Engine powered water heater?

[Scorpion Regent]

Has anyone ever rigged up a water heater off their engines cooling system?  It's probably impractical.  I'm in no position to do it.  I'm just curious if it has ever been tried.

 

[Scorpion Regent]

Well I did some research.  There is a system out there Motor Aid that allows the cooling system to heat water while driving and uses propane when the engine is off.  They have been installing them in RV's for at least 20 years, according to what I read. 
My interest is more along the lines of DIY, but knowing it can be done reliably enough to sell is something.

 

[abnorm]

https://vanlivingforum.com/showthread.php?tid=43597

 

[highdesertranger]

Plethora of guns also did it. Highdesertranger

 

[Scorpion Regent]

thanks for the thread point Abnorm 
and the mention HDR

 

[Vannautical engineer]

Yup thanks abnorm.

Yes I rigged up a coolant water heater in my Transit Connect. It works great. However, it was definitely the biggest task I did in the whole van from a labor time standpoint. Probably spent over 100 hours of work putting it all together. You might be able to slap one together with a little less work, but not much.

Like I said in the other thread, if you have the room in your rig, I would probably advise buying one of the commercial units that heat water with your coolant. I didn't have any extra room for a water heater, which is why I made my own, which takes up pretty much no room in my interior. As far as I know, none of the commercial units work like mine where they heat water on demand off of the coolant with a heat exchanger. They all use a storage tank for the hot water and heat the water in the tank.

 

[PlethoraOfGuns]

Getting hot water from your engine coolant is practical and efficient. Heat is a wasted by-product of running an engine. Might as well harness that energy and make hot water! Can be done reliably during a weekend for around $200-500.

You can throw in a water heater tank that is heated by engine coolant, or go simpler and just throw in a heat exchanger in between the engine and vehicle heater core, run water through that to make hot water. But that means you need to run the engine to get the hot water, like an on-demand system. My last rig was simple like that, but running the engine got annoying. The water heater tank setup is nice since you have plenty of hot water long after you turn off the engine.

The only person that is able to handle the setup that Vannautical engineered, is probably Vannautical. Kudos to him for making that crazy setup work. If you like complicated crazy things, check out his setup, he did a great job.

 

[Vannautical engineer]

Even though I made a pretty complicated system of electronic controls on my system, a simple way to get around having to run your engine to get hot water from an on-demand coolant water heater would be to just throw one of these 12V electric water pumps in the line between your engine coolant and the heat exchanger. You could just have it on a simple on/off switch. That way, you could continue circulating hot engine coolant through the heat exchanger even after the engine is off. You would have plenty of hot water until your engine block is cooled off.

Just one thing to note though, you need some kind of way to regulate the water temp coming out of any heat exchanger setup. Because if you don't, you will probably end up with fresh water that's about as hot as the engine coolant, around 200deg F.

For reference, I can confirm the inlet and outlet of this pump fits 3/4" inner diameter heater hose.

https://www.amazon.com/gp/product/B0016IDG6A

And heres a connector that fits it... If you want to shell out $21 for a connector. A better route is probably to figure out what car had this coolant pump in it, and get one from a junk yard.

https://www.amazon.com/gp/product/B000C9VW9M

 

[PlethoraOfGuns]

I like the idea of pumping coolant around a hot engine. But now you got two pumps, getting kinda complicated. Most people on this site probably just want to put hot water into a bucket. Having pressurized warm water come out a shower head anytime you want is the ultimate luxury. It's possible, but you really gotta want it and understand that there are more complexities as your desire for more luxuries also rises.

On my last rig where I just stuck a heat exchanger on the engine, I also had a thermostatic mixing valve right at the shower head. The hot water from the heat exchanger mixed with the cold water before the heat exchanger and bam, perfect temperature all the time. When I was really feeling pampered I would park next to a lake or river, start the truck, pump water out of the body of water and just sit under the shower for a good 20min or so. I felt like a king!

 

[Vannautical engineer]

I like the idea of pumping coolant around a hot engine. But now you got two pumps, getting kinda complicated.

I mean yeah, a little more complicated. But if you're going to run any kind of coolant water heater, you are already tearing into your cooling system, so you already need to have a little bit of skill. Just having an electric pump on an on/off switch in the loop wouldn't be too bad. Also be aware that that electric pump does not impede flow very much (if at all?) when it's not running. So even if it failed, you could still circulate coolant when the engine is running.

And I also really like the idea of being able to scavenge the heat off of a hot engine without actually running it. I have gotten hot water out of my system at least an hour after I last ran the engine. Granted that was during the summer. The engine will not retain heat so well when the weather gets cold.

 

[KarlH]

I'm assembling one that works in both directions, i.e. the engine will heat water for the living space, and the water heater will double as a block heater when parked.

If cost is no object, you could buy a Dickinson Marine stove with a built-in water heater and use a water-to-water heat exchanger and a pair of circulator pumps to trannsfer heat back and forth.

 

[KarlH]

Re: pumps, you can buy aftermarket electric water pumps for GM small block engines that are a drop-in replacement for the OEM shaft-driven pump. Maybe one of those could be jury-rigged to run from battery when the engine/ECM are turned off...?

 

[Freelander]

Winnebago installed some of these unit in their RV a few years back.

 

[maki2]

Works fine for days when you are sctively traveling. But for long stay boondocking camping when you do not want to drive. Then you would be forced to idle your engine which is not the best thing for the engine.

Not something I would be bothered with. I also do not take long showers or have a large onboard water tank. It gives very little advantage to people who wish to practice water conservation. Just because you can does not mean it is worth the effort and the expense.

