Hi all, I've seen this 48Vdc heating element with thermostat on Missouri wind&Solar website (http://www.mwands.com/index.php?main_page=product_info&cPath=40&products_id=493). It could be interesting for those who would want to divert solar excess power and do not want to use AC power from inverter to heat/preheat a water heater.
I would like to use two of these elements to power a used electric tank ahead of my propane water heater and control them with a DC SSR on Classic Aux2 waste not PWM. Now, with a DC thermostat, I think it could work fine but from what I've read in other threads, I'm in doubt. Is there a problem to PWM a DC SSR?
What do you think of that? This could be an inexpensive option to heat water.
I have also an old Tristar C60 that I could use to divert directly from battery without SSR but would prefer doing it using Classing Waste Not.
As usual, your inputs are very appreciated.
Thanks,
Erik
Never had any problems with aux2 pwm into a DC ssr. The ssr will get warm so needs a heat sink and of course a breaker to the battery. I would try with one element first and ssr like Crydom d1d100
100v @ 100A, I would probably give each element it's own ssr. The classic aux can drive two Ssrs.
Dgd
Quote
Posted by: dgd
« on: Mars 13, 2013, 02:51:30 pm »Insert Quote
I would probably give each element it's own ssr. The classic aux can drive two Ssrs.
Dgd
Hi David,
I think that I will follow your SSRs setup. I would like to begin with 2x 700/800W elements and keep it at around 1500 max.
If I use 2x 1500W/120V elements, it would give me 1500W total on 48Vdc battery (59,2V absorb), is this correct?.
Or do you think it could be more efficient to connect only the bottom element with a 3000W/120V?
Could you explain how you can set the Classic to drive two SSRs? I do not follow.
Erik
Eriik,
If you half the voltage then you roughly get a quarter the power rating, so a 120v 1.5 kw element would be about 375watts with 60volts.
(1.5kw at120v=12.5amps=9.5ohms element, 60v puts 6.25amps into 9.5ohms giving 375watts)
So it may be better to use a 120v element rated at 3kw to get 750watts at 60v
You just connect the DC inputs to the Ssrs in parallel to the aux2 output on the Classic.
I would start with one ssr and element and see how it goes then if power still available maybe put in second element.
When power scarce I would just open breaker to one of them, or else insert a miniature switch in the aux to ssr wire and open it so ssr not enabled by classic.
Dgd
QuoteIf you half the voltage then you roughly get a quarter the power rating, so a 120v 1.5 kw element would be about 375watts with 60volts.
Oops sorry, bad math! I could have a used tank for...free ;). The plumber told me that it has already 2x 3000W/120V elements, so it would be perfect!
QuoteYou just connect the DC inputs to the Ssrs in parallel to the aux2 output on the Classic.
If I read the Crydom correctly, I should use 4 and 3 for pos/neg from Aux2, 1 for DC+ from bat and 2 for DC+ to WH. Is that right?
Erik
Erik,
Yes the existing two 3Kw elements would be perfect 8) that wiring for the ssr looks right. The crydom web pages for D1Dxx series have a wiring diagram, note it shows a diode across the load to stop voltage spikes, include this in your wiring.
A schottky diode is good, ebay..
The D1D20 would be ok for your 3kw element, cheap on eBay :)
dgd
QuoteA schottky diode is good, ebay..
Hi David,
The only diode I've found which could match amp/voltage is this one: http://www.ebay.com/itm/LOT-OF-10-WIND-GENERATOR-SOLAR-40-AMP-BLOCKING-DIODE-/250742187967?pt=LH_DefaultDomain_0&hash=item3a616627bf
It could be ok for D1D20 or D1D40 SSRs. Where do you put it, in battery/SSR or in SSR/WH?
Would you have a picture on how is your SSR wiring and diode?
Erik
Hi, that diode do not have to "take" all the power, it's there to control high voltage create by rapid discharge of a inductive load, like a large coil.
JP
Hi JP,
So what do you think a good size would be (volt/amp) for this schottky diode?
Erik
Erik, as i understand, your load will be two 3kW (at 120V) heater (about 25 amps at 48 V by each) and you plan to drive those with some D1 series Crydom SSR. If it's true, the diode in the circuit is there for protecting the SSR output from overvoltage create by turning off inductive load. So, you could use, as indicated by dgd a schotkky diode, but where i'm worked till last december, we generally use zener or transorb to do the same job. With those, the protection is in both side... my recommandation for you is something like a 1.5KE100.
