240AC Electric Hot Water in Campervan

[wildebus]

Previously, I posted about a 12DC Hot Water System I was trying out. This worked pretty well but I could not find a suitable water container that would allow transportation without spillage and insulation to avoid too much heat loss.
My investigations led me to the following setup ....
originally published @ https://www.wildebus.com/blog/produ...ater-heater-part-1-installation-and-plumbing/

I wanted on-tap hot water in Clarence, my Campervan Conversion, but I don’t have – or want – on-board plumbed in Gas, and I didn’t want to fit an expensive Eberspacher water heater, so took a similar approach to this that I have done with other aspects of the build.
That is to repurpose domestic products for Campervan/Motorhome/RV use, just like I have done with the 240V Fridge and the 240V Induction Hob.

I was looking for 12V DC options initially, but while I got close, I couldn’t find a solution which ticked all the boxes , including for transportability and heat insulation. So decided to go AC, utilizing the powerful inverter I already have to be able to run the kitchen appliances.

This first part describes the basic heater and kit and the plumbing side.
Part two will go into detail on the electrical side on how to make the heater more Camper-Friendly


Part One

The Heater is an oversink semi-on-demand Water Heater by Ariston. It has a 2kW Heater Element and a 10L Water Tank in an insulated housing. This is the installation in my underbed ‘garage’ in Clarence.

Clarence Water System by David, on Flickr

This is a Pressurised & Unvented Heater, so alongside the actual Heater itself, I fitted a Pressure Release valve that automatically opens at 6BAR (the heater is rated to run between 1 – 3.5 BAR). These pressures will be virtually impossible to actually reach in a camper, but the valve also acts as a drain tap so is still handy to have (and it came with the heater anyway, so may as well use it!)
Along with the pressure release valve I have a small expansion vessel of just 2L. Again, similar to the PRV, The heater is unlikely to get to a pressure where an expansion vessel is a requirement, but as well as working as a ‘safety net’ it also provides a way to feed a small amount of water through the tap without the pump running, which is handy at nighttime, as the pumps can be rather noisy.

Talking about pumps, the entire hot and cold water system is fed via a pair of 25L water tanks with a Shurflo on-demand pump to send the water through.

The final bit of the underbed system is the stop-valve that can isolate the hot water heater plus peripherals from the basic cold-water supply.

Both hot and cold supplies then go via 12mm JG flexipipe to the Hot+Cold Mixer Tap in the Galley Kitchen.

(Pipes will get insulated in a little while - I want to monitor various joints first before they get covered up).



Part 2 (electrics) to follow.

 

[Darcar]

That’s an interesting set up.
I don’t think I’ve seen a van built without gas before!
I’ll be really interested to know how you get on, if you do any long time off grid camping.
Darcar

 

[trevskoda]

A hell of a lot of battery required there me thinks,mind you i have a 12v hand wash unit which works 100% in the loo department.

 

[wildebus]

A hell of a lot of battery required there me thinks,mind you i have a 12v hand wash unit which works 100% in the loo department.

you might be interested in the Electrics setup I think

 

[wildebus]

That’s an interesting set up.
I don’t think I’ve seen a van built without gas before!
I’ll be really interested to know how you get on, if you do any long time off grid camping.
Darcar

Summertime, the Solar has provided sufficient recharge ability to date. Wintertime, solar is a non-starter TBH and a 20 minute drive out would put more power into the batteries than a days worth of solar in Winter, so that is more of a challenge (I've been evaluating various options on this side).
I don't have a Shower fitted (this was a deliberate choice) which makes the water heating situation less critical in terms of volume.

 

[Squiffy]

I recently saw a van commercially built that everything was run on 12volt DC, heating, water heating and cooking. I think it was Bosh but can't really remember, what I do remember was it had highly specialised batteries that cost about £4000, let alone the cost of the equipment they ran, all technological wizardry. I think it is all close to being viable but not quite for us lesser mortals at the moment Phil

 

[wildebus]

I recently saw a van commercially built that everything was run on 12volt DC, heating, water heating and cooking. I think it was Bosh but can't really remember, what I do remember was it had highly specialised batteries that cost about £4000, let alone the cost of the equipment they ran, all technological wizardry. I think it is all close to being viable but not quite for us lesser mortals at the moment Phil

I can imagine
One of the objectives I have with my build is to take an alternative approach that does the same job but at a fraction of the price.

