Water Heater - Pure Sine Wave VS Modified Sine Wave Inverters

[DBK]

Illogical or not, I'm not going to change.

Battery power taken will be:
800w / 12a = 66.6ah. For half an hour / 2 = 33.3 ah. Plus 20% inefficiency 39.96 ah.

Say I add an additional battery increasing the bank from from 220 ah to 330 ah.

If I was taking them all the way down to 50% that's 165 ah usable. 165 ah - 40 ah still leaves me with 125 ah to play with.

If I was taking them only to 33% depletion that's 108.9 ah usable. 108.9 - 40 ah and I'd still have 68.9 ah to play with.

And by slowing it down and not hitting the battery with such as massive draw all at once, that will do less damage?

Give it a go if you want to try it but remember the typical Ah capacity of a battery is based on much lower rates of current draw than you are proposing, by around a decimal point.

You can boil a kettle in five minutes on the hob. I suggest that as a solution for hot water in the morning. The first kettle for your cup of tea, the next one for a wash.

Alternatively, fit a gas water heater and only turn it on when you wake up and have a gas detector in addition to the normal CO detector.

 

[hilldweller]

Not leave it open all night running the heat. Logical or not I will lay awake all night if I have it in the van worrying about it.

You don't need hot water in the night, I can't see the problem.

Our Swift had a beautiful little Truma gas water heater. Balanced flue straight out of the side. Actually it was even better, mains or gas, so on hook up we could save gas. It would be off all night yet kept a small tank of hot water for use in the night.

 

[Campervan_man]

You could just boil up a large gas whistling kettle for hot water and mix it with some cold.
Does the same thing. No electric required.

 

[stevewagner]

That's a lot of replies. Thanks a lot!

After reading peoples doubts I have re-watched a few videos online (where I got the idea) and have noticed that these people have bigger electrical systems than I remembered. The 220 ah batteries and 300w solar figures I gave are what will be installed initially. There is room on the roof, should I want to in the future, to install another big 300W panel. Same for batteries. I could always add more later. But I'm trying to spread the cost during the initial build. This game isn't cheap!

Perhaps the heater isn't such a good idea with the initial electrical system I will have.

As a work around I will spend some time and look into some of the other options given here.

Gas is not an option and I will not change my mind on this. Understand it or not that is a fact. I'm sorry if it seem totally illogical, and perhaps it is, but I will not be comfortable in the van with gas (with its open flame and all the risks that go with it). I want to go away in the van to relax. Not lay awake all night, waiting for a bang or suffocation. It doesn't bother me for cooking. Turn the gas bottle on, cook a meal, turn the gas bottle off and shut it away in its vented gas locker. Not leave it open all night running the heat. Logical or not I will lay awake all night if I have it in the van worrying about it. Therefore it's not going in.



I like this idea a lot because I plan on heating in the van with a diesel heater, eliminating the requirement for gas. If I could tap into this extra diesel tank to run the hot water that would be fantastic! This seems like the best option to me because it's not gas, uses something I'll have anyway and doesn't require the sun.



I will have a look and see if I can find something with a lower watt rating, starting with propex.

Would diesel burning at night not keep you awake then? It too gives off carbon monoxide (and other noxious gases) which is an odourless killer. As long as you have a CO alarm there should be no problem.

 

[CamperJack]

You could just boil up a large gas whistling kettle for hot water and mix it with some cold.
Does the same thing. No electric required.

That's the plan for when electric is harder to come by for example in bad weather or not driving around much.

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[CamperJack]

Would diesel burning at night not keep you awake then? It too gives off carbon monoxide (and other noxious gases) which is an odourless killer. As long as you have a CO alarm there should be no problem.

The diesel heaters suck in air from outside, burn it within the machine and exhaust everything back outside. This means no combustion occurs within the living space.

Moreover (and this point is most critical) I feel much more comfortable installing a diesel heater than gas heaters myself! I'm not a gas safe engineer. I don't want to be running gas lines around the place. I can connect a bottle to a hob and fit the bottle in a gas locker. That's my limit.

