Sun Power SPR-E19-320 to power element directly series/parallels issue

Hey guys,
I have a odd situation and I have no idea what's wrong and had called SunPower but they offer no help (rediculous). They wouldn't even speak to me because I bought the panels used locally and because I don't have an account with them.
Basically I got a few of these panels.
https://us.sunpower.com/sites/sunpower/files/media-library/data-sheets/e-series-home-solar-panels-comparison.pdf
Specs:
Nom: 320watts
VOC: 64.8 V
VMPP: 54.7
ISC: 6.24 A
I am planing to connect a few of these panels to my water heater directly, currently I have not change the element, it's still on the 220v/4500watts element. But this is only for testing purposes. I was hoping to series all the panels together and run high voltage, but upon my testing here's the issue.
If I only connect panel 1 to the element (UNDER LOAD) I am getting 52volts X 4amps = 208watts
If I only connect panel 2 to the element (UNDER LOAD) I am getting 53volts X 4amps = 212watts
So on theory, if I series two panels together, it should give me 104v X 4amps = 416watts right? Well, that's not the case. When i series them I get 70volts X 4amps = 280watts.
What the hell?
So just for the hell of it, i tried parallels.
When I parallels 2 panels together I get 52volts X 4.6amps = 239watts (each panel give 2.3amps or so).... I verify this by leaving one panel unplug and have a DC meter (coil) around one panel and it say 4.5 amps but as soon as I plug in the other panel, it drop to 2.3A or so....
SO CONFUSED? PLEASE HELP.
I have a odd situation and I have no idea what's wrong and had called SunPower but they offer no help (rediculous). They wouldn't even speak to me because I bought the panels used locally and because I don't have an account with them.
Basically I got a few of these panels.
https://us.sunpower.com/sites/sunpower/files/media-library/data-sheets/e-series-home-solar-panels-comparison.pdf
Specs:
Nom: 320watts
VOC: 64.8 V
VMPP: 54.7
ISC: 6.24 A
I am planing to connect a few of these panels to my water heater directly, currently I have not change the element, it's still on the 220v/4500watts element. But this is only for testing purposes. I was hoping to series all the panels together and run high voltage, but upon my testing here's the issue.
If I only connect panel 1 to the element (UNDER LOAD) I am getting 52volts X 4amps = 208watts
If I only connect panel 2 to the element (UNDER LOAD) I am getting 53volts X 4amps = 212watts
So on theory, if I series two panels together, it should give me 104v X 4amps = 416watts right? Well, that's not the case. When i series them I get 70volts X 4amps = 280watts.
What the hell?
So just for the hell of it, i tried parallels.
When I parallels 2 panels together I get 52volts X 4.6amps = 239watts (each panel give 2.3amps or so).... I verify this by leaving one panel unplug and have a DC meter (coil) around one panel and it say 4.5 amps but as soon as I plug in the other panel, it drop to 2.3A or so....
SO CONFUSED? PLEASE HELP.
Comments
Our host sells such elements but you would need a charge contoller to get the desired voltage.
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
But how come using the same 220v 4500watts element on 120V AC give me 1100watts of energy? Could it be that much of a difference between 120V AC vs 100V DC? 1100watts vs 200-300watts?
This hurts the brain... lol
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
Second system 1890W 3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.
5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
While I would personally like to purchase panels directly from them. Seems like a very legitimate busy model. They are not making any money off of someone buying used panels.
Getting resistence values correct like mcgivor says is key.
Getting a different element. Maybe be an ok idea.
To maximize power off current setup it is exactly as mcgivor says. You will need to
Parallel and series connect.
It is fairly easily calculated. Ohms laws I believe.
|| Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
|| VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A
solar: http://tinyurl.com/LMR-Solar
gen: http://tinyurl.com/LMR-Lister ,
Humm.... I can understand if they rejected if I was after warranty or replacement... but this is simply technical question regarding their products. I feel like a company is obligated to answer any question regarding on their products regardless of who is asking. It's not like I am asking how they make the panels... Don't worry, you won't see me buying any of their panels "USED" or "NEW"
I am convince it's most likely the element is the issue here, because there's only two variable in this equation Solar Panel vs Element. Would be hard to believe if the panels is the issue.
Am I correct to say that I do not need any diodes between the panels when wired in Series or Parralles if both panels is fully in the SUN? Diodes only would benifit if one panels is being shades? (diodes built in the panels themselves is a different thing here)?
