Manual "force" compressor start

[manoweb]

Hello, I have a common 5HP, 60gal dual stage compressor. I recently swapped the pressure switch because it got "sticky". No big deal, less than 30$ from amazon same day delivery and few minutes to connect it.

I was wondering - my compressor stops pumping at 165PSI and starts again at around 120PSI. I know I can change those values with the adjustment screws. However, for example before I start cutting with Plasma, I often would like to "top up" the compressor. Let's say it's at 130PSI, I would like to manually force it to start and fill up to 165, then do my thing. No I never had any issue, I just prefer not to work while a loud compressor is pumping.

Is there such thing as a pressure switch with manual "force" start? In principle it should be pretty simple but if it exists I am not sure how to search for it, thanks.

 

[TurnipTruck]

If the overpressure relief valve is on the pressure switch manifold, vent it briefly until it starts.
Or add a vent valve at the switch.

 

[The Cobbler]

yes, the easiest would be to blow off pressure until the compressor kicks in.
anything else would be a safety hazard and/or expensive
are those pressure parameters the same as the original switch?

 

[manoweb]

Yeah I often release pressure to start it but it's a waste of energy and time. And yes, it's the "CENTRAL PNEUMATIC 60 gallon 5 HP 165 PSI Two Stage Air Compressor (Item 93274 / 62299 / 96598)" a very, very common compressor (pump is Made in Italy)

I thought there would be pressure switches with an extra button or lever to just force start them. If that is not the case, oh well, I'll survive

 

[Leaflessshadetree]

Use it as an opportunity to drain water from the tank.

 

[Fixr]

Yeah I often release pressure to start it but it's a waste of energy and time. And yes, it's the "CENTRAL PNEUMATIC 60 gallon 5 HP 165 PSI Two Stage Air Compressor (Item 93274 / 62299 / 96598)" a very, very common compressor (pump is Made in Italy)

I thought there would be pressure switches with an extra button or lever to just force start them. If that is not the case, oh well, I'll survive

A switch that overrides the pressure switch would be a liability nightmare, especially if it were to stick or get tied down. It's just a really bad idea all around.

 

[micromind]

If the switch has a built-in unloader valve, even if it's in use, often you can manually push the tab that operates the valve and it'll start the motor. You don't need to hold the valve, just 'trip it' so to speak.

Then it turns off at its normal shutoff pressure.

 

[manoweb]

A switch that overrides the pressure switch would be a liability nightmare, especially if it were to stick or get tied down. It's just a really bad idea all around.

Hello, if you say this, it means you really have no idea what I was asking. If I wanted to bypass the pressure switch I would have simply bypassed it

 

[manoweb]

If the switch has a built-in unloader valve, even if it's in use, often you can manually push the tab that operates the valve and it'll start the motor. You don't need to hold the valve, just 'trip it' so to speak.

Then it turns off at its normal shutoff pressure.

Oh we are onto something here... yeah of course I believe virtually every pressure switch for this class of compressor have a builtin unloader valve... I need to inspect how that tab works. And of course, it has to be a momentary action like you describe

 

[The Cobbler]

I need to inspect how that tab works.

the unloader does nothing to the electrical circuit. it opens a valve to bleed air pressure off when the electrical contacts open ( pressure has been reached)
You won't find a way to start the motor with the unloader circuit.

 

[micromind]

The tab on the pressure switch unloader is connected to the contact armature and most of them will 'trip' the contacts closed and the switch will operate normally.

Most of the ones I've seen anyway......

 

[KenC]

Hello, I have a common 5HP, 60gal dual stage compressor. I recently swapped the pressure switch because it got "sticky". No big deal, less than 30$ from amazon same day delivery and few minutes to connect it.

I was wondering - my compressor stops pumping at 165PSI and starts again at around 120PSI. I know I can change those values with the adjustment screws. However, for example before I start cutting with Plasma, I often would like to "top up" the compressor. Let's say it's at 130PSI, I would like to manually force it to start and fill up to 165, then do my thing. No I never had any issue, I just prefer not to work while a loud compressor is pumping.

Is there such thing as a pressure switch with manual "force" start? In principle it should be pretty simple but if it exists I am not sure how to search for it, thanks.

You could replace the current setup with a motor starter that has a relay operated start function and a manual start button. That would also take the high current load off of the pressure switch since it would only be driving the relay coil.

 

[Norcal]

Hello, if you say this, it means you really have no idea what I was asking. If I wanted to bypass the pressure switch I would have simply bypassed it

The mag starter on my compressor would weld the contacts & continue to run, when the safety valve would let go go, knew it did it again, replaced the contacts & still continued to do it, got rid of the NEMA size 2 Westinghouse A100, starter in favor of a Furnas ESP100, it's never happened since but always have been thankful for the protection of that valve.

 

[The Cobbler]

You could replace the current setup with a motor starter that has a relay operated start function and a manual start button. That would also take the high current load off of the pressure switch since it would only be driving the relay coil.

and what is he doing for unloader?

 

[KenC]

and what is he doing for unloader?

The unloader is normally included in the pressure switch on cheaper units. The pressure switch would remain, and trigger the starter.

 

[The Cobbler]

but that still doesn't solve what the original poster wants to do , does it?

 

[Fixr]

Hello, if you say this, it means you really have no idea what I was asking. If I wanted to bypass the pressure switch I would have simply bypassed it

Ah. I thought your use of the word "force" might be meaningful. Never mind.

 

[4x4Pete]

I would use the motor starter as suggested by Ken C. Adding in a normally open solinoid valve that closes with the starter, and a compressor style check valve with the bleed port. This would unload the compressor each time it shuts off. This is exactly what I have. The compressor was from a large multistory building for pneumatic controls. The tanks were remote (which it still is in my application). The unloader was a solinoid wired into the starter and plumbed to the side port of a check valve where the piping left the floor mounted compressor heading to the tanks. It can be done safely.

 

[mikegt4]

It sounds like this question is making a mountain out of a molehill. As the OP stated he could adjust the pressure switch to restart the motor at a higher pressure (easy to do) but only wants the restart to happen occasionally, not always. In the same scenario I have just pulled the little ring on the pressure relief valve to dump some air pressure until the motor restarts. It does make a lot of noise but it also serves as a test showing that the valve isn't seized (legitimate justification for doing so). Opening the tank drain valve would achieve the same result.

 

[KenC]

but that still doesn't solve what the original poster wants to do , does it?

If that is directed at my response, the answer is, it absolutely does solve it. Just push the start button and it is 'forced' to start.

 

[The Cobbler]

If that is directed at my response, the answer is, it absolutely does solve it. Just push the start button and it is 'forced' to start.

so your start button is not connected to the pressure switch. how does the compressor shut down?

 

[KenC]

so your start button is not connected to the pressure switch. how does the compressor shut down?

Maybe I wasn't clear enough. The installation uses a starter with a 120v coil. that coil has it's power provided by the pressure switch, and in parallel a start button. So either does the trick. Common configuration

 

[BurtEggley]

There needs to be some kind of fail safe in the set up I think it a button can start the motor anytime it is pushed, even if the motor only runs for three or four seconds because the primary contactor is open and at its max. There is always one idiot or juvenile who would keep hitting the button to see how high he could get the pressure, or burn the motor up first from constant pushbutton starts.