--- product_id: 3619528 title: "RC840T-240 On/Off Switching Electric Heating Relay with Built-in 24 V Transformer, Black" brand: "aube technologies" price: "€ 198.89" currency: EUR in_stock: true reviews_count: 8 category: "Aube Technologies" url: https://www.desertcart.hr/products/3619528-rc840t-240-on-off-switching-electric-heating-relay-with-built store_origin: HR region: Croatia --- # 8A contact current rating Built-in 24V transformer Direct replacement, easy install RC840T-240 On/Off Switching Electric Heating Relay with Built-in 24 V Transformer, Black **Brand:** aube technologies **Price:** € 198.89 **Availability:** ✅ In Stock ## Summary > ⚡ Upgrade your heating game with instant, reliable control! ## Quick Answers - **What is this?** RC840T-240 On/Off Switching Electric Heating Relay with Built-in 24 V Transformer, Black by aube technologies - **How much does it cost?** € 198.89 with free shipping - **Is it available?** Yes, in stock and ready to ship - **Where can I buy it?** [www.desertcart.hr](https://www.desertcart.hr/products/3619528-rc840t-240-on-off-switching-electric-heating-relay-with-built) ## Best For - aube technologies enthusiasts ## Why This Product - Trusted aube technologies brand quality - Free international shipping included - Worldwide delivery with tracking - 15-day hassle-free returns ## Key Features - • **Plug & Play Powerhouse:** Seamlessly replaces any brand relay for hassle-free upgrades - • **Instant Activation Comfort:** Immediate relay response ensures precise temperature control - • **Integrated Transformer Magic:** Built-in 24V transformer eliminates extra wiring complexity - • **Durable Silver Alloy Contacts:** Reliable 8A switching with premium materials for long-lasting performance - • **Universal Thermostat Compatibility:** Works flawlessly with 2- or 3-wire 24V thermostats (R,W or R,W,C) ## Overview The RC840T-240 is a compact, black electric heating relay featuring a built-in 24V transformer designed for easy installation and universal compatibility with 2- and 3-wire thermostats. Rated for 8 amps with silver alloy contacts, it delivers immediate relay activation for enhanced temperature control, making it the perfect direct replacement for any brand of 24V-controlled electric baseboard heaters or similar devices. ## Description Compatible with 2- and 3-wire thermostat, this all-in-one relay includes a built-in 24 V transformer Review: Works with multiple strip units - Works great, used one thermostat to trigger 2 of baseboard resistance 8 foot length in big common room Review: Great product - Mr. Fore here- great product. Replaces any 24v controlled (typical thermostats) 220v electric baseboard heaters (or any electric device that is thermostat controlled). Perfect replacement part. Good wiring diagram on the front of the box. Easy install. This is my second order and both are going strong. A bonus- you can see when the thermostat is triggered, so you can test the whole circuit easily. ## Features - Direct replacement for any brand name relay - Built-in 24 V transformer for easy installation. - Compatible with 24V thermostats with 2-wire connections (R,W) or 3-wire connections (R,W,C) - Immediate relay activation provides improved temperature control and comfort ## Technical Specifications | Specification | Value | |---------------|-------| | ASIN | B0037MXM1C | | Batteries Included? | No | | Batteries Required? | No | | Best Sellers Rank | #177,821 in Tools & Home Improvement ( See Top 100 in Tools & Home Improvement ) #150 in HVAC Controls | | Brand | AUBE TECHNOLOGIES | | Coil Voltage | 24 Volts | | Color | Black | | Connector Type | Screw | | Contact Current Rating | 8 Amps | | Contact Material | Silver Alloy | | Contact Type | Normally Open | | Customer Reviews | 4.6 4.6 out of 5 stars (456) | | Date First Available | February 8, 2010 | | Included Components | Electromechanical heating relay with a 24V - 208/240V transformer | | Is Discontinued By Manufacturer | No | | Item Package Quantity | 1 | | Item Weight | 12.8 ounces | | Item model number | RC840T-240 | | Manufacturer | Aube Technologies | | Maximum Switching Voltage | 24 Volts | | Measurement System | Imperial | | Mounting Type | Panel Mount | | Number of Terminals | 3 | | Operation Mode | Electric | | Part Number | RC840T-240 | | Product Dimensions | 1 x 1 x 2 inches | | UPC | 775264094620 811241030264 | | Voltage | 24 Volts | ## Product Details - **Brand:** AUBE TECHNOLOGIES - **Connector Type:** Screw - **Contact Material:** Silver Alloy - **Contact Type:** Normally Open - **Mounting Type:** Panel Mount ## Images ![RC840T-240 On/Off Switching Electric Heating Relay with Built-in 24 V Transformer, Black - Image 1](https://m.media-amazon.com/images/I/61r29Rs3nHL.jpg) ## Questions & Answers **Q: For my paranoia and absolute clarity, this goes inline with a 240v baseboard and allows smart HVAC type t-stat/Nest/EcoBee etc to work** A: Yes, it has built-in relay & 24volt transformer, so it allows low voltage (24v components) control of the line voltage (240v) loads... Which is the 240 v baseboard heat er(s). Fits in heater wiring compartment. **Q: Can i use a single relay to control 2 baseboard heaters?** A: Yes, I have mine running 5, 4 1000 watt baseboards and 1 1250 watt forced air wall heater. you just run them all in parrallel after the relay. No problem as long as your total amps does not exceed22. **Q: Is anyone running two of these off of one thermostat? I contacted Aube tech support and they said you can do it but they must be in phase?** A: Yes, think of this relay as a 2 pole switch. You apply lower voltage to the coil (24 v from t-stat), and that activates the 2 pole relay switch... which turns on anything downstreat... 1 heater, 2 heaters etc. **Q: What are the options for installing this? I read the installtion manual, but I'd like to hear from some who have actually done it.