No amount of people telling me gas is cheaper/ most common/ easiest / or that other things also have risks associated with them will change my mind. I will not have gas air or gas water heaters in my van. It's that simple. I'm not going to do something that makes me feel extremely uncomfortable and anxious!

Anyone who wants to carry on suggesting gas or arguing for it is wasting their time.

I appreciate that my thought process may not be logical to most people and you're all trying to help me see what you think is an obvious solution to this issue. I genuinely greatly appreciate that. However it doesn't change the fact I'm suborn and have funny / stupid ideas which can't be changed on this subject.

 

[Lenny HB]

Your calculations seem a bit out, a 800 watt heater by the time you have allowed for inefficiency is going to be taking more like 80 amps and a 800 heater will probably take 1 - 2 hours to heat 10 Lt of water.

 

[CamperJack]

Your calculations seem a bit out, a 800 watt heater by the time you have allowed for inefficiency is going to be taking more like 80 amps and a 800 heater will probably take 1 - 2 hours to heat 10 Lt of water.

I'm looking at the 6L model, not the 10L model.

80 amps for an hour. I'm running it for half an hour so that's 40 amps.



I got half an hour heating up time from here:

6L water, water start temp 8°C, water target temp 70°C, heating power 0.8kw = 0.54 hours

Turns out there's a calculator for that.

<Broken link removed>
6L water, water start temp 8°C, water target temp 70°C, heating power 0.8kw = 0.54 hours.

It's also worth thinking that I don't actually want a shower at 70°C unless I want to give myself severe burns.

 

[Lenny HB]

Those calculations don't allow for any heat loss, the container that holds the water also gets heated and heat is dissipated into the air. In the real world more likely to take ¾ - 1 hour.

 

[Lenny HB]

I don't get why the gas hob if you are so anti gas, a hob must be far more dangerous than a balanced flue gas heater.

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[tonyidle]

The diesel heaters suck in air from outside, burn it within the machine and exhaust everything back outside. This means no combustion occurs within the living space.

Moreover (and this point is most critical) I feel much more comfortable installing a diesel heater than gas heaters myself! I'm not a gas safe engineer. I don't want to be running gas lines around the place. I can connect a bottle to a hob and fit the bottle in a gas locker. That's my limit.

No amount of people telling me gas is cheaper/ most common/ easiest / or that other things also have risks associated with them will change my mind. I will not have gas air or gas water heaters in my van. It's that simple. I'm not going to do something that makes me feel extremely uncomfortable and anxious!

Anyone who wants to carry on suggesting gas or arguing for it is wasting their time.

I appreciate that my thought process may not be logical to most people and you're all trying to help me see what you think is an obvious solution to this issue. I genuinely greatly appreciate that. However it doesn't change the fact I'm suborn and have funny / stupid ideas which can't be changed on this subject.

It isn't your resistance to the use of gas that is the problem: it's your choice of fuel to replace it. If you are striving to achieve convenience beyond use of a kettle then the only long-term, all-season, alternative is Diesel. I asked about your fridge: without gas your only option is to use electricity. Motorhomers 'stuck' with compressor fridges have to make a determined effort to run them full time on electricity in a van. You will need to direct your effort with solar and batteries to operate your fridge - trying to heat water from the same supply is going to be very difficult / expensive.

Your point about Diesel appliances using outside air and exhausting the products of combustion outside the living applies to every gas appliance installed in a motorhome with the exception of the hob / oven / grill. If you are confident running a leak-free Diesel feed then you should be confident about installing a gas line. Both can leak if installed incorrectly and Diesel sticks around and remains inflammable a lot longer than LPG. A gas engineer does not have to perform the installation but can if you wish check that it is safe.

 

[Lenny HB]

trying to heat water from the same supply is going to be very difficult / expensive.

£3000 to £4000 spent on a good lithium battery set up would sort it.

