Navitron Renewable Energy and Sustainability Forum

SOLAR PHOTOVOLTAIC => Solar Photovoltaic Systems => Topic started by: planetming on August 09, 2018, 08:24:15 PM



Title: MC4 Connector meltdown on Inverter
Post by: planetming on August 09, 2018, 08:24:15 PM
Thought I'd share my recent disaster with you in my first post.
My 3.6KW system was installed in June 2015 and has been running happily. My inverter is mounted in the garage and on a recent check I discovered one of the MC4 connectors at an angle. On closer inspection (see photos) one of the connectors had overheated and melted. Luckily it did not catch fire, modern low flamabibility plastics! I disconnected the circuit immediatly. When plugged back in you can see from the Infra red image the crimp has failed and caused the whole connector to heat up. Apparently this is quite common.

Then the fun started because I discovered my installer had gone out of business. So had to claim under the QANW insurance. Luckily I had all the paperwork and the claim has been accepted. I'm now waiting for the new company to replace the inverter. Meanwhile the system is running at less than half power during all this sunny weather :(

The warning here is to regularly check your connectors, at both ends if you can and check they are not overheating under full load. Expecially if your inverter is loft mounted.

Happy Days

Robert

(https://s33.postimg.cc/e206piv8r/20180707_113603.jpg) (https://postimg.cc/image/e206piv8r/)

(https://s33.postimg.cc/8dtvylobf/Inverter4.jpg) (https://postimg.cc/image/8dtvylobf/)

(https://s33.postimg.cc/hydilht2z/Inverter_Position_In_Garage.jpg) (https://postimg.cc/image/hydilht2z/)

(https://s33.postimg.cc/pr46dhehn/Overheated_Connector1.jpg) (https://postimg.cc/image/pr46dhehn/)


Title: Re: MC4 Connector meltdown on Inverter
Post by: Nickel2 on August 10, 2018, 07:52:13 AM
I can see 'solar' printed on the DC wires to the inverter. What puzzles me is the colour coding. I always thought that for DC applications it was red for positive and black for negative. Is this in UK?


Title: Re: MC4 Connector meltdown on Inverter
Post by: oliver90owner on August 10, 2018, 08:35:01 AM
I thought red and black were discarded years ago for brown and blue (for the benefit of those with colour deficiency).  At least for A/C live and neutral.  Why the need for different colours - the appropriate MC4 connector should determine the polarity?

Poster has a .co.uk email.

As I don’t have to make many connections, I have to admit to ‘belt and braces’ for mine - I solder them as well ( but I do try not to allow the solder to ‘wet’ the conductors beyond the joint (to avoid the risk vibration fractures beyond the connector :)).


Title: Re: MC4 Connector meltdown on Inverter
Post by: linesrg on August 10, 2018, 06:51:52 PM
Good Evening All,

My first question is are these genuine MC4's or 'mickey mouse' Chinese replica's?

Regards

Richard


Title: Re: MC4 Connector meltdown on Inverter
Post by: DonL on August 10, 2018, 08:42:58 PM
MC4 connectors are available as bulkhead fittings  and I have replaced damaged connectors into my inverter without difficulty. It should be possible to replace the bulkhead fitting and the connector on the end of the wire which may allow the inverter to go back into operation. You do need a special crimping tool to connect the lug on to the cable. Video's are available on the net showing the technique.


Title: Re: MC4 Connector meltdown on Inverter
Post by: rogeriko on August 10, 2018, 11:05:22 PM
Indeed I would just fix it. Probably only cost about £2.50. I think you will find even "genuine" MC4's are made in china.


Title: Re: MC4 Connector meltdown on Inverter
Post by: linesrg on August 11, 2018, 06:50:29 AM
Rogeriko,

I can't comment but the genuine items have the white lettering on the side and black 'O' rings and any I come across which don't have that especially the red 'O' rings ones I cut off and replace.

I'm not a professional installer just a cautious amateur who has experienced the 'cheapo' connectors not properly engaging with the 'proper' ones.

Regards

Richard


Title: Re: MC4 Connector meltdown on Inverter
Post by: planetming on August 11, 2018, 10:57:59 AM
Good Evening All,

My first question is are these genuine MC4's or 'mickey mouse' Chinese replica's?

Regards

Richard
I assumed these were the connectors suplied with the inverter, so would be genuine Chinese Solis connectors :)


Title: Re: MC4 Connector meltdown on Inverter
Post by: planetming on August 11, 2018, 11:01:16 AM
MC4 connectors are available as bulkhead fittings  and I have replaced damaged connectors into my inverter without difficulty. It should be possible to replace the bulkhead fitting and the connector on the end of the wire which may allow the inverter to go back into operation. You do need a special crimping tool to connect the lug on to the cable. Video's are available on the net showing the technique.
As a professional Electronics Engineer I was seriously tempted to just replace the connectors. But the system is still under the insurance backed gaurantee. I'm hoping to keep the inverter when it's replaced. Then I'll repair it and keep as a spare.


Title: Re: MC4 Connector meltdown on Inverter
Post by: planetming on August 11, 2018, 04:26:34 PM
I thought red and black were discarded years ago for brown and blue (for the benefit of those with colour deficiency).  At least for A/C live and neutral.  Why the need for different colours - the appropriate MC4 connector should determine the polarity?

