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Hot water for off grid 12v cabin?

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Started 8 years ago by Taswegian
Latest reply from sun2steam

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MoreBikesPlease
Member

Hey, does anyone know of a way to limit the current going into the regulator?

With solar panels being so cheap nowadays, it makes sense to get a big array to maximise generation on cloudy winter days and limit generator use. However this results in massive excess generation on sunny days, requiring a big regulator to cope. On 12V with MPPT as the OP desires, you end up spending an unnecessary amount on the regulator - as much as on panels!

One idea is to put current-cutout switches on some of the panels that turn off when the current reaches say half the panel's maximum current, then turn back on again later. That way you avoid that excess generation and can use a smaller regulator. Maybe a self-resetting circuit breaker?

How about a sunlight sensor switch - when the sunlight is above say 500 W/m2, it turns off? Switches exist to turn on lights when it gets dark, so that's getting there...

Maybe a single device just before the regulator that restricts the current somehow.

Is there a regulator that has a feature like this built-in?

What do you think?

Posted Sunday 28 Jul 2013 @ 9:21:09 pm from IP #
Taswegian
Member

Places which receive snowfall/heavy frosts are not suited to Bosch hydro systems it seems. The Country Comfort just like my aquacube will heat water no hotter than 50 degrees but it will not always heat water to that temperature it appears that Bosch, country comfort and aquacube will all only heat water to 25 degrees hotter than its ambient temperature providing that is 25 degrees or less to start with.

The Coleman Hot Water on demand system heats water to a maximum of 71 degrees from memory but I have had to contact the company to find out if it is a higher cut off temperature only or if they can heat water to a higher temp relevant to the ambient temp than the aformentioned systems.

Hoping that I hear something positive. The one design feature I really dislike about the coleman is it's own battery to power the pump which must be 12v charged and doesn't seem an easy thing to replace. Personally I think they should do away with the built in battery and just supply a male 12v plug for an external battery.

Update is I spent the past few nights up on the site with heavy rain and incredibly little light which has forced me to concede that I will probably need a back up generator even once the solar setup is in place but one of the neighbours lives off grid with a battery bank and a generator attached to an alternator to charge his batteries while the generator is in use so he will be a greatly appreciated knowledge bank I think.

Posted Friday 2 Aug 2013 @ 10:46:10 am from IP #
MoreBikesPlease
Member

Well the Bosch Hydropower 10H works well for me in the middle of winter, with heavy frosts in the mornings. The tank water must be below 10 degrees but I need to mix some cold water in my shower, or it's too hot to bear. And the temperature setting in the unit isn't even maxed out!

Posted Saturday 3 Aug 2013 @ 12:09:15 am from IP #
Taswegian
Member

Whereabouts is your cabin located?

Posted Saturday 3 Aug 2013 @ 4:40:39 am from IP #
MoreBikesPlease
Member

Central Victoria, up in the hills.

Posted Saturday 3 Aug 2013 @ 5:17:47 am from IP #
TassieMan
Member

Hi folk - first post, but years of lurking here, learning much.
I have a Bosch HW gas system, on its way out too.

I also have a Rayburn stove with a HW jacket on the back.
I can get my HW tank boiling - no problem.

Ive tried twice to get a 12v caravan pump to pump the water, but the problem seems with these type of pumps, that they fail die to the mixer valve beforehand that blends hot with cold to get the right temp.
They seem to burn out due to not enough pressure beforehand.

They fail and die, Ive been through 2 of the pumps now.
Not recommended.

Posted Monday 5 Aug 2013 @ 10:32:45 am from IP #
Taswegian
Member

One thing that has only recently occurred to me is if my water storage for non consumable water is a 1000l IBC tank in a cage and I utilise a 12v pump and smaller pressure tank I will run the risk of water freezing in the pipes. How can I prevent this sort of wasting water by having a constant drip?

Posted Tuesday 6 Aug 2013 @ 6:24:29 am from IP #
MoreBikesPlease
Member

TassieMan said:
Hi folk - first post, but years of lurking here, learning much.
I have a Bosch HW gas system, on its way out too.

I also have a Rayburn stove with a HW jacket on the back.
I can get my HW tank boiling - no problem.

Ive tried twice to get a 12v caravan pump to pump the water, but the problem seems with these type of pumps, that they fail die to the mixer valve beforehand that blends hot with cold to get the right temp.
They seem to burn out due to not enough pressure beforehand.

They fail and die, Ive been through 2 of the pumps now.
Not recommended.

Hi Tassieman - welcome!

I don't understand where your mixer valve is - could you explain? In my system there is no mixing except at the shower taps. My caravan pumps draw cold rainwater from the water tank and pushes it through the instantaneous hot water system to the hot water tap at the shower. (Also to the cold tap, bypassing the hot water system of course.)

