Hi All

New to the solar game. Put my own system together and everything worked well up to the point where I started adding bigger loads to the solar during the day. When the load is +-500watts there are no problems but when I up the load to +- 1500watt the breaker trips after a while and feels warm to the touch. The fuses are also hot. I have 4 x 460 Watt Canadian panels connected 2S2P, 5kva mecer inverter, 4 x 100 amp gel’s. 48volt system. I am using a MC4-T2 connecter to parallel the 2 serie strings. The breaker is a 63A Dc 2P breaker.

Any thoughts or suggestion would be greatly appreciated.

Calculations were wrong

Edited January 27, 20223 yr by sselmraH

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Edited January 27, 20223 yr by P1000
sselmraH deleted his calculations

First thing to check is that all your connections to the breaker and fuses are tight and free of oxidation. Are you using ferrules or is the wire bare?

5 minutes ago, P1000 said:

First thing to check is that all your connections to the breaker and fuses are tight and free of oxidation. Are you using ferrules or is the wire bare?

Hi, Thank You for the responce. 
The install is only 3 weeks old so No oxidation. No ferrules, wires connected bare.

3 minutes ago, Goosie said:

Hi, Thank You for the responce. 
The install is only 3 weeks old so No oxidation. No ferrules, wires connected bare.

That is not ideal. Nobody I know use these, but they are the correct terminal https://za.rs-online.com/web/p/blade-terminals/6241257

Since it is only 3 weeks old, check the terminals for tightness. There is usually some settling after installation, especially with bare wires, so tighten them (preferably at night).

Thank You P1000 for the suggestion Will get hold of some ferrules and let you know.

3 hours ago, Goosie said:

Thank You P1000 for the suggestion Will get hold of some ferrules and let you know.

hi! I'm afraid your issue might be more than just ferrules. There is no where I used ferrules in my installation except on battery cables which were supplied with the ferrules crimped. 14 x 400w PV panels with MC4 connectors and no ferrules at my fuse box, isolators and inverter PV termination and over a year later, my system is still running without overheating anything.  Your panels produces around 22A, according to the specs and how you connected them. It is strange that your 63A breaker trips and let alone gets heated up. Your worst case scenario, short circuit current is 23.44A. I don't think you can get anywhere near 63A,even with lose termination. Assuming that your PV connection to the inverter is correct, I would straight away throw that 63A breaker in the bin 😁 

8 hours ago, hoohloc said:

hi! I'm afraid your issue might be more than just ferrules. There is no where I used ferrules in my installation except on battery cables which were supplied with the ferrules crimped. 14 x 400w PV panels with MC4 connectors and no ferrules at my fuse box, isolators and inverter PV termination and over a year later, my system is still running without overheating anything.  Your panels produces around 22A, according to the specs and how you connected them. It is strange that your 63A breaker trips and let alone gets heated up. Your worst case scenario, short circuit current is 23.44A. I don't think you can get anywhere near 63A,even with lose termination. Assuming that your PV connection to the inverter is correct, I would straight away throw that 63A breaker in the bin 😁 

Ok, so the problem with loose connections is that it causes a higher impedance connection. So at the connection point, you have maybe 0.05Ω (as an example). At 22A, that translates into 24.2W. That is enough to get everything nice and toasty in a closed box. The connection points are a weak-point in this type of installation. I am somewhat wary of recommending ferrules, as they can make the situation worse if not done properly (because contact area can go down if you use, for instance a bootlace ferrule, unless you crimp it flat). The way to test it would be to fasten the connections first.

Morning hoohloc.

Thank You for the reply.

The funny part is that the fuses also get very hot. I have disconnected them as a process of elimination and only have the breaker connected now. Ill get another one (different brand) and give it a go. Ill also give the ferrules ago even if it just neatens up the install.

Quality DC breakers and Isolators are very expensive .  Your issue is probably not the fuses but the DC breaker.

