What are the differences in a T4 connector and a MC4?

mike-s wrote:
{TUV} it's not affiliated with Amphenol in any way, other than that Amphenol may use their services,

They may, and they did use it. TUV is an international testing and certification body. No remarks on affiliation have been made.

You responses show a lack of reading/comprehension skills :)

Tools are hardly necessary to disconnect MC4. Haven't hear of anybody being unable to do this without tools. "Required" by NEC - don't know, don't care. This is my system. Just squeeze the sides to disconnect. Easy when new and clean, more difficult after being exposed to elements.

mike-s wrote:
You never said which panels or controller,

He's been at it for a while. You would've known if read his previous threads. Parallel-serious has also been discussed.

mike-s wrote:

Almot wrote:
As said, no tools are required for disconnecting MC4 and its clones.

A tool most certainly is required for disconnecting them. Since 2008, the NEC requires it, so that's how all the current connector manufacturers make them.

Your responses show a lack of understanding about solar systems.

I guess I don't understand either. I squeeze the little tits with thumb and forefinger of one hand, pull the thing apart with the other. I have the little tool but I didn't know I was required to use it.

You never said which panels or controller, but given the controller limitations, sounds like you did it right.

Seems you're using 72 cell panels. Yeah, those can go over 50V open circuit per when you go below freezing. If you're using full power, they'd normally run at around 37V/9A.

They're considered 24 volt panels. There are also 60 cell panels, which are considered 20 volts, but are sometimes called 24 volt ones just to distinguish them from 12 V panels. It's confusing.

36 cell = "12 volt" = ~22.5 Voc
60 cell = "20 or 24 volt" = ~37.5 Voc
72 cell = "24 volt" = ~45 Voc

I had to parallel because the open circuit voltage on my panels was around 47 volts, and it is possible for me to be in near zero weather, which made the cold compensated voltage around 51.3 volts per panel. Total would exceed the 150 volt rating of my Morningstar MPPT controller. They said that could fry the controller. So I paralleled three sets of 8 gauge wires to my controller. I think my panels are considered 36 volt panels, not 24 volt. Thanks.

Almot wrote:
I recall, they are installing 3*315W in parallel. So - yeah, about tens of amps :)

Words like "and" mean things. MC4s are only rated for 20A, and a 315W panel (24V) is going to put out about 10A, so he wouldn't parallel 3 such panels through one connector, he'd have 3 runs to the controller. But with 24 volt panels, he'd need to be running an MPPT controller to get 12 V out. So why would he parallel the panels in the first place? It would make more sense to run them in series, and have ~100V @ ~ 10A into the controller.

Almot wrote:
Yes, Amphenol headquarters are in the US. TUV protocol (of their H4 testing) is by Germans.

Uh, what? TUV is the German equivalent of Underwriter's Labs (UL). It's not a protocol, and it's not affiliated with Amphenol in any way, other than that Amphenol may use their services, just as the Swiss Staubli might use UL services for products they want to sell in the US.

Almot wrote:
As said, no tools are required for disconnecting MC4 and its clones.

A tool most certainly is required for disconnecting them. Since 2008, the NEC requires it, so that's how all the current connector manufacturers make them.

Your responses show a lack of understanding about solar systems.

It's not like you are in tropical rainstorms area. Coil the pigtails and/or long MC4 extension and hide connectors under the panels.

Should I follow MEX's advise and put electric grease in the connectors? I thought they were o-ring tight. I can surely do it if it is advisable. I really don't want to get back up on my roof any more than absolutely necessary.

mike-s wrote:
For a large fixed system putting hundreds of volts and tens of amps through them, sure - stick to one brand.

I recall, they are installing 3*315W in parallel. So - yeah, about tens of amps :)

Brand and monopoly aside, MC4 clones from questionable sources like Ebay are very often hit and miss. From a biggie like CS it should be TAD better.

In the worst case, you can get a crimper and replace T4 with MC4 if any issues arise. Hide them under the panels, they will last longer. If Mex were reading this, he would've probably told to smear it all with dielectric grease or Lanolin. In humid environment I would do this.

Yes, Amphenol headquarters are in the US. TUV protocol (of their H4 testing) is by Germans.

As said, no tools are required for disconnecting MC4 and its clones. Not "very" easy after it's been sitting for more than year, collecting dust and salt deposits, but doable - with bare fingers. I would not replace T4 with a connection directly to panel unless this could be done without soldering. It's better to keep it detach-able. I would not replace T4 with Anderson, unless frequent disconnecting is in plans, like using them in a portable setup. Definitely would not replace T4 with SAE.

howardwheeler wrote:
I've never hooked up solar panels before and now face two different connectors: T4 and MC4. Is one better than the other or more suitable for particular applications? And most important, do they plug into one another, in other words, can you have a mixed system where, for example, a T4 connector on a panel must mate to a MC4 connection on an extension cable?

If you are doing a rooftop permanent install you would not need connectors. Most panels have a junction box on the back which would give you access to a terminal strip. Remove the pigtail wires and hook direct to the terminal strip.

I have two panels that I can remove and set in the sun. I cut the MC4 connectors off and replaced them with Anderson Powerpole SB50 connectors.