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Discussion Starter #1 (Edited)
On our 2015 159 HT EXT we ordered the rear heat / ac option with the idea of having an engine heated HWH. I'm thinking of a Isotherm SPA model in 4, 6.5 or 8 gallon size. I like the 750 watt heater as it will be manageable with a 2kw inverter and 460 ah battery pack if not running the engine.

I don't really know what the $96 package got us except for a pack of two 'T' fittings and clamps (pic). The 'T's are 3/4" x 3/4" x 3/8". My assumption is that they should be installed in the heater hoses near where they attach to the dash heater at the firewall (pic). My tank will be near the wheel well on the drivers side so I figure about 15' of hose each way (30' total). I'll probably go with 1/2" heater hose as 3/8" sounds pretty small for that run. I assume the flow will be adequate as it works for the dash heater. I'll install a ball valve to shut the system off if needed. Perhaps I should put a ball valve near each 'T' in case a tube would get damaged where they run underneath.

It doesn't look easy going underneath with the hoses, particularly from the firewall back to where the load floor starts. From there it looks like I can stay along the rocker panel pretty much. It would be great to go under my plywood floor (3/4" with 1" polyiso underneath) but I don't have a clue as to how to get in there from the front. I'll probably try to wrap some EZcool insulation around the hoses.

Has anyone installed this type of system yet? I read Seapro's post about his isotherm tank and he was concerned about warranty implications of an engine connection. I figure if they sell a rear heater kit it should be okay to install it. Of course I don't have any specific info from FCA on how to do it and the upfitter's guide doesn't address it.

I'd appreciate any thoughts on how to best go about this installation. Bill
Rear Heater fittings.jpg

Heater connections.jpg
 

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I'll be watching this thread. I have an electric only WH in my RV (Travato) that I'd love to exchange for an electric/engine coolant model. I wanna see how the hoses are supposed to be routed.
 

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Sportsmobile forum might have someone who can help. They've been putting those type of systems on Sportsmobiles for years.
 

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Discussion Starter #5
Zoomyn
I have purchased 3/8" silicone heater hose, fittings, and ball valves but have not yet proceeded with the installation. I plan to buy an Isotemp 11 gal HWH but may drop back to an 8 gallon. It looks like I can install the 'tees' where heater hoses go through the firewall to the front heater. The brass ball valves would be installed near the 'Tees' so the system can be completely shut off. The hoses would then go under the gas tank and be sandwiched between my 3/4" wood floor and the metal van floor (in the space where my 1" polyiso insulation will be) surrounded by detail foam. The HWT will be located beside the driver rear wheel housing (under the bed). I bought 3/8" hose because that is the size of the 'TEE' supplied by Chrysler with my rear heater option. I'm feeling my way along on this and would appreciate ideas & comments. Bill

HWH Link: http://www.defender.com/product.jsp?path=-1|51|2234308|2234312&id=2357759

Note: for some reason I can't get the 'insert link' option to work!
 

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I've been toying with ideas for a while on a long term RV trailer project, just not enough incentive to complete it, especially with $4 fuel and an aging pickup truck tow vehicle now traded in on my PM. In Minnesota thoughts of staying warm are kind of dominant, eh?

Having the engine take-off lines boost the dashboard 36,000btu output heater would make the cargo area more tolerable for passengers or camping but we got to remember CONSERVATION is key - insulation and window treatments to keep equipment & fuel cost outlay down, in a commercial vehicle someone else pays those costs that will never happen in a camper van. Running the engine without traveling makes it very expensive heat so storing some to extend comfort zone temperatures seems logical.

If* you haven't leapt yet, look closely for the water heater tanks with dual tube exchange coils, the engine coolant coil plus an additional one...

There are many things to maybe do with that extra tap, from 'instant on-demand potable water' that is double shielded from toxic coolant contamination (required under various new renewable energy health codes, "double wall heat exchanger") to having a solar input or a separate extra small radiator style forced air heater tacked into the system without much effort, so only draining the water tank itself to winterize and not the other lines.

To use coolant sourced space heating: calculate a 40°F minimum temperature difference of heat source, there is not much energy available below that to jump material phase changes, water/solid to air in a radiator etc.

11 gallons of water theoretically requires 9000btu to heat 100°F above ambient, take back the above mentioned 40°F, so there is about 5400btu usable heat held in the tank. See http://www.mhi-inc.com/Converter/watt_calculator.htm for hours of fun tweaking various situations.

My long term project is an 27' Airstream trailer - I've collected two small marine hot water tanks, an Isotemp 20 liter and an other brand both with 750w electric heater coils, and an Eberspaecher hydronic diesel fired heater, plus a couple of forced air radiators for possible use in the trailer but that project is on hold until I get my PM tow vehicle outfitted...