JP
Thanks a lot JP, but now that I 've read Chris post on NAWS, I'm really confused about using DC to power these elements. Problem is that nobody really wants to explain why and where AC would better or more efficient if batteries are close to WH. From what I've read here and there, it seems that adding a cheap inverter to power it on AC is the way to go. I don't understand why people here at Midnite are not more helpful (no offense here, please) on aux2 waste not uses. It would be a major reason (one more) for people to buy a Classic though. I know the crew is busy but...
I also believe that Aux2 diversion should be by far more important than a local app from an off-grider point of view...
Just me,
Erik
Erik,
With DC elements the distance from the battery to the element needs to be considered.
Unless fairly close to each other, a few metres, then the DC cabling will need to be large enough size to reduce voltage loss. If the elements are 30 metres away then the cable cost would be significant, 30m x2 of #2 is not cheap. So it is then much easier to use AC to keep cabling costs low.
The use of a cheap inverter just stops loading main inverter which already my be quite busy. A modified sine type is great on resistive loads like elements.
If your battery and elements are reasonably close then DC seems least costly.
The is no difference in efficiency and the elements don't care if fed DC or AC
The Classic aux will drive an AC or DC relay so long as the control inputs are DC.
Your idea of perhaps some info on aux applications, maybe with examples is good.
Not sure MN should do it, liability and all that stuff..
Dgd
QuoteErik,
With DC elements the distance from the battery to the element needs to be considered.
Unless fairly close to each other, a few metres, then the DC cabling will need to be large enough size to reduce voltage loss. If the elements are 30 metres away then the cable cost would be significant, 30m x2 of #2 is not cheap. So it is then much easier to use AC to keep cabling costs low.
The use of a cheap inverter just stops loading main inverter which already my be quite busy. A modified sine type is great on resistive loads like elements.
If your battery and elements are reasonably close then DC seems least costly.
The is no difference in efficiency and the elements don't care if fed DC or AC
The Classic aux will drive an AC or DC relay so long as the control inputs are DC.
Your idea of perhaps some info on aux applications, maybe with examples is good.
Not sure MN should do it, liability and all that stuff..
Dgd
Hi David, I could even put this secondary WH close by 36 Inches to the battery box, so DC voltage drop would not be an issue.
What would be your schottky diode choice to protect the Classic? JP thinks a 1.5KE100 could do the job, what do you think about it?
I would like to be sure to get it right.
Was thinking about AC SSR using a dedicated inverter but the only one that could match 1500 element would be a Cotek/Samlex 1500/48 inverter no charger and I'm afraid that it would be too short to power 1500W for 4/5 hours regularly, I have not Seen/found serious 2000W/48V unit even in MSW model (Ebay, Amazon).
There were comments on NAWS that recommend against DC SRR for safety/contact (arc) reasons and it seems to be a consensus, I don't understand why and where using a quality Crydom DC SSR which was built especially for this use would be dangerous ???.
Why contacts on WH could be a problem at 60Vdc??? It's over my head!
Could this problem occur when the Classic PWM the diversion? I'm pretty sure that you never have experimented this kind of problem on your DC set-up.
Not a drop of liability here, we're just talking :P.
Erik
Erik;
I wonder if the issue they are concerned with is the contacts welding shut or arcing over @ the higher DC voltages?
Seems the switches for that kind of use are "special" with protection from arcing and contact welding? A fused limit switch could be very catastrophic in nature.
Perhaps there are limit switches available for this application?
Just an idea.
Tom
Quote from: TomW on March 18, 2013, 11:35:40 AM
Erik;
I wonder if the issue they are concerned with is the contacts welding shut or arcing over @ the higher DC voltages?
Seems the switches for that kind of use are "special" with protection from arcing and contact welding? A fused limit switch could be very catastrophic in nature.
Perhaps there are limit switches available for this application?
Just an idea.
Tom
Tom, yes you're right, that's the main problem but I've never seen a safe switch for that specific use. I wonder if using Float on Aux1 (on/off switch) wouldn't be a better option for DC direct use fom batteries to supply a full steady 1500W on a voltage range. I'm not sure that Aux1 Float would worth the cost of an efficient WH/elements/SSR when only 2 or 3 hours on float are available.
Maybe waste not on Aux1? My concern would be to not overcharge the battery with that option which would result in extending the bulk charge time and therefore absorb time.
So to resume, water heating wouln't be possible/safe on PV/batt DC and very costly on AC as it needs a dedicated inverter to work :'(.
