Auto start gas powered compressor

Hi all.
We live fully off grid in northern Ontario, we use a pneumatic water pump. I run an air compressor into a larger reservoir tank to 80PSI, we usually run 2 days before preasure is down to 50 PSI, when i pump agsin.
The inverter will not start the compressor, and even if it did, it woud place higher than desired strain on it. Smaller compressor which could be run from invert would take forever...
Currently I manually: start a generator, start compressor, open valve to reservoir tank, when charged, turn compressor & gen off.
Works great, but i want to AUTOMATE IT
The compressor is a 2 HP, 6 CFM@ 90PSI.
QUESTION: has anyone here automated a gas powered compressor (which i will buy) to:
1. when preasure drops below 50psi, start gas compressor
2. pump to 80psi, compressor stops normally,
3. stop gas engine

ALTERNATIVES?
Thank you all

 

From your description, I have to agree with ghrit about all the potential failure points...to me (and I don't know your exact situation) it would seem a whole lot easier to use a solar system, battery bank, inverter and electric pump to automate you water supply.

I use a stacked pair of Trace inverters to provide power to a 1hp well pump

 

Air compressors and well pumps are natural enemies of generators and power inverters.

I have a whole post on how to reduce inrush current on air compressors for off grid use. I was successful, but my conclusion was if possible use an air compressor that is directly driven by an engine or use one driven by a DC motor ran off batteries.

There are engine driven air compressors out there that will auto start but they are kind of expensive.

 

Have worked for 30 years on gas compressors, almost all of them continuous run and gensets, auto start, but few auto start gas air compressors. Most auto start air compressors have been very expensive and seem to increase the amount of problems by many times. One of those items, like trailer mounted combo genset and air compressor units, that the boss buys at some show for thousands of dollars, gets a lot of use for 6 months, and then sits for the next 10 years in the back of the warehouse. The units that have worked well were industrial quality and often for manufacturing, diesel powered, and installed in factories or industrial sites. Like a good genset, often cost up to $20,000 or more. Used to find them in plastic factories in old days before everything went to China, and were often used to help shut the place down if power was lost. While in theory, all you need is an electric start motor and a switching system to start it when the pressure drops below some level and turn it off when it exceeds some set pressure, in real life, as with a remote car starter, you need a fairly complicated system to prevent damage if the engine doesn't start, to prevent starting while you are working on it, to shut it down and not try to start it if it is out of fuel, oil, or a major air leak to both protect the system and so it doesn't just run until the fuel is gone if there is a major leak. Most people seem to end up as you have, with a good quality electric start compressor with a larger tank connected to the system with a hose, often seem to get 1 or 2 of the 20 gal electric units air tanks after it goes bad, and just start them manually. It would seem to make more sense if solar is possible in your area to go that way with a electric pump and a genset backup if needed.

 

Unloaders for air compressor starting will solve most problems you mentioned.

 

Most gas or electric air compressors will not start without an unloader, often set up as a "cold start device" to let it get up to some speed. They work well until they don't work, at that point the breaker pops or the starter motor burns out, you need to have some sort of safety device to cover failed starts, the best one I have found is a human with some skin in the game. Some inexpensive China junk doesn't have unloaders, but they get away with it as their pumps have such small displacement that it doesn't really matter. Big problem with air compressors, both gas and electric, is that 90 % of the stuff for the home owner is total junk and almost everything they tell you is a lie. Even Honda now has units built outside of Japan and even their units can be let the buyer beware. While a lot of the big box store stuff is very cheap, it will usually only last a couple hundred hours, 10 years for a home owner or 3 weeks for a commercial user. No free lunch and get what you need. A few years ago with an American built oil lube pump and a Japan built Honda, 5,000 hours was normal for a machine that had the proper care taken, now few China junk, even name brand, will make 2,000.

 

Hi
Thank you all for your experience and advice; few thoughts in no particular order
- can use a 12V or 24V compressor, much preferred 24V due to AMP draw at 12V 180 amps (Oasis 12-Volt Continuous Duty Tankless Air Compressor - they make one w 10 gal tank as well w all controls, $2,399), the tankless is $1,949. They also have a 24V
I have 2, 6V deep cycle batteries in series to get 12V that i could use and plug them into a charger. I just dont like the 180 amps!!
The best SIMPLE solution thus far is to ran off batteries, thus removing nightmare on inrush to the inverter - i am going to go the 24V way, all needs to be done is keep batteries charged and use existing gen + electric compressor as manual backup.
It is just expensive, i was hoping to be able to auto start gas engine air compressor and avoid batteries

 

You could buy a DC motor and repower an existing 120v or 240v air compressor for much less than buying a new DC one.
You would likely need need a 24v 56 frame motor.

