Can the Shelly Pro 3EM clamp cable be extended?

[mircolino]

I have a Shelly Pro 3EM setup in single-phase mode. I'd like to monitor a load in the garage which is 30m away (where there is no WiFi). Can the clamp cable be extended? And if so, which cable do I need for the specified distance? Could I just use a couple of regular FS17 1.5mm² wires? Thank you.

Edited August 28 by mircolino

[thgoebel]

Last year, I made some inquiries about the maximum length of cables of current clamps to evaluate the design of extension cords like these:

https://shellyparts.de/products/verlangerungskabel-fur-shelly-3em-pro-3em-pro-em-50a

During this evaluation I took a standard length of cable (25 meters) and compared the measured value with those without an extension. Even though the transmitted signal is in the range of some millivolts, the measured current value behind the 25m was still in concordance with the reference value.

Thus, I would propose to use a shielded Cat-5 data cable and to go for a test. Due to the fact the wires to the current clamps are at the potential of the neutral wire, no restrictions are necessary concerning the isolation parameters. Would suggest to connect the cable shield to protective earth (PE).

[Dennis Dalgaard Gottlieb]

Does anybody know what the connector types are called? 

[thgoebel]

MOLEX Microfit 3.0

[terae]

Since I have them in own sales stock, I know you are trying to find part numbers 430250200 and 430300007 (female) and when needed also male (PN 430200201 and 430310007).

I've also tested against 50 meters of LiYY cable. You're searching for low capacitance, nothing else matters much. Cat5+ are better than good and good to over 30 meters easily.

[mircolino]

@terae @thgoebel

Since the conduit to the garage is 20mm in diameter and 30 meters long, I was looking for a F/UTP CAT5 cable small in diameter and stranded for added flexibility. Would something like this work for my application?

https://netwerkkabel.eu/en/products/cat5e-f-utp-network-cable-stranded-100-koper-100m

Other suggestions?
Thank you!

Edited September 3 by mircolino

[thgoebel]

Give it a try! I've proposed a STP network cable (and connect the shield with PE), but UTP will do the job. In addition, UTP will have less capacitance per meter, which is a significant parameter.

[mircolino]

2 hours ago, thgoebel said:

I've proposed a STP network cable (and connect the shield with PE), but UTP will do the job. In addition, UTP will have less capacitance per meter, which is a significant parameter.

Sorry, I'm not a data cable expert. The one I linked is a FTP cable which, if I'm not mistaken, doesn't have each individual pair shielded but all 4 pairs wrapped in aluminum (foiled). Would FTP be OK or do you still recommend to use STP?

Also, how do you connect the CAT5 cable to the clamp and the EM? On another document it was suggested to connect all 4 colored wires to the clamp positive and all 4 white/colored wires to the clamp negative. Is that correct?
 

[thgoebel]

You linked an F-UTP cable. And yes, it is correct that the F-UTP has a foiled shield around the four twisted pairs. As I mentioned before, this cable seems to be suitable. Unfortunately, I‘ve no experience with this type of cable. Hence, I wrote „give it a try“…

Please consider carefully to identify and to separate the twisted pairs! It is essential to connect each current clamp (which has two wire, red and black) to a twisted pair (which are usually coloured in white/green, white/brown, white/black and white/blue pairs)! Thus, the drilled structure must be maintained during the installation process: If you should lose the structure, you will have four white wires which are difficult to identify! Best practice is to fit an insulating sleeve with appropriate diameter over the twisted pairs at the dismantled end of the cable. This ensures that the pairs are kept together.

[terae]

Just give it a try. It should work good. RF shield isn't required. To magnetism it does nothing (possible high current same way routed cables effect). So no need to foil. Does not either do any harm.