It is currently 28 Mar 2024, 16:41

I don't want this NVR switch

Here's the place to talk about all your table saws, bandsaws, routers and dust extractors. In fact anything that makes noise and uses electrickery.

Re: I don't want this NVR switch

Postby 9fingers » 07 Mar 2016, 13:07

Which brings us full circle.
These remote control switches are just not man enough to start a 3hp motor.
The solution is either to use a DOL starter and modify it or Dave's cheaper solution to use a chunky relay driven by the remote control switch to start the motor.

Bob
Information on induction motors here
https://drive.google.com/file/d/1dBTVXx ... sp=sharing
Email:motors@minchin.org.uk
User avatar
9fingers
Petrified Pine
 
Posts: 10038
Joined: 21 Jul 2014, 20:22
Location: Romsey Hampshire between Southampton and the New Forest
Name: Bob

Re: I don't want this NVR switch

Postby Wizard9999 » 07 Mar 2016, 13:34

Sorry guys, I really am trying, but this is just not my thing. My dad trained as an electrician at 14, so I fear he is turning in his grave :oops:

So, on the basis I have found a remote control plug in socket job rated at 3120w (over three horse power unless I have that wrong as well) I can essentially dispense with a switch on the extractor all together. I just need to bypass the NVR switch they have fitted and wire the motor (most likely using a connection box of some sort) to a plug, put that into the remote plug thingy and plug that into my main socket. Correct :eusa-pray: .

If so, assuming I use the original flex and plug which is currently attached to the NVR switch all I need to acquire is a suitable form of connection. Am I still on the right track here? If so, are we just talking about those connector strips* that you cut to length? If I am removing the NVR switch I could tuck it into the space that sits in and make a little blaming plate with a hole for the flex to come out of.

Again, thanks for your patience!

Terry.

EDIT: * as it is running off a 13amp plug am I right in assuming a 15amp connection strip is adequate?
Last edited by Wizard9999 on 07 Mar 2016, 13:38, edited 1 time in total.
Wizard9999
Old Oak
 
Posts: 1409
Joined: 08 Aug 2014, 11:51
Location: Eversley, Hampshire
Name: Lord Radford

Re: I don't want this NVR switch

Postby 9fingers » 07 Mar 2016, 13:37

No Terry. Read my last post please.
Information on induction motors here
https://drive.google.com/file/d/1dBTVXx ... sp=sharing
Email:motors@minchin.org.uk
User avatar
9fingers
Petrified Pine
 
Posts: 10038
Joined: 21 Jul 2014, 20:22
Location: Romsey Hampshire between Southampton and the New Forest
Name: Bob

Re: I don't want this NVR switch

Postby Wizard9999 » 07 Mar 2016, 13:39

9fingers wrote:No Terry. Read my last post please.


But Bob, as said, I have located a 3120w remote switch, sure this is adequate for the 3 hp motor?
Wizard9999
Old Oak
 
Posts: 1409
Joined: 08 Aug 2014, 11:51
Location: Eversley, Hampshire
Name: Lord Radford

Re: I don't want this NVR switch

Postby 9fingers » 07 Mar 2016, 14:31

No Terry it won't. Your DC will draw something in the region of 30 amps on startup and that will weld the contact of the relay closed very soon if not immediately.
There are countless post on forums about starting surges, the need for type C breakers, lights dimming on motor start-up etc some of which you must have seen.
We even discussed it in this very thread why saying that the NVR on your DC is rather under specified.

Both Dave and I are more than willing to offer help but we would hope that some knowledge will be gained by readers in the process. This is not meant to come over as arrogant but I have to confess that a germ of frustration is creeping in.

Bob
Information on induction motors here
https://drive.google.com/file/d/1dBTVXx ... sp=sharing
Email:motors@minchin.org.uk
User avatar
9fingers
Petrified Pine
 
Posts: 10038
Joined: 21 Jul 2014, 20:22
Location: Romsey Hampshire between Southampton and the New Forest
Name: Bob

Re: I don't want this NVR switch

Postby TrimTheKing » 07 Mar 2016, 15:08

9fingers wrote:...a germ of frustration is creeping in….


