Designing a Diversion Water Heater Load For AUX 1 using an SSR - AC or DC?

[ClassicCrazy]

Looking for a diode. I can't find anywhere that suggests exactly which diode I need to purchase and where to purchase it. I can only find that says I need a diode. Where are some links to purchase the diode that I need?

Ha ha - yeah I was trying to figure that out also earlier this summer  - I believe the info is there in the technical  data I linked above.

Larry

[dgd]

most diodes would be ok, I have used 1N4000 although a schottky type diode is better
you can find these on ebay for cents to a couple of dollars.
dgd

[Matrix]

Thanks dgd. 

This morning I got back on the AC from Inverter Idea instead of DC.    I can get a DC control / AC load SSR correct?   And then the AC load can still be controlled but the DC control /  AC load SSR thru the Aux 1 settings of the Classic?  Correct?

If I go AC,  I think I can use my existing 4500w 240v element and thermostat,  but (if I did the math correctly)  ... at 120v the 4500w element would only be 1125watts. 

4500 (120v/240v) x (120v/240v) = 1125 w

and the Amps at 1125 watts / 120v = 9.37 amps

Did I do that math correctly?

This would mean:
1. An SSR rated for lower amps
2. Less copper (I could use #12 or #14 wire instead of #8)
3. No replacement parts at all.
4. And I dont even have to take my water heater apart.

Except for inverter inefficiencies ... what am I missing here?   If I can control the and AC load just like a DC load off AUX 1 ... this would give me everything I want, and all I need to buy is a 3-35v DC control / 120v AC 25 amp SSR.  My inverter could handle 1125 watts no problem. 

[mike90045]

Looking for a diode. I can't find anywhere that suggests exactly which diode I need to purchase and where to purchase it. I can only find that says I need a diode. Where are some links to purchase the diode that I need? 

the required diode size is a function of the coil voltage, and the size of the inductive "kick" the coil delivers (like an automotive spark coil).   once you settle on a relay/contactor, call the engineering support and ask them for sizing a anti-flyback diode.
the link i gave earlier has some guidelines.   Installing it properly (correct polarity) is crucial, ask a local hobbyist how to read the markings on the diode to ascertain the proper orientation.

[ClassicCrazy]

Just found this - best info on SSR I have seen yet

It has easier to understand Selecting a Diode section
http://omronfs.omron.com/en_US/ecb/products/pdf/precautions_ssr.pdf

Larry

[Matrix]

Cool thanks everyone.

Well I just found a piece of number 12 wire 27 ft long. And I ran it from my inverter off of L1 to the bottom of my hot water heater through my AC thermostat. The whole thing is AC coming off the inverter. It is a 4500 watt element at 240 volts. But I wired it 120 volts. And it is pulling exactly 1125 Watts and 8.75 amps aa tested by my clamp meter. Working perfectly. The thermostat Cycles on and off no problem. I'm using all of my Excess power. The only problem is I have no automation yet because I have not connected an SSR to the AUX 1 on the classic

So now to find an SSR that works with DC control and AC load. I know that crydom makes them no problem so this should be an easy find.   And now it only has to be 25 amps instead of 60 or 100 amps

[Taos]

Yes crydom makes good relays. Thats what im using ,also not sure if you disconected the upper thermostat wiring to the lower element as the house 240 volts upper thermostat has a switch from bottom element to upper element during high water demand , im using a lower a.c element 120 volts 500watts  wired to my inverter, with a crydom ssr dc control, a.c. Load relay on the classics aux1 using waste not , left the original a.c. Thermostats in place and it works great ,the upper element is on house a.c 240 volts and is on a timer ( its on after 7 pm until 7 am ) as our hydro rates more then double during the day ,  you will have to play with the aux 1 setting to suit your system , during a full sunny  day all my hot water is produced by solar ( were only two people  using it and are conservative ) my system is very small 1320 watts  of panels .
Don

[Matrix]