 

[vantastic]

The cool thing about building your own van is that you can get whatever you want. If you don't want gas then don't get it.

In terms of turning watts of energy into heat electricity is the most efficient fuel source out there for sure. Nothing comes close. Our problem with it is storing it, batteries are really poor and they get expensive real fast.

I know you have been talking about hot water in the morning, is that the only time you will need it? Did you consider a heat exchanger? If you can harvest some free residual engine heat it would save electricity. It won't work in the morning though.

Another option. How about gas BUUUUUT not a gas install. How about a gas heater like this one
https://www.amazon.co.uk/Camplux-AY132-Portable-Tankless-regulator/dp/B01CJPU6JI

Instant hot water as you use it. When you are done you turn the gas off. I actually have this very version in my Land Rover for camping and it can turn real cold water real hot in one go. You can use it to shower, wash, do dishes, whatever.

Another options is a slightly smaller unit like this
https://www.amazon.co.uk/Kampa-Geyser-Portable-Water-System/dp/B004T8SZ2O

It's not as fast and you may have to recirculate the water but it fits on the counter.

 

[Lenny HB]

Another option. How about gas BUUUUUT not a gas install. How about a gas heater like this one
https://www.amazon.co.uk/Camplux-AY132-Portable-Tankless-regulator/dp/B01CJPU6JI

I can't believe you suggested that one. The OP is petrified of gas and you suggest a heater that is not room sealed, burns oxygen from the air inside the vehicle, as far as I can see it does not have an external flue so it exhausts inside the van. These are the type of water heater that has caused a number of deaths in holiday lets in Europe also I don't believe it is legal to fit them in a Motorhome or Caravan in Europe.
Also noticed that it runs at 37mb of gas pressure the standard gas pressure on Motormones is 30 mb so it won't get as hot, also not suitable for use above 2000 ft.

 

[mitzimad]

why do self builders always want to reinvent the wheel?theres a tried and tested way to run vans off grid using electric to provide heat appears in none of them

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[Googlebot]

The OP asked for advice and universally has been advised it’s a bad idea.

Diesel and gas heaters work on exactly the same principle of burning a Carboniferous fuel and produce the same combustion products with a few differences in composition.

Electric won’t work well but if the OP is insistent then please carry on. Hope it does work and you don't waste thousands of pounds.

 

[Gromett]

As others have said I also strongly recommend against using batteries to heat water. If you want to avoid gas, then a cheap chinese diesel heater is probably the safest and most cost effective route.

Check out the David McLuckie channel. He plays around with chinese heaters and water heaters a lot. This is one video of many.

 

[Raul]

Thing is, storing and transporting that energy. A litre of lpg has around 7kwh of energy, costs very little and very cheap to exploit. Electricity, to store the same amount, it takes 8kwh LiFePo4 bank at a cost of 6,5k pounds and around 80kg payload, weather is charged or not. In lead would be a 14kwh bank and a payload of around 350kg. There is a fine balance, in my opinion, of how much electricity, economically is worth having. If you can’t produce it cheap on demand, you are limited by the amount stored. Opportunity use of electric for heat is fine; having a fan heater 400w if that comes right from the PV harvest. Leaving it on at night of the batteries, NO. Same goes for the water heating or cooking. Having a kettle boil not so often is not that bad, if you chose the right timing. Living of the batteries, is living off grid, and it takes a lot of understanding and adjusting to it. It’s lifestyle that is not for everyone. I live of grid on my house abroad, it’s a lifestyle that implies changes to some extent, and you need to have multiple options for redundancy and economy. There is times when electric is king, and times when lpg is a must. Economy dictates the course of use, and with practice you get better at it. You will be the best placed to take decisions and chose the right fuel at the right time.
Same for the van, we use lpg, and if there is excess PV, we make use of it as best as we can. But I will never make hot water of the batteries. To expensive. Batteries have a finite life and is too expensive for that.