Australia removes much-criticized DC isolator mandate – pv magazine International (pv-magazine.com)

4 minutes ago, Jaws said:

Australia removes much-criticized DC isolator mandate – pv magazine International (pv-magazine.com)

Yes, that is only the rooftop DC isolator. Where most fail due to the sun perishing the plastic allowing water ingress. You still need an isolator in the system. In SA that isolator can be the one built into your inverter, if it meets the requirements.

I had the same problem with one of my installations. The dc breaker was the ZBeny brand 63A 600V dc one. Changed abd put a new breaker of the same specs and beand, problem solved. My conclusion is that sometimes these products are not up to task, some are great yet some not so good.....maybe quality control is not always top notch in the production line. Are you using true dc fuses, sometimes you can get cheaper ac fuses and they are not meant for dc circuits

12 hours ago, phoenix752 said:

I had the same problem with one of my installations. The dc breaker was the ZBeny brand 63A 600V dc one. Changed abd put a new breaker of the same specs and beand, problem solved. My conclusion is that sometimes these products are not up to task, some are great yet some not so good.....maybe quality control is not always top notch in the production line. Are you using true dc fuses, sometimes you can get cheaper ac fuses and they are not meant for dc circuits

Hi Phoenix752

Thanx for the response.

Initially when I discovered the heat issue I saw the fuses were ac fuses and swooped them out with dc fuses.

I will get a different breaker and advise the outcome.

 

On 2022/01/27 at 11:11 AM, Goosie said:

The fuses are also hot.

The fuses should not be hot, On my previous installation when I had parallel strings I had a issue where my breaker would trip. The cause was cheap fuse holders, the spring action holding the fuse in place was weak and caused a bad connection, I replaced the fuses with DC circuit breakers and problem was solved. 

Also when using parallel strings you need to make sure the wire from the panels to the inverter is thick enough to compensate voltage drop in long lengths, In your case your panels can supply 10.75A x2 =21.5A. This is quite a bit of current and need a decent tight connection.

 

On 2022/01/28 at 9:39 AM, P1000 said:

Yes, that is only the rooftop DC isolator. Where most fail due to the sun perishing the plastic allowing water ingress. You still need an isolator in the system. In SA that isolator can be the one built into your inverter, if it meets the requirements.

Rooftop is nice to have, but will definitely need an appropriately IP-rated box and switchgear (and regularly maintained). I have both indoor DC isolators (with surge protection), and that provided by the inverter, it gives me peace of mind.

The Aus CEC recommends regular maintenance, but does not specify a specific period. With a similar climate to ours in SA, it would be useful to understand what they regard as regular, is it 2 or 5 years? I climbed onto my roof this past weekend to inspect a gutter leak, and noticed that my 17 month old galvanised trunking pipe was starting to rust, in a straight line along its length.     

What, in your opinion, would be a reasonable period for "regular" inspection and maintenance, particularly of those elements that are exposed to the outdoors? 

 

On 2022/01/27 at 11:11 AM, Goosie said:

Hi All

New to the solar game. Put my own system together and everything worked well up to the point where I started adding bigger loads to the solar during the day. When the load is +-500watts there are no problems but when I up the load to +- 1500watt the breaker trips after a while and feels warm to the touch. The fuses are also hot. I have 4 x 460 Watt Canadian panels connected 2S2P, 5kva mecer inverter, 4 x 100 amp gel’s. 48volt system. I am using a MC4-T2 connecter to parallel the 2 serie strings. The breaker is a 63A Dc 2P breaker.

Any thoughts or suggestion would be greatly appreciated.

Also had the 63A breaker tripping.Replaced the breaker with a Noark breaker.The tripping stopped for a few months then started again.The wires were heating up between the surge arrestor and the breaker.Then replaced the surge arrestors and wires it's running a lot cooler.The new surge arrestor is also higher rated.

1 hour ago, Chris Louw said:

The new surge arrestor is also higher rated.

If you mean higher as in voltage - that would be counterproductive. If the arrestor voltage is higher than the inverter can handle it does not protect the inverter. Luckily most inverters have surge protection built-in.