Hello all,
I've been working on a fairly novel application of PV... A 12kW roof array would meet our winter electricity needs (Outer Hebrides, Scotland) for lighting and charging small DC devices (I'm considering forgoing conventional AC ring mains). In the summer this will kick out mountains of juice - which I will dump straight into elements for hot water and cooking (think of the cooker as a modified "storage heater" or Rayburn - bricks with a high thermal mass which are heavily insulated).
There are DC Fridge/Freezers on the market (pricey, but efficient) and we're looking at off-grid alternatives to washing machines... may go full Amish! 😉
In the winter we'll probably generate some additional leccy with a few small wind turbines and we can heat water/cook using wood and peat (plenty about, free - dug by hand in an environmentally sensitive manner...).
This is for a new build, essentially I can put the money that would otherwise be spent on roofing materials on some second hand PV. I can cover 100m2 for £4,570 - this includes purpose made weather proof GSE integration fittings.
I had seen someone else using Midnite controllers in a similar application - prioritising charging a NIFE battery bank - then dumping excess into elements:
https://diysolarforum.com/threads/oil-filled-radiator-as-hydro-dump-load-w-midnite-classic-250-pwm-relay-control-solid-state-relay.8612/#post-103758
Can anyone give any pointers as to how I might best achieve my goal using Midnite's products? I will have 56 230W panels total https://www.secondsol.com/en/anzeige/24287/solar-panel/crystalline/poly/ldk-solar/ldk-230p-20
I've attached an estimate of annual PV output using this handy tool - https://re.jrc.ec.europa.eu/pvg_tools/en/tools.html
If you are talking about using AC from an inverter you can use the Aux 2 on the Midnite Classic to PWM a solid state relay controlling a resistance heating load.
But most people though use Aux 2 for Whizbang - Aux one does not have PWM capabilities but can switch things on and off.
If you are going to be using two or more Classics you can use the Aux2 on the second one for PWM .
There is a post on here where someone went into many details in his quest to dump all available extra power into water heating.
The other option is to put DC directly into resistance heating load and can be efficient if you match the heating coil elements resistance correctly to the PV .
I know someone who is talking about using IGBT transistors to be able to switch high voltage high currrent DC from PV.
I have a PV direct water heater now and am using a DC SSR rated to handle the voltage and current .
Larry
Quote from: ClassicCrazy on October 04, 2020, 06:33:46 PM
If you are talking about using AC from an inverter you can use the Aux 2 on the Midnite Classic to PWM a solid state relay controlling a resistance heating load.
But most people though use Aux 2 for Whizbang - Aux one does not have PWM capabilities but can switch things on and off.
If you are going to be using two or more Classics you can use the Aux2 on the second one for PWM .
There is a post on here where someone went into many details in his quest to dump all available extra power into water heating.
The other option is to put DC directly into resistance heating load and can be efficient if you match the heating coil elements resistance correctly to the PV .
I know someone who is talking about using IGBT transistors to be able to switch high voltage high currrent DC from PV.
I have a PV direct water heater now and am using a DC SSR rated to handle the voltage and current .
Larry
Thanks Larry!
I had been considering hooking directly up to appropriately rated DC elements for simplicity's sake. Can I find more details on your DC SSR anywhere? Sounds great.
Ta,
Sean
Quote from: moosemaster on October 06, 2020, 11:49:10 AM
Quote from: ClassicCrazy on October 04, 2020, 06:33:46 PM
If you are talking about using AC from an inverter you can use the Aux 2 on the Midnite Classic to PWM a solid state relay controlling a resistance heating load.
But most people though use Aux 2 for Whizbang - Aux one does not have PWM capabilities but can switch things on and off.
If you are going to be using two or more Classics you can use the Aux2 on the second one for PWM .
There is a post on here where someone went into many details in his quest to dump all available extra power into water heating.
The other option is to put DC directly into resistance heating load and can be efficient if you match the heating coil elements resistance correctly to the PV .
I know someone who is talking about using IGBT transistors to be able to switch high voltage high currrent DC from PV.
I have a PV direct water heater now and am using a DC SSR rated to handle the voltage and current .
Larry
Thanks Larry!
I had been considering hooking directly up to appropriately rated DC elements for simplicity's sake. Can I find more details on your DC SSR anywhere? Sounds great.