 

[stevewagner]

The diesel heaters suck in air from outside, burn it within the machine and exhaust everything back outside. This means no combustion occurs within the living space.

Moreover (and this point is most critical) I feel much more comfortable installing a diesel heater than gas heaters myself! I'm not a gas safe engineer. I don't want to be running gas lines around the place. I can connect a bottle to a hob and fit the bottle in a gas locker. That's my limit.

No amount of people telling me gas is cheaper/ most common/ easiest / or that other things also have risks associated with them will change my mind. I will not have gas air or gas water heaters in my van. It's that simple. I'm not going to do something that makes me feel extremely uncomfortable and anxious!

Anyone who wants to carry on suggesting gas or arguing for it is wasting their time.

I appreciate that my thought process may not be logical to most people and you're all trying to help me see what you think is an obvious solution to this issue. I genuinely greatly appreciate that. However it doesn't change the fact I'm suborn and have funny / stupid ideas which can't be changed on this subject.

You are right but they can still leak to the inside over time. Gas units are sealed too but bear in mind with the constant movement and vibrations within a motorhome so casings can and do work loose. Good luck with whatever you decide.

 

[Duckato]

PV solar panels get hot ? just thinking ??

yes it can work very well and hybrid Pv solutions are readily available now but the panels such as these https://dualsun.com/en/product/spring/ are not cheap at about £800 each so I am investigating a diy version.

Meanwhile I have been playing with a Portable diy solar thermal solution

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[Duckato]

In my current build I will be using a heat exchanger to heat a 30L Calorifier from the engine when driving and a Eberspacher hydronic Heater or Solar Thermal when parked up. Compared to the instantaneous gas heater in my current van it’s a heck of a lot faffing about though but I like a challenge!

 

[Ian Bosman]

You mentioned in another post about having a 12v fridge, is that's coming of the same batteries?

When we did our sprinter conversion we'd looked at going no gas, using a alcohol hob and with all the solar running the 240v fridge and everything else. But then when you start looking at heating and water heating the only viable source really was gas. And in reality if you've got to have it on board for the cooking hob may as well use it for other things. How much hot water do you need, are you going to shower regularly in the van or use sites? We only have our water heater on when we are going to shower otherwise it's just the kettle on the gas hob for strip wash, washing up etc.
Of course it's all about personal preference and choice as to what is important to you, so no right or wrong. Some self builders don't see the need for having a loo but for us it was a big yes and the van design was arranged around that as was having a full size mattress ready made all the time.

We ended up with a instant gas water heating system using a normal household boiler, I think 11ltrs but still would only use it for shower as it only had about 40cm of pipe between boiler and hot tap, so no wasting water to run hot.

Shawn

The other point to make is do not try running your laptop or smart phone charger on a modified sine wave as the charger electronic may not like it. Complex electronic device must have pure sine wave and much better to rely on

 

[aogrady]

The diesel heaters suck in air from outside, burn it within the machine and exhaust everything back outside. This means no combustion occurs within the living space.

Moreover (and this point is most critical) I feel much more comfortable installing a diesel heater than gas heaters myself! I'm not a gas safe engineer. I don't want to be running gas lines around the place. I can connect a bottle to a hob and fit the bottle in a gas locker. That's my limit.

No amount of people telling me gas is cheaper/ most common/ easiest / or that other things also have risks associated with them will change my mind. I will not have gas air or gas water heaters in my van. It's that simple. I'm not going to do something that makes me feel extremely uncomfortable and anxious!

Anyone who wants to carry on suggesting gas or arguing for it is wasting their time.

I appreciate that my thought process may not be logical to most people and you're all trying to help me see what you think is an obvious solution to this issue. I genuinely greatly appreciate that. However it doesn't change the fact I'm suborn and have funny / stupid ideas which can't be changed on this subject.

Hi,

I have. VW T5 and have a eberspacher heater, diesel powered, and the hot air blows into a Truma TT2 hot water heater, the air from the eberspacher heats it up, it holds 5 litres, it also has a built in electric heater if you are not running the hot air heating. The element is 230v 300w, and heats up pretty well

Would this be a solution?