Is this because of the amperage rating or because DC arc more than AC? Weld themselves shut on DC mean it will closed circuit? I would think even in this case 900watts, it can run all day and still wouldn't be hot enough to trigger the relief valves.
Well, I already ordered a 48volts 1000watts element.
thanks for all the advise guys.
Do you actually read 64.8 Voc ?
Do you actually read 6.24 Amps Isc ?
Let's establish that the panels are operating at baseline spec before connecting a load.
RE: Welding Contacts - it is more difficult to stop DC current (constant arc) vs AC Current (self extinguishing 120 times/second)
Second system 1890W 3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.
5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
The ISC I am not sure.... I did not short the panel to themselves and test it. I only hook each single panel to the AC(4500w) element and getting voltage under load around 55v and amps around 4. So the correct way to test specs is to cover the panel, connect negative and positive together and use a DC clamp meter to measure the ISC right? But how to measure the loaded voltage?
So best to replace with these thermostat? They are advertised for DC usages and can handle (Can handle all voltages from 12 to 220 volts, AC or DC). I am using one right now in my 600watts 22gal off grid system, but not sure if it benefit anything, as I have used the stock 120v thermostat original from the tank and it seem to work just as well (but I could be wrong in the long run where it turn off and on a lot). But with so littler wattage, it seem it always remain ON all the time.
http://mwands.com/store/dc-water-heating-elements/water-heater-thermostat
Second system 1890W 3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.
5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
http://www.sengpielaudio.com/calculator-ohm.htm
If my 4500watts element specs is below.
4500W = I x 240V
I = 4500W / 240V = 18.75A
240V = 18.75A x R
R = 240V / 18.75A = 12.8 Ohms
If I wired 2 panels in parallels, type in 55volts and 12.8ohm I get 4.29amps and 236watts (this match up with my actual result).
If I wired in series, type in 12.8ohm and 4amps and I get voltage result 51v and 208watts.
Any more or less than 5 amps and you will not be at MPP - not 320 Watts.
What is the Isc measurement ?
So the lower the resistance in the element, the higher the voltage would drop causing less wattage?
Also another question, is there any efficiency disadvantage if running 120VAC on a 220VAC element, other than it take longer to heat the water? Running on high voltage give more efficiency (power consumption wise) only apply to motor right? For resistance application, wouldn't matter?
I hook it to my charge controller and battery and with 1 panel, it put 200watts into my battery, connect a second panel in parallels it put 400watts into my battery. However I could not test the series connection because my charge controller max out at 100VDC.
I have also test with a 120VAC (900watts or so element) and the result is about 80-100watts increase over the 240VAC 4500watts element.
So I guess the right thing to do here is if your total panels is rated for 1200watts, get a 900-1000watts element would be wise. Getting the same wattage element or higher and you loose so much power.
Say for example you had a 1000W element rated at 120V and you were to apply 60V to it, this is the calculation you would use to determine the wattage.
1000×(60/120)squared = 250 watts
Now you are going to apply 60V to a 4500w element rated at 240V
4500×(60/240)squared=281.25 watts 60÷240=0.25, 0.25×0.25=0.0625, 4500×0.0625=281.25
This demonstrates why it is best to match voltage ratings, now 1000W element 24V rating using 24v
1000×(24/24)squared=1000W
Go back to your original post and use the formula with the figures you gave, the 52V single panel ones you will see the results are correct, Note, the element is probably rated fo 240V not 220V.
Second system 1890W 3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.
5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
I already ordered a rated 48VDC 1000watts element. But I think even this one might be too much, since my 3 panels all series together isn't going to be able to put out enough power to fully power this element. Maybe I should had got the 600-700watts element?
What are your thoughts on this? this claim to be a MPPT controller for PV and element. Haven't had time to read over all the details, but it said no need to change the AC element, so maybe it's just inverting to higher voltage? But at 250.00 for just the controller... seem crazy, cost almost as much as my new water heater tank.
http://techluck.com/
Anyway, as the folks above have discussed, the problem is that you have to "match" the element with the solar array. If you have a fixed resistance (heating element), then you double the voltage, the current will also double (I=V/R). So, if one panel works at ~Imp, then you would need 2x panels in series * 2x parallel strings for 4 panels total.
I do not know anything about the MPPT controller for the Heater... But it does not appear to be a classic buck/boost type controller (which is usually used in an MPPT system).
So, I do not think this is a true MPPT controller--Leaving open to question exactly what it is doing.
