How to improve the rating of a relay switch

I use these switches to control different equipment....

https://www.amazon.com/220v-remote-control-switch/s?k=220v+remote+control+switch

You can connect a 20A rated contactor, 2 pole or 1 pole, your relay switch will likely have a good enough rating for an inductive ac load to operate the contactor. The only caveat is the nature of your 4kW load, resistive, inductive, ac or dc. The coil to operate the contactor can be rated 220Vac, so the same power that you need to switch can be used to operate the contactor. Air conditioning compressor contactors are easily obtained and fairly lightweight, and should be good for your purpose.

Thanks.

My case is the running circuit to be normally kept closed. The radio control device is a wireless Emergency stop button. What should I do?

Can an auxillary reply solve my problem?

An emergency stop button should be a manual operation....

An emergency stop button is not part of the control circuit, it cuts all power to the device...

Then there’s the problem sourcing the 1200A 4000 volt 3 phase button for your coal pulverizer motor...,

I Totally Agree.

What happens when the contactor fails?

It depends on whether the coil circuit opens or the contacts weld, one is OK, the other not so good. It’s all a statistical crap shoot

Contacts failing to make, armature stuck by chemical reactions or foreign bodies in the air, spring fracture, these are some of the perils we encounter. And PN junctions fused open or closed are worrisome when you apply solid state relays...

That's why emergency stop switches are always manual and cut all power to the equipment...a switch that cannot be depended on to work without exception, is not viable...

One person’s definition of emergency stop can easily be another person’s minor inconvenience. With no understanding of what the perils are, and what constitutes an emergency, any of the solutions could easily be perfectly acceptable. In some cases, the measures taken to provide redundant control methods can actually reduce the reliability of the installation, or, as I have witnessed, created more dangerous situations than the original measure was intended to prevent.

Emergency Stop Switches rarely cut all power to any piece of equipment. In many cases, power must stay on to ensure the equipment stops or ceases movement as quickly as practical, that movement determined to be dangerous. In other cases, Emergency Stop Switches can also operate as pilot devices to cause the interruption of power by devices suitable for the task at hand, such as 480V or 4160V 30A and up circuits, unsuitable for manually operated buttons.

In one production line of coordinated roller drives, significant damage to the inverters occurred due to multiple operations of ‘safety’ equipment interrupting power to the line, where the buttons were used to make it safe to enter the machinery, because they were easy and accessible. The designer incorrectly assumed that immediate power removal was the safe state, and had no concept of how the equipment would operate in practice.

Ideally, an <...emergency stop...> circuit needs to be 2-stage reset; one wouldn't want the equipment to restart immediately on releasing the button and a 2-stage reset makes the restart a deliberate act.

SE is correct. An emergency stop function has to be a manually operated device in the circuit to be controlled. You can't rely on something controlled remotely because you can't be certain the path between the operator and the device being controlled is guaranteed to be failsafe.

Can be in both manual and remote

https://machinerysafety101.com/2009/03/06/emergency-stop-whats-so-confusing-about-that/

Even if you have a cat2 requirement for e-stop, reliability is held to a higher standard...and contact points fusing together is a well known frequent failure of contactors, so I should think that provision for this possibility must be addressed...so possibly redundancy is the answer here...this together with an aggressive preventive maintenance schedule should pass muster....

I respectfully disagree: The definitions I find all imply the E-Stop must be located where the potential danger is viewable. The following imply this as well:

SOT 13850

ISO 13850 is a British standard for safety of machinery, which

• 4.4.2

An E-Stop device shall be located at each operator control station, except where the risk assessment indicates that this is not necessary, as well as at other locations, as determined by the risk assessment. It shall be positioned such that it is readily accessible and capable of non-hazardous actuation by the operator and others who may need to actuate it. Measures against inadvertent actuation should not impair its accessibility.

https://vdocument.in/emergency-stop-system.html?page=1

“1. EMERGENCY STOP SYSTEM

4. Location They should be positioned for easy access by the operator or anyone who may need to use them, however, they should not be located where their use could endanger the user. Remember that the person using the emergency stop may not necessarily be the person in danger! It may, therefore, be prudent to position an emergency stop near an adjacent machine, or machine zone in the case of a complex system, giving the neighbouring operator the opportunity to stop the machine if the operator gets into trouble. Where this is done, the zone of effectiveness of the Emergency Stop must be clearly indicated to avoid confusion.”

Remote shutdowns are just that, remote. But they aren't E-Stops they are remote shutdowns. The idea is an operator has to have a continuous view of the area where the danger exists says he's present and not remotely so.

<...wireless Emergency stop button...>

Emergency stop switches are not allowed to be remote controlled.

They must be hard wired with nothing in between it and the main power to the circuit.It is the first switch in the control circuit.

All emergency stop switches must be in series with each other in the same control circuit.

You can have stop switches that are remote,but not Emergency Stop Switches.

If all the emergency stop switches are in series, how do you make each and every one be the first in the circuit?

https://store.clearpathrobotics.com/products/wireless-e-stop

You just want to amplify the power handling capacity of your present control system which can easily be done without altering your remote control...

I think you can easily implement the changes on the remote controlled side by using your present remote control radio to control the existing 4A relay that in turn will drive either an added 4KW contactor relay or a solid state relay at the remote site to drive the remote equipment..

Just get a bigger switch.

I got three options for the moment.

First, use your relay to control a MCB actuator that trips an MCB of desired size.

Second, use your relay (if it does not latch) to control a more powerful latch relay.

Third, if your relay can (be made to) latch, control a contactor.

I will let you know if I get more ideas.

Good luck