Hi, I have the 150pv water heating...I need help...🤔

 

The open circuit voltage cannot be higher than 150v, on single pannel it cannot be higher than 36v..I have 2 x 360w pannels and 1 x 350w pannel...how would I find the best strategy to reach 72 required by system...I also have 2 x 380w pannels...thanking you 

59 minutes ago, AndrewO said:

Hi, I have the 150pv water heating...I need help...🤔

 

The open circuit voltage cannot be higher than 150v, on single pannel it cannot be higher than 36v..I have 2 x 360w pannels and 1 x 350w pannel...how would I find the best strategy to reach 72 required by system...I also have 2 x 380w pannels...thanking you 

You will have to provide the Imp and Vmp and Voc for each panel. We can then work out the connections for best results.

380w  VOC 48.7 VMP 39.9 IMP 9.52

350 VOC 47.1 VMP 38.4 IMP 9.11

360 VOC 43 VMP 36 IMP 10

360 VOC 47.2 VMP 38.7 IMP 9.04

380 VOC 48.7 VMP 39.9 IMP 9.52

380 VOC 48.7 VMP 39.9 IMP 9.52

380 VOC 48.7 VMP 39.9 IMP 9.52

 

THANK YOU, THOSE ARE ALL THE PANNELS I HAVE ON MY ROOF

 

3 hours ago, AndrewO said:

380w  VOC 48.7 VMP 39.9 IMP 9.52

350 VOC 47.1 VMP 38.4 IMP 9.11

360 VOC 43 VMP 36 IMP 10

360 VOC 47.2 VMP 38.7 IMP 9.04

380 VOC 48.7 VMP 39.9 IMP 9.52

380 VOC 48.7 VMP 39.9 IMP 9.52

380 VOC 48.7 VMP 39.9 IMP 9.52

 

THANK YOU, THOSE ARE ALL THE PANNELS I HAVE ON MY ROOF

 

Every panel will give over 36V and you don't want a single one to give over 36V. You can also not connect any 2 to be at 72V. Also you cannot connect 3 in series not to run the risk of going over 150V on cold days. So it seems 2 in series of any of these. Then add more strings in parallel to increase the current.

Hi, it's a 150L PV Water Heating system from geyserwise

3 hours ago, AndrewO said:

Hi, it's a 150L PV Water Heating system from geyserwise

If the info from STOK is right then use 2x 360W and 1 x 380W in series. It gives a 135V with grace to the 150V Voc max rating.

In series, the 3 pannels being 360w x2 and 1 x 350w total IMP = 28,10 AND THE VMP = 113.10, the direct voltage is higher than 72v what the mmp can handle.

 

Putting in parnell the voltage is too low, it doesn't do anything to warm up 

Edited August 16, 20223 yr by AndrewO

6 minutes ago, AndrewO said:

IMP = 28,10

Your total Imp in series will be closer to the lowest Imp, so 9.11A in this case.

Otherwise you will be getting 113.1*28.10 = 3178W out of 3 ~350W panels...

19 minutes ago, AndrewO said:

In series, the 3 pannels being 360w x2 and 1 x 350w total IMP = 28,10 AND THE VMP = 113.10, the direct voltage is higher than 72v what the mmp can handle.

 

Putting in parnell the voltage is too low, it doesn't do anything to warm up 

72V is the output voltage of the MPPT. Not the input from the panels!

Please read the manufacturer notes and install accordingly:

Note from the Manufacturer

• It is important to understand the limitations of the MPPT and the size and amount of PV panels that can be connected to the MPPT
  • Limitation 1: Input voltage of 138 VOC (on average) Maximum 150 VOC
    • 3X270W PV Panels in Series = 38.7 VOC X3 = 116.1 (well withing the voltage specified)
    • 3X330W PV Panels in Series = 138.6 VOC X3  = 138.6 (this is also fine for average operation)
    • 3 LARGER PANELS OR HIGH VOLTAGE PANELS SHOULD NOT BE CONNECTED IN SERIES
    • ALL OUR DIAGRAMMES SPECIFY THE HIGHEST SIZE AS 335W AND INSTALLERS SHOULD STICK TO THIS
    • IF MORE PANELS ARE REQUIRED THE PANELS CAN BE PUT 2 in SERIES, 2 in SERIES THEN PARALLEL. BUT REMEMBER THERE ARE LIMITATIONS ON THE OUTPUT AMPERE AS WELL, SO THE VOLTAGE ALONE SHOULD NOT BE USED TO MAKE THE CALCULATION. THE OUTPUT AMPERE SHOULD BE TAKEN INTO ACCOUNT AS WELL.

