48v 1000 Watt Heating Element with Adjustable Thermostat

[TomW]

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.

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.

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

[dgd]

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

[SolarMusher]

Allo David,
Ok, I've got it  . 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

[NUMNUM]

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.

[boB]

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

[JerryB]

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

[TomW]

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

[offgridQLD]

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

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

Kurt

[TomW]

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. 

Just a few personal thoughts.

Please just think about it from that angle before passing judgement.

Tom

[offgridQLD]

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

[dgd]

...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 

Dgd

[Westbranch]

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

[TomW]

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

[offgridQLD]

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.

Hope 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

[TomW]

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