Truma Therme TT2 Electric Water Heater Caravan Motorhome Boiler 42014-01

Truma Therme TT2 Water Heater Ideal for caravans, campervans and motorhomes. This compact 5 litre water heater supplies hot water.

www.rainbow-conversions.co.uk

Alistair

 

[Gromett]

The other point to make is do not try running your laptop or smart phone charger on a modified sine wave as the charger electronic may not like it. Complex electronic device must have pure sine wave and much better to rely on

You really shouldn't be running laptops or phone chargers off an inverter. There are efficient DC-DC converters that are much better option.

Not criticising you, your point is perfectly valid.

 

[aogrady]

My eberspacher is mounted underneath the van by the way, the Truma water heater sits behind the driver seat where the air pipe from the eberspacher comes up through the floor....

Alistair.

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[Duckato]

My eberspacher is mounted underneath the van by the way, the Truma water heater sits behind the driver seat where the air pipe from the eberspacher comes up through the floor....

Alistair.

Do you still run that when it's 30+ in the shade?

That is the primary down side I can see with this kind of water heater, well that and the very long warm up time for comparatively little capacity, but for £140 that's not bad value considering its from Truma and most of their stuff costs a fair bit!

Other worrying thing that caught my eye is the low bar rating, even the lower powered 20PSI Sureflo for example exceeds that.

 

[aogrady]

Do you still run that when it's 30+ in the shade?

That is the primary down side I can see with this kind of water heater, well that and the very long warm up time for comparatively little capacity, but for £140 that's not bad value considering its from Truma and most of their stuff costs a fair bit!

Other worrying thing that caught my eye is the low bar rating, even the lower powered 20PSI Sureflo for example exceeds that.

No, as you said, I wouldn't run the eberspacher if it's hot outside, but you have a small 300w element, and even with battery and solar that wouldn't be too bad I guess?

I don't have a powerful pump. So not a problem for me personally, YMMV..

Alistair

 

[Duckato]

Here is a comparison I did a while ago of a branded modified sine wave inverter versus a pure sine wave variant the former when running an inductive load (a fridge) was a lot less efficient.

 

[Duckato]

I was curious about the TT2 Alistair mentioned there does not seem to be anything on YouTube in english but this one shows how it is put together.

I can see now why the heat up time takes so long the heat exchanger is not exactly efficient however if it was, it would probably have too much of an impact on the heaters primary function of warming the vehicle so that makes sense

As a bit of handy kit in the winter when the heaters on anyway I think it would be a great little add on.

The 300W element is handy and that would not cane batteries too much especially on a sunny day but more usefully could be used when driving.

 

[CamperJack]

Hi,

I have. VW T5 and have a eberspacher heater, diesel powered, and the hot air blows into a Truma TT2 hot water heater, the air from the eberspacher heats it up, it holds 5 litres, it also has a built in electric heater if you are not running the hot air heating. The element is 230v 300w, and heats up pretty well

Would this be a solution?

Truma Therme TT2 Electric Water Heater Caravan Motorhome Boiler 42014-01

Truma Therme TT2 Water Heater Ideal for caravans, campervans and motorhomes. This compact 5 litre water heater supplies hot water.

www.rainbow-conversions.co.uk

Alistair

Hello Alistair,

Thanks for tanking the time to reply with what looks like a good (and very affordable) solution.

Online it says it takes 50 minutes for the Truma TT2 to heat the water. Is that your experience when combining the electrical 300w element and your eberspacher hot air heater, or just the 300w electrical element?

I was planning on fitting one of those Chinese diesel heaters anyway, so this is one potability I am very much considering. 50 minutes heating time sounds okay to me. Enough time to cook a meal as the water heats up after a day climbing the hills and then jump in the shower before finding a good, local pub with local real ale. I can taste it already. Bliss. ?

Thanks again!

Jack.

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