Author Topic: Charge controller + relay for dumping into heating elements  (Read 792 times)

Mike H

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Re: Charge controller + relay for dumping into heating elements
« Reply #15 on: February 03, 2021, 08:05:49 PM »
I have 2 classic 150s and I am using the aux2 on one of them to control my two 2000 watt DC heating elements that are inline with my solar water panels.

ClassicCrazy

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Re: Charge controller + relay for dumping into heating elements
« Reply #16 on: February 03, 2021, 09:29:57 PM »
Are you changing gauge of the wire ?
Breakers protect the wire so it kind of depends on initial breaker size what  gauge wire you are using .
That is the way I see it.
What will the Aux2 on the Classic be controlling for ?
Larry
« Last Edit: February 03, 2021, 09:32:44 PM by ClassicCrazy »
system one
Classic 150 , 5s4p  Kyocera 135watt , 12s Soneil 2v 540amp lead crystal for 24v pack , Outback 3524 inverter
system two
Classic 150 ,5s 135 watt Kyocero , 16s Calb 100AH LiFePO4 , Outback VFX 3648 inverter
system three
Midnite KID MPPT 24 DC in to  12 volt AGM batterie

Mike H

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Re: Charge controller + relay for dumping into heating elements
« Reply #17 on: February 04, 2021, 12:15:18 AM »
This is a 48 volt off the grid system, and I am using Aux 2 in the waste not mode so I don't leave any power on the table so to speak.  I have a 4400-watt inverter and I do not want to use the inverter, so I am running the elements off the batteries.

Aux 2 will control the DC SSR that will control the 4000-watt DC heating elements in a micro-boiler I made.  I am using 10 ga wire from the SSR to the heating elements, I am just not sure if the CB between the SSRs and the elements is an over kill, but I think better safe than sorry.  The main breaker is 100-amp midnite solar DC breaker, the higher end of the amps in this system would be about 68 amps.

There are always questions from people on how to make hot water with the extra power, so I wanted to post a picture of how I’m doing it. I don’t have to worry about over heating because of how I built my system. We have hydronic heat with solar water panels and a masonry fireplace with water jacket.  The heating elements will add to the heat from the other sources to produce either DHW or heat.  When the DHW gets to temperature the system automatically diverts either to a slab for heat or to a 140-ton sand mass for heat storage.  The micro-boiler is a new addition to my system.
 I have friends that are off the grid that use similar systems and it works great.  If you are using it for DHW only you would have to use an aquastat to turn it off when it got to temp but other than that it should work great for that also.

mike90045

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Re: Charge controller + relay for dumping into heating elements
« Reply #18 on: February 04, 2021, 01:57:26 AM »
.......... If you are using it for DHW only you would have to use an aquastat to turn it off when it got to temp but other than that it should work great for that also.

You will need a 60VDC rated aquastat !!    To me, this seems like the perfect place to use a mod-sine inverter for water heating elements and maintain conventional thermostats
http://tinyurl.com/LMR-Solar

Classic 200| 2Kw PV, 160Voc | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph )| Listeroid 6/1, st5 gen head | XW6048 inverter/chgr | midnight ePanel & 4 SPDs | 48V, 800A NiFe battery bank | MS-TS-MPPT60 w/3Kw PV

ClassicCrazy

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Re: Charge controller + relay for dumping into heating elements
« Reply #19 on: February 04, 2021, 12:59:45 PM »
.......... If you are using it for DHW only you would have to use an aquastat to turn it off when it got to temp but other than that it should work great for that also.

You will need a 60VDC rated aquastat !!    To me, this seems like the perfect place to use a mod-sine inverter for water heating elements and maintain conventional thermostats

I have wondered along that way to  heating hot water that perhaps the simplest approach was to just use an inexpensive inverter that is dedicated to the hot water heater. But you still need to have the charge controller handling all the power in the first place.  But the AC does make life simpler for using existing controls. 

Larry
system one
Classic 150 , 5s4p  Kyocera 135watt , 12s Soneil 2v 540amp lead crystal for 24v pack , Outback 3524 inverter
system two
Classic 150 ,5s 135 watt Kyocero , 16s Calb 100AH LiFePO4 , Outback VFX 3648 inverter
system three
Midnite KID MPPT 24 DC in to  12 volt AGM batterie

boB

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Re: Charge controller + relay for dumping into heating elements
« Reply #20 on: February 05, 2021, 10:49:53 PM »

I have wondered along that way to  heating hot water that perhaps the simplest approach was to just use an inexpensive inverter that is dedicated to the hot water heater.



