Camper project - Building your own tankless water heater

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  #1  
Old 02-20-08, 02:16 PM
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Camper project - Building your own tankless water heater

I've got a camper project with a '94 Ram 2500 Diesel. I'm working on the water system now, and want to go with an electric tankless water heater.

I think this is something I could make myself, for fun. If it doesn't work out, they're only about 120 bucks.

Any tips for building one yourself?

Here's what I'm thinking so far.
Make a box out of sheetmetal, 1"X4"X6".
Put a threaded hose fitting on one corner, and then the opposite corner, for your inlet and outlet. Put a heating element, snaked up and down 3-4 times.
Then you'd need a water pressure switch to activate the heating element.
You could use a rheostat to adjust the temperature.

What do you think?
 
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Old 02-20-08, 03:51 PM
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This would be a waste of time.
Sheet metal can not take normal water pressure, a rheostat will not control the temperature and the cost to assemble the correct parts would exceed the price of buying one.

Not to mention the safety of any people who stayed in the camper.
 
  #3  
Old 02-21-08, 03:21 PM
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Originally Posted by GregH View Post
Sheet metal can not take normal water pressure
Even if a properly bonded sheet metal box wouldn't do the job, finding a suitable container shouldn't be a problem.

Originally Posted by GregH View Post
a rheostat will not control the temperature
Ok, I don't need to explain what a rheostat is. I assume you know, and I assume they make them in any resitance you want, so why would it not work?


Originally Posted by GregH View Post
the cost to assemble the correct parts would exceed the price of buying one.
Not only cost but time involved, MIGHT exceed the price of one. If you know the correct parts I'd love to hear 'em, so I know what'd be involved.


Originally Posted by GregH View Post
Not to mention the safety of any people who stayed in the camper.
Yes the safety of those who stay in the camper will be taken into consideration.

Oh also, I'll have to see how much power a commercial product uses, heating the water, and see if I could come even close to it. Otherwise if it requires too much power, i won't bother either.


I appreciate your input Greg, I'm just trying to see if this could work.
 
  #4  
Old 02-21-08, 03:34 PM
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I'm thinking that this

would be really power hungry, as it takes a lot of juice to heat water. I kind of lurk over in the electrical thread here, and I've heard of these needing over 60 amps at 220 volts.

While building something yourself might be possible, for a camper I'd look at a gas heater instead, so that you aren't running a large generator constantly.

Not an expert, but I think newer campers use an instant heat gas system. Maybe check out some dealers in your area?

I hope this helps!
 
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Old 02-21-08, 03:48 PM
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Thanks Desy,

My goal for the camper is to only use diesel or electric.
If I could find a cheap small diesel powered water heater, that might be an option.
 
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Old 02-21-08, 03:48 PM
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Don't mean to discourage you but,

Ok.
You need a pressure vessel, not a container, as I assume you will have a pressurized system.
Not even so much for the water pressure but for the excess pressure a malfunction would create before the pressure release blows.
Which leads me to say you will need a temperature/pressure relief device.

To control the temperature you need a thermostat. You could use one from a hot water tank.

You will need an over temperature thermostat which is a manual reset safety which can also be used from a hot water tank.

You will need to provide a drain at the bottom to drain it.

Your inlet fitting needs to be at the bottom of the tank or if at the top a dip tube must be used.

All this needs to be wrapped in a thick blanket of insulation with a metal cover that allows access to the electrical and fittings.

If you do build the tank from scratch you MUST hydro test it to 1 1/2 times the operating pressure to ensure your safety.

If you do try to build this it would have to be because you want the experience because it would likely cost you no less than double the cost of buying one.
 
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Old 02-21-08, 03:53 PM
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Great stuff. Thanks Greg
Oh yeah it's not discouraging in the least.
 
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Old 02-21-08, 05:36 PM
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Oh ya.
You will need to weld fpt stubs for: drain, inlet, outlet, element and the pressure/temp relief.
And, a 120 volt thread in element.
 
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Old 12-29-08, 12:21 PM
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I donít know for sure but, the concept of on demand heated water is a tank-less one isnít it?
I think that if you could serpentine your tubing so that it fits inside of any case that you would build
There would be no need to store the water. As the water is being heated it moves through the tube and out of your spout, so there may not be a need for a pressure relief valve, though for safety sake it is a good idea. One of your main concerns should be how to heat the volume of inside the serpentine tubing. The answer is yes but propane is probably going to be your best bet for this. Otherwise the forth coming ideas, pro going for tank you would build sound good. Use a good grade stainless steel, and a pressure relief valve is a must.
 
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Old 12-29-08, 08:26 PM
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You can buy a ready made tankless suitable for 1 fixture for less than $100. However as mentioned, electric takes quite a bit of power to heat water fast enough to be usable. A small shoebox sized unit is going to need about 40 amps at 240v. Anything less isn't going to have the BTU's to supply a showhead with hot water.

Even a gas powered unit is going to take a lot of fuel to run.

You might could get away with a point of use unit that uses less power, but no one's going to want to take a shower with the kind of low flow rate it would be able to produce.
 
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Old 01-02-09, 09:19 AM
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Build a water heater

Im not getting how a pressure switch is going to turn the current on.
 
  #12  
Old 01-02-09, 04:30 PM
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I don't see any reference made to a pressure switch.
We have been talking about a temperature/pressure relief valve.
This a water valve that opens to relieve water pressure in the tank if the pressure or temperature gets too high
 
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Old 01-02-09, 07:27 PM
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here is a web site with 12volt heater elements, I have used them in plastic tanks to heat water for decon of eq in the field. you don't want to run them with out either a battery isolator or your engine running.
Diversion Loads @ Survival Unlimited.com - Water Heater Elements, Air Heaters, DC water heaters, DC air heaters

if we're not supposed to eat animals why are they made out of meat?
 
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Old 01-09-09, 09:15 AM
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Tankless heater

Originally Posted by GregH View Post
I don't see any reference made to a pressure switch.
We have been talking about a temperature/pressure relief valve.
This a water valve that opens to relieve water pressure in the tank if the pressure or temperature gets too high
Look at his first post next to the last line. RW
 
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Old 01-09-09, 07:23 PM
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Geeze, now that I have my glasses on I see it!

A pressure switch is in no way needed for a hw tank.
It would be a pressure/temperature valve that would protect against over heating/pressure.

The electric element would be switched with a thermostat.
 
  #16  
Old 01-10-09, 09:24 AM
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Water heater

I used to manage a ASME pressure vessel shop and we got a publication that showed various things that had blown up. They showed a motel where a water heater had blown up and destroyed a room sized section of the building. People dont realize what a bomb they are living with.
 
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