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Relay for Extractor Fan


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I have aย 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
ย 

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

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Posted (edited)

Switching inductive loads (e.g. motors) with Shelly Dimmer2 is not recommended:

IMG_1200.thumb.jpeg.832f097a06ab83f2d2b91ca40dbeed52.jpeg

(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 by thgoebel
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in theory, the dimmer seems like the correct choice here but it was not designed for this type of use case, and as @thgoebelย said when it's for an inductive load this will kill the device and cause more harm than good.ย 

This is use case I would make sure to read the instructions and know what is going on in that fan unit.ย 
Adding something afterwords to control the boost factor might harm that device's controller.ย 

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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!

ย 

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  • 2 months later...

I have an old model MVHR Vent-Axia 181520 which run 24 * 7.ย 

https://asset.eezybridge.com/nc/ba7b9546-29dd-40c4-87a7-885627281b87/Lo-Carbon Multivent - F&W Instructions (181520).pdf

I ordered a Shelly 1 mini relay to put in place between the power isolator inside the cupboard and the extractor.

I spent hours to learn through the cabling and prepared the fuse spur with switch for the connection. (First photo)

After I cut the power cable, I find out that the power cable is a 3 phase cable instead of the typical electric cable. (Second photo)

I am not sure why the developer use a 3 phase cable for the connection of this extractor as according to the installation manual, the extractor do not consume lot of power. Sounds like the extractor speed control is based on the cable connection but there is no control switch that I can find in my apartment. Only one isolator inside the cup board to switch the system on and off.ย 

I wonder if there is any suggestion on how I can add a Shelly relay in between the 3 phase cable and the extractor?ย 

Thank you!

ย 

IMG_8107.jpg

IMG_8119.jpg

IMG_4457.jpg

Edited by hkychan
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Posted (edited)

Did you read this:

https://www.smarthome-forum.eu/thread/16076-shelly-1-ventilation-system-vasco-dx4/?postID=166552#post166552

???
ย 

One of the diagrams in the above linked thread is this:

IMG_2269.thumb.jpeg.2e86c4febbaa1bec1578d3388c22b94e.jpeg

This ย arrangement allows to control three speeds of the ventilation system plus an on/off function with a similar vent control. But it is NOT the same!

In the case your local regulations specify a two-pole cut-off of mains voltage, you must arrange a manual pole switch before the Shelly L/N for security reason. This is shown in the manual:

IMG_1606.thumb.jpeg.c3c916173b95d499bfbe64e0864bbc7b.jpeg

ย 

ย 

Edited by thgoebel
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Posted (edited)

A diagram which fits for theย MVHRย Vent-Axia 181520 is shown below:

IMG_1607.thumb.jpeg.c2328847f2e7b487c21ee03d0e8e7608.jpeg
It should be made sure that the โ€žmediumโ€œ and the โ€žhighโ€œ Shelly are NOT engaged at the same time! This can be solved by a Shelly plus 2PM in cover mode:

IMG_1609.thumb.jpeg.7f94c08d3ac5392d3f5357e818143658.jpeg

ย 

Unfortunately, the on-time of a Shelly plus 2PM cannot be set to infinite. Thus, a limited run time for โ€žmediumโ€œ and/or โ€žhighโ€œ is obligatory. This can be amended with an โ€žoldโ€œ Shelly 2.5 or a script.

ย 

Edited by thgoebel
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Hi thgoebel,ย 

Thank you so much for your response. There is an isolator installed in between the MVHR and the power source. (First photo)

The switch is placed inside a cupboard that is very difficult to reach. Hence, I wanted to place the Shelly mechanism in between the Isolator (manual pole switch) and the MVHR.

The cable is in Brown, Black, Grey + Metal Earth. I think it has no "Neutral". As I can read from the installation manual, the extractor is running at 60W which seems to be the power consumption of a light blub. Sounds like the use of this 3 phases type cable is for the control of the speed.

May I assumed hereย 

  • Grey Cable = Black/W L1
  • Black Cable = Black L2
  • Brown Cable = Brown L3
  • No Blue
  • Metal Cable = Green/Yellow (Earth)

I only wanted to control the on and off instead of the fan speed. Is this means I can just connect the Grey Cable, Black Cable and the Metal Cable directly as original. Only put the Shelly Relay in between the Brown? Now I have the Shelly 1 Mini Gen 3 (8A), assumed it should be good enough to handle the 60W power requirement.

Or

I still need to get the Shelly plus 2PM to complete the circuit connection requirement?

Looking forward to your advice.

IMG_8174.jpg

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Posted (edited)

Youโ€˜ll have to identify the wires before and after the isolator: The black/black/brown cable should end at the isolator. Check the colours and determine which is live and neutral. Double check with measurement! Next step will be to insert an appropriate Shelly device in a diagramโ€ฆ

ย 

@moderators: IMHO, it would be adequate to move this discussion in a separate thread.

Edited by thgoebel
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I think I got the idea after watching a YouTube video as the cable it mentioned is exactly same as my situation.

ย 

Black = Switch
Brown = Live
Grey = Neutral
Metal = Earth

  • I will connect the Earth (Metal) in both end, Switch (Black) in both end (It is a fixed speed setup)
  • Live (Brown of the cable from the Isolator) connect to the "L", "I" of Shelly 1 Mini Gen 3
  • Load (Brown of the cable connect to the extractor) connect to the "O" of Shelly 1 Mini Gen 3
  • Neutral (Grey of the cable from the Isolator) connect to "N" of Shelly 1 Mini Gen 3
  • Neutral (Grey of the cable from the Isolator) connect to Neutral (Grey of the cable connect to the extractor)ย 

This way I can control the on/off of the extractor with a fixed speed setup

I will of course double check the wiring inside the Isolator to confirm if Grey is used as Neutral.

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