IQ Load Controller Additional Info

Load and Solar Circuit Control using IQ System Controller Auxiliary Contacts

Overview

This document provides installers and design engineers with the information required to plan and configure

Smart Control (load and solar circuit control) using IQ System Controller Auxiliary contacts.

The Enphase Energy System (EES) must have sufficient power capability to sink all the power from the PV

system during transitions to off-grid and must source power to support all loads in intentionally islanded

(standalone) operation. This may not always be feasible. In such situations, auxiliary contacts in IQ System

Controller can be used to disconnect(shed) excess solar or heavy loads.

In addition, low priority loads with high power requirements may deplete energy storage. Auxiliary contacts

can be used to shed these large loads to help maintain energy in the storage system.

What are auxiliary contacts and how do they work?

The IQ System Controller has 5 relays rated for pilot duty at up to 24Vac/Vdc and 1A continuous current.

One is dedicated for generator function while the others are available for general use. The

contacts/terminals of the pilot relays are not energized by IQ System Controller i.e., they have no voltage

on them and are “dry”. When these contacts are connected to a voltage source, they are “wetted”. In this

document, we will be referring to these as auxiliary relays or contacts. The configuration of the relays is as

follows:

1. Two Normally Open (NO)

2. Two Normally Closed (NC), and

3. One NO relay used for starting a generator (optional)

While the auxiliary contacts have NO and NC electrical configurations, the Enphase Installer App

overrides this behavior when configuring the contacts. Once configured the contacts are closed when

on-grid and open when off-grid. In special load control modes, the contacts may be closed when off-grid if

battery charge exceeds a threshold or if a generator is running. Due to this IQ System Controller can

only be used with NO-type external definite purpose contactors or power relays to implement load

control or solar circuit control as described in this tech brief.

Note: Refer to the Generator support tech brief for documentation related to generator integration. This

tech brief covers load and solar circuit shedding using auxiliary contacts.

Auxiliary contact labelling in IQ System Controller

The figure below illustrates the auxiliary contacts at the bottom of the IQ System Controller smart switch.

It also shows the AC combiner, Generator and IQ Battery lugs.

Figure 1 Auxiliary contact labelling and usage