 

[gsfish]

One of my neighbors is hosting a friend with a Earth Roamer RV (how the other half lives).

Their rig is set up like KarlH's project (^). Engine can heat water and water heater can heat the engine.

The couple that owns the Roamer are wildlife photographers and have been boondocking in as low as -20f weather. The rig is 4X4 and air bags can lift it another 6" over what is seen in the photos.
https://earthroamer.com/

Guy

 

[KarlH]

The rig is 4X4 and air bags can lift it another 6" over what is seen in the photos.
https://earthroamer.com/

That looks excellent 

 

[Vannautical engineer]

Works fine for days when you are sctively traveling. But for long stay boondocking camping when you do not want to drive. Then you would be forced to idle your engine which is not the best thing for the engine.

Not something I would be bothered with. I also do not take long showers or have a large onboard water tank. It gives very little advantage to people who wish to practice water conservation. Just because you can does not mean it is worth the effort and the expense.

My setup takes maybe 5-10 minutes of idling from a cold engine to get enough heat in the system to have enough hot water for me to wash myself off. My shower is not completely enclosed as well, so when I take a "shower" I am really not using much water because I don't want it to go all over my van. I probably use less than a gallon each time. Water conservation is fine, but regardless of how much water I'm using to get clean, I don't want it to be ice cold.

Anyway, the point is, it does not take much idling to get enough engine heat to heat water for a shower. And despite the myth that seems to be rampant, there's nothing magically bad about idling your engine. It's just running the engine, it's what it was made to do. It's no worse than driving the same amount of time. Now if you are consistently doing it for like 12hrs at a time like a cop car or something may do, that will gradually over time put more wear on the engine than the odometer shows, but again it's all just proportional to how much idling you're doing.

Extremely extended idling without ever actually driving could also build up carbon in the engine. But idling 5-10min per day to get some hot water is absolutely nothing. You would need to do thousands of times more idling than that, along with barely ever driving, which burns out carbon deposits, to actually have an adverse effect.

 

[Vannautical engineer]

Re: pumps, you can buy aftermarket electric water pumps for GM small block engines that are a drop-in replacement for the OEM shaft-driven pump. Maybe one of those could be jury-rigged to run from battery when the engine/ECM are turned off...?

This is exactly what I use in my system to circulate coolant when the engine is off, an ACDelco electric water pump.

Just an FYI, the inlet and outlets for this pump are sized for 3/4" inner diameter heater hose. Oh and the pump does not completely restrict flow when it's not running, so don't count on it to stop flow when it's off. You need a separate shutoff valve for that. Also just for what it's worth, this pump seems to have some kind of electronic controller in it. You supply it normal 12V to run it, but I noticed there's about a 1 second delay between when you apply power and when it starts running, so there's some kind of electronic smarts within this pump. Doesn't really matter to me though. Just don't expect to reverse the voltage and try to run it backwards or anything crazy like that. It is more than just a normal motor inside. When I apply voltage to it backwards, it just doesn't run.

https://amazon.com/gp/product/B0016IDG6A/

Also it's stupidly expensive for one little connector, and if you can find it for cheaper then get it, but here is a connector to fit this pump. A cheaper alternative would be to carefully cut off the plastic connector housing around the pins on the pump, and solder wires directly to the pins on the pump.

https://amazon.com/gp/product/B000C9VW9M/

 

[Spaceman Spiff]

 . . . And despite the myth that seems to be rampant, there's nothing magically bad about idling your engine. It's just running the engine, it's what it was made to do . . .

Not a myth, fact established through extensive testing:
"Studies in laboratory engines equipped with radioactive piston rigs show the wear is highest curing a cold startup.  Corrosion by condensed combustion products is responsible."
Startup Wear In Automobile Engines, Kalinowski and Nejdl, SAE paper #600190 (fee required)

Paper states that most gasoline engine wear occurs in first 10 minutes after cold start (i.e. ambient temperature).

 

[Vannautical engineer]

Not a myth, fact established through extensive testing:
"Studies in laboratory engines equipped with radioactive piston rigs show the wear is highest curing a cold startup.  Corrosion by condensed combustion products is responsible."
Startup Wear In Automobile Engines, Kalinowski and Nejdl, SAE paper #600190 (fee required)

Paper states that most gasoline engine wear occurs in first 10 minutes after cold start (i.e. ambient temperature).

This is splitting hairs to such a degree that it has basically no relevance to the actual real world usage we're talking about here.

What's at issue is the idea that periodically starting your engine just to warm it up would cause undue wear and tear to it, presumably so severe that you need to worry about it causing the engine to fail prematurely. (Otherwise why are you even worrying about it?)

But to even have the usage that's being talked about, this is assuming a vehicle that is being used for long term stationary boondocking living where the vehicle isn't being started and driven very much anyway. So right off we're starting from a point of an engine that is being used far less than someone's daily commuter vehicle, which would have at least two cold starts on the engine per day. And we know that a vehicle used for daily commuting can have reasonably good engine reliability since millions of people use their cars like this.

So the point is, if you are using your engine so little that you aren't starting it and warming it up in your normal course of using the vehicle, so you need to start it and run it specifically just to heat water from it, you are already using your engine way less than a normal vehicle. So your engine is probably going to last for longer than a normal vehicle to begin with.

So in this case, the engine should be the least of your worries. Various other rubber seals and other rubber and plastic parts of your vehicle are likely to be dry out or fail just by age alone and that would be the death of your vehicle long before the engine that you barely run physically wears out.