Contents:
- TAP Communication Cable Requirements
- Recommended Cable Types
- Maximum Cable Length Recommendations
- Using Ethernet Cables (Cat 5 / Cat 6)
- Installation Tips!
Introduction
This article givers the requirements for the cable that connects the TAP (or Gateway), to the Data Logger (CCA, Cloud Connect or MMU).
- Tigo's TAP and Gateway are both Access Points for the MLPE.
- A TAP can replace a Gateway. (However, a gateway should not be used to replace a TAP).
- The TAP (Tigo Access Point) is the current product.
- To identify which device you are using, see TAP vs Gateway
(Because Gateways use a different wire connection method).
TAP/Gateway Cable Requirements
The Data Logger used to connect a TAP should have these features:
- At least 1 Twisted Pair (TP) of wires (for A and B connections).
- Smallest supported wire size is 22 AWG (0.33 mm²) and largest is 18 AWG.
- Max cable Outside Diameter (OD) of 0.346 inches (so it will fit through the cable gland).
- The preferred cable is RS-485 specification compliant, especially for over 100 feet to the most distant TAP.
- Shielded is preferred. May be required if cable is subject to strong EMF fields.
- Alternatively, if required, Ethernet cable (of any Category) can be used for up to 2 TAPS.
Always check the product data sheet for exact and current specifications: TAP Datasheet
Recommended Cable Types
- Remember to check with your Authority Having Jurisdiction (AHJ) to see if there are any local requirements for cabling on your project.
- If the cable is not housed in a conduit, please use an outdoor-rated (UV resistant) cable.
- Conduit is recommended to avoid damage by animals.
- Can cable be in the same conduit with PV String Home Runs?
Compliant Cables:
Belden 3107A, 3107Z and 3107DB (same cable, different insulation materials).
Non-Compliant Cables:
Ethernet cables can only be used on systems with a maximum of 2 TAPs and less than 100 feet to the farthest TAP.
Ethernet Category 5e UTP, CMP (see: Using Ethernet Cables (CAT5 / CAT6))
Ethernet Category 5e, UTP, CMR (riser rated) (see: Using Ethernet Cables (CAT5 / CAT6))
Many cables are manufactured in 2 shielding types:
- UTP - Unshielded Twisted Pair and STP - Shielded Twisted Pair
- STP (shielded) cable is highly recommended when wiring is located close to Motors (such as used in HVAC equipment), or powerful radio transmitters.
Maximum Cable Length Table
- The length of a cable along with its wire sized determines its resistance.
- Longer cables have more resistance, naturally.
The table (below) provides the maximum length recommendations per cable type and number of TAPS.
- Wire sizes are listed in American Wire Gauge (AWG) and Millimeters (mm).
- Wire Lengths are listed in Feet (ft) and Meters (m).
Wire Gauge |
Number of TAPs Employed on System |
||||||
1 |
2 |
3 |
4 |
5 |
6 |
7 |
|
RS-485 18 AWG |
2,604 |
2,604 |
1,817 |
1,363 |
1,090 |
908 |
716 |
RS-485 20 AWG |
2,604 |
1,714 |
1,143 |
857 |
686 |
571 |
456 |
RS-485 22 AWG |
2,156 |
1,078 |
719 |
539 |
431 |
359 |
287 |
Ethernet |
4,067 |
2,034 |
1,356 |
1,017 |
813 |
678 |
543 |
Ethernet |
1,357 |
678 ft |
N/A |
N/A |
N/A |
N/A |
N/A |
For commercial systems:
Use of Ethernet cable is strongly discouraged to prevent call-backs.
RS-485 has the correct electrical characteristics for minimal data corruption of the communications with the Cloud Connect to/from the TAP.
The distance combined with the number of TAPS per CCA effects the voltage at the TAP(s)
Ethernet (Cat 5 / Cat 6) cables may have a higher data-corruption rate.
Using Ethernet Cables (Cat 5 / Cat 6)
- A and B signals: Use 2-wire, from the same pair.
- To minimize voltage drop extra pairs can be combined.
(This can be helpful for distances over 100 feet, or on systems with 2 or more TAPs.) - The picture is using the pair color code of Blue, and White/Blue are used.
STEP 1
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STEP 2.
Note: This example has the required 120 ohm termination resistor across the A and B on the right hand sided, for the last TAP in a 'chain' of TAPS connected to a CCA.
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STEP 3
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STEP 4
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STEP 5.1
This example is using Ethernet cable but RS-485 cables also may use this connector. Picture NOTE: Blue and white with a blue stripe used as the twisted pair for the A and B signals.
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STEP 5.2 (Using IDC Method)
Note: Since the IDC connector cannot take multiple wires, the maximum wire length is affected and limiting the number of TAPS to 2. |
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STEP 6
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Installation Tips:
Conduit and Cable Trays also having the gateway cable:
When running the communication cable in the same conduit as an PV String Wire (home-run string wires), use a cable that has at least 600 VDC insulation or matching the inverter maximum string VDC rating.
- This eliminates the need for installation of a separate conduit for the communication cable, assuming the string voltage will never exceed 600 VDC.
- Ethernet cable is normally rated to only 300 VDC.
Termination resistor
A resistor is pre-installed on the right-hand side terminals on each TAP. It is connected to the A and B terminals, which are the RS-485 data signals. Remove the resistors from the other TAPs along the daisy-chain. The last TAP in the chain, it must have the resistor inserted in the outgoing A and B terminals.
Mounting the TAP:
- The TAP is designed to be installed under a panel (hidden from direct sunlight).
- The TAP installs to the PV-Module frame using the mounting clips.
- Mount the TAP with the label side outward (facing away from the panel).
- If the PV-Module has no frame, the clips on the TAP can be removed. The remaining holes can be used for screw-mounting them to a racking system.
- Mount the TAP in a centrally located area, as the radio distribution has a radial circumference.
- Radio signal obstructions, including opposing roof angles, drop-roofs, dormers, gables and different levels of panels, etc., require individual TAPS, in nearly all cases.
Warning: Do not mount the TAP inside an attic. Material such as roofing, insulation, sheathing and shingles, can present a physical barrier to the signal.
For complete installation directions, see page 12 of the TAP Installation Manual, and feel free to consult with a Tigo Energy Sales Engineer for any questions.
Testing communications with TAPs:
After installation is complete, the Discovery portion of the commissioning process should find all of the TAPs, quickly.If the Discovery reports fewer TAPs than configured on the Equipment page, run a TAP Test.
For legacy equipment (Tigo Cloud Connect and MMU), run a Gateway test