Have to be careful wit this Bob, I'm afraid I'm with Terry here. I am an intelligent man (as much as I like to pretend otherwise) and can turn my hand to pretty much anything, but some of your explanations on what you deem 'very simple' electrics/electronics make zero sense to me at all! You make a number of assumptions that people even know what a relay is or does, I don't (not without going away and reading up, which I do/will)!

I personally am more than capable of learning and willing to do so, about these things, but even googling some of the things you write about before coming back with 'dummy' questions, can be a fruitless exercise because a lot of these things seem to be written in a deliberately non-decipherable way unless you have a strong base level of knowledge/understanding of electronics and the terminology used.

I, and many others I'm sure, absolutely value and welcome your's and Dave's advice, help and input, but if it frustrates you that you can't get your point across then I'm afraid that isn't going to get any better as this just isn't an easy subject for someone who has never done it before… :oops:

Cheers
Mark
Cheers
Mark
TrimTheKing
Site Admin
 
Posts: 7565
Joined: 16 Jun 2014, 13:27
Location: Grappenhall, Cheshire
Name: Mark

Re: I don't want this NVR switch

Postby DaveL » 07 Mar 2016, 16:41

OK, let's try to enlighten you about starting a motor and why the remote control sockets cannot cope.
The socket rating is based on a resistive load, like an electric heater, these if rated at 3kwatt will only take 12.5 amps. At switch on they take 12.5 amps and the current will not change significantly while they are on.
An electric motor on the other hand is an inductive load, the current will vary depending on the speed of rotation and the mechanical load the motor is trying to turn. When the power is applied to a stationary motor, there is a very large in rush current, this is often 3 or 4 times the full load current that the motor would take. So for a 3HP motor the full load current is about 10 amps but the start-up current is between 30 and 40 amps, it's not that high for very long but it can often trip circuit breakers, the way round that is th use a type B or C breaker, these have a longer trip time than the type A that are used for normal house hold circuits.
The start-up current will destroy contacts that are only rated for a resistive load, the usual failure mode is the contacts weld together when they are closed. Thus the circuit cannot be broken to stop the motor. The contacts in the switches used for controlling motors are very chunky to limit the size of the spark and dissipate the heat so they don't weld together.
This is why Terry needs either a big relay, (my solution) or a DOL starter, (Bob's solution) to control his dust collector.
The other option is to use a manual switch rated at a high enough current to cope with the start-up current, the pull cord switches use to isolate electric showers are the best ones, rated at 6 kwatts or more should survive.
Hopefully this makes it clear why a remote control socket is not up to the job.
Last edited by DaveL on 07 Mar 2016, 17:56, edited 1 time in total.
Regards,
Dave
My tool kit is almost complete, only a few more to get.
User avatar
DaveL
Old Oak
 
Posts: 1917
Joined: 21 Jul 2014, 21:07
Location: Sudbury, Suffolk
Name: Dave

Re: I don't want this NVR switch

Postby Wizard9999 » 07 Mar 2016, 16:43

Bob

I really appreciate your and everyone elses help, but Mark is right I am starting from a base level of knowledge that you probably can't really get your head around. I am willing to learn, or at least try and have read up n what a relay is / does, it seems jolly clever (http://www.explainthatstuff.com/howrelayswork.html) and having done so can appreciate what it is you and Dave are trying to explain. Well at least this is what I think you are saying, I plug the extractor into the wall having removed the NVR and replaced it with a "normally open" relay. That relay is then separately plugged in to the remote control socket device. When I press the button on the remote it powers the relay which itself up uses very little power, this then powers up an electromagnet that switches the extractor on.