For the van? I'm leaning toward an engine tap and a 5 gallon holding tank dedicated for domestic use, maybe a section of baseboard heat radiator, and a small diesel-fired air heater. There is a combined Webasto diesel air/water heater but that is very expensive.

Note - just having a heated water tank built into a conversion adds to the living area baseline heat input (slow output) since the tanks usually got terrible insulation. That bonus will work against us when summer comes..

Also, being able to shunt off the engine block coolant lines from inside the Van, having an additional set of ball-valves, might readily pay for itself...
 

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Discussion Starter #7
Finally got around to running coolant lines for my Isotherm HWH. I must warn you that I could find no instructions from Ram and I'm simply doing what seems reasonable & logical. I hope that a few months from now I still have that opinion.

First thing I did was remove the coolant reservoir tank and cowl drainage tube for better access. After cutting the heater lines near where they go into the firewall I installed the two 3/4" by 3/8" tees supplied by Ram for the rear heater option. They are made of black plastic, probably with some kind of fiber reinforcing. My new coolant lines are 3/8 silicon heater hose and I found that 1/2" stainless clamps for use on PEX work perfectly. The silicone hose is rated for about 70 psi and 270 F.

As close as possible to the tees I installed ball valves in both of the new 3/8" hoses which will allow complete isolation of the rear heater system. The lines then follow the firewall down & back along the driver side box beam & above the fuel filler tube. Then under the box beam, above the emergency brake cable sheath and up through the floor. My floor will consist of 3/4" plywood over 1" polyurethane foam and the 3/8" hoses will be encased in the 1" foam back to the rear wheel housing area.

In the attached pics I have not yet fastened the hoses in place which I plan to do with zip ties to brake lines, fuel lines, and anything else which is solid and handy. I have some scrap epdm 'Water & Ice' roof membrane which will be used to protect all points of hose contact and provide extra protection for any place that seems vulnerable to flying road debris.

I would add captions to the pics but can't figure out how to do it. I created an album on this site, added captions, but can't figure out how to transfer the photos from the album to a post. The pics you see were uploaded from my computer. Hints?
 

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I am thinking of adding engine coolant heat to my hot water heater as its coolant heat exchanger loop is currently not used. Have you had any problems with your setup? Would you do anything differently the next time? Have your, I assume plastic, wire ties been OK around the hot hoses?
 

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I abandoned the idea of replacing my electric only Atwood WH with an electric/engine coolant heat exchanger supplemented WH after reading some instructions about the new heater. It turns out that Atwood does not recommend running coolant through the heat exchanger constantly as this will overheat the water. Some method of thermostatically controlling the flow of coolant is necessary and way too complex for me.
 

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Finally got around to running coolant lines for my Isotherm HWH. I must warn you that I could find no instructions from Ram and I'm simply doing what seems reasonable & logical. I hope that a few months from now I still have that opinion.

First thing I did was remove the coolant reservoir tank and cowl drainage tube for better access. After cutting the heater lines near where they go into the firewall I installed the two 3/4" by 3/8" tees supplied by Ram for the rear heater option. They are made of black plastic, probably with some kind of fiber reinforcing. My new coolant lines are 3/8 silicon heater hose and I found that 1/2" stainless clamps for use on PEX work perfectly. The silicone hose is rated for about 70 psi and 270 F.

As close as possible to the tees I installed ball valves in both of the new 3/8" hoses which will allow complete isolation of the rear heater system. The lines then follow the firewall down & back along the driver side box beam & above the fuel filler tube. Then under the box beam, above the emergency brake cable sheath and up through the floor. My floor will consist of 3/4" plywood over 1" polyurethane foam and the 3/8" hoses will be encased in the 1" foam back to the rear wheel housing area.

In the attached pics I have not yet fastened the hoses in place which I plan to do with zip ties to brake lines, fuel lines, and anything else which is solid and handy. I have some scrap epdm 'Water & Ice' roof membrane which will be used to protect all points of hose contact and provide extra protection for any place that seems vulnerable to flying road debris.

I would add captions to the pics but can't figure out how to do it. I created an album on this site, added captions, but can't figure out how to transfer the photos from the album to a post. The pics you see were uploaded from my computer. Hints?
Great info, thanks for posting it.
FWIW - you can just cut and paste links into your posts without doing anything else and if you use something like the free postimg http://postimg.org you don't have to fool around with the sites image solution.
 

