Outer Limits 4x4 Board

I've bought an old shitter 240v Air Compressor and am gunna strip it for parts to install an on-board air in my ute. I'm hoping to use pretty much everything accept the motor and Twin-V compressor already on it.

My question is, what are the implications of using a 240v (and I assume 10A @ 240v) Condor Pressure switch in a 12v application? Will it work but burn out or will it just not engage at all?

I assume there is some sort of solenoid coil in it and am not sure if it will charge enough to engage.

The compressor I am considering will be a 12v, 30-40A MAX current draw, constant duty unit.

Any and all help appreciated.

Cheers,
Kris

Ignoring issues associated with start surge and arcing at switch-off , there is no escaping that current is current. If the original pressure switch is rated to 10A at 240V it won't be happy carrying 30-40A at any voltage.

You'll probably get away with it for a little while, but I wouldn't trust the switch to last for long.

Cheers,

Scott

I assume it's an all in one unit with the pressure switch and 240V relay combined? I can think of two options:
1. pull it apart and replace the 240v relay with a suitable 12v one.
2. use the 240v relay to switch in a suitable 12v relay (assuming 12v will activate the 240v relay?)

get a new relay for it. i can almost garuntee that youll end up welding the contacts together. If its what im thinkin of, it will be a 240 V relay coil, youll get away with just changing the coil to 12V, but the current draw will surely weld the contacts as mentioned above. the actuall pressure switch should be able to handle it though.........i think


insert disclaimer here

RoldIT wrote:I've bought an old shitter 240v Air Compressor and am gunna strip it for parts to install an on-board air in my ute. I'm hoping to use pretty much everything accept the motor and Twin-V compressor already on it.

My question is, what are the implications of using a 240v (and I assume 10A @ 240v) Condor Pressure switch in a 12v application? Will it work but burn out or will it just not engage at all?

I assume there is some sort of solenoid coil in it and am not sure if it will charge enough to engage.

The compressor I am considering will be a 12v, 30-40A MAX current draw, constant duty unit.

Any and all help appreciated.

Cheers,
Kris

If it's the condor swicth I'm thinking of and most compressor mounted units are the same, it has no internal coil, just a air operated plunger that pushes the contacts open at pressure, you probably can also adjust the pressure it cuts out at and the gap between that and what pressure it cuts back in, it will run fine on 12v other than the ampage issue, so just wire it to operate a correctly rated 12v relay.

Rainbow Warrior wrote:

RoldIT wrote:I've bought an old shitter 240v Air Compressor and am gunna strip it for parts to install an on-board air in my ute. I'm hoping to use pretty much everything accept the motor and Twin-V compressor already on it.

My question is, what are the implications of using a 240v (and I assume 10A @ 240v) Condor Pressure switch in a 12v application? Will it work but burn out or will it just not engage at all?

I assume there is some sort of solenoid coil in it and am not sure if it will charge enough to engage.

The compressor I am considering will be a 12v, 30-40A MAX current draw, constant duty unit.

Any and all help appreciated.

Cheers,
Kris

If it's the condor swicth I'm thinking of and most compressor mounted units are the same, it has no internal coil, just a air operated plunger that pushes the contacts open at pressure, you probably can also adjust the pressure it cuts out at and the gap between that and what pressure it cuts back in, it will run fine on 12v other than the ampage issue, so just wire it to operate a correctly rated 12v relay.

Yeah, I think you might be right come to think of it. I believe it may be just an air pressure contact breaker.

I also understand what people as saying about "current is current" so I guess as it's already a second hand jobby and the smoke escapes and shiats itself I've got nothing to lose.

I'll just make sure I've got a safety valve in case it does weld the contacts shut.

Cheers for the input.

Hi RoldIT, you should try and avoid using switches that are specifically designed for AC use. They have a much low arc tolerance.

AC switches exploit the fact that the voltage cycles and this causes the current to be completely off during the zero crossing of the AC cycle, thus the contacts are pretty well protected against high current arcing.

Whereas with DC the current remains until there is a large enough air gap between the switch contacts, so DC switch contacts are designed to tolerate much, much higher current arcing.

In the use you are planning, I think you would be better off looking at a DC switch set up.

Cheers

I purchased a pressure switch from ARB for $30, to cut the compressor in and out..

apart from that i reckon what was said before about using your condor box to activate a 30 or 50amp 12volt relay for the compressor would be the alernative.

Only other thing to consider is purchasing a 1 way valve (check valve) to stop back pressure to the compressor, which i got for $30 from a hose fitting type place.

Toy80Diesel wrote:I purchased a pressure switch from ARB for $30, to cut the compressor in and out..

apart from that i reckon what was said before about using your condor box to activate a 30 or 50amp 12volt relay for the compressor would be the alernative.

Only other thing to consider is purchasing a 1 way valve (check valve) to stop back pressure to the compressor, which i got for $30 from a hose fitting type place.

I am familiar with the DC pressure switch alternatives available but did like the way the Condor switch unloads the pressure from between the compressor and the first check valve in the system. That's the main reason why I wanted to run this setup.

That said, I'm nearly positive I can get a DC version of the exact same switch from Condor but was hoping to get away with out the extra $$$.

drivesafe wrote:Hi RoldIT, you should try and avoid using switches that are specifically designed for AC use. They have a much low arc tolerance.

AC switches exploit the fact that the voltage cycles and this causes the current to be completely off during the zero crossing of the AC cycle, thus the contacts are pretty well protected against high current arcing.

Whereas with DC the current remains until there is a large enough air gap between the switch contacts, so DC switch contacts are designed to tolerate much, much higher current arcing.

In the use you are planning, I think you would be better off looking at a DC switch set up.

Cheers

Thanks mate, great info, I'll keep that in mind.

drivesafe wrote:Hi RoldIT, you should try and avoid using switches that are specifically designed for AC use. They have a much low arc tolerance.

AC switches exploit the fact that the voltage cycles and this causes the current to be completely off during the zero crossing of the AC cycle, thus the contacts are pretty well protected against high current arcing.

Whereas with DC the current remains until there is a large enough air gap between the switch contacts, so DC switch contacts are designed to tolerate much, much higher current arcing.

In the use you are planning, I think you would be better off looking at a DC switch set up.

Cheers

Just plonk in a relay, the difference between the contacts starting a 10A 240v motor and firng a 50mA 12v DC relay is heaps, the contacts should outlast the seals & mechanical bits.

Rainbow hit the nail on the head! There is no relay coil in a pressure switch, just a pressure operated switching contact. Use the switching contact to switch a 12v Relay, and you will never have any problems from it.
I'd give it about 15minutes before the smoke escapes if you try to run the compressor straight off the 10A contacts.......Been there, done that, I was an industrial maintance electrician.

And what Scott said is right, a 240v 10A contact will generally handle about 6-10 amps DC, but will burn out quicker due to the arc currents of DC.

Cheers, Dean