• • Limitation 2:  the load: The element is only rated at 900W on average (MAXIMUM 1200W). Any excess energy connected to the MPPT cannot be used by the load. The MPPT would have to get rid of this energy somehow. For example, if 1600W is connected to the MPPT and PV panels are producing 1600W, but the element can only use 1200W of energy. Somehow the MPPT would need to absorb an extra 400W.
    • Consequence: MPPT will run at higher temperatures than what it should
    • Components will be put under severe
    • It is important to stick to the Maximum 1200W PV Panels to be connected to the MPPT
    • PLEASE MAKE ALL INSTALLERS AWARE OF THIS AS MANY INSTALLERS ARE CONNECTED TOO MANY PANELS (IN TERMS OF TOTAL WATTAGE) TO THE SYSTEM AND NEITHER THE MPPT OR ELEMENT IS DESIGNED FOR THIS. IT IS NOT APPROPRIATE TO CONNECT 4x410W PANELS ON THE SYSTEM. IT DOES NOT MATTER IN WHAT CONFIGURATIONS YOU CONNECT THE PV PANELS
    • OUR DIAGRAMMES ARE VERY CLEAR ON WHAT COMBINATIONS OF PV PANELS ARE ALLOWED
    • WITH ANY RETURNS – PLEASE CONFIRM THE CONFIGURATION AND AMOUNT OF PV PANELS – WE WILL NOT EXCHANGE UNITS THAT HAVE NOT BEEN CONNECTED PROPERLY.
    • We can try and repair these units, but the same will happen again if the number of PV panels are not reduced

• • Limitation 3: Maximum output Amps: 25A (per attached sheet)

It is important to understand that if the PV panels are connected in parallel that the input Current increases (compared to the series connection). For example, two series, so series then parallel on 270W or 330W PV panels will give you an input current in the region of 16A to 18 A. For a series connection, the input current will be in the region of 8A and 9A for 270 W PV panels and 330W PV Panels.

As per the picture below, the job of the MPPT is to ensure that the output voltage matches the load voltage. In our case, the load voltage is between 48V and 72V. If the voltage is reduced, the output current must increase.

Edited August 16, 20223 yr by PowerUser

Hi @AndrewO

I have two geysers using the same PTC elements, but without the the MPPT tracker. Please note that GeyserWise components are advertised with contradicting specifications. I found that you can push the voltage above 72V, in the region of 90V if I remember correctly. As such you should be able to put all three panels in series as advised by this forum. However, ask GeyserWise themselves and they will advise.

Edited August 16, 20223 yr by Pieter Lourens

2 hours ago, P1000 said:

Your total Imp in series will be closer to the lowest Imp, so 9.11A in this case.

Otherwise you will be getting 113.1*28.10 = 3178W out of 3 ~350W panels...

Great to point this out. The panels in my reply is based on the lowest voltage and the 3 panels with highest current.

Take away as you spelled out. Panels in series provide the current of the lowest panel and voltages are added up. In parallel the voltage is the same as the lowest panel voltage and currents are added up.

Speak to the guys at Geyserwise, they are incredibly helpful.

I ran that PV heating system with great success for a number of years and they always assisted with my questions.

Thanks for your reply BUT they were NOT helpful...they couldn't give the closest variations of pannels to be used to get closest to what could be used...ONLY what they had stipulated to use. So my honest opinion.....IT WAS OUT OF THEIR LEAGUE...a simply I DON'T KNOW.

 

However thanks for replying 

And I spoke to 2 technical chaps there and the same answer from both...I DON'T KNOW