Replacing 12v on/off switch with a 240v pneumatic switch
Treecrest said
08:51 PM Mar 21, 2018
Gday
I want to replace the water pump 12v switch with an auto-off one. I've looked for a 12v auto-off switch, but to no avail. My question is would a 240v pneumatic switch (like you see in caravan park toilet blocks etc) work on the 12v positive?
Thanks
Glen
erad said
10:54 PM Mar 21, 2018
Simple answer - yes. However, there are more complications to consider. The main one is the current rating of the switch. If you are switching the same load - say 1 kW, the 12 V switch will have to handle 20 times the current (forgetting the inrush current to the motor). This is a significant increase. Then you have the difference between AC and DC. When you make contact, no problem, but when you break the contact, the DC will try to maintain an arc at the contacts a lot longer. The DC switch would not last as long. You can overcome this problem by using the 12V switch to operate a relay, which would then switch the mains power. The current required to operate the relay would be a lot less than the motor current
bobsa said
03:31 PM Mar 22, 2018
Give it a go
my van has a 240 volt light switch good for 10 amps, as do most vans
to operate the pump.
yes they can get dirty contacts from dust , i do a lot of dirt roads
and have only had one fail
the 240 volt and 12 volt dc switch rating are different ,but they use 240 because they look nice
bob
oldtrack123 said
01:42 AM Mar 25, 2018
erad wrote:
Simple answer - yes. However, there are more complications to consider. The main one is the current rating of the switch. If you are switching the same load - say 1 kW, the 12 V switch will have to handle 20 times the current (forgetting the inrush current to the motor). This is a significant increase. Then you have the difference between AC and DC. When you make contact, no problem, but when you break the contact, the DC will try to maintain an arc at the contacts a lot longer. The DC switch would not last as long. You can overcome this problem by using the 12V switch to operate a relay, which would then switch the mains power. The current required to operate the relay would be a lot less than the motor current
DITTO to all above
Risky , unless the switch also has a DC rating on it
Especially if a micro switch [with a very small "contact open "gap.
Switching a DC motor [ inductive arcing] is a lot different to a light [ non inductive,very little arcing]
hako said
11:40 AM Mar 25, 2018
Just use a relay operated by the micro switch - contacts will last forever.
Gday
I want to replace the water pump 12v switch with an auto-off one. I've looked for a 12v auto-off switch, but to no avail. My question is would a 240v pneumatic switch (like you see in caravan park toilet blocks etc) work on the 12v positive?
Thanks
Glen
Give it a go
my van has a 240 volt light switch good for 10 amps, as do most vans
to operate the pump.
yes they can get dirty contacts from dust , i do a lot of dirt roads
and have only had one fail
the 240 volt and 12 volt dc switch rating are different ,but they use 240 because they look nice
bob
DITTO to all above
Risky , unless the switch also has a DC rating on it
Especially if a micro switch [with a very small "contact open "gap.
Switching a DC motor [ inductive arcing] is a lot different to a light [ non inductive,very little arcing]
Good Luck.