Poster has a .co.uk email.

As I don’t have to make many connections, I have to admit to ‘belt and braces’ for mine - I solder them as well ( but I do try not to allow the solder to ‘wet’ the conductors beyond the joint (to avoid the risk vibration fractures beyond the connector :)).
Hi There, yes a UK installation in 2015. Found an interesting article on the IET forums about harmonised colour codings.
https://www.theiet.org/forums/forum/messageview.cfm?catid=205&threadid=40584 (https://www.theiet.org/forums/forum/messageview.cfm?catid=205&threadid=40584)
"So a 2-wire negative-earth circuit will be brown & blue, a 2-wire positive-earth circuit will be gray & blue, and a 2-wire circuit with neither pole earthed will be brown & gray."
So I'm guessing a PV installation is 2 wire non-earthed, hence Brown and grey.

Robert




Title: Re: MC4 Connector meltdown on Inverter
Post by: rogeriko on August 11, 2018, 10:32:33 PM

As a professional Electronics Engineer I was seriously tempted to just replace the connectors. But the system is still under the insurance backed gaurantee. I'm hoping to keep the inverter when it's replaced. Then I'll repair it and keep as a spare.


And all our insurance premiums go up. Personally I would fix it. I have never claimed anything on any insurance policy in my 65 years, (we have 4 cars). stir: stir:


Title: Re: MC4 Connector meltdown on Inverter
Post by: Westie on August 12, 2018, 09:32:10 AM

Hi There, yes a UK installation in 2015. Found an interesting article on the IET forums about harmonised colour codings.
https://www.theiet.org/forums/forum/messageview.cfm?catid=205&threadid=40584 (https://www.theiet.org/forums/forum/messageview.cfm?catid=205&threadid=40584)
"So a 2-wire negative-earth circuit will be brown & blue, a 2-wire positive-earth circuit will be gray & blue, and a 2-wire circuit with neither pole earthed will be brown & gray."
So I'm guessing a PV installation is 2 wire non-earthed, hence Brown and grey.

Robert



[/quote]

Well worth reading thro that thread ...  The IET seems to have completely lost the plot....  Going by wire colour you can no longer tell a 12V DC neg earth circuit from a 240V ac circuit! (both brown and blue).


Title: Re: MC4 Connector meltdown on Inverter
Post by: glyndwr1998 on August 12, 2018, 10:57:57 AM
That connector is such an easy fix for someone with the right skill set, not at all a difficult task. I too would be fixing it rather than scrapping a £1000 inverter thats working ok. Ok, i see the idea about keeping the inverter as a spare, thats IF thr repair company offer that, they will more than probably take it away, fix it themselves and stick it on ebay for their own profit.


Title: Re: MC4 Connector meltdown on Inverter
Post by: Westie on August 12, 2018, 12:05:39 PM
Why bother even using an MC4...  just remove the connector completely, use the hole to  direct wire it to the TB inside the inverter... if the cable is too short just replace it, actually i would do both MC4 at the same time,  every MC4 is a potential problem, even a good one has a small volt drop across it at full load,  so minimise the number used... SMA don't use MC4's into the inverter they're direct wired.
 


Title: Re: MC4 Connector meltdown on Inverter
Post by: Tinbum on August 12, 2018, 06:34:31 PM
I re-socketed an SMA tripower that had damaged connectors from a fire nearby. Bought them already with a length of wire on them and then just soldered that to the PCB. The soldering was the hardest part as the PCB tracks conducted the heat away very efficiently.


Title: Re: MC4 Connector meltdown on Inverter
Post by: planetming on September 09, 2018, 12:28:43 PM
Just thought I'd update. New inverter installed in August. All up and running now. Though not sure this dual input, single MPPT inverter is equivalent to my old dual MPPT inverter.

(https://s8.postimg.cc/bvjnwqq5d/new_Inverter.jpg) (https://postimg.cc/image/bvjnwqq5d/)


Title: Re: MC4 Connector meltdown on Inverter
Post by: Westie on September 09, 2018, 06:35:23 PM
Well you definitely have two arrays, if they're on the same roof with same orientation then single MPPT is fine... if each array has different orientation or one is subject to shading then dual MPPT is recommended.  What model is the inverter?



Title: Re: MC4 Connector meltdown on Inverter
Post by: planetming on September 19, 2018, 06:09:10 PM
Hi Westie,
One string is 7 panels the other is 8 panels on the same roof. Model is GoodWe GW3600S-UK.

Robert



Title: Re: MC4 Connector meltdown on Inverter
Post by: Fionn on October 02, 2018, 09:31:31 AM
I've got to say I'm with Rogeriko on this one, you could have replaced the connector (or rewired direct to the terminals) in the time it took to find the contact details for the insurer


Title: Re: MC4 Connector meltdown on Inverter
Post by: rogeriko on October 02, 2018, 10:39:35 PM
We just live in a wastefull society nowadays. I fix things at work and my boss is always mad at me because I could have sold a new part and made a profit. My wife buys a new microwave every few months just because the old one is dirty. The world has gone mad. facepalm facepalm