Was your Bosch hot water system instantaneous or hot water storage tank?

Posted Tuesday 6 Aug 2013 @ 10:55:41 am from IP #
MoreBikesPlease
Member

Taswegian said:
One thing that has only recently occurred to me is if my water storage for non consumable water is a 1000l IBC tank in a cage and I utilise a 12v pump and smaller pressure tank I will run the risk of water freezing in the pipes. How can I prevent this sort of wasting water by having a constant drip?

By pressure tank, do you mean a water-filled header tank? Why not just supply water from the 12v pump directly?

I would guess that you'd probably be OK if you bury the pipe from your IBC tank and house the pump in your cabin, or at least some kind of cover like a carport or lean-to shed.

Why not test this next time you're up there? You could place a large plastic container of water and a buried piece of poly pipe, and see if they freeze.

What do the neighbours do to prevent freezing?

Also, why separate out non-consumable water? Wouldn't your rainwater be the purest in the world?

Posted Tuesday 6 Aug 2013 @ 11:03:32 am from IP #
Taswegian
Member

MoreBikesPlease said:
Pump specifications give a flow rate in litres per minute, but this is only the rate at zero pressure, ie no restrictions to the flow. When the pump has to push water through plumbing, up to a shower head etc, back-pressure builds up, the pump has to work harder and the flow rate will be reduced. This flowrate/pressure relationship is shown on a pump curve.

A standard caravan pump has a simple pressure switch. The pump runs until the pressure at the pump's outlet reaches a certain level, then the pump stops. When you open a tap water flows out, pressure is relieved, and the pump starts up again. So the water out of the pump tends to pulse rather than flow, and the hot water system is unlikely to work reliably. Here's some info on pressure tanks /accumulators:
http://caravansplus.com.au/catalog/help-tips6.php

Hope this helps!

This is why I thought a pressure tank wold be a good idea and figured water would be pumped up to it for greater pressure as well.

The reason is the IBC tank I can lay hands on used to hold insecticides and is $50. A good clean out and it is a large water holder for washing dishes, clothes, showering but still wouldn't want to chance consuming water from it.

Posted Tuesday 6 Aug 2013 @ 4:15:13 pm from IP #
Taswegian
Member

I'm not sure what the neighbours do to prevet freezing one is going around Australia in a campervan for the next few months and the others have gone up to Ladley in QLD to finish off a house and tie up loose ends before moving back down for good; they've been back and forth for years. I will message the ones in QLD to find out though.

I remember as a kid dad putting the kettle in the fridge at night so as to guarantee water for a coffee in the morning and that's no fun.

Posted Tuesday 6 Aug 2013 @ 4:19:37 pm from IP #
MoreBikesPlease
Member

Taswegian said:
This is why I thought a pressure tank wold be a good idea and figured water would be pumped up to it for greater pressure as well.

The reason is the IBC tank I can lay hands on used to hold insecticides and is $50. A good clean out and it is a large water holder for washing dishes, clothes, showering but still wouldn't want to chance consuming water from it.

A header tank can't deliver higher pressure that what your pump can do. But it can deliver a high flow at that pressure, just depending on how big the outlet pipe is. A header tank would allow you to use a small pump, since it can fill the header tank at its leisure. However, for 30PSI of pressure the header tank has to be over 20 meters higher than your shower. That's a lot of pipe, plus you would need valves, fittings etc!

I think instead of a header tank you might find it simpler and cheaper (and easier to freeze-proof) to just use a good pump (or two small ones), plus an accumulator tank such as:
http://caravansplus.com.au/catalog/product_info.php?products_id=5749

Does the IBC tank have a mesh screen to exclude mozzies and leaf particles from the inlet water? Does it have an overflow outlet? I suspect that by the time you add on these plus a separate container and fittings for drinking water, a proper water tank would be a better option.

Posted Wednesday 7 Aug 2013 @ 9:25:07 pm from IP #
MoreBikesPlease
Member

Taswegian said:
I remember as a kid dad putting the kettle in the fridge at night so as to guarantee water for a coffee in the morning and that's no fun.

Wow that must be a pretty unique area in Australia! You'll definitely need to get some local advice.

Posted Wednesday 7 Aug 2013 @ 9:27:24 pm from IP #
Lance
Key Master

I think most of tassie is like that, we are in the north-west and it's been getting well below zero here this winter, half inch thick plates of ice in the pet water bowls, garden hoses unusuable for at least a couple of hours in the morning due to being frozen solid, despite being in contact with the ground all night, frozen paths and roads, lots of fun stuff like that...

Posted Thursday 8 Aug 2013 @ 1:44:01 am from IP #
MoreBikesPlease
Member

Bet you're looking forward to the global warming then.

