nJoin Power Module with Class A GFCI (USG-4000)

Name: nJoin Power Module with Class A GFCI
Brand: WarmlyYours
SKU: USG-4000
Price: 199.0 CAD
Availability: InStock

Part Number: USG-4000Past Model
It was replaced by the nJoin 2.0 Power Module with Class A GFCI (USG5-4000).
The nJoin is an intuitive Power Module with built-in GFCI for large electric floor heating applications. The nSpire Touch, nSpire Touch Wifi, nHance and nTrust thermostats can be extended with additional nJoin power modules. Output can be increased by 15 A per nJoin module.
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Quebec Repairability Notice

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Notices

Quebec Repairability Notice

Avis important pour les consommateurs du Québec:

WarmlyYours ne fournit ni services de réparation ni pièces de rechange pour ce produit. Si votre thermostat de chauffage de sol intérieur tombe en panne pendant la période de garantie, nous remplacerons l'unité complète conformément à notre politique de garantie. Notre équipe de soutien technique est disponible par téléphone 24h/24 et 7j/7 pour l'assistance à l'installation et au dépannage. Pour tous les détails, veuillez consulter notre Politique de Retour. Cet avis est fourni conformément à l'article 39 de la Loi sur la protection du consommateur du Québec (telle que modifiée en 2025).

Important Notice for Québec Consumers:

WarmlyYours does not provide repair services or replacement parts for this product. If your indoor floor heating thermostat fails within the warranty period, we will replace the entire unit according to our warranty policy. Our technical support team is available 24/7 by phone for installation and troubleshooting assistance. For full details, see our Return Policy. This notice is provided in accordance with Québec’s Consumer Protection Act, section 39 (as amended in 2025).

Support Questions

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What does the Ground Fault Circuit Interrupter (GFCI/GFEP) do that the Circuit Breaker doesn't?

A GFCI/GFEP (Ground Fault Circuit Interrupter / Ground Fault Equipment Protection) works differently than a circuit breaker by specifically detecting a small imbalance in electrical current between the hot and neutral wires, which indicates a potential ground fault (like a person touching a live wire), and instantly shutting off the power to prevent shock, while a circuit breaker only trips when there's a significant overload in current flow on the circuit, like a short circuit or too many appliances plugged in.

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How do I turn off the OJ Microline?

Pressing and holding (2-3 sec) physical power/reset button will turn the unit completely OFF. Same process turns the unit back on.

(nHance and nJoin units will have the button on the front faceplate, nSpire Touch WiFi, nSpire Touch and nTrust will have the button on the right side of the faceplate.)

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Why do relays fail?

Relays can fail due to excessive current or voltage. When a relay is exposed to too much current, the contacts can burn out. High voltage can also damage the coil. Other reasons include mechanical wear and tear, dust or dirt buildup, and moisture. These factors can cause the relay to malfunction or stop working entirely. Regular maintenance and using the relay within its specified limits can help prevent failures.

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How do you make the USG (nJoin USG-4000 power module) shut off when the thermostat switches off?

Check the connections between the thermostat and power module. If the power module is connected incorrectly to the thermostat, the power module won't switch off.

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Does the adaptive function reset when making a factory reset?

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Is the OJ Microline nJoin power module a direct replacement for the CT230?

No. The nJoin power module is not compatible with a Honeywell system.

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The GFI Red Light is permanently ON

This indicates a fault, current to ground. The thermostat has cut off the power for your safety. Please contact your local electrician or WarmlyYours Technical Support.

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Why does a GFCI (Ground Fault Circuit Interrupter) fail?

GFCI can fail for various reasons, such as wear and tear, moisture, corrosion, power surges, faulty wiring, or improper installation. Some of these causes can be prevented by regular inspection and maintenance, while others may require professional assistance. It is important to note that GFCI devices (ex. thermostat, breakers, outlets) should be tested regularly as these do wear out over time.

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Documents

Wiring Diagrams

Specifications

Warranty / Certifications

Approvals	cULus listed
Ingress Protection (IPxx) Rating	IP21
Warranty	Limited 3-year warranty and lifetime technical support

Electrical

Connection	4 wires, double pole
Connection Method	Hardwired
Ground Fault Protection	GFCI, Class A, 5 mA
Maximum Current	15 A
Maximum Power	1800 W @ 120 V, 3120 W @ 208 V, 3600 W @ 240 V
Supply	120 VAC, 208 VAC, 240 VAC (50/60Hz)