Ta,
Sean
I have been using one of these that are rated to 220v DC . Not very expensive but works. At first I didn't think it was working , then read the note that said the polarity on the output needed to be the right way. So I switched the sides I had the wires connected and then it worked right. I have it mounted on one of their bigger heatsinks . I have gotten the relays fairly quickly from them.
https://www.aliexpress.com/store/group/Single-DC-To-DC/5105062_515838821.html?spm=a2g0o.detail.0.0.75b667bb81ErSA
I have a thermostat contact in series with the control voltage to the relay to shut off when it gets to temperature .
Larry
Quote from: ClassicCrazy on October 06, 2020, 07:49:35 PM
I have been using one of these that are rated to 220v DC . Not very expensive but works. At first I didn't think it was working , then read the note that said the polarity on the output needed to be the right way. So I switched the sides I had the wires connected and then it worked right. I have it mounted on one of their bigger heatsinks . I have gotten the relays fairly quickly from them.
https://www.aliexpress.com/store/group/Single-DC-To-DC/5105062_515838821.html?spm=a2g0o.detail.0.0.75b667bb81ErSA
I have a thermostat contact in series with the control voltage to the relay to shut off when it gets to temperature .
Larry
Amazing, thanks for your help Larry :)
I know you are talking about DC loads and the SSR will work well for those, but if you ever decide to hook up an AC load I'm using this with my Midnite Solar and it works *perfectly*. It's very simple.
https://www.adafruit.com/product/2935
Quote from: coniferous on November 16, 2020, 02:47:10 PM
I know you are talking about DC loads and the SSR will work well for those, but if you ever decide to hook up an AC load I'm using this with my Midnite Solar and it works *perfectly*. It's very simple.
https://www.adafruit.com/product/2935
Interesting. Do you know how you control it with the control input ? It shows an polarized AC input. Maybe it can take AC or DC input for on/off.
Too bad it is only rated for 12 amps AC (maybe ?) but I don't think it is listed by UL or ETL or CSA, etc. Says "QC" on the label though whatever that means.
Quote from: boB on November 16, 2020, 04:05:42 PM
Quote from: coniferous on November 16, 2020, 02:47:10 PM
I know you are talking about DC loads and the SSR will work well for those, but if you ever decide to hook up an AC load I'm using this with my Midnite Solar and it works *perfectly*. It's very simple.
https://www.adafruit.com/product/2935
Interesting. Do you know how you control it with the control input ? It shows an polarized AC input. Maybe it can take AC or DC input for on/off.
Too bad it is only rated for 12 amps AC (maybe ?) but I don't think it is listed by UL or ETL or CSA, etc. Says "QC" on the label though whatever that means.
It can take DC input. I have it on my Aux1 right now and I configured the output to be 12v. The writing on the actual device isn't super intuitive, but the datasheet says "Universal control voltage 3-60VDC or 12-120VAC, or connect directly to a 12V, 48VDC, or even 120VAC circuit."
And the 12 amp rating is for the 120 AC relay, it can do 1440 watts. I wouldn't switch it on an off rapidly (traditional relay), but still.
Quote from: coniferous on November 19, 2020, 12:17:19 PM
Quote from: boB on November 16, 2020, 04:05:42 PM
Quote from: coniferous on November 16, 2020, 02:47:10 PM
I know you are talking about DC loads and the SSR will work well for those, but if you ever decide to hook up an AC load I'm using this with my Midnite Solar and it works *perfectly*. It's very simple.
https://www.adafruit.com/product/2935
Interesting. Do you know how you control it with the control input ? It shows an polarized AC input. Maybe it can take AC or DC input for on/off.
Too bad it is only rated for 12 amps AC (maybe ?) but I don't think it is listed by UL or ETL or CSA, etc. Says "QC" on the label though whatever that means.
It can take DC input. I have it on my Aux1 right now and I configured the output to be 12v. The writing on the actual device isn't super intuitive, but the datasheet says "Universal control voltage 3-60VDC or 12-120VAC, or connect directly to a 12V, 48VDC, or even 120VAC circuit."
And the 12 amp rating is for the 120 AC relay, it can do 1440 watts. I wouldn't switch it on an off rapidly (traditional relay), but still.
I looked those up after you posted . They look like a nice handy way to control stuff using the classic Aux. All the associated safety components to make sure the relay coil doesn't get zapped by flyback voltages is built in . So plug and play .
Can't use them for PWM so would still have to go with an SSR for that if PWM wanted.
Larry
I have been working on something like this for a while and I would like to attach a picture but it will not let me, any ideas why?
Quote from: Mike H on February 03, 2021, 07:23:01 PM
I have been working on something like this for a while and I would like to attach a picture but it will not let me, any ideas why?
