24V 15A plunger switch wanted

[20 degrees left]

Complete amateur here.
I am looking for a 24V plunger switch that can carry up to 15A load. Can't find anything on the internet but I guess I am not looking at the right spots.
Any suggestions mor than welcome.

 

[kellys_eye]

Don't bother. Use a lower current rated switch to activate a relay carrying the heavy load current.

i.e simple plunger button activating a car accessory relay.

 

[20 degrees left]

I'd like to avoid the relay if that can be done. Keeps away another failure source.

 

[kellys_eye]

Wrong attitude. Relays have reliability in the 100's thousands of operations. If you can find a plunger rated at that current (they do exists - not cheap) then go ahead but any designer would use the relay route rather than rely on a heavy duty switch if they can.

Additionally you will find a MUCH larger choice of smaller rated buttons and be able to locate it 'anywhere' whereas poking large cables into small places isn't fun!

 

[20 degrees left]

Amateur here, trying to tap the knowledge of the experts;-)
Where can I find such a switch? Any link?

 

[kellys_eye]

Typical push button switches listed in this link. Actually cheaper than I expected!

https://uk.rs-online.com/web/c/swit...h+button+switch&applied-dimensions=4294436440

 

[20 degrees left]

This is the type of swicth that I am looking for. But I fail to find any that accept 15A at 24V DC.

https://www.ene2u.com/highly/highly-d5000-push-plunger-type-switch

 

[20 degrees left]

Ok, I think I just learned something here.

The switch mentioned above takes 10A at 125V (DC I assume?)

10 x 125 =1250W
1250W / 24V = 52A

Am I correct that this switch accepts 52A at 24 V?

 

[Bluejets]

It's shown as 0.5A @ 125V DC
I wouldn't expect much more than 1A @ 24V DC

 

[20 degrees left]

Could't find the values you mention, but I guess you're right.

Here's another one which looks promising to me.

https://www.grainger.com/product/HONEYWELL-15-A-120-V-Panel-Mount-24A042

 

[Martaine2005]

Could't find the values you mention, but I guess you're right.

It’s right there on the label underneath the 10A 125VAC.
I remember reading on a manufacturers website about a ‘rule of thumb’, but can’t remember where. Anyway, it said a 10A 125VAC switch should be ok for 10A up to 30VDC.
Not sure if this applies generally or to that manufactures products only.

Martin

 

[Bluejets]

Usually dc switches require a different switch action to that of ac, hence the much lower rating on dc in this instance.

 

[20 degrees left]

So I would assume that this switch has the right action built in to carry at least 15 A at 24V?

https://www.grainger.com/product/HONEYWELL-15-A-120-V-Panel-Mount-24A042

The specs give 15A at 125V AC and 15A at 240V DC. Am I reading this correctly?

 

[Martaine2005]

Am I reading this correctly?

I don’t think so.
The specs say 15A 125VAC and 250VAC.
Also 1/2A 125VDC. Which I read as 0.5A (500mA).
It also gives a Horse power rating.
Switches are rated higher for AC because of the alternating current where as DC current (generally) is constant. So the arc across the contacts is greater with DC. Switches sometimes are rated for horse power too for resistive and inductive circuits. Inductive loads require a much higher inrush current therefore the MAX ratings will differ.
Example: your link. 1/8HP and 1/4Hp ratings.

Martin

 

[Harald Kapp]

The switch mentioned above takes 10A at 125V (DC I assume?)

10 x 125 =1250W
1250W / 24V = 52A

Wrong reasoning. The switch capacity is not determined by the power but by the current.

The problem is arcing when the switch opens. The switch rating is 10 A @ 125 V and is valid for AC. When a switch for AC opens he contacts, the air gap between the opening contacts will become ionized and current will continue to flow between the contacts. As the ionized gas has a comparatively high resistance, lots of power is being dissipated and the contacts can melt. With AC this problem is solved as with every zero crossing of the AC current the electric arc is interrupted giving the air a chance to cool down while the contacts open further until they reach the end position. Thus the arc is extinguished, no current flows, no power is dissipated.

With DC there is no zero crossing of the current. The arc may be sustained and the contacts can burn away. This can be solved by one of two methods:

1. A wider gap between open contacts. A wider gap will eventually lead to a breakdown of the electric arc and the current will stop.
2. An additional blowout magnet within the switch placed directly next to the contacts. This magnet creates a magnetic field which in turn will push away the arc from the contacts, thus lenghtening the path and quenching (extinguishing) the arc.

It is not uncommon that a switch can, for example, operate 1000 W with AC but only around 30 W with DC.
I second the recommendation by @kellys_eye to use an automotive relay. These are made to handle high current at 12 V DC.

 

[20 degrees left]

Not sure if we talk about the same switch. I wish I could upload a pic of the sepcifications but can't figure out how.

So here's the switch I talk about:
https://www.grainger.com/product/HONEYWELL-15-A-120-V-Panel-Mount-24A042
https://www.grainger.com/product/HONEYWELL-15-A-120-V-Panel-Mount-24A042
The specs give DC a Contact Rating - Snap Action Switch 15 A @ 240 V. That should cover the required 15A at 24V I suppose?

Thanks Harald for the explanation. Makes total sense. If the switch above is no option I may have to opt for the relais solution then.

 

[Harald Kapp]

Assuming the rating as shown on the linked website is correct, you could use this switch at 12 V.

I have my doubts, however, as to the correctness of the ratings. The brochure linked on the website shows only AC ratings for this switch:


And the label on the switch states 1/2 A @ 125 V DC:

As mentioned before, you cannot scale amperage inversely proportional to voltage due to the effect of arcing.

 

[20 degrees left]

Decision made, I will opt for the relais function.

Thanks for all the advice! I think you all saved me from some unneccessary trouble with smoking switches. Besides having learnt another thing or two ;-)