Outback FXR/VFXR Renewable Series Installation Manual

Planning
900-0166-01-00 Rev B 13
EXAMPLE #2
A. Backup loads: 720 W
B. Hours of use: 3
C. Days of autonomy: 2
D. Off-grid system (VFXR3524A inverter)
E. Conductor efficiency: 97% (0.97)
F. Inverter efficiency: 92% (0.9)
G. System voltage: 24 Vdc
H. Batteries: OutBack EnergyCell 200RE (12 Vdc)
I. Capacity at 8-hour rate: 167.5 Ahr
J. Maximum DoD: 50% (0.5)
Generator

FXR inverters can accept power from a single-phase generator that delivers clean AC power in the range of
voltage and frequency specified for that model.
~ Inverters stacked for split-phase output (120/240 Vac) can work with both output lines of a
split-phase generator.
~ Inverters stacked for three-phase output can work with three-phase generators.

The inverter/charger can provide a start signal to control an automatic start generator. If automatic generator
starting is required, the generator must be an electric-start model with automatic choke. It should have
two-wire start capability. For other configurations, additional equipment may be required.

In any configuration, the inverter may need to be specifically programmed using the system display.
Perform all programming according to the specifications of the generator and the required operation of the
inverter. Parameters to be programmed may include generator size, automatic starting requirements, and
potential fluctuations in generator AC voltage.

A generator that is to be installed in a building usually should
not
have a bond between the neutral and
ground connections. The generator should only be bonded if there is a specific need. Installations in North
America are expected to bond the neutral and ground at the main electrical panel. See page 18 for more
information on neutral-ground bonding.
Generator Sizing
A generator should be sized to provide enough power for all the loads and the battery charger.
The generator size should assume maximum loads and maximum charging at the same time.

Available generator power may be limited by ratings for circuit breakers and/or generator connectors.

The generator must be able to provide current to all inverters on a given phase or output. Minimum
generator size
2
is usually recommended to be twice the power of the inverter system. For example, a 2 kVA
inverter should have a 4 kVA generator. Many generators may not be able to maintain AC voltage or
frequency for long periods of time if they are loaded more than 80% of rated capacity.

In addition, if a split-phase 120/240 Vac generator is powering a single-phase 120 Vac inverter system with
no other compensation, it is
required
to be at least twice the power of the inverters. A split-phase
generator that is heavily loaded on one output line may suffer severely from balancing issues. The OutBack
FW-X240 or PSX-240 balancing transformers may compensate for this condition.
2
This is the generator size after derating for environment, use, and other factors.
1) A ÷ [E x F] 720 ÷ (0.97 x 0.9) = 801.8 W
2) 1 ÷ G 824.7 ÷ 24 = 34.4 Adc
3) 2 x B 34.4 x 3 = 103.1 Ahr
4) [3 x C] ÷ J [103.1 x 2] ÷ 0.5 = 412.4 Ahr
5) 4 ÷ I 412.4 ÷ 167.5 = 2.5 (rounded to 3)
6) [G ÷ H] x 5 [24 ÷ 12] x 3 strings = 6 batteries