ABAC B312-100 compressor

[snotters64]

Was given this compressor plugged it in and it won't power up . Done the obvious checked fuses , motor and compressor turns freely . One thing that confuses me , it has a household 3 pin plug but it has what looks to me 3 phase capacitors ? Can anyone advise/help .

 

[snotters64]

Power cables from household plug

 

[Chippie]

The 2 caps pictured are the Start and Run capacitors.
If it won’t run, check all the wiring from the plug right through to the motor windings….Plenty of schematics for cap start/cap run motor wiring…check the thermal cut out if fitted…and the pressure switch…

 

[snotters64]

Any reason why the capacitors are 450 volts

 

[Chippie]

Longevity, 250 V AC capacitors seem to give up earlier….less reliable.

 

[snotters64]

I've checked for continuity from household plug to pressure switch (seems good) checked from pressure switch to where power comes into the box on top of the motor again seems fine . Not sure on how to check further .

 

[snotters64]

Longevity, 250 V AC capacitors seem to give up earlier….less reliable.

Ah right , makes sense

 

[Chippie]

With no pressure in the tank, is the pressure switch contacts closed? ( meter should read 0 ohms..)

 

[snotters64]

With no pressure in the tank, is the pressure switch contacts closed? ( meter should read 0 ohms..)

I've taken the cover of the pressure switch , switch stays in the on position without the cover . Can you guess that I don't have a clue

 

[Seadog]

but it has what looks to me 3 phase capacitors ? Can anyone advise/help .

No such thing. Don't be mislead by the voltages, they're usually rated higher than supply voltage.

 

[snotters64]

Bypassed thermal switch ,still doesn't fire up .

 

[Seadog]

Remove the belt, apply power to the motor and spin the pulley. Two fingers to twist, don't grasp it because if it does spin up it'll happen quickly.

 

[snotters64]

Trie

Remove the belt, apply power to the motor and spin the pulley. Two fingers to twist, don't grasp it because if it does spin up it'll happen quickly.

Tried that still nothing How do check if the motors good or bad ?

 

[hermetic]

I hope you have checked the plug fuse? sounds like the pressure switch is not making contact, if the motor was burnt out you would smell it as soon as you took the cover off the terminals. you need a multimeter or a continuity tester to go any further!
Phil

 

[snotters64]

I hope you have checked the plug fuse? sounds like the pressure switch is not making contact, if the motor was burnt out you would smell it as soon as you took the cover off the terminals. you need a multimeter or a continuity tester to go any further!
Phil

I noticed the pressure switch power connector points are a bit corroded , I'll clean them up and try that . Definitely no smell from the motor and it turns smoothly.

 

[carbon]

Any reason why the capacitors are 450 volts

Because 240v ac is the rms value the actual peek valve is approx 320v so using a 250v rated capacitor will probably result in it failing prematurely

 

[carbon]

You can directly connect the mains to the motor to test but leave the drain tap open and only run it for a few seconds. If that works then the pressure switch has problems

 

[snotters64]

You can directly connect the mains to the motor to test but leave the drain tap open and only run it for a few seconds. If that works then the pressure switch has problems

Bypass the pressure switch you mean ?

 

[not done it yet]

Longevity, 250 V AC capacitors seem to give up earlier….less reliable.

Much more basic than that. AC voltage is measured as the root mean square of voltage, as it alternates. It is the equivalent of a DC voltage wrt Ohm’s Law and resistive loads.

That means the peak voltage of a UK 230V supply will be ~360 volts - not allowing for any spikes above the normal range. Some capacitors supplied may only have an overload of a few %. 450V rating is a fair measure for longevity versus cost, but higher voltage rating is not unknown on high quality kit.

The above post, which quotes a lower voltage is flawed - because the UK AC voltage can be + 10%, of the nominal figure. Obviously there are a lot that don’t know the actual range we can be supplied with, from the grid.

Edited, further, to add that local generators (ie off-grid) may operate a) outside the legal grid requirement and b) may not be a true sine-wave supply, thus likely to include harmonics which may further complicate those supply voltages.

 

[carbon]

Yes but only to test the motor. Don’t use the compressor if the motor starts. If you can remove the drive belt