Hawk hot water heater

[4wsilver]

I have a 1990 Hawk and of course it came without a hot water heater. Putting one inside takes up too much valuable storage space. I saw a thread discussing something else and ran across someone who put an ecotemp L5 heater on one of the FWC models. Searching led me to many who have used this and the similar competitors on RV's. The one problem seems to be that the flow rate has to be too high and this uses too much water for dishes, etc. My Vixen Motorhome uses a hot water heater that heats water by heat exchange from the engine/Webasto cooling system. It probably only holds a quart of hot water or so. (In operation, the tank produces plenty of hot water till the main tank in the Motorhome runs out.) I thought, hey, get a separate pump, put antifreeze in an ecotemp/exchanger system and heat the potable water by heat exchange. This would allow a sufficient flow to turn on the ecotemp and the small tank would buffer the heat cycling. I will need a temperature switch (old electric hot water heater?), a pump that can withstand hot water and deliver the pressure to force 0.5 gpm through the 1/4 inch inch tubing on the ecotemp (about 20 PSI), and a small heat exchange water tank. Unfortunately, although the ecotemp is resonable in cost (around $100), the cost of a hot water pump and heat exchange tank is not. I have decided on the following:
1. Mount the ecotemp to the left of the door, relocating the rear light when converted to LED.
2. Mount the new pump on the wall behind the sink.
3. Use a pump that is $19.95 for a centrifugal stainless steel unit but only rated for 120 F. The pump seal is the only item that lowers the rating and a seal kit for the 250 degree pump is $6.95. They even state on the internet that the seals are interchangeable between the pumps. The 250 degree pump is $185. Is that what they call fuzzy math?
4. Use an internal Bunn coffee pot tank from an old coffee maker. It is stainless, holds one quart, It has a temperature control, dip tube, 110 volt standby and can be disassembled to clean the inside. Plus I can get another at Goodwill for under $10.
5. Use the smallest pressurized expansion tank I can find from a junk yard car with a 15 psi radiator cap to fill the antifreeze system. Mount outside near the ecotemp. Put on cover to please the aesthetic director.
6. Wrap the tank with electrically insulating but heat transfer tape. Then coil 3/8 copper tubing around that.
7. Change out the existing water pump for the small flo-jet pressurized pump.
8. Change the kitchen faucet to a normal hot/cold unit.
9. Mount the insulated heat exchanger to the right under the sink against the wall.
10. Learn new curse words for plumbing it all up in such tight spaces. Praise FWC for making the front of the cabinet so easy to remove.

If this sounds interesting or stupid, let me know any ideas or suggestions you might have before I start. I will post results with pictures when I get it started.

 

[pods8]

Unless you're going to use it a ton why not just add in a hot water holding tank and pump and just fill it with hot water when you'll occasionally use it (either from a pot off the stove or this ecotemp deal, or other on demand water heater)? You've then cut out the heat exchanger and antifreeze from the mix.

 

[Sam]

I thought you wanted to save space? Sounds like by the time your done adding tanks, pumps, & heat exchangers the camper will be full? On a serious note, I have an Ecotemp on demand heater, and it fires at an impressively low flow rate. I only use it for showers so the flow for showering may be more than you want for dishes?

 

[davinski]

I gotta say that hot water is a definite plus and very impressive to newbies when on a trip. When showering, man does it feel good.

That being said, i think that the KISS aspect of water heating is always good. Save space and don't over engineer. Your setup sounds good, but might be overkill.

I have the tankless water heater. It attaches outside, I use a simple 12v pump. buckets of water. in the winter, it stays at home saving space. sets up in a few, works like a charm.

Just my 2 cents worth. Good luck.

dave

 

[4wsilver]

I guess there were always 2 different KISS principles that should be considered. One is the simplicity of the design or modification, and I understand that. The other is the simplicity of repeated tasks. I guess I am probably going for the latter, since the day to day operation of the unit involves more total time than the modification does. I also have studied the product, and the ability to heat the water in the small tank to 180F allows the use of it to make drip coffee in my one-cup filter. We usually don't go just for the weekend and on our extended trips, the heating of water for dishes is a chore. I also think it uses more water when poured from a pot to rinse the dishes. Did I say, it also delays my COFFEE!!!

The space for the various interior parts take up a lot less space than a regular tank type heater. They are distributed in small pieces so they can be tucked away in otherwise unusable locations. The demand unit will be located on the back of the unit and will not take up any interior space.

I still plan to make this mod, even though many of you have about the same opinion as my wife does.

Wally

 

[pods8]

Here's what I'm hearing though (pardon if I'm thick, working on my morning caffeine).

You're concerned the on demand unit might not work with too low of flow. So you're going to end up adding a coolant loop, heat exchanger, and pump which will be heated and then you'll use that to heat your water and use the on-demand unit to heat the coolant. Right?

It still seems KISS to me on both installation and use if you just use the on demand unit to heat hot water, on the discharge of it have a direct line to faucet for when you want high flow hot water and a diversion to a small holding tank (take the place of your heat exchanger) which you can draw water out of more slowly with a small pump.

But good luck either way and be safe!