Yes crydom makes good relays. Thats what im using ,also not sure if you disconected the upper thermostat wiring to the lower element as the house 240 volts upper thermostat has a switch from bottom element to upper element during high water demand , im using a lower a.c element 120 volts 500watts  wired to my inverter, with a crydom ssr dc control, a.c. Load relay on the classics aux1 using waste not , left the original a.c. Thermostats in place and it works great ,the upper element is on house a.c 240 volts and is on a timer ( its on after 7 pm until 7 am ) as our hydro rates more then double during the day ,  you will have to play with the aux 1 setting to suit your system , during a full sunny  day all my hot water is produced by solar ( were only two people  using it and are conservative ) my system is very small 1320 watts  of panels .
Don

Hi Don. 

Yes I have the Upper and lower disconnected from each other.

Upper = 240v AC Line with 4500watt element.  No timer ... that that is a really good idea

Lower = 120v AC Solar/Battery at 1,125 watts using the stock Element and lower Thermostat.  Element is 4500w, but at 120v it is 1,125w   (4500 (120v/240v) x (120v/240v) = 1,125)

Ordered a Crydom D1240 SSR, which is a DC 3-32v control / AC 24-140v Load.   should be just right. 

Can you give me any starting suggestions on using Waste Not as far as Aux 1 Settings?   I really do not under stand how it is suppose to work.  I realize the - volt values you enter will not start / stop the Water heater element until those user set points,  But I read some where that it controls it for each of the charging stages as well - Bulk / Absorb / Float.  How does that work?    Does Waste Not wait until there is enough power coming off the array to power the element with out jeopardizing charge? 

Some good starter point settings and tips would be helpful.

[Matrix]

The links posted in this Thread so far have been very helpful.   I know that your time is valuable and most if not all are merely fellow users and not MidNite Solar employees.  My questions may at time seem elementary and redundant, But Thanks for your patience and all the input from the Forum participants.

To further help anyone else who may see this thread in the future, and to help make a comprehensive guide to setting up Hot Water Heating as a Diversion for Excess power ... I have compiled a list of what I considered helpful Discussions on this forum that I found, and other links I have found that seemed to be helpful on this subject.

Forum Threads

Basics of Diversion to Hot Water Tank
http://midniteftp.com/forum/index.php?topic=3666.0

Using a Classic with DC heating Element
http://midniteftp.com/forum/index.php?topic=727.0

AUX 1 and AUX 2 Modes in the Classic Explained (complete list)
http://midniteftp.com/forum/index.php?topic=289.msg1667#msg1667

DC wire SSR with Classic
http://midniteftp.com/forum/index.php?topic=3352.0

DC SSR sizing?
http://midniteftp.com/forum/index.php?topic=3595.0

Diversion Load AUX 1 settings
http://midniteftp.com/forum/index.php?topic=3754.0


Off Site Links

Harvesting Surplus Energy
https://www.homepower.com/articles/solar-electricity/design-installation/harvesting-surplus-energy-grid/page/0/1?v=print

Managing Battery Charging Using Diversion Loads
https://www.homepower.com/articles/wind-power/design-installation/managing-battery-charging-using-diversion-loads

Water Heating Controlled by a Classic 150
http://www.fieldlines.com/index.php?topic=147132.0

How to Convert an AC water heater to DC
http://waterheatertimer.org/Convert-AC-water-heater-to-DC-water-heater.html

http://waterheatertimer.org/convert-AC-water-heater-to-DC-using-low-voltage.html


MidNite Solar Classic Papers and Documents

Diversion Load Control with 2 Types of Relays
http://www.midnitesolar.com/pdfs/CLASSIC_DIVERSION_CONTROL_2_RELAYS.pdf

Low Voltage Disconnect with 2 Types of Relays
http://www.midnitesolar.com/pdfs/LVD_2RELAYS.pdf


Other Helpful PDFs

Pete's Diversion for Hot Water Paper
http://midniteftp.com/forum/index.php?action=dlattach;topic=3457.0;attach=5306

Crydom's PDF on Diodes
http://www.crydom.com/en/tech/newsletters/solid%20statements%20-%20coil%20suppression%20&%20dc%20output%20ssrs.pdf

[Matrix]

As for my set up so far ... For now I think It will be an AC set up controlled by AUX 1 using an SSR. 
- AC seems to be the least expensive and least complicated route  if you have a large enough Inverter.  But it is not the most efficient.
-  due to being able to use already existing parts
- Less copper due to lower amps

I already have the AC system set up.  I am presently controlling the On / Off to the element with a breaker and / or the lower AC thermostat of the DWH. Hopefully by the weekend I will have an SSR and will start working with Automation.

