Thread: Switch on generic 2 HP duct collector

Protective chainsaw pants/trousers/chaps are designed with an inner and outer layer of a material like ripstop/ballistic nylon in between which are long woolly of kevlar fibre. When the chain comes into contact with the outer layer it cuts through the nylon and pulls great handfuls of the kevlar fibres out and this jams the saw in a split second usually before the chain manages to cut through the inner ayer of nylon. Now the sort of trousers that work very effectively on a 90 cc (7HP) chainsaw won't work on 3HP electric. The electric has much more torque at low revs than a combustion engine but the electric will keep on going and cut right though these trousers.

If the impeller is jammed then of course there's no problem because the breaker will cut out pretty quickly. But it only needs to be turning a little bit where it might pull 50-60-80A of starting current which is an awful lot of oomph to try and stop with soft skin. Thing is it all happens so quickly you don't have time to react. Like I said a 12" impeller has a lot of angular momentum and it takes a lot to stop it. Just turn your DC off and wait till it spins down enough to where you can just see the individual blades moving (~ 2 rpm), it won't even look like its moving that fast, and then try to stop it by hand - NO please don't do it. How do I know - you should be able to work that out.

Just a quick add on. If you are switching dc you should not use an ac switch as the flash over with dc is much higher and it will have a much shorter life. Use a dc contactor with a 12vdc coil on the unit and then you can switch that remotely. The 12v switch for the contactor coil can be where ever you are working and powered by a 240vac/12dc transformer plugged in some where handy.

DC as in Dust Collector not DC as in Direct Current

I set my unit up by removing the switch and placing it in an enclosure for switches and where the switch was fitted a couple of 15 amp inline fuses used to connect the wires. A plastic plate was fitted in place of the switch, to prevent entry of unwanted fingers.
The original switch was then mounted next to my lathe, which is central in the shed, a short extension cord was wired to one side of the switch, then another was run to the dusty and terminated at a 3 pin socket as used for lights.
The original cord was then plugged into it.
Can get a couple of pics tomorrow if needed.
Had a sparky look at it and he OK'd it.
Kryn

Originally Posted by Lappa

DC as in Dust Collector not DC as in Direct Current

That keeps catching me too...

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Well I'm a silly bunt. DC. Anyway back to the original problem, bypass the switch on the dc, use a 2 pole contactor with a 12vdc coil instead. Have a separate 12v supply. Wire it to a switch mounted on a small box with a 2 core cable back to the contactor and switch the dc from where ever you are working. A contactor is not that expensive and you can chose the coil voltage to suit. It doesn't need to be the same voltage as the unit that it is switching and then you only have a low voltage cable lying around the workshop floor.😁

Originally Posted by BobL

It would be simpler to hardwire one of these in between the DC switch and the DC.
https://www.ebay.com.au/itm/271968342893


2HP DCs draw up to ~30A on start up.
The ones above handle more 15A continuously and 30A peak power.

Thanks for that suggestion, Bob.
I got one of those doohickeys and inserted between the switch and the motor and now it works perfectly


If 'twere done, when 'tis done, 'twere well it were done quickly

Originally Posted by pintek

AC motors have about 7 times start up current - so a 10A motor can draw up to 70 amps when starting so normal 10A contacts in a wireless unit will burn out as you have found. If you have a tamed sparky that drinks (spolier: most of us do) get him to wire your wireless remote output onto a control contactor. The contactor does the heavy lifting and your wireless unit will last for ages.

Excuse my ignorance, these remote power switches are all rated up to 1200 watts. Any issues in plugging a 1600 watt shop vac into it or a 2000w compound mitre saw?

Originally Posted by Charlie_6ft

Excuse my ignorance, these remote power switches are all rated up to 1200 watts. Any issues in plugging a 1600 watt shop vac into it or a 2000w compound mitre saw?

Which remote switch are you referring to?

Originally Posted by BobL

Which remote switch are you referring to?

OK I think I got my wires crossed somehow, both the below are rated to 2400w:

https://www.arlec.com.au/wp-content/files/RC10.pdf

kogan.com

Let me restate my question. I have a Protool Shop Vac. The 'Power Tool Activation' is rated to 1200w. I know the Makita 42L L-Class is rated to 1100w. Machines like larger routers and compound mitre saws are 1600w - 2000w. So I assume plugging these sort of machines into these vacs is a no go.

They will work for a while.
“while” could be a few years or a few months.
It depends on a few things like start up loads, actual load, and number of times the switch is used.
some folks get away with it others don’t.

Just because a machine says its eg 2000W doesn’t mean that much as is just a nominal max output but if the machine is pushed HARD it can draw a lot more power than this. Most machines, circuits, and breakers can tolerate brief overloads but remote switch like those are far less tolerant.

Originally Posted by BobL

They will work for a while.
“while” could be a few years or a few months.
It depends on a few things like start up loads, actual load, and number of times the switch is used.
some folks get away with it others don’t.

Just because a machine says its eg 2000W doesn’t mean that much as is just a nominal max output but if the machine is pushed HARD it can draw a lot more power than this. Most machines, circuits, and breakers can tolerate brief overloads but remote switch like those are far less tolerant.

Thanks Bob, good to know