Is It Safe to Hard-Wire an AC Input SSR for Automatic Shop-Vac Control in Garage?

Hi Everyone, I'm new to the forum, I have a relatively simple question about hard-wiring an automatic shop vac turn on into the outlets which supply my tools in the garage. I've attached a diagram of what i'd like to wire (i've left out the earth, but this IS there!). just wanted to know if this will be ok to wire an AC input SSR like this? The SSR is essentially a black box to me.
Each tool is on a standard 13A type G plug. they each have a separate socket, all on its own MCB, via an isolator which i turn off when i'm out of the garage.
Suggestions/modifications welcome.
Are there use issues? (heat, voltage drop, etc.)
Is it safe?

Thanks in advance

Doesn't look right, but I'd need to know more about the SSR (Solid State Relay?) before advising further - do you have a type number so I can look up the datasheet?I assume what you're trying to do is make sure the shop vac is on before any of the other tools will operate?

Hi thanks for looking. I thought i put a link to the ssr i found, maybe it got modded out. Try this: https://www.thermosensedirect.com/acatalog/ssr-a1241_solid_state_relay_41_amp.htmlIm open to suggestions for parts though. (Within reason price wise)I dont think i explained the usage quite right. When i turn on a tool, i just want the shop vac to turn on automatically, and then turn off when i turn the tool off.  I dont necessarily need any delay. Then the changeover switch just bypasses the Ssr so i can use the vac separately too. Hope that makes sense?

Hi Dashiell.  OK, makes sense.  But the SSR you are using needs 240V across terminals 4 and 3 to put a short on terminals 1 and 2 (and hence switch your shop vac on).    As you have it, the other equipment will never come on, but when you switch any of the other equipments on, only the shop vac will come on.You need a relay that, when any of the other equipments draws CURRENT, will switch the shop vac on.  I don't know any commercially available unit that does that, except some power boards where current drawn in one outlet switches the other outlets on.  You can use them for things like computers, so switching your computer on will switch power on to the monitors, speakers etc.Theoretically they would work for you but they are not made for high currents cush as your power tools would draw, and would probably overload if you tried to use one of these.It sounds like you don't have much experience with electronics, and coupled with the fact that you are dealing with lethal voltages here, I am not going to suggest you build something to do what you want.Leave this with me for a day or two and I'll see if I can find something ready-made that will do what you need.

Dashiell this is the kind of thing I was thinking of.  But max 10A - probably not enough for your application.  Also this is Australian - but you'd find similar things with UK plugs I am sure.I'll keep looking.

Hi, thanks again. you are right, i dont have much electronics experience (did it for gcse, but i accept that means approximately zero), but am fine with household electrical stuff (which I have had signed off by a part p person).Thanks for clarifying, I had an inkling that placing the switch in series with the tools might give a voltage drop such that it stops the power tools from actually working (hence why i posted the question!).Yes, i have the automatic power strip for my hifi which is all separates, so would have to power on 5 different things. the problem with them is that they only allow one "master" controller, not several different ones.
I had a thought today that i could use one of the current sensing relays, which would avoid the need to hard wire in to the radial for the tools. and like you said, it's actually sensing current rather than voltage - something like this:https://www.measurementsystems.co.uk/sensors_and_meters/energy_sensors_and_meters/csg-650-series-solid-core-current-transducer-up-to-200a-0-5v-op
I cant see anything which has a 240VAC 15A output switch directly so would have to then go via a small plug in transformer (old phone charger etc) to an SSR which has a DC input and AC output.like this SSR:https://www.amazon.co.uk/KKmoon-24V-380V-SSR-40-Temperature-Controller/dp/B010Q6898C/
with all that in mind, i've drawn up a new (very badly drawn) circuit in the attachment.

Dashiell, that's the idea but- the current sensor won't drive the relay directly.- you only need the live wire going through the hole in the current sensor.  If you have both (live and neutral) they counteract each other....The current sensor will put out a voltage between 0 and 5V AC depending on the current that is going through the wire, and the type of sensor - a 10A sensor would put out 5V AC if there's 10A going through the wire in the middle hole.So you'd need to - rectify that voltage- have an amplifier and comparator so that any voltage over (say) o.5V from the sensor (corresponding to 1A drawn) switches on a relay that powers the rest or the equipment.From you previous link I see the same company makes an SSD with a 12V input which would be  fine to use - you'd need a 12V supply which could power the Amplifier / Comparator and also the relay.  It's not a difficult thing to do but would need a bit of electronics experience to construct.Here's how that fits into your diagram
I'd hope someone makes something that does this, I'll keep looking, sorry been at work and busy.....