Larry, you heat "hot water" ?    :) ;) 

I usually just heat cold water   ;D

K7IQ

boB

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Re: Charge controller + relay for dumping into heating elements
« Reply #21 on: February 05, 2021, 10:56:00 PM »

You will need a 60VDC rated aquastat !!    To me, this seems like the perfect place to use a mod-sine inverter for water heating elements and maintain conventional thermostats


I LIKE the idea of using a modified square wave inverter for load dump applications IF you can just adjust its RMS output AC voltage. Is that the idea you are referring to, Mike ?

 Just give it the proper voltage and forget having to PWM some  normally DC load.    Even better than trying to use a triac dimmer.  Especially on a MSW inverter output.
K7IQ

mike90045

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Re: Charge controller + relay for dumping into heating elements
« Reply #22 on: February 06, 2021, 02:29:27 AM »
A mod sine inverter "ought" to deliver 120VRMS to a resistive load.   The catch is getting one that will start up with a big heater load on it, might have to oversize it some .

it would save all the messy large gauge DC and pitted contacts/blown SSR's
http://tinyurl.com/LMR-Solar

Classic 200| 2Kw PV, 160Voc | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph )| Listeroid 6/1, st5 gen head | XW6048 inverter/chgr | midnight ePanel & 4 SPDs | 48V, 800A NiFe battery bank | MS-TS-MPPT60 w/3Kw PV

moosemaster

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Re: Charge controller + relay for dumping into heating elements
« Reply #23 on: February 16, 2021, 06:36:05 PM »
Completely missed all these replies and discussion, lots of good information!

Still wrapping my head around a few things. This chap takes issue using dump loads this way in that it "micro-cycles" his batteries:

https://www.youtube.com/watch?v=A9Meq8wLbME

Proposes putting a couple of SSR's between the PV and midnite classic. Not seen any follow up videos on this though - this would knock off the power to the charge controller and thus the SSR's, doesn't sound like a solution...

I'm looking at diverting to a few of these nifty things - be great to get any thoughts on them (you might have to use Google translate!)

https://www.polskieprzetwornice.pl/sklep/przetwornica-solarna-eco-solar-boost-mppt-3000-3kw


ClassicCrazy

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Re: Charge controller + relay for dumping into heating elements
« Reply #24 on: February 16, 2021, 07:22:38 PM »
Completely missed all these replies and discussion, lots of good information!

Still wrapping my head around a few things. This chap takes issue using dump loads this way in that it "micro-cycles" his batteries:

https://www.youtube.com/watch?v=A9Meq8wLbME

Proposes putting a couple of SSR's between the PV and midnite classic. Not seen any follow up videos on this though - this would knock off the power to the charge controller and thus the SSR's, doesn't sound like a solution...

I'm looking at diverting to a few of these nifty things - be great to get any thoughts on them (you might have to use Google translate!)

https://www.polskieprzetwornice.pl/sklep/przetwornica-solarna-eco-solar-boost-mppt-3000-3kw

The guy in the first link has a Midnite Classic there and could be using AUX 2 Waste Not to PWM his resistance loads. It only takes off the extra above what the battery setpoints are for each stage Absorb and Float.

Larry
system one
Classic 150 , 5s4p  Kyocera 135watt , 12s Soneil 2v 540amp lead crystal for 24v pack , Outback 3524 inverter
system two
Classic 150 ,5s 135 watt Kyocero , 16s Calb 100AH LiFePO4 , Outback VFX 3648 inverter
system three
Midnite KID MPPT 24 DC in to  12 volt AGM batterie

moosemaster

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Re: Charge controller + relay for dumping into heating elements
« Reply #25 on: February 21, 2021, 06:30:56 AM »

The guy in the first link has a Midnite Classic there and could be using AUX 2 Waste Not to PWM his resistance loads. It only takes off the extra above what the battery setpoints are for each stage Absorb and Float.

Larry

Thanks Larry!

I'm weighing up using Aux 1 - diverting to these MPPT heater controllers - https://www.polskieprzetwornice.pl/sklep/przetwornica-solarna-eco-solar-boost-mppt-3000-3kw

Or using AUX 2 Waste Not as you mentioned. I've done a bit of searching of the forums and still wrapping my head around how this function works - it would certainly be a fair more elegant solution than adding yet more components.