I Think a last option would be to go with Nyle Geyser pump 600/800W through an AC/SSR on Aux1 opportunity or Float only as Mtdoc
had proposed.
Erik
Quote from: SolarMusher on March 18, 2013, 01:10:19 PM
Tom, yes you're right, that's the main problem but I've never seen a safe switch for that specific use. I wonder if using Float on Aux1 (on/off switch) wouldn't be a better option for DC direct use fom batteries to supply a full steady 1500W on a voltage range. I'm not sure that Aux1 Float would worth the cost of an efficient WH/elements/SSR when only 2 or 3 hours on float are available.
Maybe waste not on Aux1 ? I'm afraid to overcharge battery with it.
Erik
Erik;
OK, maybe I am crazy here but perhaps there is a way to use the standard limit switch to drive a low voltage pilot relay that disconnects the element if the temp hits the limit?
Probably not the best way but a pilot relay can likely be had for most voltages and certainly for 12 or 24 volt?
I am just tossing ideas as they pop in to my feeble mind so take with a grain of salt.
Tom
Tom, you're too fast to me.
I was still adding content to my previous post ;D.
Hi Erik,
SSRs or Solid State Relays like the Crydom we are considering don't have contacts that can arc and weld together like a mechanical relay. They use a FET for switching and I have not heard of one failing when used within its current and voltage specs.
Aux2 PWM signalling is ideal to use with a DC SSR as it gradually introduces/removes the load
The classic manual has a nice explanation of how this works.
I used a Schottky diode I had in spares box, I remember it was rated about 300v so anything you find on ebay rated a few hundred volts should be ok. Jp's suggestion is good.
Dgd
Quote from: dgd on March 18, 2013, 02:22:36 PM
Hi Erik,
SSRs or Solid State Relays like the Crydom we are considering don't have contacts that can arc and weld together like a mechanical relay. They use a FET for switching and I have not heard of one failing when used within its current and voltage specs.
Dgd
Dgd;
I think the main concern is for the limit switch[es] on the water heater?
That is what I was addressing WRT welded contacts and arcing.
Just FYI.
Tom
Tom, are you talking about the thermostat? if so, there are cheap 48Vdc units that could be used.
Erik
QuoteHi Erik,
SSRs or Solid State Relays like the Crydom we are considering don't have contacts that can arc and weld together like a mechanical relay. They use a FET for switching and I have not heard of one failing when used within its current and voltage specs.
Aux2 PWM signalling is ideal to use with a DC SSR as it gradually introduces/removes the load
The classic manual has a nice explanation of how this works.
I used a Schottky diode I had in spares box, I remember it was rated about 300v so anything you find on ebay rated a few hundred volts should be ok. Jp's suggestion is good.
Dgd
David,
Does this diode connect directly output 1 to 2 on the crydom relay?
Erik
Quote from: SolarMusher on March 18, 2013, 02:44:37 PM
Tom, are you talking about the thermostat? if so, there are cheap 48Vdc units that could be used.
Erik
Erik;
Yes. Or the high limit switch many water heaters used to have.
Personally, I wouldn't use DC for several reasons including the issues that can arise WRT cable sizing and proper switches.
There are usually many ways to accomplish the same ends. I use AC to dump power to a water heater with Aux1 as the switch to activate a relay on the AC OUT that feeds the heater. My hot water is pretty minimal with 2 10 gallon units plumbed in series and I dump power into the first one when I have excess production. It heats 10 gallons up in about 40 to 60 minutes with a 120 VAC 1600? watt element. The second or main heater is connected to the grid to keep some hot water on hand all the time. I think of the #1 as a preheater. Just how I do it.
I know relays are old school but I have them on hand and these are 2 pole with NO and NC connections so act like a transfer switch for my water heater load.
Just rambling now and likely no help.
Tom
Tom, what does your Classic look like when it hits absorb and then begins to divert a full steady 1600W?
Does it revert on bulk for a long time before reaching anew absorb and is overcharging a problem for you in this case?
Also does the Outback suffer from flickering on Aux1 or is it only a Aux2 PWM issue when triggering on Outback/Magnum?
Erik
For temperature control I used this device
http://www.jaycar.co.nz/productView.asp?ID=ST3821&form=CAT2&SUBCATID=969#1 (http://www.jaycar.co.nz/productView.asp?ID=ST3821&form=CAT2&SUBCATID=969#1)
I placed it near top of 180 litre hot water cyclinder on copper at top outlet pipe.