For example, how much is 12V 100L Compressor Fridge? North of £700 easily I think. My Fridge is more efficient then any regular 12V Compressor Fridge and cost £170; and a Three-Way Gas Fridge is in 4 figures I understand?
Hob? a typical SMEV dual burner Gas Hob is over £200. My 240V Induction Hob was £20 brand new. (And induction Hobs are are far faster and more energy efficient than a gas hob - except in winter where the gas hob warms the whole camper when boiling a kettle)
Hot Water - I've seen prices for Gas Hot Water Systems quoted at around £300-£400? My Hot Water system (heater, expansion, valves and pipework) works out to be around £130 all in. And is a Class B Heater in terms of energy efficiency, which is very good for a Water Heater.
Those peripherals and their cost savings over the gas equivalents, plus the savings of not having gas tanks, locker and pipework go a very long to pay for the energy store (especially bearing in mind that most "gas vans" also have a reasonable battery setup and solar, so we are talking about additional upgrade costs, not full installation costs).

 

[Squiffy]

Are you using your induction hob on an inverter then wildebus or can you only use it on shore power. Have to admit I hav'nt read the whole thread , Phil.

 

[wildebus]

Are you using your induction hob on an inverter then wildebus or can you only use it on shore power. Have to admit I hav'nt read the whole thread , Phil.

Everything is available off-grid.

 

[Squiffy]

Very interesting

 

[Darcar]

i guess you have LiFePO4 lithium-ion batteries? I’v read a lot about them recently, very interesting but bloody expensive.

If I was going to reto install them I’d have to change pretty much all my charging system! Even though it’s still something I’m considering? But not in a hurry to do.
Darren.

 

[wildebus]

i guess you have LiFePO4 lithium-ion batteries? I’v read a lot about them recently, very interesting but bloody expensive.

If I was going to reto install them I’d have to change pretty much all my charging system! Even though it’s still something I’m considering? But not in a hurry to do.
Darren.

Lithium is a big investment and not one I am ready for, due to the cost. It would be ideal for my setup with the inverter use and high current draws but if used in a 'Sympathetic' way (the electrical followup will explain better), deep cycle AGMs work well with Inverters.
My setup is not ideal for being parked up in for weekends in the winter off-grid. I've looked at 3 options to help address this and have chosen one (but that is for a different thread - maybe it would be worth while having a specific topic - or even a sub-section? - considering energy options when building a Campervan, covering pros and cons).

 

[wildebus]

Part 2 - Electrics

Brief Recap - Fitted a 2kW 240V AC Water Heater in my Campervan and want to be able to use it off-grid. The following is the process I used to get to what I think is an optimum setup for my Camper.

Electrical Source: EDECOA 2500W (5000W Peak) PSW Inverter; connected to Battery Bank compromising 4 x 95Ah (C20) 12V AGM Deep Cycle Batteries.

My Test Routine was to set the Heater at "E" for Eco Mode (this doesn't change the power setting, it just sets the thermostat lower so the heater will turn off sooner);
Check the water temp at start (running tap to remove any pre-heated stored water) & check water at end to ensure the heater has operated as required;
Remove any intermittant or high loads to avoid skewing data (so Victron Inverter off and only real loads were lights in garage and power to Pi Logger running Venus GX)
Then turn the Inverter on, then the remote switch on and leave until the heater has hit the set temperature;
Finally check the data recorded by the Victron Venus GX software via the VRM Portal (I sample the battery voltage, current draw and battery SOC on a 1 minute cycle)


Run 1. Use as Supplied
The Battery was at 85% SOC when the run started

Heater ran for around 30 minutes, drawing around 2100W - so around 1kWh of power
WH-2kW-Watts by David, on Flickr

There is a significant voltage drop, dropping to 11.7V initially and by the end of the test, the battery voltage had dropped to below 11.5V
WH-2kW-VandC by David, on Flickr

By the time the heater had finished, the SOC had gone from 85% to just under 60% - so a drop of 25% using 1kWh of Power, which is pretty well as expected for the size of battery bank and the C-rating of the current draw
WH-2kW-SOC by David, on Flickr

A constant 180A current draw for nearly 30 minutes is a big ask on a battery bank. I monitored the cable run temperatures and the cabling got pretty warm, and there was an isolated hotspot that reached >100 Celcius around the 300A 'catastrophic' fuse holder.