So far on hand I have:
- The stock 240v 4500w element already installed in the DWH.  Running at 120v 1,125 watts
- Ordered a Crydom D1240 SSR for control off of AUX 1 (should be here friday)
- Got a Heat Sink for the Crydom and the Crydom K100 SSR cover
- Will probably get a 240v 3500 watt element for 875 watts wired 120v
- and a 240v 3000 watt element for 750 watts wired 120v
- A DC 900 watt 24v Element (that I will just keep to try if I go back to DC)

Will get the last 2 AC elements to try if I find I am diverting too much load and the batteries are not getting charged using the stock 4500 watt 240v element.  But the lower watt options would also be good choices for people who did not have as much unused power from the inverter as i do.    I have a 4000 watt inverter and i never use more than 2200 watts. 

After I get the SSR I will post up pictures  and diagrams of the set up.  Will also update on how it is working and the settings I am trying in the Classic AUX 1.   

Any suggestions for initial settings  starting out on AUX 1 would be appreciated. 

[Matrix]

Got the SSR installed and wiring cleaned up last night.    Tested from the Local App,  and it seems to be working as an on/off switch.  Aux 1 is coming on and going off, and when on 118v is passing thru the SSR.   But no sun to test and see how it performs during a charge cycle.    Today is cloudy in the morning so far,  but it is suppose to clear by the afternoon.  So I have starting to tinker with the Waste Not Hi settings.

Set up as of now:
- Stock 4500 w element and thermostat in lower portion of DWH disconnected from the top of the DWH.
- Connected to a 12 awg AC line wire at 120v coming from my inverter.   At 120v the element runs at 1145 watts and Less than 9 amps when on.
- Crydom Series 1, 3-32vdc / 24-140vac 40 amp,  modle D1240
- Mounted to Head sink and set with thermal paste
- Running on Aux 1

Now to try some settings ... I found this thread a very good starting point ...

http://midniteftp.com/forum/index.php?topic=3754.0

But Taos,  I do not understand one thing.   You Say ...

Update, well (the waste not high) function is the way to go for me , i set the V high setting to -.2 volt and the V low  setting to -.4 volt, delay time of 5 seconds and hold time of 10 seconds ...
Don

Trying that ... But in the Local App, If I have my V Low set to -.4,  And I try and set my V hi to -.2 ... the V Low goes to 0.  It will not let me set it like that.  Are the Settings for the V Hi and Low in the Local app measured in tenths?  So that -2 in the setting is actually -.2 etc.?  Do you mean -2 and -4?   

[Taos]

