT to male garden hose adapter to the coupler. The thin rubber tubing supplied with the "Charge n Flow" pump kit kinked at the tank outlet and prevented water flow. Decided to use a standard garden hose instead. A 10' hose will go up to the ceiling hang from a hook and drop into shower enclosure. A plain lever type garden spray nozzle will be used. With 10' I can run hose out the sliding door to shower outside. Also can put hot water in sink. I am adding another 12 volt switched plug behind the drivers seat for the pump power outlet. The switch will be located at top of shower enclosure so I can turn pump on/off while in the shower. Turn pump on,wet down,turn pump off, soap, turn pump back on to rinse. Waiting for 10' white sanitary hose, air vent muffler and special solar panel black paint for tank.

Click to expand...

Nice design work and follow through. Truly impressed!

A bit more information: Remounted the thermostat and set it for 90 degrees. Following is heating information on 120 volt power:

10:45 @ 68 degrees (initial water temperature in tank)
11:00 @ 75 degrees
11:15 @ 82 degrees
11;30 @ 90 degrees
11:45 @ 98 degrees
12:00 @ 105 degrees and power off by thermostat

So 30 degrees/hr. Pump draws 3.77 amps or 400 watts.

Pump instructions say temperature limit for pump is 105 degrees so it just works. Thermostat is set at 90 degrees but due to how I mounted it, it does not have enough contact with tank to read accurately.

The rubber hose supplied by Rule in the kit was too flexible and kinked at the tank fitting preventing water flow. Replaced tubing with a 10' white sanitary RV garden hose. Rule nozzle was not easily turned off so replaced it with one from hardware store that includes a switch. It takes 7 minutes to pump all the water out of the tank. Less than a cup of water is left in the tank. Water spray is adequate for a shower. Not like a home shower but it will work fine.

The Rule instructions says the pump should not run for more than 2 minutes without water or with the flow stopped at the nozzle. Installing a switch above shower so I can turn pump on/off while in the shower. (12 volts and standing on a fiberglass shower pan should be OK?) Put a 12 volt female plug behind drivers seat for pump.

Have painted the tank black with Thermalox 250 solar collector coating. Waiting for my air vent to arrive and a day I can retest the time to heat water by setting tank in the sun.

Maybe then I can get back to the conversion and off this detour. This has been interesting and it definitely will work. On next conversion I can simplify the water system. Just the tank for shower water and a simple switch operated centrifugal pump for sink water. No plumbing, pump noise or water freezing issues.

System is completed. Ran another test placing the full tank in the sun. Slightly windy.

time/ambient temperature/water temperature

11:00/76 deg./68 deg.
12:00/74 deg./74 deg.
1:00/80 deg./78 deg.
2:00/79 deg.81 deg.
3:00/76 deg./84 deg.
4;00/66 deg/87 deg.
5:00/65 deg./88 deg.

Black solar panel paint did not seem to make much difference. Would probably help by tilting tank so tank side was exposed to the sun instead of sun just from above on a vertical tank. But it works.

System is very flexible. Can be used in following ways:

1. In shower enclosure. I have a dedicated 12 volt plug for the pump that is controlled by a switch located above the shower. wet/soap/rinse. Turn pump on and off with the switch. Power from house battery.
2. Run hose out drivers window or sliding door to shower outside with house battery power.
3. Move tank outside away from van and use the rechargeable battery that came with the pump. I sawed up the pump carrying case to extract the rechargeable battery so now have a 3" cube battery that is easy to carry.
4. Take nozzle over to sink to get hot water in sink.
5. When shore power is available use 120 volt adapter to run pump.
6. Heat water with sun/shore power/ or 120 volt power from my "vehicle inverter" while
driving.
7. Could even use pump out of tank to fill freshwater tank from a stream.
8. The 10' white garden hose will also be used to fill the freshwater tank. I have a gas station radiator fill valve to use on end of hose for that purpose.
9. When shore power is available, use tank to heat the interior. Would be quieter than my catalytic electric heater.

I did add a carpet cover on the bottom to protect the wiring on the bottom of the tank. I will have water available at the tank to refill it when it is strapped to structure. Another advantage using the tank for shower water is the van water system can be simpler. Do not need a pressure water system. If I build another conversion, I would just buy a small switch operated quiet centrifugal water pump to get water to the sink. Minimal amount of plumbing. The tank with water at shower temperature does not require a cold/hot water mixing valve and water temperature will be constant. Kind of a fun project that would change how I build the next van. Now I need to complete the shower enclosure and install the gray water tank to complete the water system.

I'm sure the paint works. Wind will kill the heating effect, too much convection scrubbing the heat away from the tank. In still air or even in some type of a clear plastic bag with an air space you will get a lot of heating.

Chris

Hi Graphite Dave

Like what you created here and am considering building similar. Have a couple quick followup questions please.

Do you find the tstat to be fairly accurate or consistent ? Wondering how much ambient air impacts reading etc.

Would you recommend heating element on bottom as you did or side if enough clearance. Seems bottom might allow for use of larger 10 gallon element (higher wattage) but side might allow for partial fills.

I'm looking to use a soda keg http://www.amazon.com/Pin-Lock-Gall...=UTF8&qid=1356313122&sr=8-1&keywords=Soda+keg that has the larger opening at the top so may have a bit more option to fasten pump. Also am considering giving a cheaper pump a try such as here http://www.amazon.com/gp/product/B000O8D8QG although not sure in regards to that pumps ability like the one you used which nearly empties the container.

Anything in particular you would change if doing over?


Many thanks for all of the details you already posted in this thread and for any follow up thoughts.

Have not used it enough to know how consistent the thermostat is. Plus or minus 5 degrees should not make much difference. Think it is closer than that.

Element in the bottom protected it and thermostat from damage. The 10 gallon element would just heat faster. I figured that one hour of driving to heat the water was OK. Do you have enough electrical power to run the larger element? I run mine off a 600 watt inverter powered by the Sprinter 12 volt system. Do not know why you would want a partial fill. Full gives about 7 minutes of shower time with the pump I used.

Soda canister looks fine and is cheaper than the beer keg. The pump on mine is not fastened to the keg. The beer keg has a lip at the bottom of the top opening. The plastic PVC coupling just sits on that lip and the pump is suspended in keg.

Have not used it enough to have any more comments. Have not finished the shower enclosure so can not use system. If I build another conversion, the keg will allow me to simplify the water system. The only piping will be a pipe from the bottom the freshwater tank to the sink. Will use a small quiet solar centrifugal pump. Plumb in two faucets lower than the tank bottom. One before the pump to drain the tank and one after that I can attach a hose to fill the keg. There will be a small bleed hose after the pump to return a small amount of the water to the tank. The bleed hose is needed to keep the pump cool if I forget to electrically turn off the pump. (At my age
anything can happen). I have tested the above system to see how well it would work. Test proved the design.

Keep us informed on your progress.

Will Rule 24 pump handle 90 degree water? My pump had inlet at the bottom and outlet at the top which made it easy to install.