DavidAnstee Posted July 9 Share Posted July 9 I have a Vent Axia 498502 MVDC-MSH Multivent Uniflex Extractor Unit that I wish to control the boost mode by using a smart switch. I am hoping that I can find a solution using a Shelly Relay. I am not an electrician, reading the manual for the extractor unit here: https://asset.eezybridge.com/ba7b9546-29dd-40c4-87a7-885627281b87/VA_LC_Sent_Multivent_FW.pdf I see that a low voltage 5V output can be switched to turn boost on. However, there is no neutral, only ground. can someone help make a recommendation on how I would best achieve this please Quote Link to comment Share on other sites More sharing options...
DavidAnstee Posted July 9 Author Share Posted July 9 I am thinking I would need to use the Shelly Dimmer 2 with Bypass wired as per this illustration. please could someone validate this for me Quote Link to comment Share on other sites More sharing options...
Members thgoebel Posted July 10 Members Share Posted July 10 (edited) Switching inductive loads (e.g. motors) with Shelly Dimmer2 is not recommended: (Excerpt of manual). To your issue: In the Vent box, there is live and neutral. You may control the vent with low voltage signals, which can be driven by a Shelly UNI plus. Even the supply voltage of the Shelly UNI plus may be furnished by the vent (5V DC), if I read the manual correctly. Edited July 10 by thgoebel 1 Quote Link to comment Share on other sites More sharing options...
Heinz Posted July 10 Share Posted July 10 in theory, the dimmer seems like the correct choice here but it was not designed for this type of use case, and as @thgoebel said when it's for an inductive load this will kill the device and cause more harm than good. This is use case I would make sure to read the instructions and know what is going on in that fan unit. Adding something afterwords to control the boost factor might harm that device's controller. Quote Link to comment Share on other sites More sharing options...
Members thgoebel Posted July 10 Members Share Posted July 10 (edited) A sketch may be helpful to visualise my thoughts: This follows the rules of the manual: Edited July 10 by thgoebel 1 Quote Link to comment Share on other sites More sharing options...
Members thgoebel Posted July 10 Members Share Posted July 10 A bit late (but not too late) I recognised that the inputs for speed control are working with positive logic. Hence, the diagram has to be amended: Sorry for this failure! 1 Quote Link to comment Share on other sites More sharing options...
DavidAnstee Posted July 10 Author Share Posted July 10 Thank you for the responses, super helpful and I truly appreciate it. thgoebel, on your updated diagram, the RS485 connections are labelled +5V and COM The extractor connections are +5V and GROUND. I want to double check, does Ground from Shelly Plus Uni go to GROUND on the RS485 connection on the extractor? sorry if this is a silly question! Quote Link to comment Share on other sites More sharing options...
Members thgoebel Posted July 10 Members Share Posted July 10 (edited) This is a typo: Replace „COM“ with „GND“. This is the correct diagram: Edited July 10 by thgoebel Quote Link to comment Share on other sites More sharing options...
DavidAnstee Posted July 10 Author Share Posted July 10 I figured that was the case, but wanted to double check. Thank you so much 1 Quote Link to comment Share on other sites More sharing options...
Heinz Posted July 11 Share Posted July 11 let us know when it worked for you would be a good thing to add to a use case Quote Link to comment Share on other sites More sharing options...
DavidAnstee Posted July 14 Author Share Posted July 14 I wired this up today and got it working. There was one thing missing in the diagram, in that the ground also needs to run to the D IN 1, I attempted to update the diagram here: 1 1 Quote Link to comment Share on other sites More sharing options...
Members thgoebel Posted July 14 Members Share Posted July 14 (edited) Thanks for the feedback and the update! The missing connection should have been detected right from the design stage. Obviously, this connection is essential for proper operations… Edited July 14 by thgoebel Quote Link to comment Share on other sites More sharing options...
Heinz Posted July 15 Share Posted July 15 awesome glad it worked for you Quote Link to comment Share on other sites More sharing options...
Members thgoebel Posted July 15 Members Share Posted July 15 This was my text, @Heinz! 🤓 1 Quote Link to comment Share on other sites More sharing options...
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