One aspect I was impressed with was the Inverter. Inverters outside of the top brand names are very often capable of much less then their marketing suggests. On this test, the EDECOA Inverter casing (which works as a heatsink) only touched 30C in very isolated spots and the cooling fan only came on around 15 minutes into the run. There is also a voltage drop (checked with meter) of 0.44V between battery and inverter terminals, which means the inverter was operating without problems at just above 11V.


Run 2. Cycle power on and off 50/50
The Battery was recharged back to 85% SOC when the run started (I didn't leave time for the voltage to settle after charging so voltage appears higher)

This time the Heater was set to run for 60 seconds, then power removed for 60 seconds, then power restored. This loop was continuous and left running until the heater turned itself off.
WH-2kW-OnOff-Watts by David, on Flickr
This graph shows how the power is cycling on and off;
The run time is just over 40 minutes this time. One reason why it is not longer (you might expect twice as long to run with the power interupted half the time) is the water start temp was 7C higher (11C instead of 4C) as the test was carried out in the afternoon when the ambient temp was higher.

The voltage drop on Run 2 is noticebly less
WH-2kW-OnOff-VandC by David, on Flickr
I believe allowing the batteries to have a 50% recovery time during the Run helped reduce this, and this will be better for the bank

And the SOC went from 85% to around 63%. Not as low because the Heater started off with a warmer volume of water, but the longer time is definately more battery friendly.


This Graph is interesting as it shows side by side the two different approachs and how the Voltage and Current looks for each (of particular interest is the blue - voltage - line)
WH-Comp-2kW-VandC by David, on Flickr


Run 3. Cycle power on and off 30/60 whilst Charger on
The results of Run 2 made me think I can improve further on a Campervan-friendly configuration.
For this next run (#3), I set up the control to have the heater on for 60 seconds, off for 120 seconds, then back on for for 60 seconds, etc on a constant loop, with the heater eventually turning itself off when water upto temperature.
This will give an average power of 700W on the overall cycle; the Time taken to heat the water will be 3 times longer but speed of water heating is not a priority. What I also did in Run 3 was plug into the Grid so the battery charger (35A capable) will be replenishing power. Not at the rate the heater is using it but if the heater runs for an hour, that power could be put back in 2-3 hours potentially. See the chart below which illustrates this for Run 3.
WH-2kW-3060Mains-Back to Full SOC by David, on Flickr
I should make it clear that the Heater is powered by the Inverter regardless of any hookup. This is deliberate as if plugged into a current-limited EHU, the water heater coming on could overload the external feed if I am using other AC loads. (when hooked up, all other devices plugged into both the EDECOA and the Victron Inverters will be switched automatically to external AC power).

This is the power use pattern
WH-2kW-3060Mains-Watts by David, on Flickr
Run time is around 35 minutes (I think the ambient water temp was again higher), and what is intriging is the power hits 2400W each time. TBH I am not fully sure why, but if that was extra power used by the heater it would explain the quicker then expected heater cycle run.

The most important graph is the Voltage and Current one though.
WH-2kW-3060Mains-VandC by David, on Flickr
Now this time, we started from a fully charged battery bank, but at no time did we drop below 12.2V and the current draw was around 20A less due to the charger providing direct help.


Clearly the EHU helped here, but is this an ok test if I am claiming this is useable as an off-grid solution?
Well, actually yes it is.
I have a 35A Smart Charger - this puts in a maximum of ~400W into the battery.
I also have 400W of Solar Panels. So while I wouldn't expect 400W most of the time, in the summer they will provide a very useful recharge (and in the summer I am usually fully recharged by lunchtime, so the afternoon charge could effectively feed the Water Heater)
And driving I have a 40A B2B - so again, very similar to the Mains Charger (I also have a 100A VSR which I have tested at 80A output when the load demands it so can switch to that if the heater is on and the batteries are at a lower SOC)

Lithium Batteries for this application would be perfect of course as there would be no voltage drops, but the Inverter seems to cope fine at the voltages tested at and the batteries in the bank are spec'ed to allow a higher than C/4 discharge so that aspect is ok as well.


