actii 7392 MPPT

[Courter]

Hi, The Spec. page for the actii 7392 controller (from Europe for 3KW resistance heat) reads "Panel Voltage 10 to 350VDC". The User Manual reads "Panel tension From 120V to 350V DC", (tension is usually same as voltage). Does any know why this is, my poor understanding, or a translation misprint?

I have this controller on order, based on the 10V spec. page, and will be reluctant to connect it if a return is required. My 4 series panels will produce between 80 and 140 VDC, 1280 rated watts. (northern latitude less than optimum orientation). I intend to connect (via 7392) to one water heater element. It appears the 7392 is designed with the higher European voltage in mind and I am afraid it may not function, or not function well, in the 80/140V range. Some controllers specify a voltage where the MPPT starts to function, this one does not.

There are other controller options, but I like the onboard thermostat and the higher capacity for future growth.
Thanks for the help, Edward

PWM MPPT 3KW Heater Charging Controller for Solar Solar Panels ACTii AC7392

PWM controller for heaters with the algorithm of searching for the maximum MPPT power point from photovoltaic panels. The controller enables the supply of standard DHW electric boilers from solar panels The solar panel works at maximum power only at optimal voltage. Connecting the heater...

actii.pl

 

[efficientPV]

While I have never touched this unit, I believe the unit will operate as low as 10V if the control electronics is powered externally. I don't see where 4 panels would produce as low as 80V. The internal converter should be OK under 120V. If not, power can always be supplied by an external wall wart or other very cheap switching supply. I build designs similar to this and can resolve any issue. Surprised you found one available.

 

[Courter]

Thanks, This unit is powered internally but I do see provisions for external 12VDC. My panels are spec'd at 20V/320W The Vmp is 34.1V Imp 9.37A. If I understand you, I will have 34x4 at full power but closer to 30x4 at say 50%.

Where are the details for your control?

Heliene Solar Panels

Heliene Solar Panels - made with pride in North America! Up to 20% efficiency, high quality solar panels with clean all black aesthetics.

www.altestore.com

 

[efficientPV]

I was wondering where you came up with that wild number. The data sheet 20V is a misprint and the two panels referenced have different voltages. Each 320W panel will approximately be from 30V in summer to 37V in winter. You wouldn't want a panel with higher current. The panels you selected are correct for this device in series.

My design is based on four 37V grid tie panels having 200V components installed and can handle currents up to 13A. It uses FET to switch the currents and has arc interrupt so multiple heating elements can be daisy chained. No external temperature sensor is used. As example, one user heats a water tank and after up to temperature the thermostat switches to a room heater. The FET output in the 170V version produce less than 2W of heat in switching. Your unit uses an IGBT commonly used in over 200V designs for lower cost. This can produce about 15W of heat in operation. In a prior version the ACTii had an option of fixed voltage which would allow it to be used in parallel with a charge controller for excess diversion. I wish they would have kept that option. Other than that, the new design looks more robust and you should be happy with it. Below is my board.

 

[Courter]

Thanks, is the pictured board sold anywhere?

 

[CitroM]

@Courter: Have you received / installed this controller? I am also considering the purchase. A bit concerned with the seller's lack of replies to several of my messages, both direct and through ebay.

The unit looks very good in theory. Why did you go with AC7392 instead of the earlier and less expensive version?

 

[Courter]

@Courter: Have you received / installed this controller? I am also considering the purchase. A bit concerned with the seller's lack of replies to several of my messages, both direct and through ebay.

The unit looks very good in theory. Why did you go with AC7392 instead of the earlier and less expensive version?

Hi, The newer one is higher wattage. I have it installed with my 4 panels/series. I can't get any data yet because with the panels under load I have less than 100v with winter sun (lat 45). The unit instructions say it will only function MPPT at more than 100v and suggest the setting for turn on at 150v. I am assuming that with more sun and/or the power supply it will go into MPPT. I'll try to get some watt readings both ways. It seems designed for the higher voltages used in Europe. I have one 400w element. My contacts with company were sent and received via Google Translate in Polish. I'll post initial data here.

 

[CitroM]

What is the resistance of your 400W heating element and is it a correct match to your array?

Isn't continuously sending the maximum current to the heating element, regardless of suboptimal current production (due to sun angles and shading) the whole point of MPPT? Why only over 100V? Can you post a PDF of their instructions or a link.

What email address did you use for the Polish supplier?

Thank you for sharing your experience.

 

[Courter]

What is the resistance of your 400W heating element and is it a correct match to your array?

Isn't continuously sending the maximum current to the heating element, regardless of suboptimal current production (due to sun angles and shading) the whole point of MPPT? Why only over 100V? Can you post a PDF of their instructions or a link.

What email address did you use for the Polish supplier?

Thank you for sharing your experience.