For high voltage single phase The over best and easiest most effective soft start I found involved some sort of clutch, either an electromagnetic clutch on a 56TC frame moror or a go cart clutch.
The simplest was just going to a 4 pole more with a bigger motor pully, but that was kind of expensive.
The easiest was to reduce start up amps was adjust voltage down about 10 to 15% with a variac.
Ultimately a resistor limited free spin motor start that engages the compressor with full power, a clutch after the motor was at full speed on a 4 pole moror ended up making the lowest single phase start up I was able to achieve.

 

Oh well,All I can think of in the equipment we used was an ON/OFF/AUTO start switch.
Pressure switches HI/LOW which can be a nightmare to adjust and keep adjusted + a bit of fluid of trash in the diaphragms or line is a nightmare for some to trouble shoot....
We had air operated robot arms on the PTO'S that engaged the clutch after a minute of run time to allow the engine to come up to speed and warm up a bit....Trick is not to engage at full RPM...Only at an high idle like 700/800 rpm
Hope this helps?

 

Gator brought up an important point, some method has to be used to even out the pressure pulses inherent in a piston pump. Both gauges and pressure switches tend to use a very small orifice to the gauge or the pressure switch to smooth out that pulse effect that will cause the gauge to flutter or the switch pressure control to be off. Well over half of the failures I see in these items is caused by water or crud blocking that small hole, often a semisolid blockage of water, rust and oil. In switches often the contacts either burn out due to starting surges or weld themselves together. If you drain the tank every day, use short or no extension cords, keep the air filters clean, use only a good air compressor oil, keep fresh gas in the tank, always turn off fuel and let tun dry if stopping for more than one day and start compressor for the first time each day from an empty pressure tank. you can at least double the life of your compressor, the one I use daily is connected directly to the 220 volts at the entrance panel, meets the rest of the requirements, and has been used daily by me, with it starting at 125 and off at 140, for 35 years. Only service other than oil and filters was a new belt 10 years ago, and a starting cap that went bad. American made motor and old Emglo pump.

 

I built for a customer an auto start and shut down air compressor.
It is not all that complicated.
The pressure switch remains.
The starter solenoid is in circuit with a governor arm microswitch.once the engine starts the governor arm moves opening the circut through the micro switch to the starter.
The primary coil wire ( NOT the high voltage side that attaches to the spark plug) is wired through the pressure switch.
The check valve on the compressor is replaced with a load Gene which unloads the compressor head to check any time it is not operating.
the pressure switch has 4 contacts 2 circuits
When the air pressure drops and the pressure switch closes circuits the starter solenoid is engaged, driving the starter. After the engine starts the governor arm opens the micro switch disengaging the starter. the unit runs till it gets up to pressure and the pressure switch opens and the circut to the ignition and shuts down the engine. the load gene then releases the pressure between the compressor head and the check valve in the gene.
I have built a lot of different air compressors even those the run on both gas and electric. I have one in my own shop.
Problems occur if there is water in the gas, or service is lax and the starter cranks the engine till the battery is dead.
For this you need a time delay switch so that the starter can only run for a set limit, custom to the engine.

 

I have heard the battery may not die before something catches on fire.

 

Decades ago we used 555/556 chip circuits controlling standard Bosch 12v relays to time starter and low oil switch bypass circuits. They can be used for magnetic governor and unloaders. Easy, cheap, and simple circuits to build. Probably better ways now days but it worked for us back then.

 

I have seen an oil pressure switch to drop out the starter,Like an 5# make or break switch,Worked well too.

 

I saw those used on waukesha-pearce (ICK?) and larger engines.

 

An oil pressure fed engine is the best there is, usually they have a filter as well, makes for a good investment.
Same with an oil pressure fed air compressor like the Quincy. these are expensive tools though.
Tough enough finding a small engine with access on the primary coil wire.
Kohler engines use to have external automotive coils perfect for the job.
if it uses points, you're golden.

 

Yes sir,and smaller,

 

The option of a DC motor driving a small air compressor might be more appealing, avoiding the use of an inverter.
Compressing air is one of the hardest loads motors can be tasked with simply because the load and amperage increases progressively, not to mention starting loads.
Just for the experiment, I thought I'd try using a cheap 12-volt inflator for maintaining pressure in my system at a minimal level. they are cheap and only need an adjustable pressure switch.
Any automatic system should have some sort of auto shut down capability for low voltage.
Now something else you might consider is running an automotive alternator along with the air compressor being driven by the engine, killing two birds with one stone.

 

How are you doing?