But, in addition to little knowledge I have a number of people trying to help. Given my limited knowledge it seems to me that the advice I am getting from others is not the same as yours and Dave's as they seem to suggest I can just bypass the NVR, not add a relay and then plug the extractor into the power socket. Maybe the difference is that they are not trying to use a remote control socket, because at least one of them says this direct wiring has worked for them. Maybe it is just the case that, as in so many things there are a number of different ways to skin a cat, maybe you disagree with the other advice I am getting.

But I do still struggle to understand why when a remote socket is rated at 3120w it is unsuitable for a piece of equipment which is only c.2200w. Is it that an extractor draws a particularly large current on start up, whereas other 2200w devices won't?

Again, I am not trying to frustrate and apologies if that is what is happening.

Terry.
Wizard9999
Old Oak
 
Posts: 1409
Joined: 08 Aug 2014, 11:51
Location: Eversley, Hampshire
Name: Lord Radford

Re: I don't want this NVR switch

Postby Wizard9999 » 07 Mar 2016, 17:04

Wizard9999 wrote:But I do still struggle to understand why when a remote socket is rated at 3120w it is unsuitable for a piece of equipment which is only c.2200w. Is it that an extractor draws a particularly large current on start up, whereas other 2200w devices won't?

OK, done some more reading, so I will try and answer my own question. A 2100w hairdrier needs roughly the same power to run it as my extractor when it is up and going, but the difference is that my extractor has a great big impeller that needs to be moved from being stationary to spinning really fast (queue Newton's laws of motion), whatever is going on inside the hairdrier the moving parts are no where near as big or heavy. Therefore, to go from not working to working my extractor needs a big boost of extra power well above the stated 3HP, whereas the hairdrier probably needs only a little bit of a boost. As the power relates to the voltage and the current (I=P/V) and the voltage is fixed at 220, the only way to increase the power (P) (measured in watts) needed for start up is if the current (I) being drawn by the motor is increased and this is measured in amps. Am I even close?

EDIT: what I still don't really get is why this does not blow the 13amp fuse in the plug.

Terry.
Last edited by Wizard9999 on 07 Mar 2016, 17:14, edited 1 time in total.
Wizard9999
Old Oak
 
Posts: 1409
Joined: 08 Aug 2014, 11:51
Location: Eversley, Hampshire
Name: Lord Radford

Re: I don't want this NVR switch

Postby Wizard9999 » 07 Mar 2016, 17:08

DaveL wrote:OK, let's try to enlighten you about starting a motor and why the remote control sockets cannot cope.
The socket rating is based on a resistive load, like an electric heater, these if rated at 3watt will only take 12.5 amps. At switch on they take 12.5 amps and the current will not change significantly while they are on.
An electric motor on the other hand is an inductive load, the current will vary depending on the speed of rotation and the mechanical load the motor is trying to turn. When the power is applied to a stationary motor, there is a very large in rush current, this is often 3 or 4 times the full load current that the motor would take. So for a 3HP motor the full load current is about 10 amps but the start-up current is between 30 and 40 amps, it's not that high for very long but it can often trip circuit breakers, the way round that is th use a type B or C breaker, these have a longer trip time than the type A that are used for normal house hold circuits.
The start-up current will destroy contacts that are only rated for a resistive load, the usual failure mode is the contacts weld together when they are closed. Thus the circuit cannot be broken to stop the motor. The contacts in the switches used for controlling motors are very chunky to limit the size of the spark and dissipate the heat so they don't weld together.
This is why Terry needs either a big relay, (my solution) or a DOL starter, (Bob's solution) to control his dust collector.
The other option is to use a manual switch rated at a high enough current to cope with the start-up current, the pull cord switches use to isolate electric showers are the best ones, rated at 6 kwatts or more should survive.
Hopefully this makes it clear why a remote control socket is not up to the job.


Dave, so busy reading and typing I missed your post :oops: .

Terry.