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Re post 10 above: For decades on boats we have run the coolant continuously through the heaters heating the water to a scalding about 190 degrees -- the temperature of the engine. Regulations now require the newer heaters to have a bypass with cold water from the input at the bottom going to a thermostatic mixing valve at the output top end of the heater. This controls the output to about the same temperature (about 120 F ?) as that obtained by the thermostatically controlled electric element.

Thermostatic control of the coolant flow is, I think, not practical.
 

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CUT.........
Thermostatic control of the coolant flow is, I think, not practical.
I agree but why would you need it or care? For years I heated our domestic hot water from a coil in my wood-fired furnace. On cold winter nights up near the Canadian border that baby would get the 40 gallons of water in my hot water heater to boiling. And yes I had a good Pressure/Temperature relief valve I changed out occasionally to protect everything. We then had a tempering valve which mixed that scalding water with the cold side to get it down to 135º as back then that was considered safe. All this worked fine for 30+ years. Nice free hot water, "safe" temperature, simple plumbing, whats not to like? Man did I hate to pay for the propane in the summer!
 

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I was not correcting you as I understood what you meant I just think letting the coolant circulate freely and tempering the hot water avoids the issue you raised which was valid too. I expect there is some code or rule about heating the hot water to 190 but in Vermont when I was building up there they had the hot water heated to 165º+ and tempered the hot water coming out just like I used to so it might be allowed. The issue was that the hotter water killed the Legionnaires bacteria so you didn't get sick after using the hot tub (or shower I expect.)
 

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Discussion Starter #16
I bought an Isotherm Spa 40 ISO 6P4023SPA0003 HWH from Fisheries Supply for $500 shipped (xmas special). This model comes with a tempering valve which is essential for this kind of installation. As others have mentioned controlling the heat may be an issue as my Promaster coolant temperature often gets in the 210F area according to my Ultragauge OBDII monitor. The manual for the tank says 200F max. I did use small 3/8" silicone heater hose rated for 270F and perhaps there will be some temp drop in the 15' run to the tank. I have quite a bit of experience with my home solar HW system so I'm not too intimidated (yet). It may be that I have to limit the flow by leaving one of the ball valves partially shut. Or perhaps I'll just shut off the flow manually when the HWT gets up to temp. In a few months I'll post the good (or bad) news.
 

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RE: Continuously circulating coolant.


Reading the manual for the Atwood Marine water heaters it states "Engine coolant circulating through the heat exchanger for more than two hours will create excessively hot water". Then it goes on to say "The EHP-10 is equipped with a thermostatically controlled...heat exchanger...which will prevent the water from becoming excessively hot".


In my coach I wouldn't be considering the 10 gallon version but the EHM4, so I assumed, maybe incorrectly, that I would have to come up with some system that would limit the temp of the heated water.


Maybe I need to contact Atwood directly as I would love to use engine heat to warm water. Now I need 110v available only when I plug into shore or run the generator.


 

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I don't think trying to control the temperature by just cracking one of the ball valves will work. In the 1970s we had a boat that tried this. If the valve was only very slightly open a trip of an hour or so "around the corner" to a close by anchorage would give us only lukewarm water. A trip much longer gave scalding water. The only control was manual control of the valve.

Engine coolant can be over normal boiling temperature but it is restrained from boiling as it consists of a chemical mixture with water and it is under pressure. It can possibly get to well over 212F. The water in the hot water tank could conceivably boil putting high pressure on the piping/hoses until the tank's pressure relief valve pops open. If there is no water pump on to refill the tank a very dangerous situation can develop with the tank partly empty. If the electrical element is later turned on it could burn out.
 

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Discussion Starter #19
Seems like the answer would be to have a thermostatic control valve in the hot line from the engine with selectable set point between about 150F & 200F. The engine thermostat controls pressure in the antifreeze lines but it would probably be good to have a pressure relief valve in the domestic HW line at around 50 psi (a little higher than the water pump max pressure) or an expansion tank. I know the expansion tank and pressure relief valve are readily available as standard plumbing items but I haven't found an ideal thermostatic control valve.
 

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Look in home heating Thermostatic Radiator Actuator(TRV) here's a link to one to get you started.
http://www.supplyhouse.com/Honeywell-T1002W0NA-Thermostatic-Radiator-Actuator-w-Integral-Sensor
Seems like the answer would be to have a thermostatic control valve in the hot line from the engine with selectable set point between about 150F & 200F. The engine thermostat controls pressure in the antifreeze lines but it would probably be good to have a pressure relief valve in the domestic HW line at around 50 psi (a little higher than the water pump max pressure) or an expansion tank. I know the expansion tank and pressure relief valve are readily available as standard plumbing items but I haven't found an ideal thermostatic control valve.
 
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