** A: I had an existing baseboard heating system, with a round Honeywell thermostat, and an older relay module that works exactly the same way as the Aube. The older relay was sticking and no longer reliable, so I replaced it with the Aube, and, at the same time, I replaced the mechanical Honeywell thermostat with a Nest. Physically, the little Aube box goes on the side of an electrical junction box, fitting in one of the "knockouts." This is because no electrical code would allow the low-voltage circuitry of the Aube, or your low-voltage thermostat wires, to occupy the SAME junction box as your 240v heating wiring. So the tube sticks into the knockout of the junction box, and fastens on with the nut, and that's how the Aube's three high-voltage wires safely enter the junction box. Electrically, it's also pretty simple. You have two wires providing 240v power from your panel, a black hot wire and a white neutral. (These should be coming into the same junction box where you're attaching the Aube.) And, you have a black and a white wire heading off to your baseboard heater. You can just connect the white wire from the panel to the white wire for the heater, i.e. the heater's neutral wire is just connected all the time and not switched. If you also connected the black wire from the panel directly to the black wire of the heater, your heat would run, but it would be on 24/7/365, and you'd be living in the tropics, and maybe burn your house down. Obviously, you don't want that. You want the heat to switch on and off. The Aube is your switch, so it sits BETWEEN the panel's hot wire and the heater's hot wire. The Aube's BLACK wire connects to the black power wire from the panel, and the Aube's RED wire connects to the black wire leading to your baseboard heater. The Aube turns the red wire on and off, to turn your heat on and off. So that leaves the blue wire. The blue wire is ONLY there to power the little transformer inside the Aube that runs the relay and your thermostat. So, the blue wire connects to the white neutral power wire from your panel. Remember when you connected the white panel neutral to the white heater neutral? You can just also twist the Aube's blue wire together with those two white wires, and you're set. You might notice that the Aube's red and black wires are 12 gauge, because they switch the full current load of your heater. But the blue wire is only thinner 16 gauge, because it's only there to power the Aube's internal transformer. In all cases, use good heavy-duty wire nuts or other wire connectors that are rated for 240V 12 gauge wire. And, do I even need to tell you to turn OFF the circuit breaker that runs your heat FIRST? (If I HAVE to tell you that, you probably should get a professional to hook this up for you!) Now, you have your thermostat wires. If you have a simple two-wire mechanical thermostat like a round Honeywell mercury-bulb thermostat, it connects across the Aube's R and W screws. And probably your existing thermostat wires -- thin-conductor wires that look like telephone wiring -- will actually BE red and white. The R screw terminal is low-voltage 24v power, provided by the Aube's internal transformer. The W terminal is the signal wire to turn the Aube's relay (and your heat) on and off. The C is the common terminal often discussed in setting up smart thermostats like the Nest. Having that third "common" wire lets your thermostat draw 24v power for itself all the time, independently from turning your heat on and off via the white wire. My existing installation already HAD an unused third wire in the cable leading to the thermostat. It happened to be colored green, not the blue that is more standard now, but it worked just as well. The three thermostat wires, red, white, and green, went on the R, W, and C screws on the Aube, and, on the Rh, W, and C terminals of the Nest base plate on the other end. Voila! ## Customer Reviews ### ⭐⭐⭐⭐⭐ Works with multiple strip units *by A***R on January 17, 2026* Works great, used one thermostat to trigger 2 of baseboard resistance 8 foot length in big common room ### ⭐⭐⭐⭐⭐ Great product *by J***E on December 4, 2025* Mr. Fore here- great product. Replaces any 24v controlled (typical thermostats) 220v electric baseboard heaters (or any electric device that is thermostat controlled). Perfect replacement part. Good wiring diagram on the front of the box. Easy install. This is my second order and both are going strong. A bonus- you can see when the thermostat is triggered, so you can test the whole circuit easily. ### ⭐⭐⭐⭐⭐ Works well! *by A***N on January 20, 2026* Works well! ## Frequently Bought Together - Aube Technologies RC840T-240 On/Off Switching Electric Heating Relay with Built-in 24 V Transformer, Black - Amazon Smart Thermostat – Save money and energy - Works with Alexa and Ring - C-wire required - Southwire 64169622 5 Conductor 18/5 Thermostat Wire; 18-Gauge Solid Copper Class 2 Power-Limited Circuit Cable; 50-Feet; Brown --- ## Why Shop on Desertcart? - 🛒 **Trusted by 1.3+ Million Shoppers** — Serving international shoppers since 2016 - 🌍 **Shop Globally** — Access 737+ million products across 21 categories - 💰 **No Hidden Fees** — All customs, duties, and taxes included in the price - 🔄 **15-Day Free Returns** — Hassle-free returns (30 days for PRO members) - 🔒 **Secure Payments** — Trusted payment options with buyer protection - ⭐ **TrustPilot Rated 4.5/5** — Based on 8,000+ happy customer reviews **Shop now:** [https://www.desertcart.hr/products/3619528-rc840t-240-on-off-switching-electric-heating-relay-with-built](https://www.desertcart.hr/products/3619528-rc840t-240-on-off-switching-electric-heating-relay-with-built) --- *Product available on Desertcart Croatia* *Store origin: HR* *Last updated: 2026-05-14*