Edit: Dave when talked about the heater did you mean 3w or 3kw?
Wizard9999
Old Oak
 
Posts: 1409
Joined: 08 Aug 2014, 11:51
Location: Eversley, Hampshire
Name: Lord Radford

Re: I don't want this NVR switch

Postby 9fingers » 07 Mar 2016, 17:36

Wizard9999 wrote:
EDIT: what I still don't really get is why this does not blow the 13amp fuse in the plug.

Terry.



The 13amp plug top fuse is a slow blow device and it takes a while to heat up and rupture. It is also a fairly crude device and not intened to be an accurate switch off at 13.01 amps.
Experiments i've done should that it you increase the current very slowly through a typical plug fuse you can get up to 25-30% more current through it. this is because the heat going into the wire to make it melt gets conducted to the body of the fuse and the wire takes longer/more current to melt.

Your dust collector, because it is a fan, the load on the fan increases with speed so the starting current is mainly devoted to overcoming the inetria of the rotor say about 3kg of iron acceleraring from zero to nearly 3000 rpm is nas a couple of seconds. The current drops with motor speed during acceleration and the load only comes on slowly so the 13 amp fuse just about copes.

However your saw (and mine) also has 3hp motor but has a belt drive desinged to increase the motor shaft speed to say 4500 rpm and a second shaft with a 10" blade to accelerate up to 4500rpm as well. This will eat 13amp fuses as fast as you like and why it has to have a 16 amp supply and a type C breaker which will take much longer to trip and by then the motor is up to speed and the current drawn is much reduced.

hth

Bob
Information on induction motors here
https://drive.google.com/file/d/1dBTVXx ... sp=sharing
Email:motors@minchin.org.uk
User avatar
9fingers
Petrified Pine
 
Posts: 10038
Joined: 21 Jul 2014, 20:22
Location: Romsey Hampshire between Southampton and the New Forest
Name: Bob

Re: I don't want this NVR switch

Postby old » 07 Mar 2016, 17:57

Yes that is it, its switched on from the socket .However i use the remote control switching unit that you are advised will not work ,but it has for three years and if it fails they are not expensive. I am only switching my SIP extractor unit about one hp. so 746 watts say 3 amps.It all works for me and is quite convenient.
User avatar
old
New Shoots
 
Posts: 101
Joined: 27 Jul 2014, 07:20
Location: Nantwich Cheshire
Name: Chris

Re: I don't want this NVR switch

Postby DaveL » 07 Mar 2016, 18:05

old wrote:Yes that is it, its switched on from the socket .However i use the remote control switching unit that you are advised will not work ,but it has for three years and if it fails they are not expensive. I am only switching my SIP extractor unit about one hp. so 746 watts say 3 amps.It all works for me and is quite convenient.

I have used a 1HP unit on a remote socket, it worked most of the time, but the start up current is 1/3 of that required for a 3HP unit that Terry is trying to switch. I upgraded from the 1HP blower and did not try the remote, I know they would fail. Some of them have a none replaceable internal fuse, having blown one and disassembled the unit to find out why it did not work. I find the buttons on the cheaper remote units are the weakest part of the system.
Regards,
Dave
My tool kit is almost complete, only a few more to get.
User avatar
DaveL
Old Oak
 
Posts: 1917
Joined: 21 Jul 2014, 21:07
Location: Sudbury, Suffolk
Name: Dave

Re: I don't want this NVR switch

Postby DaveL » 07 Mar 2016, 18:07

Terry,
Sorry yes it should have said 3kwatt, I have been back and corrected it, it was due to the auto correct on my tablet changing it when I was not looking.
Regards,
Dave
My tool kit is almost complete, only a few more to get.
User avatar
DaveL
Old Oak
 
Posts: 1917
Joined: 21 Jul 2014, 21:07
Location: Sudbury, Suffolk
Name: Dave

Re: I don't want this NVR switch

Postby Wizard9999 » 07 Mar 2016, 18:29

DaveL wrote:Terry,
Sorry yes it should have said 3kwatt, I have been back and corrected it, it was due to the auto correct on my tablet changing it when I was not looking.