It won't let you upload large photos. I usually use irfanview and make them into a smaller photo that isn't as large and then it works.
Larry
I just did an update video of my PV solar water heater project.
I use both direct DC and also use PWM from Aux 2 .
Here is the link
https://youtu.be/s7trVpHLts4
Larry
This guy designed a board that will take excess power from PV system ( at DC source I think ) and dump it into water heater.
I don't understand exactly how it is wired in and other details .
https://youtu.be/yegjGYDMDJg
Larry
Quote from: ClassicCrazy on February 03, 2021, 07:30:38 PM
Quote from: Mike H on February 03, 2021, 07:23:01 PM
I have been working on something like this for a while and I would like to attach a picture but it will not let me, any ideas why?
It won't let you upload large photos. I usually use irfanview and make them into a smaller photo that isn't as large and then it works.
Larry
Thanks Larry, it's a 40.9kb jpg. When I hit the attach button it shows the jpg but will not add it to the post.
lol, it posted.
So question, do I need the 2 CB between the heating ele. and the SSR?
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.
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
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.
Quote from: Mike H on February 04, 2021, 12:15:18 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
Quote from: mike90045 on February 04, 2021, 01:57:26 AM
Quote from: Mike H on February 04, 2021, 12:15:18 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
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
Quote from: ClassicCrazy on February 04, 2021, 12:59:45 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
Quote from: mike90045 on February 04, 2021, 01:57:26 AM
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.
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
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
Quote from: moosemaster 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
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
Quote from: ClassicCrazy on February 16, 2021, 07:22:38 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.
Quote from: moosemaster on February 21, 2021, 06:30:56 AM
Quote from: ClassicCrazy on February 16, 2021, 07:22:38 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
Quote from: ClassicCrazy on February 21, 2021, 01:14:20 PM
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!
Quote from: moosemaster on February 22, 2021, 11:17:36 AM
Quote from: ClassicCrazy on February 21, 2021, 01:14:20 PM
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
Quote from: ClassicCrazy on February 23, 2021, 11:35:00 AM
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.
It will take some good design if you want to be able to switch the PV input from one controller to another.
If you are talking about switching high DC voltages then it gets more complicated in a way .
That is why I have been using the IGBT block since it can switch those high DC voltages.
I think maybe you should watch this guys video's in link below and perhaps contact him. He has some ideas on how to divert power from input I believe.
Let me know what you find out from him.
https://www.youtube.com/channel/UCgjG28Ml0hEO_jueEKEjdAg/videos
Larry
Thanks Larry - do you control the IGBT with the thermostat controller you have?
These look like they might do the job for switching DC - just trying to get a price - https://ep-fr.mersen.com/en/products/engineering/hybrid-dc-power-relay
"Xs-EV features a DC power relay that can repetitively clear up to 2kA at 1,000 VDC. Xs-EV has been engineered to provide high DC switching performances versus conventional mechanical DC power relay, switch and contactor. This power relay is a hybrid technology with the capability of switching both high voltage and high current designed specially for electrical vehicle applications."
Will try and wrap my head around opera's videos, a bit beyond my technological grasp but there seems to be some good nuggets of information.
Sean
Quote from: moosemaster on February 24, 2021, 04:41:56 AM
Thanks Larry - do you control the IGBT with the thermostat controller you have?
These look like they might do the job for switching DC - just trying to get a price - https://ep-fr.mersen.com/en/products/engineering/hybrid-dc-power-relay
"Xs-EV features a DC power relay that can repetitively clear up to 2kA at 1,000 VDC. Xs-EV has been engineered to provide high DC switching performances versus conventional mechanical DC power relay, switch and contactor. This power relay is a hybrid technology with the capability of switching both high voltage and high current designed specially for electrical vehicle applications."
Will try and wrap my head around opera's videos, a bit beyond my technological grasp but there seems to be some good nuggets of information.
Sean
There was a guy selling the igbt blocks on ebay for real good price - but he might be sold out. I paid $20 to 30 for the ones I have . Seems like everyone else sells them for twice as much.
I am no expert on all these things. I had someone help me a bit , and the one I have installed has been working for what I am doing with it.
There are lots of IGBT blocks for sale on ebay but I forget which specs you need to look for to make sure you get one that works.
I made a couple videos of my exploring those IGBT details for reference.
Not sure if you saw those or not.
http://midniteftp.com/forum/index.php?topic=5064.15
Larry