Hi Matrix
Sorry i wasnt checking the forums for a bit , here is how i have mine setup , since my lower tank heating element is a 240 heating element and im running it on 120 volt a.c. Powered by my outback 3600 watt 48 volt inverter , Using the original a.c.thermostat , it draws around 500 watts on the inverter , its a way for me to get some heat in the water tank ,its not the main source of heat but a supplement as my system is small , i have experienced a 100% heat supply from the lower 500 watt element on days in the summer of full sun ,the element is on steady from 10:00 am until 4:00 pm ( and no use of hot water durring that time ) ,before 10:00 am and after 4:00 pm the classic charge controller  will try if battery voltages are met according to my settings ,(  cycle on and off ) here is what i have for settings im using waste not hi on the classic  aux 1 , voltage low -0.4 , volt high -0.2 , and time delay of 5.0 seconds , and a hold time of 2.0 seconds , these are setup on the classics display , not the local app , the way it works is when the battery voltage is at my on setting (just below  )my charge voltage settings( for different charge stages ) for my batteries programed in charge settings ( different for different battery types and brands ) once this voltage was met for a delay time of ( my setting 5seconds ) the heating element is powered on ,and if voltage drops( below my aux 1 setting  for more then (2 seconds) (my hold time ) the classic turns off the ssr relay ( crydom  brand)and power is cut to the lower tank heating element , this cycle repeats itself , and when there is lots of power from my array( ussualy after 10:00 am on a sunny summer day )  and conditions are met the element stays on most of the day , i have found with these settings for my system and house power usage it works good for me and my batteries stay fully charged and i get hot water as a bonus, my kw for the day produced are close to double from not having the waste not water heating set up !  I have found that this maybe isnt the most efficient way of doing hot water heating  ( loss from using aux 1 , inverter, ) but found it to be the simplest and i think the safest way , as im using a a.c. Thermostat and heating element thats csa approved( for canada ) and since  the wizbang junior is used on aux 2 i didnt want to loose it usefulness ,aux 2 and dc element is more effiencient but for me it worked out the best . Im going to say like most theres not a lot of info on this ,you will have to try different setting in aux 1 and see what works for your system . Matrix you may try setting your v low and v high 0.1 volt lower in aux setting . I   think  i heard this  from bob .

Don

[Matrix]

Thanks Don,

Your set up and Mine are nearly exactly alike.
- I cannot use Aux 2 because of the Whiz Bang Jr
- I am using AC for the water heater load as I have plenty of excess inverter power
- Like you I felt this was the easiest and safest method as it would require no changes to the hot water heater

I may swap out my lower thermostat for an upper type thermostat on the tank leaving an upper up top and an upper on the bottom because my lower stat does not have the reset button for thermal over load. it was integrated into the upper stat when they were connected together via 240v... And I have an extra.

Besides that,  the only differences in our system are:
1. My array is 2.5Kw charging 4 Trojan L16H-AC 435s that usually get discharged no more than 32% a nite
2. My element is running at 120v 1140 watts .... but even with the larger array at full sun this element is not staying on and cycling off to much to be effective when running on the automation of the SSR
- I tested it last week with out the SSR.  As long as it stays on, it is capable of heating my tank to 120* in 3.5 hrs. 
- But I cant get it to stay on using the SSR and AUX 1.  it cycles about every 20 seconds due to voltage drops below the Low V set point because i such a large load

So I will change that 1125w element out to a 750w element tomorrow which should make things just about perfect. 

I will then be able to try your settings (I actually have already but the element is too big to see how it really works) ... but I will try them tomorrow with a smaller element and see if I am golden. 

Thanks for the reply
Mike

[Matrix]

For what its worth ... here is a link to the final end product of my entire Off-Grid Grid assist solar system. 

http://midniteftp.com/forum/index.php?topic=3907.msg37991#msg37991

[Taos]

Hi Mike
I was thinking you had too much load of the water heating element for your system ,since your running off your batteries at night it will not work as good ,as in the morning on a good sunny day you have to get those batteries charged and the lower the state of charge the more the ssr will cycle until your batteries get close to full then your water heating element will stay on constant , i think if you size the heating element around what you stated 800 -900 watts it should work good for you , also you can try lowering the aux 1 ,volt low and volt high and also change the delay to longer time and the same with hold time , i think if you size the lower water heater element corectly it will work for you , im sure using a dc element right from the batteries and aux 2  would work a lot better  ( pwm) but theres a trade off as loosing wizbang junior , and finding a safe d.c. Thermostat,and element , i didnt like the way mine worked when i had it set up on aux1 diversion load ,i thought  this sucks the way it works ,and also gave up ,but once i got aux1 using waste not high ,things worked so much better and its a keeper , (until theres a safe d.c. Element and thermostat available !  ) Like you i tried without the ssr in the system and worked good and once ssr was hooked up in diversion load it didnt work good until i tried aux1 waste not high !   And played with aux1 settings

Don