Using a 7.3 coolant line for hot water heater

[bemerritt]

SO I am planning my water system and found a good deal on a water heater:

Webasto Isotemp 602521 Slim 25 Round Electric Water Heater



I've read somewhere on here about performance of something like this, but I cant find it.

Basically, want it for post surfing showers. I surf a lot that is about a 10-15 minute drive away. Any idea if that length of drive will be long enough to heat up the 6.5 gallons? I'll have the option to plug this into my honda for extended stays, but I think between the drive to the surf spot, and this being my daily driver, I should be able to maintain hot water pretty easily.

Bonus question: Any idea how easy it is to tie into the coolant loop? I would have this mounted next to my water tank in the rear spare tire area, so the coolant line would be lower than the highest part of the loop under the hood, which I have found out to be important.

Tanks for any and all info regarding this!

[rallypanam]

No info, but I'm intrigued. Keep meaning to rig up hot water in my van.

[bemerritt]

Feel like 6.5 gallons should heat up quickly. Also keep reading how the water should stay hot for 24 hours. So should be perfect for my uses. This plus a 20 gallon tank/pump should just be able to fit in the spare tire.

I guess my main concern is my ability to hook up the coolant line, but maybe this is an order first, figure out later situation.

[daveb]

750 watt is a hefty load around 6.5 amps at 110 voltages and a bit over 60 amps at 12vDC. Is the idea to heat the water at home, drive to go surf and hope the 6.5 gallons of water is hot enough after you get out?

[bemerritt]

Its a two way heater. When driving, I'll insert it in the coolant loop. So "free" heat while Im driving. Pretty much after a certain distance of driving, I should have 6.5 gallons of 160 *F water. It should remain hot/warm enough for showers for quite some time.

edit: its the distance needed to travel to get hte water up to temp and how long it stays hot/warm that are the unknowns. Well that and how hard it will be to put it in the coolant loop

If boondocking for a long period of time in one place, which i rarely do, i could fire up the generator and power the 750 watt element that way. In theory you could use the house batteris/inverter, but that would really drain them.

[daveb]

Oh yeah not to mention if you aren't running a high amp alternator there can be issues. A heat exchanger isn't a problem but I'd be researching how long (coolant line) runs and heat loss affect the temps at the flat plate.

[bemerritt]

Not sure if I follow the alternator comment, if the engine is running, the coolant loop would be heating up the water, not the 750 watt element.

The extra coolant shouldnt be too big of a problem. But yeah, keep the run as short as possible and have the heat exchanger be below the highest point in the loop is what I have gathered online.

It seems people do this quite a bit with the espar d5 and a plate heat exchanger. The benefit to this design is keeping the water warm after heating. Ofcourse, a d5 could always be added down the line.

[daveb]

No I agree with you. That would be if you wanted to run an inverter to power the element and not install a flat plate. That would probably cost more than dealing with a installing a heat exchanger. You just have to deal with winterizing unless the lines and flat plate are inside. I've already lost a flat plate to cold temps but at least it didn't contaminate my water system. I also worry a bit about a ruptured coolant line while off roading but so far so good.

[schluchtenflitzer]

I have nearly the same in mine. It is the quader shaped.
Of course it depends on the outside temp and where you have conected it on the engine.
I made some "T" in the line to the inside radiator (in the engine room) and than have loooong lines to the end of the van where my boiler is. At mine it takes about 10 to 15 min drive till the water is warm enough for shower. Maybe 30 min till the water is hot so you need to mix it with cold water. The water stays over night warm enough to take a shower in the morning without runing the engine.
I also built in a warm water heater (webasto) that is also conected to the system. So in case i stay longer i do not need to run the engine. I just switch on the heater and after 15 min the water ist hot ;-)

[arctictraveller]

I have no direct experience with that heater, but as a point of reference I have a similar 14 gallon set-up in my boat. Starting with ambiant temp water (possibly colder than where ever you are) and only heating it using the coolant loop from the engine, it takes a solid 1.5 to 2 hours to fully heat. The coolant loop is from a 6cyl 350CI diesel running at a continous load of about 50 to 70% the entire time. Once it's hot, it will easily stay that way overnight. And when I say hot, I mean really hot, like the same as the engine coolant (perhaps 170 deg's) and that's hot enough to burn you if your not carefull. The nice part about that is you mix in much less hot water and more cold, so it lasts longer. The electric element (1200W I think) is set to cut off at about 120deg's. Using shore power, we can heat the water in a similar amount of time as using the engine alone. My guess is that your short drive won't fully heat the water, but if you are plugged in prior to leaving home, it will still be really hot at the end of the day. A 10 minute drive is barely enough to even get the engine hot enough to open the thermostat.