OK Dave, hope it didn't come across as an attempt at a cheap shot, was just that if it had been 3w it would have meant I still didn't understand anything ;) .

OK, so I think I have learnt enough now to understand why direct wiring won't work for me but would work if I had a 1hp extractor and the 3120w remote plug I mentioned, i.e 735w x 4 for start up load is still only 2940w so ok for the plug, 2200 x 4 for start up is 8800w and would therefore fry everything very quickly. Sorry that it took me so long to get there.

But please, if anything in what I said above or in the last few posts I made in terms of my understanding is wildly wrong please point it out.

I have ordered the remote plug and will now order the relay, on reflection I may as well get the one from China as I have now hung the extractor on the wall so I won't be able to use it until all the ducting is installed which is bound to take a few weeks. I already have a double socket where the extractor will be, so using the 'Dave method' should work fine.

Terry.
Wizard9999
Old Oak
 
Posts: 1409
Joined: 08 Aug 2014, 11:51
Location: Eversley, Hampshire
Name: Lord Radford

Re: I don't want this NVR switch

Postby 9fingers » 07 Mar 2016, 18:50

Terry,

Something else to keep in mind is that Ohms law ( Voltage = Current x Resistance) and the power variant

(power = voltage x current) only apply for DC circuits and so it is dangerous to extend it to AC calculations.

In virtually every case the usable Power will be less than voltage x current but the supply, the switches will have to be rated for the voltage, the current and where appropriate the product of the two which is referred to as VA
ie VxA

Complicated init!

Bob
Information on induction motors here
https://drive.google.com/file/d/1dBTVXx ... sp=sharing
Email:motors@minchin.org.uk
User avatar
9fingers
Petrified Pine
 
Posts: 10038
Joined: 21 Jul 2014, 20:22
Location: Romsey Hampshire between Southampton and the New Forest
Name: Bob

Re: I don't want this NVR switch

Postby Andyp » 07 Mar 2016, 19:50

Oh dear. I have a twin motor Camvac rated ar 2kw ( 2x1kw) which I switch on via a remote controlled socket. Is this an accident waiting to happen?
I never even thought to ask before, ignorance is bliss.
I do not think therefore I do not am.

cheers
Andy
User avatar
Andyp
Petrified Pine
 
Posts: 11716
Joined: 22 Jul 2014, 07:05
Location: 14860 Normandy, France
Name: Andy

Re: I don't want this NVR switch

Postby 9fingers » 07 Mar 2016, 19:57

Andyp wrote:Oh dear. I have a twin motor Camvac rated ar 2kw ( 2x1kw) which I switch on via a remote controlled socket. Is this an accident waiting to happen?
I never even thought to ask before, ignorance is bliss.



Screamy- screechy brush motors have far lower mass armatures and so get up to speed faster than their more discreet induction motor relatives so you are far less likely to have a problem with your remote switch.

Bob
Information on induction motors here
https://drive.google.com/file/d/1dBTVXx ... sp=sharing
Email:motors@minchin.org.uk
User avatar
9fingers
Petrified Pine
 
Posts: 10038
Joined: 21 Jul 2014, 20:22
Location: Romsey Hampshire between Southampton and the New Forest
Name: Bob

Re: I don't want this NVR switch

Postby Wizard9999 » 07 Mar 2016, 22:10

Andyp wrote:Oh dear. I have a twin motor Camvac rated ar 2kw ( 2x1kw) which I switch on via a remote controlled socket. Is this an accident waiting to happen?
I never even thought to ask before, ignorance is bliss.


Whilst ignorance is bliss, my Dad used to say "a little knowledge is a dangerous thing". So you are no doubt safer than me :lol: That said, deploying my little knowledge, surely it depends on the rating of your remote socket. Somebody on another forum site was pointing people to one that was rated at less than 300w, the one I have bought is rated at 3100w, one would hope one would last longer than others.

