PV opportunity hot water heating

[tecnodave]

Has anyone tried using an auxiliary controller to control excess power for hot water heating. I am using WBjr. on aux 2 and don't want to give that up. My idea is to use a C-40 to do this as I have one around that needs a better use than as a doorstop or maybe being nailed to a tree. (Just kidding about the tree, I will let Robin have that one, tee hee)


td

[zoneblue]

Im working on a blackbox solution. Its currently on a breadboard in a half chaotic state. It has a small solar panel which tells blackbox via an ardiuno nano the total available power. Subtract that from what the controller is putting out and run back through the nanos PWM timer, and bobs yer uncle.

[tecnodave]

ZB,

I will stay tuned to that. I was hoping that I could use a Trace C-40 PWM controller between the battery bank and the dump load. I think it would be an issue with the voltage settings between the Classic and the C-40 but with the right settings I think it will work. The big issue I see is the C-40 has a fixed bulk charge timer and the Classic is voltage based ending of bulk. I would need to find a way to get the C-40 to switch charge stages in time with the Classic.  Any ideas anyone?

I went to your website!  Some mountains you have in your backyard. I was born in the Matanauska Valley in Alaska and could see Denali Mount from our homestead 20,320 feet, highest point in North America. Your pics reminded me of that. Gorgeous country! Thanx for sharing. Are the huts for travelers? We have trail cabins in Alaska maintained by State Parks for visitors to use. One is an old railroad caboose, some are former fishing cabins donated to the state. I think no two are the same.
Will manage to visit NZ within my lifetime.

td

[mtdoc]

Im working on a blackbox solution. Its currently on a breadboard in a half chaotic state. It has a small solar panel which tells blackbox via an ardiuno nano the total available power. Subtract that from what the controller is putting out and run back through the nanos PWM timer

Very nice!

and bobs yer uncle

Ah - another Dave Jones fan ?

[zoneblue]

If im clear about how you are wanting to use the C40, youd put it diversion mode. The setpoints will as you say be the challenge. But its a bunch of fets mounted on a big heatsink with very little fuss to implement. And not overly expensive.

Im thinking that if you set it too high it wont turn on, too low and it will stop the classic setpoints being reached. Maybe the trick is to size the diversion low enough to leave something for the classic. I also heard that the C40/60 does have a serial port of some description accessible inside the case somewhere. Forget where i heard that. If you could get the two to communicate?

Mountains, yes lots of mountains. NZ has a network of around 900 huts for use by hikers. They have bunks, stoves and water tanks, and maintained by the department of conservation, largely for tourism purposes now adays,.

[dgd]

The big issue I see is the C-40 has a fixed bulk charge timer and the Classic is voltage based ending of bulk. I would need to find a way to get the C-40 to switch charge stages in time with the Classic.  Any ideas anyone?

Too complicated 
A simple water heating solution is to simply divert some of your PVs to a  heating element when the Classic is in Float. This way the power for water heating is not going through your Classic and you get to retain your doorstop.
All you need is an SSR and diode
Dgd

[tecnodave]

Zoneblue

That is exactly what I am trying to do. I am going to need PWM control of the load side due to my summertime fog here. If I just do on off control through aux 1 I will not have enough control.

The C-40 does have a serial port but I think that the controller puts out data , volts , amps , watts , batt temp.  It does not accept input.

Dgd ,

Thanks for the idea, I had read that but I think that is too limited and the ssr would cost more than a well used original Trace C-40 that I acquired in a trade.

td

[ChrisOlson]

Hello and thanks to all who have made it possible for me to have a winter of waste not powered hot showers! I set it up pretty much as Chris White describes
At first I was worried about that flickering light problem but got over it until I was giving myself my self inflicted spring haircut.  The surging power to the hair clippers made me wonder what harm I may be doing to the compressors on my fridge and freezer.
Anyone?

I assume you mean me, Chris Olson.

I don't think the flickering light problem or "surging power" as you describe is a problem at all, other than being an annoyance.  With some inverters the voltage regulation is not good enough to prevent this.  But as far as I know it does not change the frequency of the AC output of the inverter, just the voltage varies due to the PWM pulsing the SSR.  Your refrigeration compressors can handle a pretty wide variation of voltage without hurting them at all.  But they can't handle a wildly varying AC frequency, since it is the frequency that determines their operating speed, and not voltage.