My error... 240v/4000W element 14/15 ohms. & Please note I have 4 20v panels where 24v panels may break the 100v lower limit. (my 20's produce 154v open circuit, but 94v under load). I can add one panel (5 20's) to get into range. I'll know when I get some sun and good instrument readings. I assume there is simple non MPPT charging below 100v and the energy may not be worth my effort in the yearly picture. At my latitude I'm low on installed panel size. 10 20's may be my ultimate array. My exchange with ACTii was threw E-bay message. ACTii has a site with instructions.pdf. Beware, this is my first installation. Best Edward

PWM MPPT 3KW Heater Charging Controller for Solar Solar Panels ACTii AC7392

PWM controller for heaters with the algorithm of searching for the maximum MPPT power point from photovoltaic panels. The controller enables the supply of standard DHW electric boilers from solar panels The solar panel works at maximum power only at optimal voltage. Connecting the heater...

actii.pl

 

[efficientPV]

I assume the 100V rating is for the internal DC to DC converter which supplies the electronic control system. In reality, that should start working easily with the open circuit voltage and work down to at least 80V. If you have a display working, it is in MPPT mode.

 

[Courter]

I assume the 100V rating is for the internal DC to DC converter which supplies the electronic control system. In reality, that should start working easily with the open circuit voltage and work down to at least 80V. If you have a display working, it is in MPPT mode.

The display is working at <100v and the Out LED is Flashing "Flashing out LED indicates that power is feeding to the heater." from supplied (and online) instructions.

 

[efficientPV]

I build designs like this and have a lot of experience with these types of circuits, been heating water like this for years. If it ever breaks keep me in mind for repair.

 

[CitroM]

@efficientPV ...I read a lot of your commentary (here and in other places) and learn a lot, although your info is usually above my paygrade. I'll reach out in the future when embarking on my project in earnest.

***

@Courter, right now some of the numbers you've posted are not adding up. 4 x 20V panels producing 94V under load does not make sense.

Can you post the actual numbers from your panels, Vmp and Imp ...and how your array is arranged, series or parallel?

 

[CitroM]

@Courter, I reread the early thread and found the array specs. you posted.

With Vmp 34.1 and Imp 9.37, 4S, your 240v/4000W element, at 14.4 ohms, might be just a bit below where the formulas point, which is an element of 14.56

Also, the "magic formula" says your element could be as high as 20.38 ohms.

If you got your hands on a 240v/3000W or 3500 or 3800 you may get more power into the element. With your installation already in place, it should be easy to get several 240 elements in the 3000 range and check how much current each one pulls.

Would love to hear your results if you try it out.

 

[efficientPV]

Actually, in a capacitor dump type circuit it can be advantageous to go well under the ideal resistance to compensate for lower PV voltages when panels are hot. This is of course if the circuit is well designed and can handle the extra current.

 

[Courter]

@Courter, I reread the early thread and found the array specs. you posted.

With Vmp 34.1 and Imp 9.37, 4S, your 240v/4000W element, at 14.4 ohms, might be just a bit below where the formulas point, which is an element of 14.56

Also, the "magic formula" says your element could be as high as 20.38 ohms.

If you got your hands on a 240v/3000W or 3500 or 3800 you may get more power into the element. With your installation already in place, it should be easy to get several 240 elements in the 3000 range and check how much current each one pulls.

Would love to hear your results if you try it out.

I used the davidpoz.com Spreadsheet but derated (lowered) the factory volts and amp outputs. This seemed to raise the wattage from 35/38 to 4000 at 240V. I am assuming I will produce the factory specified output little or no time. Still not enough sun here to gauge any real output.

 

[Courter]

Got some readings today, 164 open volts, 133 under load, Input to actii model 7392 Controller, 1.8amps is 230w and close to displayed output. Although output to element measures 2 amps times 30V?? Would assume measure Technique error as not AC or DC?

 

[efficientPV]

My clamp meter measures the current fairly accurately. Don't bother measuring output voltage as that will be meaningless. Just multiply the output current by the input voltage. The element in theory is always powered with the full input voltage. The average current of the input should be the same as the output in this circuit. The calculation should be better than 5% accurate.

 

[CitroM]

So you have either 240 or 60 or 266 Watts of power? Let's decide which it is.

Afterwards, if this were my system, I'd want to do two things:

1) Observe whether and how these values change during the day as a result of MPP tracking by ACTii (and)
2) I would be curious to experiment with different heating elements

Maybe the heating element should be sized by the actual wattage your array can produce rather than the factory label values?

Just ideas...

 

[Courter]

So you have either 240 or 60 or 266 Watts of power? Let's decide which it is.

Afterwards, if this were my system, I'd want to do two things:

1) Observe whether and how these values change during the day as a result of MPP tracking by ACTii (and)
2) I would be curious to experiment with different heating elements

Maybe the heating element should be sized by the actual wattage your array can produce rather than the factory label values?

Just ideas...

133 X 1.8 = 239w The element is rated 240v and 4000W. The 30v was the failed Voltage measurement that could not be used (termed above "meaningless") due to the output frequency. Above 35/38 to 4000, Read 3500/3800 to 4000. Kinda sloppy on my part, Edward