Lance, do you have any tips for freeze-protecting a caravan pump etc?

Posted Thursday 8 Aug 2013 @ 3:04:24 am from IP #
TassieMan
Member

More Bikes please:

To clarify my situation, I'm using the Rayburn stove to heat my water through a hot water jacket (except in summer when I use gas hot water via my old Bosch).

The rayburn makes the water boil at 100 deg - enough to put one in hospital if it comes out of the tap.
Also - the pump would melt at 100 degrees.

And its illegal to install HW system that puts out boiling water. Imagine a child visiting and standing under the shower when the hot water hits - I shudder to think....

So - a mixer valve blends cold with the boiling water to get the temp down to roughly 70 deg before going into the 12v pump.

But - the mixer valve slows down the flow of water, then this slower input into the 12v caravan pump makes the pump fail as the it cannot get enough water pressure from the mixer valve.

So twice I have had these caravan pumps fail - and they were top quality caravan pumps rated to 90 deg.

Stuck! Even my plumbers cant give me another work around.
Surely many other have done this successfully?

Posted Friday 9 Aug 2013 @ 8:46:27 am from IP #
MoreBikesPlease
Member

TassieMan said:
So - a mixer valve blends cold with the boiling water to get the temp down to roughly 70 deg before going into the 12v pump.

But - the mixer valve slows down the flow of water, then this slower input into the 12v caravan pump makes the pump fail as the it cannot get enough water pressure from the mixer valve.

So twice I have had these caravan pumps fail - and they were top quality caravan pumps rated to 90 deg.

Stuck! Even my plumbers cant give me another work around.
Surely many other have done this successfully?

Ok that clarifies things thanks Tassieman! You've got a hot water storage system rather than instantaneous. I guess your Bosch gas unit is a booster to heat up the hot water tank. Your mixer valve is what is often called a tempering valve.

Is your hot water tank pressurised or unpressurised (ie open to the air and able to overflow)? How high is it? And where does your cold water pressure come from - a high tank or a pump, or mains?

Posted Friday 9 Aug 2013 @ 9:44:21 pm from IP #
TassieMan
Member

Ive got a gravity copper HW tank off the Rayburn, with a pressure tube out onto the roof.
It works extremely well.

The cold water is coming off a grundfos pump from my tank water - plenty of pressure.

I do have instantaneous too.
I had my plumber put a crossover valve so that when summer comes, I turn a handle on this valve, and then I am switched onto my instantaneous Bosch hot water.

Good to know that the mixer is called a tempering valve.

But I still have this problem with 12v pumps failing because of the tempering valve..

Posted Friday 9 Aug 2013 @ 11:44:21 pm from IP #
MoreBikesPlease
Member

Tassieman this is only an educated guess, but perhaps your problem is due to the difference in pressure between the cold water (grundfos pump) and the hot water (low height gravity only). Your tempering valve sees cold water straining to get in, and hot water just "sitting there". To mix the two streams in proportion, it has to really choke off the cold water hard. This restricts the flow to your 12V hot water pump.

If this is the problem, then one solution would be to increase the pressure of the hot water before it reaches the tempering valve. Maybe something like the tank in the RunOnSun system? It holds a bath of unpressurised hot water, through which runs pressurised cold water in copper tubing. The tank has fittings to connect your rayburn.

You wouldn't need a hot water pump - your grundfos would supply cold water to the hot water tank, where it's heated in the copper tubing before reaching the tempering valve. The tempering valve would then be mixing two streams at the same pressure, which should work well.

What do you think?

Posted Saturday 10 Aug 2013 @ 12:12:19 am from IP #
TassieMan
Member

MBP -
"Your tempering valve sees cold water straining to get in, and hot water just "sitting there". To mix the two streams in proportion, it has to really choke off the cold water hard. This restricts the flow to your 12V hot water pump."

## > that makes total sense - I cannot see it being anything else as there is heaps of CW pressure - and almost no HW pressure.

When I fist had the plumber rig up the system, the HW tank cold only dribble out HW.
Then once the tempering valve was added it was even worse.

I'm living in this shack - very little funds to keep experimenting with plumbers...
Also after blowing up 2 pumps - I'm reluctant to experiment further with my wallet.

I'm going to give it another go and suggest your approach to a new plumber.
At least he will come around and have a look/quote.

Thanks a lot for helping me through this, and helping me get a better understanding of why the pumps fail.
Cheers!

Posted Saturday 10 Aug 2013 @ 9:02:22 am from IP #
MoreBikesPlease
Member

No worries!

Maybe a plumber that does a lot of solar hot water and/or wetback hot water? They might have more experience with gravity feeds and stuff. I guess most plumbers see mostly mains pressure systems.