Terry.
Wizard9999
Old Oak
 
Posts: 1409
Joined: 08 Aug 2014, 11:51
Location: Eversley, Hampshire
Name: Lord Radford

Re: I don't want this NVR switch

Postby Robert » 07 Mar 2016, 23:06

As these remote socket things are reasonably cheap why not just bypass the NVR and try it.

What's the worst that could happen? :)

I ran my old extractor off a 3KVA site transformer plugged in to a remote socket adaptor. It shouldn't have worked given the surge current but it did without problem for years and the same socket now powers my 240V extractor.
Robert
Old Oak
 
Posts: 2489
Joined: 21 Jul 2014, 19:31
Location: Woodford Green
Name: Robert

Re: I don't want this NVR switch

Postby Wizard9999 » 08 Mar 2016, 00:20

Robert wrote:As these remote socket things are reasonably cheap why not just bypass the NVR and try it.

What's the worst that could happen? :)


True, but the relay is less, so one failed remote plug would cost more. Not exactly life changing amounts though at £9 for the plug and £6 for the relay :lol: .

Terry
Wizard9999
Old Oak
 
Posts: 1409
Joined: 08 Aug 2014, 11:51
Location: Eversley, Hampshire
Name: Lord Radford

Re: I don't want this NVR switch

Postby RogerS » 08 Mar 2016, 07:19

DaveL wrote:.... I find the buttons on the cheaper remote units are the weakest part of the system.


:text-+1:

I've been using the Maplin remote sockets for sometime now. One feeds the Axminster ADE 2200 extractor (with a modified NVR switch as Terry would like to have his...ie no NVR function). The power of this is only about 1kw rating (Terry, that is some serious extractor you've got there !!) and no problems with contacts.

Ditto the twin-motor Camvac ....but if I follow the line of reasoning correctly, the inrush current is significantly less than an induction motor...because the Camvac is brushed. So no fears there, Andy.
If opportunity doesn't knock, build a door.
User avatar
RogerS
Petrified Pine
 
Posts: 13290
Joined: 21 Jul 2014, 21:07
Location: Nearly finished. OK OK...call me Pinocchio.
Name:

Re: I don't want this NVR switch

Postby Andyp » 08 Mar 2016, 09:31

Thanks Bob/Roger. reassuring to know. I never bothered to check if the remote socket had any sort of capacity/limit.
I do not think therefore I do not am.

cheers
Andy
User avatar
Andyp
Petrified Pine
 
Posts: 11716
Joined: 22 Jul 2014, 07:05
Location: 14860 Normandy, France
Name: Andy

Re: I don't want this NVR switch

Postby Wizard9999 » 15 Mar 2016, 21:40

Wizard9999 wrote:As usual, I am working at a rather pedestrian pace :oops: and have just come back to this topic. I followed Dave's link again and was going to buy one of these, but delivery could be lengthy with estimate anything up to 18 April. As the seller is sending it to me from Hong Kong at their cost I have no complaints, but ideally I'd like it sooner so that I can maintain my limited momentum.


Well, the chaps in Hong Kong have excelled themselves and the relay arrived today :eusa-clap: . So, what is my next step?

Terry.
Wizard9999
Old Oak
 
Posts: 1409
Joined: 08 Aug 2014, 11:51
Location: Eversley, Hampshire
Name: Lord Radford

Re: I don't want this NVR switch

Postby DaveL » 15 Mar 2016, 22:37

Oh bum, I have not sorted out the other bits you need.
Regards,
Dave
My tool kit is almost complete, only a few more to get.
User avatar
DaveL
Old Oak
 
Posts: 1917
Joined: 21 Jul 2014, 21:07
Location: Sudbury, Suffolk
Name: Dave

PreviousNext

Return to Machines & Power Toolery

Who is online

Users browsing this forum: No registered users and 8 guests