Part 3 will discuss how I control the heater on/off cycles

 

[Squiffy]

Wildebus, I have great respect for your write up in what your doing and the explanations are very good, but in all honesty the proof is in the pudding as they say, as I have previously stated I have not read the whole thread, but have you used this setup in real anger or is it only really viable when near shore power or over night on long daily transits or have you a battery bank that a second world war 'U'boat would be proud of. ( Bearing in mind they had to travel on the surface for 6hrs to recharge from generators)
This is not ment as a criticism, more of perpetual motion theory that I'm trying to understand. Phil

 

[wildebus]

Wildebus, I have great respect for your write up in what your doing and the explanations are very good, but in all honesty the proof is in the pudding as they say, as I have previously stated I have not read the whole thread, but have you used this setup in real anger or is it only really viable when near shore power or over night on long daily transits or have you a battery bank that a second world war 'U'boat would be proud of. ( Bearing in mind they had to travel on the surface for 6hrs to recharge from generators)
This is not ment as a criticism, more of perpetual motion theory that I'm trying to understand. Phil

The 2nd paragraph of part 2 tells you precisely what battery bank I have installed.

When I go to VW Festivals (where I do trading), I arrive on the Thursday (or Friday Morning); I get home on Sunday Evening and the batteries are usually as full when I get home as when I arrive. I haven't actually stayed anywhere where I have had hookup as it happens.
The Hot Water is something I have just added and from my testing I know exactly how much power it takes and if I can afford to use it (in the Summer, the answer will almost always be yes; in the Winter it depends on if I am static or not).
I don't believe in perpetual motion any more than you do. But neither do I believe in paying over the odds for "Motorhome" accessories that are overpriced and no better then other options which are much more sensibly priced.

To be frank, maybe you should read the whole thread before you ask questions as the answers (such as the battery bank) may well be within it?
Apologies, but my posts do tend to quite wordy as I try to include all the information I think may be useful.

 

[Squiffy]

A well deserved bollocking . Your right I should read the whole thread, can't help feeling though that if it was financially viable as you say cheaper than conventional, then many others would be doing it, but for the life of me I have yet to see any adverts that proliferate this sort of ideal and componants to achieve it. However I will follow your thread with interest.May be you are the "Bill Gates" of electrical trickery, I really sincerely hope you are and that is not ment to be a wind up. Phil

 

[wildebus]

3rd and Final Part - Controlling the Heater

The Water Heater is a 2kW System and has no power control available - But I want to control it. Hmmm

An aside but an idea ...
Now I have a 2kW Induction Hob also in the Camperbus. Like all hobs, it has different settings - There are 8 power settings available between 200W and 2000W and I tend to use the 800W setting for something like boiling a kettle as I find it both plenty fast enough AND it is kinder to the battery bank.
For anyone who has used an Induction Hob, they have probably noticed that if they are doing something like simmering soup or veg, the liquid will bubble every second or two? This is because the Induction Hob does not really run at a lower power at the lower settings, but switches between full power and off at a frequency that gives the selected power. And it is this method of working which made me think the same approach could work on a 2kW Water Heater.

1) Remote Control of the Water Heater
The Heater, the Inverter that drives it and the sockets and plugs are all located in the Garage below the permanent bed. So I didn't want to have to crawl under the bed to turn the Water Heater on every time.
So I have a switch in the kitchen to allow me to remotely control this
BMV & Water Switches by David, on Flickr
The BMV-712 Monitor is on the left; The switch set on the right has the Water Pump on/off switch on the right, and the Water Heater switch on the left. The Heater is a two way switch - Position II turns the heater on; Position 0 is the off one of course; and position I is a BMV controlled position.
I can set the BMV Relay to turn on and off on various selected parameters. I have it set for the relay to turn on and off depending on the SOC (State of Charge) values. The relay is also controllable remotely via the Victron Bluetooth App.
Of course, this does also rely on the Inverter being on. I use the high power Inverter as an "On Demand" Inverter so tend to only switch it on when using selected devices (the Fridge and Internet Router/Radio work off a different always-on Inverter), so if I wanted the Water Heater to come on automatically at the set SOC level, I'd have to remember to leave the Inverter on as well (luckily that also has a Remote Control On/Off as well)

The output of the BMV Relay is a DC signal, so I fitted an SSR (Solid State Relay), in line with the power from Inverter to Heater, which allows a DC control over an AC Circuit.