Edit - I don't know if you saw this link from another thread:
http://klinkfamilyadventures.blogspot.com.au/2011/01/solar-hot-water-heater.html

It's got a picture of the copper tubes going through the hot water tank in the RunOnSun unit.

Posted Saturday 10 Aug 2013 @ 9:58:33 am from IP #
Taswegian
Member

http://www.youtube.com/watch?feature=player_embedded&v=DJDk6QEVKfA

I liked this so much I have decided to steal the idea but without his cold tap.

I plan on using his idea for the shower and running my aquacube for the sink/using an urn for cold water.

Posted Monday 12 Aug 2013 @ 2:13:29 pm from IP #
MoreBikesPlease
Member

Taswegian said:
http://www.youtube.com/watch?feature=player_embedded&v=DJDk6QEVKfA

I liked this so much I have decided to steal the idea but without his cold tap.

I plan on using his idea for the shower and running my aquacube for the sink/using an urn for cold water.

The setup in that video is very similar to mine! Like me, he's used two caravan pumps in parallel. The differences are:
- My instantaneous hot water unit is for external use only, and is mounted in the carport.
- My pumps and gas bottle are in the carport too. I reckon they should have some shelter from the elements, and I'd be wary of a gas bottle inside the living space.

Before you do your plumbing, maybe check how stable the water temperature is from the hot water unit. If you don't put in a cold water flow as well as hot, you might find yourself hopping in and out of the shower to adjust the setting!

Posted Tuesday 13 Aug 2013 @ 9:08:03 pm from IP #
Taswegian
Member

How do people go about obtaining drinkable water? I have lived in places with tanks that have no first flush type devices or water filters that I am aware of but have been reading about rain breaking down aluminium (roofing/guttering I guess) over time and needing certain filters. I have also seen one guy on youtube saying he adds chlorine to his tank to kill bacteria and then his charcoal filter removes any residual chlorine.

First I figures I'd solve the biggest water consumer being washing the cheap way and worry about potable water with a smaller capacity hopefully inexpensive setup after but may well need to guard against algae in both systems and am not sure what will be necessary.

I figures roof guttering, mesh on guttering as a filter, first flush system, tank, mosquito guard, overflow/run-off piping, tap attached to hose and that would connect to a pump and I'd be sorted but now I am second guessing my initial logic.

Guidance?

Posted Thursday 15 Aug 2013 @ 2:43:16 pm from IP #
johnmath
Member

Firstly, let me say I am not a public health expert so please take my comments as opinion.

I, like many people my age in rural areas as a child, was raised on rainwater. We had no first flush systems or filters and never cleaned gutters or tanks except if they flooded. I still drink un-purified rainwater today in preference to reticulated mains water, which contains chlorine, bad tasting minerals and (in SA at least) occasionally enough very nasty pathogens (e-coli and giardia) to cause a public health scare. I have never heard of a rainwater tank contamination issue causing a health problem.

We also use rainwater throughout the house in preference to mains water. It uses less detergent/soap and produces better results for washing clothes, dishes and people. My biggest gripe is that I have to waste rainwater flushing the toilet, a function I feel better suited to mains water!

Todays obsession with purity is misplaced, IMHO. Humans life cannot survive in a sterile environment. Our bodies contain and need 1000s of different species of bacteria to function properly. Mild exposure to pathogens is necessary for proper immune system development and functioning.

Human faeces are up to 50% dead bacteria from the digestion process. During the late stages of pregnancy, the mother's birth canal changes to breed the bacteria that the baby will need in its gut for proper functioning. During natural birth, the newborn child is coated with this bacteria which, if left to natural processes, finds its way into the newborn's mouth and into the gut. Caesarian Sections and an obsession with sterility is thought to be a cause of many of the modern diseases that didn't exist just a few decades ago, such as asthma and gluten intolerance, for example.

Rant over... (apologies)

I do have a separate 1000 lt tank for drinking water and it is fed from the highest, cleanest part of the roof. It has a first flush system and a 0.5mm mesh filter before the tank. Keeping this stuff functioning properly is a PITA as the components all need maintenance every couple of months. I have a 1 micron filter prior to the tap to take out any visible material for the sake of guests. My main concern with contamination is from motor vehicle pollution as I live in the centre of the city 100 meters from one of the busiest roads.

Posted Thursday 15 Aug 2013 @ 9:26:50 pm from IP #
sun2steam
Member

I must say, I find it rude to drift so far off topic in a thread.
It is also pretty pointless because no one will later investigate a thread about 'Hot water for off grid 12v cabin?' to find out about the hygiene of tank water.

Posted Thursday 15 Aug 2013 @ 10:09:21 pm from IP #

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