The hair clippers is a different deal than a fridge compressor because hair clippers are not a rotary motor (unless you're using sheep shears or something).  The hair clippers is a linear motor so it will be affected just like light bulbs are by varying voltage varying the magnetic field in the two windings that makes the motor oscillate.

If you have some other super-sensitive stuff like HDTV and it's causing "snow" on the screen of the TV, then I would think twice about it.  But otherwise I just can't see it hurting anything.  What causes it is the fact that the SSR's are zero cross so they continue to conduct even after the PWM pulse is done, and conduct until the sine wave goes to zero before they shut off.  So the voltage varies with the AC frequency on inverters that are not able to regulate this, and that's what makes it so pronounced with some loads.  It takes a big inverter with a dang big transformer with a heavy core and with lots of copper in it (Xantrex SW/SW Plus/XW) to not be affected by this.  The lighter duty units are going to flicker your lights.

[dgd]

... I am going to need PWM control of the load side due to my summertime fog here. If I just do on off control through aux 1 I will not have enough control.

I seem to remember that (slow?) PWM was available via AUX1. This was in a discussion about using AUX1 to provide CLIPPER CONTROL signalling to a Clipper.

dgd

[Halfcrazy]

Yes Aux1 can be dialed down (or up) to 0.1 seconds

[zoneblue]

I imagine even 10s or 20s would work ok. Without knowing more about battery "capacitance" aka how batterys manage pulse loads, i couldnt say what the difference is between a 1000Hz, v 0.1Hz pulse frequency is on battery cycle life. 

[dgd]

So now you have a suitable PWM signal from AUX1, I suppose the question is how to use this to manage your water heating diversion load. The obvious method is via an SSR of some type and circuits for this are easy.

The expense of an SSR aside the ideal scenario would be to use the Classic's AUX1 to somehow control the C40 - or just the FETs which in effect will do the same as an ssr. Looks reasonably complicated but if you can work out the C40 circuit it should not be impossible to do.
Maybe selling/swapping the C40 for a DC SSR is the way to go
Ebay has cheap chinese SSRs, a mere fraction price of Crydom, Teledyne etc..

dgd

[zoneblue]

Nah id stay away from cheap ebay SSRS. I bought some and later found out they pop real easy. Peace of mind, spend the bucks.

[tecnodave]

I did figure out a way to do it. The C-40 voltage sets are pots, very easy to lift the leads and have the aux1 out control a daughter board in the c-40 to change voltage state when the Classic commands it.,
Now to work out the details. I want to divert some of the power in absorb as well as in float. I don't see a way to do that easily. I do see pv on high which will do want I want as the cc will begin to unload the panels when in absorb due to the reduction in current drawn, but this will be on-off only , not PWM on the control side. Maybe this will be enough and let the C-40 do the PWM for the load.

I had sort of this arrangement to turn on my refrigeration when my PV arrays went 15-20% over V@Pmax. On my system before I bought the Classic. This logic board then fed 12 volts to the referigerator board "ignition signal" causing it to switch from propane to 12 power source derived from a Pyle buck converter.
I now have compressor referigator. This was done when I was using a  Tracer dumb controller which had no aux function at all.

The C-40 does have other duties as well so I just might hook up the Classic and kid in follow me and let the kid handle the BTM and WBjr. and share that with the Classic and use Aux 2 opportunity to do the PWM to the diversion load.

Sad note:  the Trace C-40 is connected with the epSolar Tracer to charge the aux battery bank. The Tracer voltage cannot be set so the C-40 is switched on by clock @ 1:00 pm to top off the batteries.
Outputs in parallel, inputs switched by time clock derived relay.

The Trace (a PWM controller with a 70 volt series string) tops the batteries better than the Tracer which is MPPT with the same string of 4 series Siemens SM-55 panels.

Yeah, I know, wasted power, the PWM controller is running maybe 20 % efficiency like this but Mario is babysitting my kid right now.

Half the fun of solar is tweeking it to get a little more. There is no "Final finished form".

td

[vtmaps]

Half the fun of solar is tweeking it to get a little more. There is no "Final finished form".

The other half of the fun is tweaking your consumption to use a little less      
--vtMaps