Simple Electrics Question:

[Scrums]

Hi all,

simple, I expect, but not to me.....I have an extractor working off it's own nvr swith (240v).....what I'd like is to have a pull cord switch, handier to the machine it extracts....do I 'loose' the nvr switch altogether and wire mains directly from the pull cord to the motor or what?

PS: I know I need to check the wattage/amperage first and may need to use a heavier rated switch.

Chris.

 

[PeterSk]

The point of the NVR is to stop tools bursting back into life after a power cut which could well be dangerous depending how they've been left. OTOH an extractor switching on by itself really doesn't seem to be a hazard to me, so I'd be quite comfortable running it from a normal switch.

I would guess that a pull switch for an electric shower might be man enough to handle a decent sized extractor

 

[CHJ]

For safety you do not want to have a permanent direct connection, best to have your pull switch feeding a power socket extension for the extractor to plug into, that way you retain the fusing in the plug and provide safety for servicing.

You can possibly just in-line connect the switch leads that are feeding the switch with spade connectors at the back of the NVR so that it is easily re-instated if reqd. later. and this will allow the connectors to be well protected.

I would strongly advise that you instigate some form of safety arrangement for when you are servicing the extractor that enforces you to disconnect (unplug it) from the supply before you can remove the input hose from the machine. Don't want hands clearing shavings from a blocked fan with the potential for power to be engaged.

Mine is arranged such that I have to unplug it from local remotely switched socket before it can be pulled out to service (short Power lead)

 

[Jonzjob]

Another option would be to put your pull switch after the 'no volt' switch. That way you have the convenience and the safety.

Something that I found with the 'no volt' switch that I fitted onto the 3ø converter for my lathe was that ude to the vaguries of French wiring (they don't give 2 short pony poos which is line or nuetral!) I had connected line to neutral on the input and as soon as the converter was plugged in it swithced the no volts switch on! If you pushed the off it dropped but as soon as you let go so it switched back on again! I reconnected the supply correctly and all works OK now. I have NO idea as to how, but there was 27 volts on the pull coil on the relay in the switch and it was enough to pull it in as soon as the converter was plugged in. Perfectly OK on my router table though!?

 

[CHJ]

Another option would be to put your pull switch after the 'no volt' switch. That way you have the convenience and the safety.

John that is a NO NO. a potentially dangerous situation as the NVR will remain live and afford no protection other than after a power disruption at source. If the extractor is not running there is no reminder to kill the supplies at source, Hobby type equipements are usually fitted with light duty NVR's and the coils may not stand up to being powered 24/7.

Having said that regardless of whether an NVR or standard switch is fitted in the supply line to any equipment it should always be isolated from the main source of power by unplugging or throwing the master isolator switch before any work, switches/NVR's can and do fail and you don't want to be working on something with a local welded switch contact in the line just waiting for the circuit to be completed with a knock etc.

 

[Jonzjob]

Point taken Chas. But the idea would be to switch it on when entering the workshop and off when you leave, using the pull switch for on/off as wanted through the course of the day. Also off for any time that you need to stick personal bits in the machine..

The 2 that I have in my workshop, one on my router table which is not in contiuous use and always unplugged when not in use and the other on the new setup on my lathe which is the supply for the converter so I can see if it's no purely by the fact that the display is illuminated. Once again not in continuous use..

 

[Scrums]

Well people....wasn't intending to get the elf and safety contingent out of bed on a Saturday :lol:

It occurred to me immediately after I posted the question, that if you retain the NVR switch, even if you do have a pull cord - you still have to go to the switch after shutting it down.

So - to keep everyone happy - mains power into Shower heater type Pull cord switch, from there to Fused spur, thence directly to Motor of aforementioned dust extractor. (pull fuse whenever maintenance to be done)

...sound feasible?

Chris.

 

[CHJ]

....So - to keep everyone happy - mains power into Shower heater type Pull cord switch, from there to Fused spur, thence directly to Motor of aforementioned dust extractor. (pull fuse whenever maintenance to be done)

...sound feasible?

Chris.

Better still make that spur termination a socket outlet and plug your extractor (minus it's (bypassed) NVR switch) into that. You can then pull the plug out when servicing, then all mains wiring will be disconnected.

No chance of the extractor starting up or you testing any RCD in your workshop supplies to see if it works.

 

[dickm]

Not an electrician, so don't know if this is feasible, but could you connect a normally open switch across from live to the starter relay part of the NVR switch? (effectively parallelling the start button). This could be anywhere convenient - even in the ceiling with a cord - and would give remote starting without affecting safety? Wouldn't it?
Where's Bob (9fingers?)

 

[GPB]

I've suspended my extractor NVR switch from the roof by a length of chain which keeps the strain off the cable.

This way its near the saw but being above head height it's out of the way.

 

[9fingers]

Not an electrician, so don't know if this is feasible, but could you connect a normally open switch across from live to the starter relay part of the NVR switch? (effectively parallelling the start button). This could be anywhere convenient - even in the ceiling with a cord - and would give remote starting without affecting safety? Wouldn't it?
Where's Bob (9fingers?)

Who Me? I'm just wearing my "if they need to ask then they maybe should not be contemplating doing this" hat and watching! :lol:

DickM -This would give remote starting but no ability to stop the extractor.

I'd possibly go for the shower switch fitted after the optional NVR.
If the NVR is used then it is just a case of pushing the start button for the first time in the shop and hitting stop when you leave.
A long string running around the workshop with pulleys if needed can be used to start the extractor from easy reach of any machine.

In my shop, all the sort of functions needed only when in the shop are enabled when the door is unlocked just leaving battery charging, background heating and security powered up when the door is locked.
Saves all those 'Did I turn off the xxxx?' doubts.
Even better is my rather over-the-top indicator in the house as to whether the shop door is locked or not.

Bob

 

[dickm]

Not an electrician, so don't know if this is feasible, but could you connect a normally open switch across from live to the starter relay part of the NVR switch? (effectively parallelling the start button). This could be anywhere convenient - even in the ceiling with a cord - and would give remote starting without affecting safety? Wouldn't it?
Where's Bob (9fingers?)

Who Me? I'm just wearing my "if they need to ask then they maybe should not be contemplating doing this" hat and watching! :lol:

DickM -This would give remote starting but no ability to stop the extractor.

Bob

.
Hadn't thought that far! But, somewhere around my "come in useful sometime" corner, there's a remote start/stop switch. Presumably, you could use my suggestion, but pair it with a remote stop as well?