Isolator breaker resistance

[AlanH]

Hi Guys,

Im trying to fit a breaker between the controller and panels at the controller. Regardless which I use, the resistance is great. The controller will not recognise the voltage. If I bypass, the controller recognises the solar. Ive tried two breakers and two isolators.

Cheers guys.

 

[Bud Martin]

Hi Guys,

Im trying to fit a breaker between the controller and panels at the controller. Regardless which I use, the resistance is great. The controller will not recognise the voltage. If I bypass, the controller recognises the solar. Ive tried two breakers and two isolators.

Cheers guys.

Can you clarify the 'resistance' value?
What do you mean the 'Controller will not recognize the Voltage'? It shows Zero Volt at the PV input of the controller?
Can you provide the pictures of your setup and the info about the 'breaker and the isolators'?

 

[AlanH]

Can you clarify the 'resistance' value?
What do you mean the 'Controller will not recognize the Voltage'? It shows Zero Volt at the PV input of the controller?
Can you provide the pictures of your setup and the info about the 'breaker and the isolators'?

Bud, the voltage from the array is 120 odd volts. On the controller side of the breaker it reads 40 volts. The controller doesnt read or acknowledge any input. When I bypass a breaker, the controller reads and charges as it should.

 

[Bud Martin]

So 120V on the input side of the breaker and 40V on the output side of the breaker feeding the controller, correct?
Can we see the pictures of the breakers and isolators and your wiring?
To have two breakers and isolators failed in the same way is not likely.

 

[AlanH]

So 120V on the input side of the breaker and 40V on the output side of the breaker feeding the controller, correct?
Can we see the pictures of the breakers and isolators and your wiring?
To have two breakers and isolators failed in the same way is not likely.

Yeah I woulda thought.

Now, I brought the breakers inside and checked resistance with the Klein multimeter. Zero resistance! Be buggered if I know what is going on. A severe voltage drop to the point the controller will not recognise it. Bypass the breaker and away it goes!

 

[AlanH]

Bud, I added more strings of 3. I’m now up to about 49 amps. These breakers are 32A. On a sunny day, which its not ATM, I only got 120V. I didnt measure the amps actually but it would have been quite low considering the weather. Cable is 6mm.

 

[AlanH]

I tested the breakers and isolators and I get zero resistance but if I put DC voltage through them, the voltage drops by two thirds.

 

[Bud Martin]

I tested the breakers and isolators and I get zero resistance but if I put DC voltage through them, the voltage drops by two thirds.

Please show us how you go about testing the breakers by putting the DC voltage the breakers? What did you use for the load?

 

[Bud Martin]

Bud, I added more strings of 3. I’m now up to about 49 amps. These breakers are 32A. On a sunny day, which its not ATM, So now you. I didnt measure the amps actually but it would have been quite low considering the weather. Cable is 6mm.

So now you get 120VDC at the input of the controller?
49A of battery charging current or the PV panels current, which one is it?
How did you measure the 49A?
Make, model, and spec of the charger and the panels?

 

[AlanH]

Please show us how you go about testing the breakers by putting the DC voltage the breakers? What did you use for the load?

DC voltage coming from the panels. Tested with the multimeter. On the panel side of the breaker I was getting my full voltage. On the controller side of the breaker I was only getting 25-35% of the voltage. The controller couldn’t read any input until I bypassed the breaker. This happened regardless of breaker or isolator.

 

[Bud Martin]

DC voltage coming from the panels. Tested with the multimeter. On the panel side of the breaker I was getting my full voltage. On the controller side of the breaker I was only getting 25-35% of the voltage. The controller couldn’t read any input until I bypassed the breaker. This happened regardless of breaker or isolator.

So the controller shows about 40V on the display panel of the controller?
It makes no sense to me on what you are experiencing on your system.
I need to see the pictures of your wiring and Make, model, and spec of the charger and the panels?

Reply

 

[AlanH]

So now you get 120VDC at the input of the controller?
49A of battery charging current or the PV panels current, which one is it?
How did you measure the 49A?
Make, model, and spec of the charger and the panels?

120VDC can be measured with the multimeter. The 49A is only an assumption made off the current rating of the panels until the clamp meter arrives.

Controller is a Growatt SPF5000TL. Panels, refer to pic below.
Panels are 3 in series with 6 parallel.

 

[burgerking]

if there is this much voltage drop across the breaker, either:
1. Breaker has poor contact (you can use a volt meter, measure the voltage drop across the terminals) (but this would burn/melt the breaker)
2. Or panel (source) drops when load (SCC/Inverter) is connected (you can measure the voltage on the Source vs Load side of the breaker) (sign of bad panel, bad mppt, or just plain NO SUN)

 

[AlanH]

So this morning everything works as it should do.

Yesterday I was getting a low voltage reading on the output side of the breakers and isolator. It wasnt my imagination as the controller was confirming it. It wouldn’t acknowledge any input.

 

[burgerking]

Panels are 3 in series with 6 parallel

SOP: You should have individual fuse/breaker per string before combining them.
This should isolate bad string from ruining the whole array.

 

[Bud Martin]

Is this the correct user manual for it?

Growatt

Startup Voltage is 150VDC for the unit to start running but you have 3s for the panel which is about 120V.
Max PV input current is clipped at 22A and you have 3s6p with Isc of 9.37A 8.22imp per panel, so no way you will see 40A at the input of the controller.
You also say the controller works fine if you bypass the breakers, so how much charging current, PV input Voltage are shown on the contrller display.

 

[burgerking]

Growatt inverters are high PV voltage, low Max PV Input Current MPPT designs as shown from Bud's photo above.

Dumping 6 parallel strings, 9A each will overload Growatt's MPPT.

 

[AlanH]

Is this the correct user manual for it?

Growatt

Startup Voltage is 150VDC for the unit to start running but you have 3s for the panel which is about 120V.
Max PV input current is clipped at 22A and you have 3s6p with Isc of 9.37A 8.22imp per panel, so no way you will see 40A at the input of the controller.
You also say the controller works fine if you bypass the breakers, so how much charging current, PV input Voltage are shown on the contrller display.
View attachment 116287
View attachment 116288

Yes it is Budd.

 

[AlanH]

Growatt inverters are high PV voltage, low Max PV Input Current MPPT designs as shown from Bud's photo above.

Dumping 6 parallel strings, 9A each will overload Growatt's MPPT.

8.2A per panel. Yesterday it wouldn’t have been even half that with the weather we had. Today is a better day and it is reading fine. I haven’t had an issue previously. Its because I have been trying to implement a breaker.

 

[AlanH]

Growatt inverters are high PV voltage, low Max PV Input Current MPPT designs as shown from Bud's photo above.

Dumping 6 parallel strings, 9A each will overload Growatt's MPPT.

Not happening. It has been working fine. Today it is working fine.