using excess power to heat water (For Dummies)

[kauaisolarman]

thank you sir.

any link to show what you mean?   possibly where to purchase 1?

[ClassicCrazy]

thanks larry looked into that route also, but, i cant seem to find a high voltage DC thermostat that can work with the setup so the water doesn't boil over.

You need a temperatre controlled switch. These usually have a flat sensor area that presses onto the heat area to be measured such as copper pipe from tank top where hot water is supplied from.
This switch controls an ssr that connects the pvs to the heating element
These switches come in preset temperatures, I use a 65degC one.
The switch is normally closed and opens when preset temp is reached
Dgd

Do you use this type Dgd ?
http://www.ebay.com/itm/Plastic-Head-40-130-Temperature-Control-Switch-Thermostat-Normal-Open-Closed-/371646622367?var=&hash=item5687dd6a9f:m:mN5KhKkwM3U1m7Fm_I6B-hw

Or this round type ?
http://www.ebay.com/itm/2-Pcs-149F-65C-KSD302-Normal-Close-NC-Temperature-Control-Switch-Thermostat-/231326554859?hash=item35dc231aeb:g:rlkAAOSwcLxYDjHd

Larry

[kauaisolarman]

hard thing is to find high voltage DC type thermostats.

i have read that if you put DV voltage through those AC thermostats they will burn up.

i see the 12-48VDC thermostats, but is you want to wire your panels in parallel for higher DC voltage they dont seem to be able to handle that.   

thats the only reason i was looking at the DC-AC converter so i can run high voltage DC direct to the AC heating element/thermostat.

[ClassicCrazy]

hard thing is to find high voltage DC type thermostats.

i have read that if you put DV voltage through those AC thermostats they will burn up.

i see the 12-48VDC thermostats, but is you want to wire your panels in parallel for higher DC voltage they dont seem to be able to handle that.   

thats the only reason i was looking at the DC-AC converter so i can run high voltage DC direct to the AC heating element/thermostat.

Dgd said  he uses  the little thermostat to a SSR - so the SSR is handling the higher DC voltage and current - not the thermostat . The thermostat would be able to work with a DC control voltage like 12v or lower .

Larry

[dgd]

Or this round type ?
http://www.ebay.com/itm/2-Pcs-149F-65C-KSD302-Normal-Close-NC-Temperature-Control-Switch-Thermostat-/231326554859?hash=item35dc231aeb:g:rlkAAOSwcLxYDjHd

Thats it. Very reliable too, i bought a few but the original is still working 2 years..

Dgd

[kauaisolarman]

so you wire the thermostat to the AUX side of the SSR inline with AUX 2 ?
and run the high voltage DC on the other end of the SSR connected directly to the PV array?

sorry i'm just  not exactly sure how you have the AC thermostat connected to the DC power.

[ClassicCrazy]

Dgd can correct me if I am wrong -   you would wire Aux + in series with thermostat switch to + control contacts of SSR ( the other side of control contacts goes to ground for Aux. ) So if power is available on Aux it has to go through closed thermostat to activate the SSR. If water gets hot the normally closed contact  of thermostat opens and shuts off SSR .

Your PV +   goes  to SSR load contacts to one side of the water heater element . The other side would go to PV negative. Depending on how you are feeding that PV if from system with Classic Dgd says he isolates it with the diode rectifier he described. If direct from a PV you wouldn't need any diode protection but should have it go through appropriate sized breaker.

Larry

[kauaisolarman]

thanks for clearing that up larry , but at that point what would "turn on" aux 1 to tell the SSR to send send power?

if the panels were connected directly to the heating element wouldn't you want them to always be putting power to the element and only stop when the tank reaches desired temperature?  wouldn't you want the SSR to be "on" all/most of the time only turning off for max temps?   what aux 1 for?

should SSR be connected in series to the battery (12V) and the temp sensor for continual "on" power?  that way when sun is shining all power from solar panels go to heating element and only when temps are reached thermostat would stop power to SSR turning "off"solar panels?

is that correct way to do it?  obviously with OCP between panels and heating element.

thanks again for the inputs

[ClassicCrazy]

I should have clarified. If you are going direct from PV to water heater then you would not use AUX but use some other battery powered source of voltage to go through the thermostat control circuit.  If you have a 12v battery that would work but could be less if SSR will operate on less.  You could use any source of voltage for that - example wall wart as long as voltage and current is sufficient to operate SSR.  And you would of course want to fuse the control circuit as well as have a breaker in the load circuit.

These are general wiring - read up in Arduino section for some other controls people have made.


Your original questions were about using Aux on Classic and Dgd described earlier how he has his wired up to take power from PV that is also connected to Classic.

Larry

[dgd]

I have used one of those 1.5 watt 12v solar trickle charge PVs, the type you often see for mounting in a car window and with cable/cig lighter connector. These tend to cost a couple of dollars.
Just connect thru ssr controls and temperature switch, include a 12v switch if you want manual control as well.
It will produce enough power to enable the SSR and only does this when there is sunshine!

dgd

[kauaisolarman]

thanks again everything making more and more sense every day.

so i currently am running AUX 2 "waste not HI" and here is where my dilemma is.

when i set the settings to 1.0V and 1.0 "width"  the absorb stage work great for diverting excess power.  it keeps me right at absorb voltage and can complete the entire absorb stage with this setting, however the problem comes when is Float.

with the 1.0/1.0 settings during absorb the most current that can be pulled is about 850 watts, but, there is more than this to be had.  if i move the settings to 0.6V/1.0"width" during float  then the controller can use the entire 1190 watts that the element can pull.

problem is if i leave the settings to 0.6/1.0  the next day the controller does not want to stay in absorb voltage.  when absorb voltage hits aux 2 is putting too much power to the element and  dropping voltage not allowing for absorb stage to start.  then i need to reset to 1.0/1.0 for charging to be completed.

any thoughts on this?

i am currently running an AC heating element off my inverter with a max power of 1190W @ 120V.

[David]

kauaisolarman,
Did you get your water heater working with dgd's setup?

[Vic]

Hi David,

You might want to send a PM to kauaisolarman,   as it looks like he has not been here for about six months.

FWIW,    Vic