If you want to see what a true MPPT controller for a similar application (Linear Current Booster for DC well pumps), take a look at this:
https://www.solar-electric.com/solar-converters-ppt-16-linear-current-booster.html
See the capacitors + relatively large coil (torriod type here)... You need these energy storage units to perform Buck and Boost type DC to DC conversions.
This type of device could work well (I think) for water heater element driving--But it all depends on your heating element/solar array/desired power... I am not sure there is a ready supply for higher voltage off the self MPPT solutions for water heating.
Regarding AC on a DC switch--This Youtube video does a nice job of showing what the difference is:
Lastly--There is also the question of what you eventually want to do... A true Hybrid Water heater (uses a refrigeration compressor to heat the water", electrical heater as backup)--They are about 2-3x as efficient as a resistance type heater and an work well with an off grid power system--Or even with an on grid home.
The plus and minus of this--They output cold/dry air. If you live in a warm humid environment--That is not a bad thing. But if you have a "cold basement" (less than ~55F), more cold air may not be a good thing (folks have ducted outside air to these hybrid water heaters). And if you have cold winters, they may not work well during cold weather (fall back to resistance heating).
http://www.geappliances.com/ge/heat-pump-hot-water-heater.htm
-Bill
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
Thank you for taking your time to reply. It seem using PV for water heater is getting very popular and now make sense. On my house, I have been using the extra power coming off my (2.2kw) off grid system to preheat a 22gal tank with just 24v/ 600w and it work amazing. During summer months my gas heater is completely off, during winter it come on maybe once a day and this has saved a lot. But this is using charge controller/relay and a bunch of other stuff that just cost too much.
I am doing this new project for my parent house. I want to simplify thing this time and decided to do PV directly to thermostat/element. Eliminating everything else to be cost effective and simple. Therefor with those controller at that price make no sense.
I guess the right way to do it here is to get the right rating element and more solar panels.. after all, I got them 320watts panel at 150.00ea locally... and can get as many as I needed. 300dollars and I can get a extra 600watts, there's no way those controller can increase 600watts.
As for the DC ARC using AC thermostat... the video clearly demonstrated this. But my question is... that's at 220VDC and unlimited supply of amps... or a lot of amps is available.
How different would the result be on 120-150VDC at 5-10amps + voltage drop under load like what we have seen when the element is hook to it...
http://www.mouser.com/Electromechanical/Relays/Solid-State-Relays/Solid-State-Relays-Industrial-Mount/_/N-ay0tw/
Not cheap--But can be a help.
I have a long (not pretty) thread from somebody that wanted to do this--The math, and even simulations (focused on winter--because that was his question). Non-winter/sunnier climates, yes this can make good sense. However, for the deep winter up north, did not seem to make a lot of sense.
https://forum.solar-electric.com/discussion/comment/307090/
Sorry for the lost of formatting (we went through a software vendor change--I guess I can fixing if it would be of help the detailed data--if anyone cares).
-Bill
http://mwands.com/store/dc-water-heating-elements/water-heater-thermostat
Sun in winter isn't a issue here in Phoenix Arizona.... It can be 30F outside and the sun is shining and clear blue sky almost everyday. Although the day is much shorter, but you can still get 4-5 hours of usable sun light. This is why it's a no brainer to not use PV in Arizona.
Note many switches have very different AC and DC ratings--Read the label information closely.
-Bill
Hate to keep posting about this issue... but got 3 panels mounted today... hook it to the 240v/4500 element and getting this.
Noon time, so should be getting 70-80% of total solar power (3x of 320watts/ea)
240v/4500watts element, panels= VOC = 180volts, under load is 75volts and 6amps = 450watts. As expected.
Also received my.... 48volts DC 1000watts, put that on and give it a try... and I'm now puzzled.
240v/4500watts element, panels= VOC = 180volts, under load is 15volts and 6amps = 90watts. ???
I thought getting the lowered voltage element and the closed rated watts would give me more than the AC 4500watts element... but that's NOT the case. I haven't got the time to parallels all 3 panels together and run it closer to the rated 48v at 15amps and see what happen...
If I have 4x of these panels. Which configured should I go with and what element would give me the best result?
Specs:
Nom: 320watts
VOC: 64.8 V
VMPP: 54.7
ISC: 6.24 A
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
I guess after all, proper voltage rating on ELEMENT is a must.... Feeding higher voltage to a lower voltage rated element DIRECTLY does not work, it dragged the voltage down too much...