Can anyone enlighten me as to how I might best select an element with the best resistance to be used with the AUX 2 Waste Not mode? Dummy here.

ClassicCrazy

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Re: Charge controller + relay for dumping into heating elements
« Reply #26 on: February 21, 2021, 01:14:20 PM »

The guy in the first link has a Midnite Classic there and could be using AUX 2 Waste Not to PWM his resistance loads. It only takes off the extra above what the battery setpoints are for each stage Absorb and Float.

Larry

Thanks Larry!

I'm weighing up using Aux 1 - diverting to these MPPT heater controllers - https://www.polskieprzetwornice.pl/sklep/przetwornica-solarna-eco-solar-boost-mppt-3000-3kw

Or using AUX 2 Waste Not as you mentioned. I've done a bit of searching of the forums and still wrapping my head around how this function works - it would certainly be a fair more elegant solution than adding yet more components.

Can anyone enlighten me as to how I might best select an element with the best resistance to be used with the AUX 2 Waste Not mode? Dummy here.

Not sure your exact question . I will explain how I use it.
I have an inverter that  puts out 120v ac . This AC goes to a small 120v water heater so the heating coil in it is designed for 1200 watts at 120v ( or whatever it is actually I forget but you get the idea) .  If you just hook the water heater up to the inverter it draws it's full 1200 watt load until shut off by water heater thermostat. 
But if you put a SSR relay in the AC line and control that with AUX 2 Waste Not - then what happens is the Classic will control the input to the water heater by PWM . That means the Classic will charge the batteries but any power above what is needed to hold the batteries at the Absorb or Float levels will go into the water heater. So if there are only 2 amps extra available the Classic Aux 2 will PWM switch on and off the relay so that only 2 amps is going into the water heater. If the sun comes out and there is 5 amps extra then it will PWM switch on and off faster letting the 5 amps go to water heater, etc.
My water heating setup is prototype but works for now . I made this video to try and explain . I use both direct DC to it from one solar system  and also Aux2 pwm AC from inverter from the other solar system.
maybe I already shared this on the discussion but here it is again.
https://youtu.be/s7trVpHLts4

Larry
system one
Classic 150 , 5s4p  Kyocera 135watt , 12s Soneil 2v 540amp lead crystal for 24v pack , Outback 3524 inverter
system two
Classic 150 ,5s 135 watt Kyocero , 16s Calb 100AH LiFePO4 , Outback VFX 3648 inverter
system three
Midnite KID MPPT 24 DC in to  12 volt AGM batterie

moosemaster

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Re: Charge controller + relay for dumping into heating elements
« Reply #27 on: February 22, 2021, 11:17:36 AM »
Not sure your exact question . I will explain how I use it.
I have an inverter that  puts out 120v ac . This AC goes to a small 120v water heater so the heating coil in it is designed for 1200 watts at 120v ( or whatever it is actually I forget but you get the idea) .  If you just hook the water heater up to the inverter it draws it's full 1200 watt load until shut off by water heater thermostat. 
But if you put a SSR relay in the AC line and control that with AUX 2 Waste Not - then what happens is the Classic will control the input to the water heater by PWM . That means the Classic will charge the batteries but any power above what is needed to hold the batteries at the Absorb or Float levels will go into the water heater. So if there are only 2 amps extra available the Classic Aux 2 will PWM switch on and off the relay so that only 2 amps is going into the water heater. If the sun comes out and there is 5 amps extra then it will PWM switch on and off faster letting the 5 amps go to water heater, etc.
My water heating setup is prototype but works for now . I made this video to try and explain . I use both direct DC to it from one solar system  and also Aux2 pwm AC from inverter from the other solar system.
maybe I already shared this on the discussion but here it is again.
https://youtu.be/s7trVpHLts4

Larry

Thanks again Larry, took a look at your video - seems to be working nicely for you.

Is there anything in place like MPPT for the AC heater? From what I understand - the resistance of the element needs to match that of the system. In your example - 1200w 120v element has a resistance of 12Ω - drawing 10 amps.

At 3 or 5 amps, the resistance isn't matched and there are losses.

Again, dummy here - I'm probably missing something!

