amps watts kva etc

[mitzimad]

IN my workshop i have a 15 amp mitre saw which is 110volts ive recently got a dust extract vacuum which has the outlet socket to turn on the vac when a power tool is turned on,this socket is rated at 1400watts .I'd like to use it on the saw but im guessing the 2.25kva transformer is to big for the outlet socket.Is there a way round this?
first thought is could i use a smaller tranformer for the saw which would draw less than 1400 watts or can i rig up a relay to be activetd from the 1400 watt socket and switch the existing transormer on or any other sugestions
Ive just realised that using it to fire the tranformer might switch the vac on even with out the saw being activated so maybe i need to put a relay on the 110 side so it only sends power to the saw when saw is activated obviously with a 240 supply to the transformer as it is now
im now rambling so input welcome

 

[St3v3]

Show us the data plate for the saw.

 

[tinkertaylor]

110v x 15A = 1650 kva, the transformer will pull more than that as they run at about 90% efficiency. You need to use a contactor from the fan supply socket to the contactors coil and supply the saw through the contactors main contacts.

 

[DBK]

I suspect you could get away with it if you use the mitre saw gently so it doesn't draw full current. If you fit a 10A fuse to the saw this should protect things but there will be a risk. Matching things correctly is the only real answer.

 

[mitzimad]

110v x 15A = 1650 kva, the transformer will pull more than that as they run at about 90% efficiency. You need to use a contactor from the fan supply socket to the contactors coil and supply the saw through the contactors main contacts.

any links to the type of contator i need

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[mitzimad]

British General Fortress 20A DP Contactor NO - Screwfix

Order online at Screwfix.com. 20A. Double pole. Single-module. For use with consumer units and enclosures. Used to switch a circuit on or off from another circuit. Ideal for controlling large lighting loads, heating or ventilation systems. FREE next day delivery available, free collection in 1...

www.screwfix.com

and

Wylex NH ESE2 IP40 2-Module Unpopulated DIN Enclosure - Screwfix

Order online at Screwfix.com. Insulated enclosure for double pole RCDs. FREE next day delivery available, free collection in 1 minute.

www.screwfix.com

 

[mitzimad]

anyone confirm these will work

 

[tinkertaylor]

any links to the type of contator i need

AC 240V Contactor AC Coil <10kw load 3-Phase 1NO Motor Starter Relay | eBay

Find many great new & used options and get the best deals for AC 240V Contactor AC Coil <10kw load 3-Phase 1NO Motor Starter Relay at the best online prices at eBay! Free delivery for many products.

www.ebay.co.uk

This type, no guarantee on the quality of this particular one but its information listed would meet your requirements. I'm assuming the supply socket from the fan is 240 volts?

 

[St3v3]

You need to use a contactor from the fan supply socket to the contactors coil and supply the saw through the contactors main contacts.

You're missing the point here. The outlet from the vacuum is current sensing. When you start the saw, it senses the current and starts the vacuum. A contactor won't work.

mitzimad What exactly does it say on the saw data plate?

 

[tinkertaylor]

You're missing the point here. The outlet from the vacuum is current sensing. When you start the saw, it senses the current and starts the vacuum. A contactor won't work.

mitzimad What exactly does it say on the saw data plate?

I havent explained myself very well.Split the load through the contactor. Feed from the fan socket and a live feed through the contactor. Contactors coil fed from the fan socket supply socket. Probably be better to draw it tbh.

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[mitzimad]

Saw

 

[mitzimad]

Transformer

 

[St3v3]

Contactors coil fed from the fan socket supply socket. Probably be better to draw it tbh.

The socket will always have a voltage on it, so the contactor will be energised all the time. And you're potentially feeding back into the vacuum which could cause all sorts of problems not least it's plug remaining live...

Even how you were describing puts the full load on the vacuum socket before the contactor comes in. It might work for a while I suppose...

It's just an all round bad idea.

mitzimad I think you need a different vacuum or use it manually. Sorry.

 

[tinkertaylor]

Plug the transformer into the fan supply and see if it triggers the fan with no load on the transformer it it doesn't then I will draw a schematic tomorrow to show you how it could be wired.

 

[St3v3]

Plug the transformer into the fan supply and see if it triggers the fan with no load on the transformer....

What do you think that is going to prove?

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[Itsmcb]

Why not keep it simple and just turn the extractor on when your going to use the same

 

[tinkertaylor]

What do you think that is going to prove?

If the transformer triggers the fans sensing circuit with no load on it then there's no point in persisting with any possible solution, the fan will be permanently on.

I'm trying to offer a solution to a problem, I'm sorry if that has upset you.

 

[St3v3]

If the transformer triggers the fans sensing circuit with no load on it then there's no point in persisting with any possible solution, the fan will be permanently on.

How does that tell you if the output, and therefore your contactor, is live/energised?

I'm trying to offer a solution to a problem, I'm sorry if that has upset you.

What upsets me is people ignoring logical advice to prevent a premature failure or potentially dangerous solution and encouraging others to spend money to achieve this.

 

[mitzimad]

manual it is then for the saw ,vac will be ok auto for my hand held for small tools

 

[Itsmcb]

Why not keep it simple and just turn the extractor on when your going to use the same

same? I'm sure I typed saw

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[tinkertaylor]

How does that tell you if the output, and therefore your contactor, is live/energised?



What upsets me is people ignoring logical advice to prevent a premature failure or potentially dangerous solution and encouraging others to spend money to achieve this.

Forget the contactor, the fan could be triggered by the transformer primary windings without load on the secondary. Anyway spent to much time on this, time to move on.