Dashiell there are things that do this but they also cause a sharp intake of breath - price $200 +What sort of price would be acceptable to you for something that you just wire in?

David, your advice on this is ace!I didnt realise the current sensor would output proportional to input current, I thought it was more like a switch.magnetic fields cancelling out makes sense, in my head I had it as designed to have a whole twin and earth wire though the hole - oops.This looks more like a switch output:https://www.amazon.co.uk/Normally-Current-Sensing-Adjustable-SZC23-NO-AL-CH/dp/B07PLXC82G/
If I use that, could i remove the 4.8v supply and the amplifier/comparator? Then power the solid state relay from a 12Vdc supply, via the current sensing switch's output??Or since the current sensing switch says its output switch is rated at 0.5A 240Vac, i could wire it to the 240vac live, and then to the original (ACinput to ACoutput) SSR? would that give the desired result? if so would it require a resistor to limit current draw to 0.5A? (I dont particularly like the idea of having an extra transformer plugged in the whole time)Price wise when i dreamed up the project i thought there would be a solution already able to be purchased for maybe £10-20 (similar to the master/slave power strips). Having the ideas go round my head a lot since starting this thread, i'd like to see the project through to the end. design specs are: use as few components as possible, aim for elegance, simplicity and reliability. AU$200 I feel is excessive.Sorry i must seem like an annoying child asking so many dumb questions.

Dashiell, it's no problem giving advice that is appreciated, so don't be afraid to ask questions.That current sensor you found is exactly what you need, and a very reasonable price.  As you say, its output capability is a bit low, but you can use it to drive the SSR you already have.  For clarity here's a new diagram (though it's not a very clear diagram after being copied so many times).  If anything is not clear let me know and I'll get a better one to you.  The LIVE feed wire to the machines passes through the hole in the sensor.Note - the sensor itself will drive 240V x 0.5A = 125W.  If your Shop Vac is 100W or less you could drive it directly from the sensor.  But the SSR is a good idea in any case.You don't need a resistor - the current sensor output can switch the mains live direct to the SSR, the SSR input will not take a lot of current so does not need limiting.Note that with this or any current sensor, you can increase the sensitivity by looping the wire through the hole one or more times.  If the minimum sensitivity of the sensor is 0.2A, and one of your machines only takes 0.1A,  if you loop the wire twice through the hole in the sensor, that will simulate a 0.2A current (2 x 0.1A).  However as the maximum current is 30A you could then only draw 15A max for the same reason.  However 0.2A x 240V  is around 50W and I'm sure all of your machines would draw that, so you probably won't need to do this - any machine taking above 50W will make the ShopVac come on.I think this will do what you want, but do take care and I'd strongly suggest getting a qualified electrician to wire this up or at least check it for you.  Let me know how you go.

david, fantastic! that diagram is what i imagined. after reading the first paragraph of your reply, I wondered whether looping the wire would increase sensitivity, and then you explained that too!I've ordered parts and will post follow up when i've hooked it up and it knocks out the local substation - haha.I didnt realise that the current detector would overload at sensed current greater than 30A, i thought it was just the adjustable minimum sensing range was 0.2-30A, so thanks for the clarification.Shop vac is 1250Watts, tools are between 300W and 1200W each, though i find it unlikely they constantly run at full power, and these numbers probably dont reflect inrush current. Each tool is on an individual 13A fuse. I never use more than one tool at a time, so double loop to increase sensitivity should be fine, but i'll try without first. It's also on a 16A circuit breaker, so a double loop should trip above 32A sensed, hopefully there's some redundancy in the 30A figure if a double loop is required.i find it amusing that the shop vac is the highest powered device!

also found the current sensing switch at an even lower price, fingers crossed for quality control.https://www.amazon.co.uk/gp/product/B07WSDD596/

Dashiell as you say the range is 0.2 to 30A, I would imagine it would be able to take a fair bit more than that though, but to be safe stick to that range.If you loop the sensing wire, your adjustment range would be 0.1 - 15A, you have a 16A breaker so you'd probably be ok.  There is no datasheet on the web page so best not to assume.  I'd try it with single wire first and if it does not switch the ShopVac on for some things, double it.Great you found it cheaper too, that's a very handy gadget.