Component Guide

M250 Installation Planning

Planning for Cable Lengths and Type

The Engage Cable is flexible enough to adapt to almost any solar design. To determine the length and

cable type that you need, take into account the following considerations:

 Calculate the number of Enphase Microinverters to be installed on the AC branch. Be certain to

allocate the correct number of connectors, including extra connectors for gaps and turns.

 Account for any additional length required to reach from the AC branch circuit junction box to

the first microinverter. If greater than half a connector cable interval is needed, it may be necessary

to include one (or more) unused connectors in order to span this distance. Unused connectors must

be covered with Enphase sealing caps.

 Plan to minimize the number of unused connectors with three-phase systems. If cable connectors are

left unused on a three-phase system, it creates a phase imbalance on the branch circuit. If multiple

cable connectors are skipped over multiple branch circuits, the imbalance can multiply.

You can avoid skipping Engage Cable connectors with the use of Engage Couplers. For instance,

use the Engage Coupler to connect two Engage Cables or to connect Engage Cable to field cable.

There are many possible scenarios for each type of connection, but they generally fall into four

categories:

Engage Cable to Engage Cable:

1. Make use of leftover lengths of Engage Cable

2. Transition between portrait and landscape Engage Cable

Engage Cable to Field Cable (#12 TC-ER):

3. Transition between sub-arrays on the same circuit

4. Create wiring extensions for Engage Cable

NOTE: The Engage Coupler only supports #12 TC-ER, which may not be sufficient for

homerun wiring. Enphase Energy recommends maintaining less than 2% voltage drop

across all wiring.

In situations where you cannot use an Engage Coupler, you can use an electrical junction box to

transition between cable types.

You must account for all lengths of cable when calculating total VRise. Refer to the following

documents (at http://www.enphase.com/support) for more information on the Engage Coupler and to

maintain AC VRise at less than 2%:

o Applications of the Engage Coupler

o Circuit Calculations for the M250 Microinverter

o Calculating AC Line Voltage Drop for M250 Microinverters with Engage Cables

 Additional length required to reach from one row of PV modules to the next. If the PV modules

are laid out in multiple rows, plan for any additional cable needed to cover the distance from one row

to the next.

 Bend radius. When planning cabling turns or loops, you must account for a minimum bend radius of

4.75 inches (12 cm).

 Multiple sub-arrays. Often, the AC branch circuit may be composed of several smaller sub-arrays

across more than one roof plane. In this case, cut the cable to service each smaller array, and

connect the sub-arrays using appropriately rated runs of conduit. Accomplish the transition from cable

to conduit by using an outdoor rated junction box, as required by the NEC and local code. You must

cover unused connectors with Enphase sealing caps.