Its wired into the cable that connects the AUX2 to the Crydom SSR. When the temp gets high enough it open circuits, disables the SSR
so no power to the heating element. Works good and no high current switching involved.
dgd
But why don't just control the SSR directly by the thermostat?
JP
What i realy mean is why not use a similar set-up that dgd use, but instaed of the thermostatic switch he use, take the WH thermostat ?
JP
..because I use elements that do not have inbuilt thermostats.
Dgd
Hi dgd, i was talking about the Erik case, your set-up is perfect.
JP
Quote from: jp_le_gros on March 18, 2013, 06:20:00 PM
Hi dgd, i was talking about the Erik case, your set-up is perfect.
JP
..sorry, I was too quick replying. Then realised what you referred to.
I think Erik has two 3kw elements that probably have inbuilt thermostats so just depending on those should be ok. My setup was built from scratch so I ordered plain $15 elements from eBay and added the temp control as an afterthought. It also appealed to me to switch the control line to the SSR rather than trying to switch the full load current to the element.
Dgd
realy a good choice, it's a lot easier and cheaper to make the control of a circuit on the low power side.
JP
Quote from: SolarMusher on March 18, 2013, 03:28:36 PM
Tom, what does your Classic look like when it hits absorb and then begins to divert a full steady 1600W?
The Classic may revert to bulk MPPT depending on the incoming power.
Quote
Does it revert on bulk for a long time before reaching anew absorb and is overcharging a problem for you in this case?
On a good solar day I get a bit over 2.5KW from solar so it can often run the heater without much impact on battery state while charging from full on solar.
I have not noticed it being a problem but then I have a fairly large bank so overcharging is not much of an issue.
Quote
Also does the Outback suffer from flickering on Aux1 or is it only a Aux2 PWM issue when triggering on Outback/Magnum?
Erik
I use the AUX1 in automatic mode, simply on or off and it is steady with no cycling. The Outback FX is not used other than as an inverter with no interaction with the Classic other than sharing the same battery bank.
Again, I use a relay and on / off because I had one on hand and use 120 VAC due to the batteries and inverter being 120 feet or so across the driveway from the water heater in the house. I may give the PWM /SSR a try at some point but I have a LOT of irons in the fire these days.
Hope that helps.
Tom
Hi Erik,
Wiring the element, diode and SSR
+ve from battery to connector 2 on SSR, from connector 1 SSR to element, then other side of element to battery -ve.
Diode goes cathode end ( usually end of diode with white line marked around it), to the SSR PIN 1,
Other end, anode, of diode goes to battery -ve
Dgd
Allo David,
Ok, I've got it :P. It was the V symbol on the diagram that confused me (to say the least :-\). If I'm right, V is equivalent to battery (+/-), or another DC source.
Thanks a lot David! DC SSR is still my first choice and I will use it with a 48Vdc standalone thermostat.
Erik
just wondering what would happen if we wired one of these 600 watt dc heating units in front of the cc.would the watter get hot first,then charge the battery.
Quote from: NUMNUM on March 31, 2013, 08:42:21 PM
just wondering what would happen if we wired one of these 600 watt dc heating units in front of the cc.would the watter get hot first,then charge the battery.
It may be easier to think of what happens to battery charging when thinking about this... That whatever the voltage is
when that load is on is the same voltage that the battery is at.
So, if the charge controller and battery voltage is at say, the absorb voltage and the load comes on, and the battery voltage
is still able to be at the absorb voltage, then the battery is still being charged just like it was before the load came on.
The only difference is that the charge controller and its source (solar, wind, hydro, etc) is just putting out more
power to keep that voltage up.
If there is not enough power to keep the voltage up to absorb or float, THEN you might be discharging the battery because
the voltage drops and the battery may be supplying that power... Especially if you see the battery voltage start dropping.
This is where PWM (making the load variable) comes in handy. It only gives the load enough power so that the
voltage does not drop (hopefully)
boB
Hi Folks,
I wanted to offer some advice based on my experience with diverting power to heat water. I built a PWM diversion system operating from the PV array (90 volt nominal) which feeds a conventional RV style water heater. It worked very well, HOWEVER, I had two instances of a failed primary thermostat on the HW heater (failed CLOSED e.g. won't turn OFF). I am now convinced that the contacts were welded by the DC power from the array. So my counsel is to avoid the use of DC on water heaters IF you plan to use the normal thermostat (e.g. the tank-mounted assembly). With an SSR and an external temperature regulation apparatus, it should be fine.
