It is currently 29 Mar 2024, 01:10
9fingers wrote:No Terry. Read my last post please.
9fingers wrote:...a germ of frustration is creeping in….
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?
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.
Wizard9999 wrote:
EDIT: what I still don't really get is why this does not blow the 13amp fuse in the plug.
Terry.
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.
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.
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.
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.
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?
DaveL wrote:.... I find the buttons on the cheaper remote units are the weakest part of the system.
Wizard9999 wrote:As usual, I am working at a rather pedestrian pace 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.
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