DC Electric Water Heater with Heat Exchanger

[charlesrg]

I will add my input to this discussion.

Our campervan is all electric, with exception of the Webasto header and V10 engine, which both run off the fuel tank.

The specs are 400 W of solar feeding 200 kWh of lithium batteries, along with the alternator charging when we drive. With this set up we cook with an InstaPot, microwave and induction cooktop. We also have adequate hot water from the 2.5 gal water heater. The heater is a 110V heater from Home Depot with the heating element replaced with a 12V, 300 W heating element. The system is designed to divert the excessive solar power (after the batteries are charged) to the hot water heater. The hot water system cost about $250. The solar/battery system cost substantially more.

Here is a link to the build thread. The hot water system starts on post #133.

https://www.sportsmobileforum.com/forums/f24/2012-e-350-eb-v10-4x4-ccv-top-20698-14.html

We have over 150 nights in the van and we have never ran out of hot water. We have adequate hot water to wash up and clean the dishes each day and both take a shower at night, if we want to. If we get some sun during the day, the battery is topped off and the water is heated. Now, if the day was overcast or we camped in total shade, the battery power would only last a day or two, depending how we conserved power while cooking. Usually we drive most days, so we have never lacked in battery power or hot water.

>> Corey

Awesome info you share on the Home Depot heater. I almost went that route, but after going back and forth of cost and time spent I decided to go with the Isotemp Basic. I gave up on Elgena as I tried contacting them and they took several days to reply, they also have lower pressure ratings. The Isotemp despite not being 24V can handle higher pressure so I assumed it was better built, an advantage of the Isotemp vs Kuuma is it eliminates the need to change an Anode. Yes I could carry an Anode, but rather pay a bit more and not worry about the anode.

The Isotemp is 750Watts at 110 so Inverter will have to be on to heat up water. I'm building a controller to turn on/off loads and I will have an algorithm that will auto turn on the inveter and water heater once batteries are at 90% or if the user requests.

 

[RAM5500 CAMPERTHING]

I'm building a controller to turn on/off loads and I will have an algorithm that will auto turn on the inveter and water heater once batteries are at 90% or if the user requests.

That sounds awesome! Never heard of such things and don’t know anything about it, but sounds like it would work for me as well. Any advice on what to research? Thanks

 

[Mongoloveshammer]

No.
With the low cost of solar and the advent of Li batteries it is quite viable to have no propane or butane and go all electric and diesel.
We are part way there, others are well in front of us with this transition.
Hot water and central heating are diesel or engine waste heat. At times of plenty of sun, hot water can be electric (1,000W immersion element in 22L storage tank). Fridge and freezer are compressor. Our cooking is still propane, but the usage is down to about 1kg per month full time on the road.
The next step is to get rid of the gas and go induction cook top via solar and inverter.
Cheers,
Peter
OKA196 motorhome

So If I understand you correctly Propane isnt your bag( i get it one more tank to fill) but tapping your fuel tank ( I assume a extra fuel pump or running your engine and tapping off of fuel line while the engine is running? The diesel heater makes more sense than a straight forward small tankless water heater? Im curious about utilizing engine waste heat? Run the engine and somehow tap into the cooling system or employ a plate and fin heat exchanger while the engine idling away? That is a lot of plumbing.and more points of failure under the hood. No thanks.
You are correct it does not take much to imersion heat an 22L/8 gallon tank power/time wise but I have 38 gallons and an imersion just wont cut it. I would have to heat the entire 38 gallons then circulate it. Then re heat it all in the morning after it cools off. Not going to work for me. I only want to heat what I need not the whole tank.
Tankless is on demand hot water and only burns fuel for those brief moments when it is actually making hot water. Imersion is going to run until a cetain temp is reached and I guess as long as you have sun its all good. I could not even begin to imagine how long your vehicle would have to run burning 3 dollar/gallon diesel to heat 38 gallons of water using a plate exchanger or tapped into the cooling system.And besides my Cummins engine would take forever to build enough heat at idle. If its cold out it may be never. LOL. Just my two cents here anyway.

The wonderfull thing about bulding your own rigs we each have our own ideas about what is best for us.Its interesting to see what everbody come up with. You do you

 

[charlesrg]

That sounds awesome! Never heard of such things and don’t know anything about it, but sounds like it would work for me as well. Any advice on what to research? Thanks

I'm using ESP32 and SSR to turn on and off loads. Can also use them to turn Inverter on/off or a victron battery protect.
Wemos on ESP32 + Blynk https://github.com/blynkkk/blynk-server
ESP32 is similar to arduino but 3.3V and with built in Wifi so things can talk without wiring.

 

[charlesrg]

So If I understand you correctly Propane isnt your bag( i get it one more tank to fill) but tapping your fuel tank ( I assume a extra fuel pump or running your engine and tapping off of fuel line while the engine is running? for the diesel heater makes more sense than a staright forward small tankless water? Im curious about utilizing engine waste heat? Run the engine and somehow tap into the cooling system or employ a plate and fin heat exchanger while the engine idling away?
I am not sure how efficient that is but its just two cent anyway. And yes it doest take much to imersion heat an 22L/8 gallon tank power wise but I have 38 gallons and an imersion just wont cut it. I would have to heat the entire 38 gallons then circulate it. Then re heat it all in the moring after it cools off.
Tankless is on demand hot water and only burns fuel for those brief moments when it is actually making hot water. Imersion is going to run until a cetain temp is reached and I could not even begin to imagine how long your vehicle would have to run burning 3 dollar/gallon diesel to heat 38 gallons of water using a plate exchanger or tapped into the cooling system.

