I'm adding to this thread because of the topic title
"Are automatic vac switches safe?".
Yesterday evening when I was shutting things down and closing up my garage shop for the day I happened to have a tool plugged into the duplex outlet where my miter saw is also powered from. I have an iVac Tool installed there to activate the dust collector when the MS starts. It has worked fine for years, and still does.
Note: I want to say up front that my iVac system is old, very old. Most of the sensors are over 10 years in service with me and I bought all of them new. I may have bought them as far back as 2005. The serial numbers on my devices are low, only three digits, so I think they are very early models. I did replace the iVac Switch not long ago (see my post above). I don't think they even make the same model tool sensors as I have today. It is possible the condition I am seeing is due to aging of components in the sensors and not any design flaw or other issue with the iVac system. I'm not faulting iVac in any way here.
But what concerned me was when I went to unplug the other tool my hand brushed up against the plastic box of the iVac Tool sensor and it was warm. Problem is it is NOT warm in the shop. It was at that time about 59°F in the shop but this felt warm to my hand so certainly warmer than 59 and probably more like 90°F. I had not used the MS all day, so I knew it was not from current flow to the tool that was causing the sensor to feel warm.
I unplugged the iVac sensor from the wall and went in the house to retrieve my IR thermometer. By the time I got back and measured the outside of the sensor box it was 84°F. I then opened the box to see if I could identify the bad component. I was thinking there is probably a voltage regulator for the transmitter (that sends the start signal to the Switch on the DC) that might be ready to fail after 10+ years. I wanted to see if I could visually ID the overheating component or possibly use the IR thermometer to locate it. There is plenty of room in the box as I found out and narrowed the hot spot to that where you see the red from the aiming laser of the thermometer in the photo. Now 76°F is not hot I know but this is after being unplugged for at least 10 minutes, so it has cooled off from when I first discovered the issue. It's out of focus but if you look at the display on the thermometer closely you'll see at the bottom the max temp recorded was 80.4°F for that scan. When I plugged the iVac sensor back in with the back cover off the temperature started to rise after a couple minutes so I unplugged it. I went around the shop and unplugged all the other tool sensors and the DC switch until I figure this out.
I checked my other 4 iVac Tool sensors I have in the shop and they were all cold. So I think this is an isolated incident related to age of my particular devices. I've removed this iVac Tool sensor from service and will be looking for a replacement. I might have one spare that I bought in the original batch but not sure. If not I will get one of the new sensors which clamp over the tool's power cord. Only thing I don't like about the new design is now you need an additional receptacle to power the sensor since the sensor no longer passes power through to the tool.
https://www.leevalley.com/en-us/sho...o-dust-collection-control-system?item=03J6225
If anyone else has any of the older sensors or switches, it might pay to check on them. I'm going to email iVac and see what they think and I will add their reply to this post when I hear back from them. Until then I won't be leaving any of my iVac devices plugged into the receptacles when I am not in the shop. It will be a PITA but not as much as dealing with a fire however how small it might be. I wish I had a sub-panel for all the shop power that I could throw one lever and disconnect the whole shop when I walk out of there but it's not wired that way. I am lucky in that there are three 120V, 20A circuits for tools and one 240V, 30A circuit for the table saw plus the lighting circuit in there so can't complain.