Heat exchanger/calorifier questions for hot water!

[Wanted]

So I'm ditching my motorcycle after months of traveling for more comforts of home. While in the planning phase of a van build out, I discovered the heat exchangers used to heat water using the waste heat from your engine. I had a couple of questions about this, if anyone has experience in this, your input will be valued.

1) My preference is to heat the water while on the move, circulating it through a hot water storage tank. However, as the engine can get quite hot I suspect the water in turn would get quite hot too. Is it typical for the heat exchangers, if left circulating, would heat the water over 212°F (100°C)?

2) If so, what is a suitable material to store the water in while it is at, or close to boiling point? I saw the polypropylene tanks maximum storage temperature was 212°F. Maybe it is better to have a temperature gauge on the dash so once the desired temperature is reached, you can just turn the pump off. I always forget to turn that kind of stuff off, maybe something can cut the pump off once the desired temperature is reached?

3) Has anyone had experience storing hot water, and has any idea of how long it would stay hot for after turning the vehicle off? I figure I'd have a 15 gallon hot water tank inside the vehicle, and wrapped in decent insulation to try maximize the heat retention (however long that may be)

The intended use for this is mainly a shower system and washing up water, I'd have a small tankless water heater as a redundancy.

 

[Joe917]

Our engine runs a constant 80 deg C, an hour or so of driving heats our 5 gal Spa Isotemp tank. The longer you drive the closer to coolant temp the water will get.
A mixer valve is essential protection to prevent scalding. The valve mixes cold water with the tank water to give safe hot water. The added bonus is you get more usable hot water than the tank's volume.
Water stays hot 24hrs or more, I have added extra insulation.
Our tank is 5 gallons and is enough for 2 showers, dishes and a load of laundry.

We use the 5 gallon version of this:
http://www.defender.com/product.jsp?path=-1|51|2234308|2234311&id=2357713

That is a good deal from Defender Marine.
BTW it was a replacement for the original Isotemp heater in our truck, 23 yrs of service.

 

[Wanted]

Our engine runs a constant 80 deg C, an hour or so of driving heats our 5 gal Spa Isotemp tank. The longer you drive the closer to coolant temp the water will get.
A mixer valve is essential protection to prevent scalding. The valve mixes cold water with the tank water to give safe hot water. The added bonus is you get more usable hot water than the tank's volume.
Water stays hot 24hrs or more, I have added extra insulation.
Our tank is 5 gallons and is enough for 2 showers, dishes and a load of laundry.

We use the 5 gallon version of this:
http://www.defender.com/product.jsp?path=-1|51|2234308|2234311&id=2357713

That is a good deal from Defender Marine.
BTW it was a replacement for the original Isotemp heater in our truck, 23 yrs of service.

Thanks for the reply Joe. As I am unfamiliar with that unit, is the heating element for when you turn off the engine to keep it heated for longer? If so, can that be turned off if you won't be needing hot water for a while? And do you have to get a pump to circulate the water from the engine cooling system, or is that built into the unit?

Thanks for the info, it looks great!

 

[dwh]

The engine has a water pump that circulates the coolant. It doesn't switch on/off.

You can rig a bypass valve just like the heater core has. They make them in manual or electric. If you got the electric bypass valve you could probably keep rigging and add a thermostat.

Better off with the mixing valve...which you'll almost certainly need anyway.

 

[Joe917]

The electric heating element is just another way to heat the water, you do not have to use it but it is a nice option. When we get a full charge from solar we will sometimes use the electric element.
The engine coolant pump is all that is needed. A bypass valve is not needed.
Shut off valves are always a good idea to make maintenance simpler.

 

[Wanted]

The electric heating element is just another way to heat the water, you do not have to use it but it is a nice option. When we get a full charge from solar we will sometimes use the electric element.
The engine coolant pump is all that is needed. A bypass valve is not needed.
Shut off valves are always a good idea to make maintenance simpler.

Hi Joe, have another question for you. Is it possible to mount this thing behind the rear axle?, or is it just too far away from the engine to be feasible to pump? I'm working on a layout of my van but can't really find room further forward.