Jerry
Quote from: JerryB on May 07, 2013, 12:35:08 PM
Hi Folks,
I wanted to offer some advice based on my experience with diverting power to heat water. I built a PWM diversion system operating from the PV array (90 volt nominal) which feeds a conventional RV style water heater. It worked very well, HOWEVER, I had two instances of a failed primary thermostat on the HW heater (failed CLOSED e.g. won't turn OFF). I am now convinced that the contacts were welded by the DC power from the array. So my counsel is to avoid the use of DC on water heaters IF you plan to use the normal thermostat (e.g. the tank-mounted assembly). With an SSR and an external temperature regulation apparatus, it should be fine.
Jerry
Jerry;
The easy fix for that would be to drive an SSR thru the thermostat with a low voltage. Thermostat on turns on the SSR and off shuts it off.
Just a thought. Someone on here (I think) brought this up recently and it would be a much safer method on a DC setup with an AC thermostat.
Tom
I'm all for using the features of the classic but why hot water. Not sure how popular they are in other country's but in Australia no one would use electricity to heat water. Actually element style hot water systems are being outlawed here.
If your off grid like me. Why not just do what we do and use the sun directly to heat your water with a Vac tube solar hot water panel. Save your electricity AC & DC to power things that cant be done directly from the sun.
My thinking is on a particular day if you have enough sun to provide spare pv output you will have have enough sun to heat the water directly and you don't need to put it on hold until battery's are on absorb or float wasting 1/2 the days sun. It's a independent system that starts heating the water the second the sun comes up until it sets in the evening.
No moving parts nothing to burn out and no extra load on your battery's or inverter.
Something like this. All you need to do is feed it cold water and let it do its magic.
http://www.ebay.com.au/itm/BRAND-NEW-200L-DIRECT-CONNECT-TO-MAIN-SUPPLY-SOLAR-HOT-WATER-SYSTEM-/321117123582?pt=AU_HotWaterSystems&hash=item4ac41273fe (http://www.ebay.com.au/itm/BRAND-NEW-200L-DIRECT-CONNECT-TO-MAIN-SUPPLY-SOLAR-HOT-WATER-SYSTEM-/321117123582?pt=AU_HotWaterSystems&hash=item4ac41273fe)
Or if you have a 4 fitting tank already something like this (this example is double the size you would need) This with a small dc recirculation pump and thematic control.
http://www.ebay.com.au/itm/60-Tube-Solar-Hot-Water-System-suit-600L-system-/260648737488?pt=AU_HotWaterSystems&hash=item3cafe01ad0 (ftp://www.ebay.com.au/itm/60-Tube-Solar-Hot-Water-System-suit-600L-system-/260648737488?pt=AU_HotWaterSystems&hash=item3cafe01ad0)
Kurt
Quote
I'm all for using the features of the classic but why hot water. Not sure how popular they are in other country's but in Australia no one would use electricity to heat water. Actually element style hot water systems are being outlawed here.
Kurt;
Not everyone lives where it never freezes. Some of us live where it never gets above freezing for months on end so domestic solar hot water is problematic and / or expensive.
Anyway, I think you miss the point from tunnel vision due to your location.
Don't get me wrong, solar water heating is a great idea in many climates like Australia, for instance, but certainly not up here in the Great White North of the Americas when the sun only peaks out occasionally and only for a few hours on the best of mid winter days.
We already have too many laws and more being manufactured daily here. Lets not get started on that. :o
Just a few personal thoughts.
Please just think about it from that angle before passing judgement.
Tom
I did mention other country's could be different for many reasons. But my point was the feature u are trying to use on the classic assume you have excess pv energy to burn in this case that energy is burnt on a electric heater element. Then if that is true the same excess energy from the sun can heat a solar hot water system or perhaps not.
Kurt
Quote from: offgridQLD on May 08, 2013, 08:25:44 AM
...my point was the feature u are trying to use on the classic assume you have excess pv energy to burn in this case that energy is burnt on a electric heater element. Then if that is true the same excess energy from the sun can heat a solar hot water system...
So very true, if making water hot is a priority then direct heating via a vac tube system is definitely the way to go. Using excess PV power to heat water seems IMHO to work best to reduce usage of other expensive (grid, LPG, propane etc..) methods that are the primary water heating energy source.
The idea being that if you generate excess 'free' energy you may as well use it.
