Hi. I need some advice as my current setup is causing the fuses to melt. 

My hardware:

I have 1x Synapse 5.0k inverter with the following ratings:
Solar Charger Mode:
Rated Current: 80A
System Voltage: 48VDC
Min. Solar Voltage: 40VDC
Max. Solar Voltage (VOC): 145VDC

The panels are 6x Trina solar TSM-545DE 19 panels. Their ratings are: 
Maximum Power (Pmax) 545W*
Maximum Power Voltage (Vmp) 31.4V
Maximum Power Current (Imp) 17.37A
Open Circuit Voltage (Voc) 37.7V*
Short Circuit Current (Isc) 18.47A*
Maximum Series Fuse 30A

Due to the 145VDC limitation of the inverter, the installer thought it well to setup the panels in a configuration of 3x in series, the other 3x in series, and then combine those to series sets a parrallel configuration. The parrallel configuration then goes throught  690v 63A fuse holders with 40A fuses in them. The problem that I've experienced is that when there is a big load in the house and the sun shining truley brightly the fuses start to melt inside the holders, and then eventually they fuse and stop the current. The amps coming though is so much that the 40A fuse starts to heat up and melts the surroung plasting of the fuse holder. 

I thought of getting the installer to disconnect the parrallel connection. It would then be 3x Panels in series going through the one 40A fuse, and the other 3x Panels in series going through the one 40A fuse. Then only after the fuses letting the cables run into the inverter in a Parrallel way. Will this solve the problem, is this solution adviseable, or is there another better solution that I didn't think of? Or is there a way or device that can block, regulate, limit, the input from the panels so the excessive current doens't case the fuses to melt the fuse holders. 

 

 

 

 

 

 

 

 

 

 

Edited December 12, 20241 yr by Jakes Prinsloo

Good afternoon @Jakes Prinsloo and welcome to the forum.

 

The only reason I see why the fuse holders are melting is that there is contact resistance between the fuse contact and the contact in the fuse holder and if there is contact resistance between the fuse contact and the contact in the fuse holder the fuse holder heats up because there is current flowing through the fuse holder and fuse, if it is possible please post photos of the fuse holders and the fuses then a better diagnosis can be given.

One solution is to separate the strings and let each string have its own fuse and parallel the strings after the fuse holders another solution is to replace the current fuse holders and fuses with a known good brand fuse holders and fuses or replace the fuse holders with a dual pole DC rated Miniature Circuit Breakers (MCB's).

 

If the fuse holder and fuse has been replaced one can always measure the resistance before the cables are connected to the fuse holder and make sure that the fuse makes proper contact in the holder.

 

Kind Regards

GerhardK83

When current flow through the fuses measure the voltage(mv range) across the fuse that will give you the watts it dissipates the higher the voltage the hotter these fuses will become. What is the rating of the fuse holder in DC?

3 hours ago, Jakes Prinsloo said:

The parrallel configuration then goes throught  690v 63A fuse holders with 40A fuses in them.

Send us a picture of the fuse holder.

Below the Bushmann CH modular fuse range DC fuse holders for pv applications. See below data sheet attached. Hope this helps.

bus-ele-ds-10430-chcc-chm-chpv.pdf

 

 

Edited December 12, 20241 yr by TaliaB

19 hours ago, TaliaB said:

Send us a picture of the fuse holder.

 

 

20 hours ago, GerhardK83 said:

replace the fuse holders with a dual pole DC rated Miniature Circuit Breakers (MCB's).

Thank you so much for the reply. I really like this idea.

1. If I understand correcly, the fuse holders are completely removed and the break takes its place? Would it really be that simple as just disconnecting the fuses and placing a break in its place without anything else?
2. Should I also use a 40A breaker?
3. Are there any specific make/models that you can recommend? 

 

23 hours ago, Jakes Prinsloo said:

Maximum Power Current (Imp) 17.37A

1. Seeing that the 2x series string of 3 panels are then connected in parrallel, the max current should the be double the 17,37A as in 34.74A, hence my thinking of using a 40A fuse. Is my assumptions correct?

3 hours ago, Jakes Prinsloo said:

Thank you so much for the reply. I really like this idea.

1. If I understand correcly, the fuse holders are completely removed and the break takes its place? Would it really be that simple as just disconnecting the fuses and placing a break in its place without anything else?
2. Should I also use a 40A breaker?
3. Are there any specific make/models that you can recommend? 

 

1. Seeing that the 2x series string of 3 panels are then connected in parrallel, the max current should the be double the 17,37A as in 34.74A, hence my thinking of using a 40A fuse. Is my assumptions correct?

The fuse holder are AC rated you need a DC fuse holder and a 40A dc fuse that should be ok.

5 hours ago, Jakes Prinsloo said:

If I understand correcly, the fuse holders are completely removed and the break takes its place? Would it really be that simple as just disconnecting the fuses and placing a break in its place without anything else?

Yes the DC rated MCB replaces the fuse holder and it is easy to replace if it is fitted in a DIN rail DB box provided that there are enough space in the DB box.

If the strings are separated then I would suggest the following ACDC 2 pole MCB's
CSMBS2DC20

For fuse holders and fuses I would suggest the following
SRD-30 and 30F20PV
SRD-63 and 30F20PV-L
SRD-32L and F1085GPV-20
221PV and 30F20PV-L

If both strings are in parallel then I would suggest the following ACDC 2 pole MCB's
CSMBS2DC40

I do not see any 40A fuses in ACDC's catalogue

 

5 hours ago, Jakes Prinsloo said:

Should I also use a 40A breaker?

Personally I would separate each string and provide a fuse holder or MCB for each string and after the fuse holder or MCB parallel the strings which goes to the inverter.