The wonderfull thing about bulding your own rigs we each have our own ideas about what is best for us.Its interesting to see what everbody come up with. You do you

I forgot to mention, what discouraged me the DIY route was that a Kuuma with 1500 watts Filament only costs $288. Cheap enough.

 

[Cthayn]

I'm building a controller to turn on/off loads and I will have an algorithm that will auto turn on the inveter and water heater once batteries are at 90% or if the user requests.

I am using the Victron BMV-712 Smart to control power distribution to the hot water heater. When the battery is 95% or higher, the BMV triggers a 40 amp relay to send the 12 volt power to the water heater. If the battery fall below 95%, the relay is opened and the solar or alternator energy is sent back to charge the battery.

I also have a manual bypass switch that can close the relay even if the battery is below the 95% threshold. I usually keep it in auto mode so the water is heated after the solar panels fully charge the battery.


Sent from my iPad using Tapatalk

 

[Peter_n_Margaret]

We use a Webasto diesel heater with 22L calorifier (smaller/larger ones are also available).
It is connected to the engine so after a drive of 30 minutes or so we have 22L of water at 85C. It stays hot for up to a couple of days so if we are exploring, we always have plenty of hot water by default.
If parked up with lots of sun, the electric element can do the heating from solar power. Automation can also be provided using an Arduno.
If there is no sun we can run the Webasto for half an hour.
Nothing like a nice hot shower.
The same hardware also distributes hot glycol which provides central heating when required.
Cheers,
Peter
OKA196 motorhome

 

[charlesrg]

Sorry for the topic deviation, but I have to ask
@Peter_n_Margaret @Cthayn what are you guys using for air handling ? (radiators)
I was looking to put 2 Kalori Silencio 2 on my 19 foot box but I think it's overkill. I believe a single fan like Kalori Siliencio 1 or Kalori Siliencio FAI should do the job. The issue is that I'm having a hard time finding those with 24V fans. So I would either modify them or find an alternative. I think it's not work paying USD $170 and still having to fund for a good 24V fan.

Silencio 2 | Kalori

- Water heat-exchanger for caravan, motorhome or boat, minibus or ambulance - Installed in a wall, can be connected to the engine cooling circuit or to an autonomous gas or diesel-powered heater - Equipped with a noiseless, low power consumption fan

kalori.com

Silencio FAI | Kalori

– Water heat-exchanger for caravan, motorhome or boat – Installed in a bulkhead, can be connected to the engine cooling circuit or to an autonomous gas or diesel-powered heater – Noiseless,low power consumption fan. – It is available without fan control knob (Silencio FA version)

kalori.com

To control the temperature I will most likely be using a PWM Fan remote controlled via software. I can control the heat output of the diesel heater if necessary and then increase decrease the fan speed to fine tune the internal temperature.

 

[charlesrg]

We use a Webasto diesel heater with 22L calorifier (smaller/larger ones are also available).
It is connected to the engine so after a drive of 30 minutes or so we have 22L of water at 85C. It stays hot for up to a couple of days so if we are exploring, we always have plenty of hot water by default.
If parked up with lots of sun, the electric element can do the heating from solar power. Automation can also be provided using an Arduno.
If there is no sun we can run the Webasto for half an hour.
Nothing like a nice hot shower.
The same hardware also distributes hot glycol which provides central heating when required.
Cheers,
Peter
OKA196 motorhome

That's a great way to control it. Very clever and simple.

 

[Peter_n_Margaret]

what are you guys using for air handling ? (radiators)

I looked at all the commercial radiators and rejected them all due to noise level. They are simply unacceptable, in my view.
Instead, I built my own.
Single core copper radiator, 4 x 120mm fans. SILENT WINGS 3 | 120mm silent high-end Fans from be quiet!

Two sets like the above - one for the bathroom plus one for the general living area.
They really are silent, for all intense and purposes which is excellent, but don't shift quite enough air to stop the Webasto from cycling on and off from time to time.
"Next time" I would go for 6 fans per and PWM control. This fan maker offers PWM fans.
Cheers,
Peter
OKA196 motorhome

 

[Madoxen]

I looked at all the commercial radiators and rejected them all due to noise level. They are simply unacceptable, in my view.
Instead, I built my own.
Single core copper radiator, 4 x 120mm fans. SILENT WINGS 3 | 120mm silent high-end Fans from be quiet!
View attachment 630981
Two sets like the above - one for the bathroom plus one for the general living area.
They really are silent, for all intense and purposes which is excellent, but don't shift quite enough air to stop the Webasto from cycling on and off from time to time.
"Next time" I would go for 6 fans per and PWM control. This fan maker offers PWM fans.
Cheers,
Peter
OKA196 motorhome

Hey what did the radiator come off ? Its a nice size

 

[Peter_n_Margaret]

Hey what did the radiator come off ? Its a nice size

Custom made from scratch.
Cheers,
Peter
OKA196 motorhome

 

[Madoxen]

Well that was not an answer i expected, it looks like u did a good job of it. Are they hard to make ? I cant imagin it being easy or quick

 

[Peter_n_Margaret]

Not made by me on this occasion, but made by an automotive radiator specialist. An old fashioned tradesman.
Cheers,
Peter
OKA196 motorhome

 

[broncobowsher]

Also look at motorcycle radiators. Small and common. Just put your PC fan on one of those.