All registers return NaN or zero. What is wrong?

SunSpec inverters report NaN for unimplemented or unsupported registers. Verify the inverter is running (st register should not indicate off or sleeping state), that Modbus TCP is enabled and not just the RTU interface, and that the model block start address in the portal matches the actual offset reported by the inverter's SunSpec discovery scan.

The gateway connects but the id register reads an unexpected value.

The id register at address 0 within the model block identifies the phase topology: 111 for single phase, 112 for split phase, 113 for three phase. If you see 112 or 113, the inverter is presenting a different model variant. Select the matching template in the portal to ensure all phase registers are mapped correctly.

Phase B and C current and voltage registers always read zero on a single-phase inverter.

This is normal. On a single-phase inverter (model ID 111), registers apha carries the sole phase current and phvpha the sole phase voltage. Registers aphb, aphc, phvphb, phvphc, and all phase-to-phase voltage registers are not implemented and will return zero or NaN per the SunSpec specification.

Float32 values look scrambled or implausibly large. How do I fix byte order?

SunSpec float32 registers use big-endian word order: the most significant 16-bit word occupies the lower register address, the least significant word the next address. If your readings appear garbled, confirm that the ModbusCloud Gateway is configured for big-endian (Modbus standard) word order. Swapping the two words typically resolves implausible values immediately.

Free Modbus template: SunSpec Model 111 — Inverter (Single Phase) FLOAT

Name: SunSpec Model 111 — Inverter (Single Phase) FLOAT
Brand: SunSpec
SKU: 47dd145d-e439-4bfd-a386-8b77b34b74d2

SunSpec Model 111 is an open, vendor-neutral Modbus TCP register model defined by the SunSpec Alliance for monitoring single-phase PV inverters, with companion models 112 (split phase) and 113 (three phase) sharing the same layout. This template reads AC-side measurements including per-phase current, phase-to-phase and phase-to-neutral voltage, active power, apparent power, reactive power, power factor, and cumulative energy production. DC-side registers cover array current, voltage, and power, while four temperature registers track cabinet, heat sink, transformer, and other sensors. Operating state, standard event bitfields, and four vendor event bitfields complete the picture, giving installers a full health snapshot of any SunSpec-certified inverter.

Registers (33)

33 read / 0 write

Name	Address	Function	Type	Unit	Access
id SunSpec model ID: 111 single phase, 112 split phase, 113 three phase.	0	FC03	uint16		R
l Length of the inverter model block in 16-bit registers.	1	FC03	uint16		R
a AC total output current, sum of all phases, amperes.	2	FC03	float32	A	R
apha AC current on phase A, amperes.	4	FC03	float32	A	R
aphb AC current on phase B, amperes.	6	FC03	float32	A	R
aphc AC current on phase C, amperes.	8	FC03	float32	A	R
ppvphab AC phase-to-phase voltage between phases A and B, volts.	10	FC03	float32	V	R
ppvphbc AC phase-to-phase voltage between phases B and C, volts.	12	FC03	float32	V	R
ppvphca AC phase-to-phase voltage between phases C and A, volts.	14	FC03	float32	V	R
phvpha AC phase-to-neutral voltage on phase A, volts.	16	FC03	float32	V	R
phvphb AC phase-to-neutral voltage on phase B, volts.	18	FC03	float32	V	R
phvphc AC phase-to-neutral voltage on phase C, volts.	20	FC03	float32	V	R
w AC active power output, total across all phases, watts.	22	FC03	float32	W	R
hz AC grid frequency, hertz.	24	FC03	float32	Hz	R
va AC apparent power output, volt-amperes.	26	FC03	float32	VA	R
var AC reactive power output, volt-amperes reactive.	28	FC03	float32	var	R
pf AC power factor, expressed as a percentage.	30	FC03	float32	Pct	R
wh Cumulative AC energy produced since inverter installation, watt-hours.	32	FC03	float32	Wh	R
dca DC input current from PV array, amperes.	34	FC03	float32	A	R
dcv DC input voltage from PV array, volts.	36	FC03	float32	V	R
dcw DC input power from PV array, watts.	38	FC03	float32	W	R
tmpcab Cabinet or enclosure internal temperature, degrees Celsius.	40	FC03	float32	°C	R
tmpsnk Heat sink temperature, degrees Celsius.	42	FC03	float32	°C	R
tmptrns Transformer temperature, degrees Celsius.	44	FC03	float32	°C	R
tmpot Other internal temperature sensor reading, degrees Celsius.	46	FC03	float32	°C	R
st SunSpec operating state code: off, sleeping, starting, running, throttled, fault, or standby.	48	FC03	uint16		R
stvnd Vendor-defined operating state code, manufacturer-specific enumeration.	49	FC03	uint16		R
evt1 Standard event bitfield, bits 0 to 31, indicating active fault and warning flags.	50	FC03	uint32		R
evt2 Standard event bitfield, bits 32 to 63, extending evt1 fault and warning flags.	52	FC03	uint32		R
evtvnd1 Vendor-defined event bitfield, bits 0 to 31, manufacturer-specific fault flags.	54	FC03	uint32		R
evtvnd2 Vendor-defined event bitfield, bits 32 to 63, manufacturer-specific fault flags.	56	FC03	uint32		R
evtvnd3 Vendor-defined event bitfield, bits 64 to 95, manufacturer-specific fault flags.	58	FC03	uint32		R
evtvnd4 Vendor-defined event bitfield, bits 96 to 127, manufacturer-specific fault flags.	60	FC03	uint32		R

SunSpec Model 111 — Inverter (Single Phase) FLOAT

Overview

Use cases

Installation

Things to watch for

Registers (33)

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