ClassicCrazy

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Re: Charge controller + relay for dumping into heating elements
« Reply #28 on: February 23, 2021, 11:35:00 AM »
Not sure your exact question . I will explain how I use it.
I have an inverter that  puts out 120v ac . This AC goes to a small 120v water heater so the heating coil in it is designed for 1200 watts at 120v ( or whatever it is actually I forget but you get the idea) .  If you just hook the water heater up to the inverter it draws it's full 1200 watt load until shut off by water heater thermostat. 
But if you put a SSR relay in the AC line and control that with AUX 2 Waste Not - then what happens is the Classic will control the input to the water heater by PWM . That means the Classic will charge the batteries but any power above what is needed to hold the batteries at the Absorb or Float levels will go into the water heater. So if there are only 2 amps extra available the Classic Aux 2 will PWM switch on and off the relay so that only 2 amps is going into the water heater. If the sun comes out and there is 5 amps extra then it will PWM switch on and off faster letting the 5 amps go to water heater, etc.
My water heating setup is prototype but works for now . I made this video to try and explain . I use both direct DC to it from one solar system  and also Aux2 pwm AC from inverter from the other solar system.
maybe I already shared this on the discussion but here it is again.
https://youtu.be/s7trVpHLts4

Larry

Thanks again Larry, took a look at your video - seems to be working nicely for you.

Is there anything in place like MPPT for the AC heater? From what I understand - the resistance of the element needs to match that of the system. In your example - 1200w 120v element has a resistance of 12Ω - drawing 10 amps.

At 3 or 5 amps, the resistance isn't matched and there are losses.

Again, dummy here - I'm probably missing something!

There are some direct DC mppt controllers for water heaters out there.
here is one I have seen on ebay
https://www.ebay.com/itm/PWM-MPPT-Heater-Charger-Regulator-Solar-Photovoltaic-Solar-Panels-Hot-Water-PV/263523458861?hash=item3d5b38df2d:g:72sAAOSwTj9fFrzV
For my setup I have enough extra power that it doesn't matter so much if I squeeze every last amp out.
If you look at comments on my youtube video someone replied who made a board that he puts in DC input line and I guess it shunts off power somehow - I don't really get exactly how that works but he has lots of videos about design . But I don't think he has a product on market yet.
What I might do is in summer is change the present small AC heater element and rewire it in series or parallel with the present DC element to try and find the more perfect match for ohms.
I have a real smart friend who tells me about ways to pwm the DC to get better match and performance and that maybe can all be done with some hardware or writing some pwm magic formulas in Node Red to control the igbt that I use. But I am not up to that geek master code  level yet.

Larry
system one
Classic 150 , 5s4p  Kyocera 135watt , 12s Soneil 2v 540amp lead crystal for 24v pack , Outback 3524 inverter
system two
Classic 150 ,5s 135 watt Kyocero , 16s Calb 100AH LiFePO4 , Outback VFX 3648 inverter
system three
Midnite KID MPPT 24 DC in to  12 volt AGM batterie

moosemaster

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Re: Charge controller + relay for dumping into heating elements
« Reply #29 on: February 23, 2021, 04:21:23 PM »
There are some direct DC mppt controllers for water heaters out there.
here is one I have seen on ebay
https://www.ebay.com/itm/PWM-MPPT-Heater-Charger-Regulator-Solar-Photovoltaic-Solar-Panels-Hot-Water-PV/263523458861?hash=item3d5b38df2d:g:72sAAOSwTj9fFrzV
For my setup I have enough extra power that it doesn't matter so much if I squeeze every last amp out.
If you look at comments on my youtube video someone replied who made a board that he puts in DC input line and I guess it shunts off power somehow - I don't really get exactly how that works but he has lots of videos about design . But I don't think he has a product on market yet.
What I might do is in summer is change the present small AC heater element and rewire it in series or parallel with the present DC element to try and find the more perfect match for ohms.
I have a real smart friend who tells me about ways to pwm the DC to get better match and performance and that maybe can all be done with some hardware or writing some pwm magic formulas in Node Red to control the igbt that I use. But I am not up to that geek master code  level yet.

Larry


Grateful to have your ear Larry, really appreciate the time you take to reply and share your thoughts.

I actually purchased the controller you linked to a while back, I just don't have any panels to test it with yet!

I'll in fact be looking at dumping from a 16kW array, using 4 midnite classics...

So I'm looking at investing in 4 of these 3.5kW mppt heater controllers - for dumping into various elements (hot water and cooking). All these controllers seem to come from Poland!

https://www.polskieprzetwornice.pl/sklep/przetwornica-solarna-eco-solar-boost-mppt-3000-3500w-pro

How do you think I would best switch to these when the batteries are full? I imagine using Aux 1 to divert the PV to them, before the midnite classic - but I'm pretty clueless.