Thomson Power Systems · TS910 Series (Residential)

New

Thomson TS910 Automatic Transfer Switch

Automatic Transfer Switches

Residential and light-commercial automatic transfer switch. 100-400A, single and three-phase, open transition, contactor switching, TSC 9 controller. UL 1008 listed for optional standby.

Overview#

The Thomson TS910 is a residential and light-commercial automatic transfer switch available in 100A, 200A, and 400A configurations. Despite its residential positioning, the TS910 is available in both single-phase (2-pole, 120/240V) and three-phase (3-pole, 120/208V or 120/240V) configurations. A service-entrance rated variant (TS910SE) is also available. It uses contactor-based switching with in-phase transfer detection for clean, open-transition transfers that minimize disruption to sensitive electronics.

The TSC 9 controller handles all automatic transfer functions including engine start signaling, voltage and frequency monitoring, and programmable exercise scheduling. The compact NEMA 1 enclosure (27.1" x 18.9" x 8.3" at 200A 1Ph, 30 lbs) fits standard residential installations, with an optional NEMA 3R outdoor enclosure and enclosure heater kit available for outdoor deployments.

Important UL listing distinction: The TS910 is UL 1008 listed for optional standby systems (NEC Article 702). For legally required emergency or standby systems (NEC Articles 700/701), specify the Thomson TS920 instead.

TS910 vs TS920: which to specify#

The TS910 and TS920 share the TSC 9 controller and contactor switching mechanism, but serve different markets:

The critical difference is the UL listing scope: if the AHJ requires the ATS to be listed for emergency or legally required standby, you must specify the TS920. For residential whole-house generators (optional standby), the TS910 is the correct and more cost-effective choice.

Our service experience#

We install and service Thomson TS910 units on residential whole-house generator installations across the Bay Area and Central Coast, primarily in the 200A rating paired with 20-48 kW home standby generators. The compact size and straightforward TSC 9 programming make it a reliable residential ATS.

The most common service call is programming adjustments — homeowners or electricians who set the time delays incorrectly during initial installation. The engine start delay, warm-up timer, and utility return delay all need to be tuned to the specific generator model. The TSC 9's front-panel interface makes field adjustments straightforward without special software.

Frequently Asked Questions

What amperage ratings are available for the Thomson TS910?
The TS910 is available in 100A, 200A, and 400A ratings in both single-phase (2-pole, 120/240V) and three-phase (3-pole, 120/208V or 120/240V) configurations. All ratings carry 100% continuous current capacity for all load types. Short circuit withstand at 240V ranges from 10,000A (1Ph 100-200A) to 50,000A (3Ph 400A).
Is the TS910 service-entrance rated?
Yes — the TS910SE variant is service-entrance rated, allowing the ATS to function as the main service disconnect without a separate upstream main breaker. SE variants are available in both single-phase and three-phase configurations. Note that SE units are physically larger and heavier than their standard counterparts at the same amperage and may have different short circuit withstand ratings.
What safety features does the TS910 include?
The TS910 features an electrical and mechanical interlocked mechanism that prevents simultaneous closure of utility and generator sources. The TSC 9 controller provides voltage sensing on both utility and generator sources, programmable timers for engine warm-up, utility return, and engine cool-down, plus integrated exercise scheduling and optional load shed functionality via a 5A/120-240VAC relay contact.
What are the physical dimensions of the TS910?
The 200A unit measures 27.1 inches high by 18.9 inches wide by 8.3 inches deep and weighs 30 pounds in the standard NEMA 1 indoor enclosure. This compact size fits standard residential garage and utility room installations. An optional NEMA 3R outdoor enclosure is available.
What is the short circuit withstand rating?
Withstand varies by phase and frame: the 1Ph 100-200A frames are rated 10,000A at 240V, the 3Ph 100A is 22,000A, the 3Ph 200A is 25,000A, and the 3Ph 400A reaches 50,000A at 240V. These ratings assume upstream circuit breaker or fuse protection.

Service Specifications

ServiceFrequencyNotes
Exercise under loadMonthlyRun generator and transfer load; TSC 9 has built-in exercise timer
Connection torque inspectionAnnuallyRetorque power lugs per Thomson spec
Contactor inspectionEvery 5 yearsCheck contactor contacts for pitting; verify snap-action operation
Controller batteryEvery 5 yearsTSC 9 internal backup for clock and event log

Key Terms

Open-transition transfer
A brief (typically 100-500ms) interruption between disconnecting from one source and connecting to the other. Standard for residential backup where a momentary blink is acceptable.
In-phase transfer detection
The TSC 9 controller monitors both source waveforms and initiates transfer only when they are in phase, preventing damaging out-of-phase switching that could harm motors and sensitive electronics.
Contactor switching
Electromagnetic switching mechanism that uses a coil to snap contacts closed. Fast transfer speed, compact size, and lower cost compared to mechanically-held designs. Well-suited to residential and light-commercial applications.
Optional standby system
Per NEC Article 702, a standby system that is not legally required but is installed to protect selected loads. Residential whole-house generators are typically optional standby, not emergency (Article 700) or legally required (Article 701).

Need service for the Thomson TS910 Automatic Transfer Switch?

Our technicians work on every major component OEM. We stock common parts and source rare ones.

Get A QuoteOr call (831) 375-1463