Doing so has reduced my annual bottled LPG gas costs by about 75%.
However if rebuilding my HW system I would go the vac tube way :P
Dgd
go about half way down this page to SHED HEATING, I would call it a shop, NOTE the heat produced in -30C weather in SASKATCHEWAN Canada!
http://www.wsetech.com/waterheaters.php
Quote from: Westbranch on May 08, 2013, 04:21:28 PM
go about half way down this page to SHED HEATING, I would call it a shop, NOTE the heat produced in -30C weather in SASKATCHEWAN Canada!
http://www.wsetech.com/waterheaters.php
I think this is not exactly an apples to apples comparison. Big difference in using excess or intentionally oversized existing RE system and installing a multi thousand dollar dedicated evacuated tube water heating system. I haven't priced that panel but I am certain they are pretty expensive.
This will be like a political / religious debate where nobody will be able to or even should convince the other they are wrong so I will leave it at that. Whatever works for you is what works for you...
That linked system is sweet, don't get me wrong.
Different strokes for different folks as the saying goes. I use excess power to opportunity heat water myself and it works for me.
Tom
The cost isn't as much as you would first think (I'm not talking about that massive shed hydro room heating system but a simple domestic hot water unit) A complete system can be purchased for as low as $800 locally The 30tube system I have is $1200 completely SS tank, fitting and mount. I linked to two systems earlier. But yes what ever works for you everyone's situation is different and we all have our reasons. there is no correct way to do it just throwing options out there.
It was my understanding that they work fine in cold weather as they say below but I have no experience with it in that kind of climate.
QuoteHope all is well on your end. We are seeing more sun these days. Today started at -33c warming to -25c I watched the heat in the system go up to 72c it was so hot one could not put your hand near any of the lines.
Given that most domestic hot water is tempered to a max 50C for safety reasons 72c on a -33 to -25 deg day sounds good to me.
I do see that if you already have a tank with a element and it all works out simple to set up without much additional outlay Then I guess if you have it why not use some excess pv power to heat your water that way. But when you start needing to purchase additional inverters or complex control systems and additional hardware. You would have to wonder if the same outlay isn't better off put towards a vac tube system.
They are often used in unison with additional boost heating. My personal system doesn't need it due to location but I do have it in the form of a instantaneous LPG gas heater outside on the wall The water from the SHW system flows through it all the time but its switched off. I can flick a switch inside to activate the LPG gas boosting if the water temperature ever needs some boosting. (for example to many guests sucking the heat out of the holding tank).
I guess you could still boost with a electric element controlled by the classic and the load or element size required for it would be dramatically reduced with the addition of SHW pre heat.
I would like to use the wast not feature to charge a modest size battery on a small electric car but it's most likely better to purchase another higher voltage classic version and charge the cars battery directly from that - keep it simple separate system.
kurt
Quote from: offgridQLD on May 08, 2013, 05:19:36 PM
I would like to use the wast not feature to charge a modest size battery on a small electric car but it's most likely better to purchase another higher voltage classic version and charge the cars battery directly from that - keep it simple separate system.
kurt
Wheres the fun in that? ::)
I often think true elegance in design occurs when nothing more can be taken away and accomplish the task. Less is more kind of thing.
Don't tell boB, please.
Tom
Quote from: TomW on May 08, 2013, 08:55:33 PM
I often think true elegance in design occurs when nothing more can be taken away and accomplish the task. Less is more kind of thing.
Occam's razor, a wonderful tool :P but obfuscation and faff always seem to find a way, much like modbus cripples meaningful data communications.
dgd
Quote from: offgridQLD on May 08, 2013, 06:37:18 AM
but in Australia no one would use electricity to heat water. Actually element style hot water systems are being outlawed here.
And I thought the US was bad for passing stupid laws.
Electric water heating is almost 100% efficient at the element, converting the energy input into heat. Many of us live in the Frozen North and have chosen electric water heating for our off-grid homes because we use wind turbines in the winter time when the sun doesn't shine for weeks at a time. When the sun doesn't shine, direct solar water heating don't work very good. Wind turbines that run 24 hours a day produce plenty of electricity to heat water with.
So it's a matter of choice:
- direct solar water heating - only works when the sun shines.
- electric water heating - works with solar, wind, or propane, gasoline, diesel fuel (heating water with generator power if necessary).
In other words, electric water heating is reliable because we can use a variety of power sources for it. Direct solar isn't reliable in our climate.
--
Chris