IQ Load Controller Additional Info

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Load and Solar Circuit Control using IQ System Controller Auxiliary Contacts

Appendix B: Controlling air conditioning unit using a thermostat.

Auxiliary contact can be wired to intercept the control wire of a thermostat to an air conditioner

Figure 31: Using auxiliary contact for controlling air conditioning unit

Normally the air conditioning units are controlled by the thermostat. The air conditioner starts when it

receives a signal from a thermostat. The signal from the thermostat usually goes into an air handler unit

(typically indoors). The air handler unit in turn signals the condenser unit which is outdoors.

An auxiliary contact can be used to intercept the “cool” wire from the thermostat to the air handler. The

“cool” wire may also be called a “cool call” wire. Once this is done the IQ System Controller auxiliary

contacts need to be configured to shed loads automatically in off-grid as outlined in sections above.

When this is done:

• When the system is on-grid the auxiliary contact stays closed. This ensures that the thermostat’s

signal goes to the air handler thereby ensuring the air handler and condenser operate as normal.

• When the system goes off-grid, the auxiliary contact opens, interrupting the control signal from

thermostat to the air handling unit. Depending on the state of the condenser during the grid

transition the following can happen:

o If the condenser was running during grid transition, it will run for a cool down period,

typically a few minutes. The IQ Batteries must be sized appropriately to support the

steady state current requirement of the condenser, to ensure there is no microgrid

collapse during the cooldown period.

o If the condenser was not running during the grid transition, it will not start again during the

off-grid mode.

• If the condenser is signaled to start at the same instant as the grid transition happens, the

condenser may try to start. The surge current may collapse the microgrid unless the system has

been designed to support the surge current. This is a very rare scenario, and the system recovers

within a few seconds to form the microgrid again. Since the thermostat has been disconnected

during the initial microgrid transition, the condenser will not start again in off-grid mode.

Note: IQ Battery must be sized appropriately to handle the power requirements of the external

compressor.

Note: Use Normally Closed Auxiliary contact to wire the thermostat as the contact opens when the grid

power goes off by default.

SHEET:

DRAWN BY:SCALE:REVs:

DWG TYPE:

DWG #:

DWG SERIES:

iQ combiner

Autotransformer

GeneratorEncharge

Enpower 200G

Wireless

comms

NO1

NO2

NC1

NC2

NO3

Thermostat

To Air

conditioning

control unit