Electric tankless hot water system

We investigated all the alternatives when setting up our Oka motorhome/camper and trying to heat water with 12v is pretty much an exercise in futility, takes way too long and uses way too much power.
We ended up fitting a Webasto Thermo Top which provides hot water and central heating, we have no LPG so use a Webasto diesel cooktop for cooking. An electric jug and toaster running off the PSW inverter take care of cuppa's and toast.

From an electrician POV, I'm not sure that you will find one. If you do, the current draw would be very high. Without a tank we are talking about instantaneous hot water which requires the water to be heated up within a few seconds. If you think it takes a 2400W (10A) kettle maybe 1 min to heat up a few cups (500-1000mL) of hot water (admittedly they are going to boiling point), you can only imagine how long the same 10A would take to heat up 20L for a shower, then if you add to the equation that the 20L is flowing through then you start to get some big number in terms of amps.

If someone is bothered you could calculate the actual energy required to do the job.

Bescat - try to google Hey Presto RV hot water - the space you gain by not having a hot water tank is taken up by the 3kva generator you will need to operate it.


A J

Have a look at these mate. I don't have any personal experience of them but was talking to a caravan salesman and he said they were beginning to become widely used. They use water as required and don't heat up a tank of what often becomes unused hot water. Most shower systems in the UK are run on a similar system as it eliminates the inevitable wasted energy. The hot water is just as instant as the usual 240v systems as it is heated through an element/heat exchanger.

Hi Bestcat,

Many RVs have their water heated by the engine water via a heat exchanger fitted inside the hot water tank.

I had one which I made up on a 38 foot cruiser I owned about 35 years ago. It worked brilliantly. I started the engine to charge the batteries and ran it for 20 mins and there was enpough hot water for 2 quick showers.

So in the case of an RV, at the end of a days driving there would be more than enough hot water for any use.

Is there some reason you cannot fit a tank?

These tanks can be fitted with a 240Volt element if required also.

Regards, Bruce.

The best solution will depend on how much hot water you need, how hot it needs to be, and how often you use it. You'll be carting the water whether its hot or cold. My needs (shower, dishwashing) are met by a Coleman on demand water heater. It runs on gas cannisters. Being portable, it can be placed outside the vehicle when in use. If you need instant boiling water at any time there bare gas cannister fired units. The other option that has been mention is the Glind which transfers engine heat to the water. I can't imagine electricity playing much of role.

We had a an instaneous in our last bus run on 12v and 240 volt and was excellent no problem with losing power didnt draw anything hardly but we cant remember the brand ,i need the unit so we can run it on power or battery ,diesel ones are ok if youre travelling what happens when you are parked up, we havent the space for a tank instaneous.

Maybe have a look at the Duoetto
Duoetto

G'day bescat.
Bunnings have a 240 volt instantaneous h/water heater for $99.00. draws 13.9 amps.I think. It is not pressure rated so could only be used on an open ended line.
that is between the tap and a shower rose. regards mick