Compressor fault

[pauliil1948]

hi guys , my compressor was a 3phase abac 200 Ltr brand new ,so I changed the motor and a electrician wired it up ,but when i switch it on it builds up pressure and switches of when it's at the cut off pressure but it switches the on off switch off also ,so I have to keep switching it Back on Whitch is a bit annoying ,any help would be great thanks .

 

[rtbcomp]

What do you mean by the "on-off switch"?

 

[brightspark]

probably wired the pressure switch through a dol starter and wired it through the stop switch so it wont re start till he pushes the button

 

[pauliil1948]

What do you mean by the "on-off switch"?

The white turn button ,thanks when it gets up to pressure it clicks off

 

[pauliil1948]

probably wired the pressure switch through a dol starter and wired it through the stop switch so it wont re start till he pushes the button

Not sure what you mean I will ask the spark to have another look ,but it occasionally stays on but rarely dose ,thanks .

 

[rtbcomp]

Did you notice whether it switches off when the compressor stops or when it tries to restart?

If the latter and if the yellow knob is an overload setting maybe a tweak on that will help? I've not seen that type of switch before, so just guessing.

What does the black lettering on the yellow knob say?

 

[pauliil1948]

Did you notice whether it switches off when the compressor stops or when it tries to restart?

If the latter and if the yellow knob is an overload setting maybe a tweak on that will help? I've not seen that type of switch before, so just guessing.

What does the black lettering on the yellow knob say?

 

[pauliil1948]

Thanks again ,it switches off when it reaches pressure, the yellow dial has numbers on

 

[rtbcomp]

When it switches off do you get a short hiss as the pipe between the pump and the tank empties?

I'm thinking if that yellow knob is a thermal overload then it may be that that's tripping rather than the pressure switch itself. As the pressure increases the load on the motor increases and so the current taken by the motor increases. If the cutout (if that's what it is) is set too low it may be tripping.

What pressure does it cut out at?

 

[pauliil1948]

When it switches off do you get a short hiss as the pipe between the pump and the tank empties?

I'm thinking if that yellow knob is a thermal overload then it may be that that's tripping rather than the pressure switch itself. As the pressure increases the load on the motor increases and so the current taken by the motor increases. If the cutout (if that's what it is) is set too low it may be tripping.

What pressure does it cut out at?

Just now its set at 120 psi and when I empty the tank it comes back on at 45 psi ,I have been trying to adjust it today but can't get it to come on before 45 psi, I can adjust the cut of up and down but not to get it back on ,been at it ages ,been turning the yellow button so sometimes the switch stays on sometimes it goes off , thanks ,paul

 

[brightspark]

yellow knob look like the thermal trip for current overload 4 to 6.5 amp that would be fine on a 3 phase motor giving about 18 amp over the 3 phases but on a single phase only 6 amps . it would need to be at least 12 amp min on a 3hp single phase motor or it would trip as pressure increases due to a higher current draw than the overload

 

[carbon]

my compressor was a 3phase abac 200 Ltr

Does this mean that it’s now single phase rather than three phase as a single phase motor will probably need a higher rated overload to run correctly

 

[rtbcomp]

In this image:



"PRESSURE" is the screw you adjust cut-off pressure with, tighten to increase.

"DELTA PRESSURE" sets the difference between cut-out and cut-in pressures, this is usually set to a 30 psi difference, and may need tweeking if you adjust the cut-out pressure.

Do these adjustments with some pressure in the tank.

As Brightspark alludes to, set the yellow knob to the highest number and maybe try reducing the cut-out pressure. Once you've got it working adjust the delta pressure.

This hot weather won't be helping much if it is a thermal cutout.

 

[pauliil1948]

In this image:

View attachment 148522

"PRESSURE" is the screw you adjust cut-off pressure with, tighten to increase.

"DELTA PRESSURE" sets the difference between cut-out and cut-in pressures, this is usually set to a 30 psi difference, and may need tweeking if you adjust the cut-out pressure.

Do these adjustments with some pressure in the tank.

As Brightspark alludes to, set the yellow knob to the highest number and maybe try reducing the cut-out pressure. Once you've got it working adjust the delta pressure.

This hot weather won't be helping much if it is a thermal cutout.

It's beginning to make sense now ,if it doesn't work will it be best to change it for a single phase switch ,your help is much appreciated ,thanks guys .

 

[brightspark]

most pressure switches aren't fitted with built in overload protection you could change it for a new one without overload protection . depends on how fussy you are . I don't bother with them as im always there when the comps running

 

[pauliil1948]

Thanks , iam always there when mine is running so I will get a new switch without the overload protection see how it goes thanks guys ,will keep you posted ,Paul .

 

[rtbcomp]

There should be an overload protection on the motor anyway.

 

[Hopefuldave]

There should be an overload protection on the motor anyway.

Unlikely on a bare single-phase motor, they usually rely on the plug fuse or an upstream breaker - I know mine does

Dave H. (the other one)

 

[pauliil1948]

Hi guys ,bought a new pressure switch and wired it up correct I think , the compressor ir running and cutting of at 125 psi then coming back on at 75 psi ,iam just using diy stuff in my garage like a impact gun for taking my wheels of , is this pressure ok ,there is only one screw for adjusting on the switch, I also noticed the copper pipe gets a bit hot along with the ( cylinder head ) is this normal , is it possible the motor is running the wrong way one more question the oil level is this low or OK ,many thanks guys for your help ,Paul.

 

[WorkshopChris]

Oil level is OK if you look on the compressor fly wheel it should have a directional arrow cast into it,(most but not all do).