2) Power Control of the Water Heater
As I said, the Water Heater has no Power Control, but I want to run at a lower power than 2kW. So I decide to copy the way the Induction Hob works (as would have been seen if you read Part 2). But How?
Actually, very easily. I just installed a DC On-Off timer between the SSR DC side and the Remote Control Switch. After a few experiments, I have decided on a 1 minute on; 2 minute off cycle to give a calculated ~700W average power output (1 Minute at 2000W, 2 Minutes at 0W).

And this is what the Control Box looks like
Control Relay Box by David, on Flickr
The Board with the Display is the DC On/Off Timer (currently counting up to 60 seconds before it turns the output off for 120 seconds).
The White Block just below that is the SSR, on which is fitted a large heatsink to disipate the heat.


In terms of longevity, the On-Off Timer is designed to just run all the time (I will actually be running it pretty infrequently); and the SSR has a typical MTBF in excess of 200 Years when in regular use (far far higher than a EMR)
Now the Heater will be turning on and off around 30 times on each run. I don't yet know how this will react to this in the long term, but it is a pretty dumb heater with no electronics anywhere, just a heater element, so I think it will be fine, just like a kettle. And similar to a kettle, I am expecting the element to fail through furring up before it would fail electrically.
The Inverter load will be going up and down and that could be a concern - but this inverter has been successfully running the Induction Hob for 6 months without complaint, so hopefully all good there.
But if anyone is interested in this kind of project, take the above notes as a disclaimer. I am not making any claims or suggestions anyone should do this themseleves unless they want to experiment.

 

[Squiffy]

 

[wildebus]

A well deserved bollocking . Your right I should read the whole thread, can't help feeling though that if it was financially viable as you say cheaper than conventional, then many others would be doing it, but for the life of me I have yet to see any adverts that proliferate this sort of ideal and componants to achieve it. However I will follow your thread with interest.May be you are the "Bill Gates" of electrical trickery, I really sincerely hope you are and that is not ment to be a wind up. Phil

I appreciate the comments and interest
Something which I think allows me to do some of these tests is I can read all the data on a minute-by-minute basis so get a good handle on what seems to be working and what does not.
In terms of any of this stuff becoming mainstream, I have noticed from watching some US YouTubers that Non-Propane RVs are starting to come out in a limited way, fitted with an Induction Hob, 12V Compessor Fridges and Diesel Heaters - but also fitted with Lithium Batteries.

I won't deny I would be wary of "handing over" my camperbus to someone to borrow for example as incorrect (or rather indiscriminate) use of the applicances could drain the batteries really fast. With an LPG setup, using something 'too much' means the tank is empty and just needs filling. A drained battery is more awkward. And the amount of Motorhome owners who seem to kill batteries on a frequent basis likely explains why gas is still king for most Motorhome and Motorhomers


My setup would be better without a shadow of doubt with Lithium Batteries. But the cost of a Lithium Setup with the same usable capacity (I can run my 380Ah Bank down to 40% SOC safely) would be over £2,000. I paid less than £500 for my Battery Bank and it is doing the job I need.
I looked at increased run time options for Wintertime (in Summer I have not yet had and don't think I will have any real issues, but Winter IS another matter).
Lithium is out due to price. I was very seriously considering the Victron Super Deep Cycle Batteries as found a seller that had a really good deal on them - I could have fitted 780Ah in my existing battery housing (and that is 780Ah USABLE on a relatively frequent basis) for around £1,200. That is a great deal I believe.
However, as it is only Winter I will have potential battery limits, that still seems too much to pay even though it is a good price for good batteries.
Instead, I have gone for a 3rd option - the backup plan of the hated genny . I don't think I will need to use this very often, if at all, when away, but it is something I have uses for away from the Campervan anyway, and I paid under £400 for a brand new Briggs and Stratton P2200 1700W Inverter-Generator, so I got a good deal on a product I am sure I will find useful over the years.
To go with the Generator, when I go away, I will also take my original 20A Victron Charger to work in conjunction with the Multiplus' 35A Charger - so a total potential of 55A charging if I do use it (or if I happen to get on a hookup for that matter).
And finally, Lithium will be coming down in price all the time I am sure, so by the time it comes to refresh the batteries, Lithium is likely to have come into the 'reasonably affordable' category (hopefully!)

 

[Squiffy]

While your away, dont forget your on holiday to enjoy yourself wildebus, standing around whatching dials and oscilloscopes to make sure you dont run out of make me happy and comfortable juice is obviously an inventors bain. But go for it!! Anyway