Use a 10amp switch to control immersion heater

[LorryG]

I run a UK charity for disabled kids in Asia. The power supply is 240v, but electrical safety here is a nightmare.

I want to turn on and off a 6kw immersion heater using a 10amp switch. Specifically a 10amp key switch to stop people turning it on and off by accident. Is there a way to use a 10amp rated switch to trigger a higher rated switch?

 

[JohnD]

Yes you can do it using a contactor but it would be expensive.

Immersion heaters are a particularly arduous load because they run at maximum rated power for long periods.

 

[LorryG]

Thanks @JohnD I am guessing a 32amp contactor would be sufficient? Is it as simple as just connecting the 10amp switch into the contactor as an on off switch for the contactor or is there more to the system? And what should I look for when buying a contactor - you say it is a heavy load because of the consistent draw of power - how do I know which would be rated for something like this? The cost (within reason) is less important as the safety improvement that this would offer.

 

[JohnD]

32A would be adequate.

In UK, electric showers are the biggest common domestic load, and the switches and their connections are more prone to failure than other switches, especially if the user is in the habit of switching them while the shower is running at full power.

Contactors are more an industrial than a domestic accessory, and the major brands are made to good standards, though I am no longer involved in such things. Generally, avoid Chinese imports and brands of unknown provenance.

The copper cables distort under pressure, so it is helpful to retighten the terminals after a few weeks. If they are allowed to become loose, they overheat, which creates a vicious cycle of softening, loosening, overheating, and ultimately burning out. It is not very common, but happens often enough to be recognised.

 

[JohnD]

P.s.

I just had a look, and they seem to be offered in 25A, 40A and 63A ratings.

25A would be the minimum you need, but I would suggest 40A. They seem to be bigger.

 

[SFK]

How about using one of these with a padlock?:

roatary 240 switch - Google Search

25A

British General CPRSD425 25A 4-Pole Rotary Isolator Switch NO - Screwfix

Order online at Screwfix.com. 4-pole rotary isolator switch disconnector used to switch power to commercial / light industrial applications. Can be used as an emergency stop and can be locked in the off position using a padlock (not supplied). Switch is interlocked with the lid to prevent...

www.screwfix.com

32A

British General CPRSD432 32A 4-Pole Rotary Isolator Switch NO - Screwfix

Order online at Screwfix.com. 4-pole rotary isolator switch disconnector used to switch power to commercial / light industrial applications. Can be used as an emergency stop and can be locked in the off position using a padlock (not supplied). Switch is interlocked with the lid to prevent...

www.screwfix.com

40A

RS PRO 4P Pole DIN Rail Isolator Switch - 40A Maximum Current, 15kW Power Rating, IP65 | RS

uk.rs-online.com

SFK

 

[JohnD]

Yes, that would be simpler.

Though a contactor would also be compatible with a timer or other controls