Electrical issues with Bauer K-14

[Vieques Arnaud]

Having some issues with the electrical on this K14. The dual element fuse blew on the main transformer, I replaced it and the compressor won't start. If I push the manual override on the "mag switch" the compressor comes to life and runs as long as I keep pressing it. I have of course no electrical schematic. I did notice that the small transformer (dc?) on the board looks carbonized.
I'm trying to determine why the mag switch does not engage. What does this board control ? If the board/transformer was fried would that keep the mag switch from engaging ?

There is power to the unit, to the mag switch and to the main transformer.

pictures: https://www.dropbox.com/sh/22iqha4bp3uqw7v/gg4QysNdhp

Any help would be greatly appreciated.

 

[Wookie]

DC is not transformed, but you can do lots of other stuff to it. What is the coil voltage on the mag starter? I'm betting 12 or 24 volts DC or 24 volts AC. I'm betting that if you blew the fuse, you might have blown the rectifier or the AC transformer for control voltage. With the compressor energized but not running, check for control voltage at the mag coil on the starter. Make sure that it is the rated voltage for the coil. If not, find the transformer (usually it's quite big, the size of the fist you re clenching at it) and also the rectifier if it's a DC mag coil. Usually it's a little square thingy about the size of a quarter and 3/8" thick with 4 electrical contacts on it. I've had those go bad too... Did you fix the electrical problem that caused you to blow a fuse?

If the control voltage is correct and the mag still won't pick up, look for a blown pressure switch or low oil pressure switch or high temp switch. Any of those things will cause the circuit to fail dropping out the starter.

 

[Vieques Arnaud]

DC is not transformed, but you can do lots of other stuff to it. What is the coil voltage on the mag starter? I'm betting 12 or 24 volts DC or 24 volts AC. I'm betting that if you blew the fuse, you might have blown the rectifier or the AC transformer for control voltage. With the compressor energized but not running, check for control voltage at the mag coil on the starter. Make sure that it is the rated voltage for the coil. If not, find the transformer (usually it's quite big, the size of the fist you re clenching at it) and also the rectifier if it's a DC mag coil. Usually it's a little square thingy about the size of a quarter and 3/8" thick with 4 electrical contacts on it. I've had those go bad too... Did you fix the electrical problem that caused you to blow a fuse?

If the control voltage is correct and the mag still won't pick up, look for a blown pressure switch or low oil pressure switch or high temp switch. Any of those things will cause the circuit to fail dropping out the starter.

thanks a lot for the pointers, I'll have to get the electrician to help as this way beyond my pay grade.
If you have a chance would you take a peak at the pictures (right folder this time!), there is a circuit board with a small transformer that says 115-20 with what I think is a rectifier next it (black squarish box), is that the one you're talking about ? Also Have no idea what caused the fuse to blow originally ?

 

[Vieques Arnaud]

bump.

 

[Wookie]

Wow. You've got what I would call a mess. Looking more closely at your pictures, you've got single phase power running into your motor starter, and single phase out, but a jumper from the output side of phase 1 to the input side of phase 3? Somebody built this thing custom, and I think that you're going to have to start from scratch. It's what I would do. Is the motor 3 phase or single phase?

The way the circuit should work is that control voltage is energized all the time. Oil pressure is on a time delay, typically 15 seconds. If oil pressure doesn't come up to the rated pressure within 15 seconds, the control circuit drops out and the machine shuts down. Same with air pressure. The circuit is energized through the air pressure switch, and when air pressure reaches the setpoint, it opens the switch and drops out the control voltage, causing the compressor to shut down. The auto drain is energized when the compressor starts, starting the minute timer (the left hand knob on the auto drain timer) and when the timer counts down, it opens the auto drain solenoid for a short period of time, typically 5 seconds. The auto drain will not cause your compressor to not start. Somewhere is a start switch. All this does is complete the loop for the control voltage closing the main contactor. Either the oil pressure switch or the air pressure switch will cause the compressor to not start.

Check the voltage into and out of your air pressure switch, into and out of your oil pressure switch, and into and out of your start switch. With all switches in their normal run settings, they should all read the same, and you should have the same voltage on the control side of your contactor, and your starter should pick up.

I am in port all day. Call me when you have checked these things at 281-300-4748. Meanwhile, I'll call my Bauer guy (Porter Stiles) and figure out twhere to get that circuit board.

---------- Post Merged at 12:44 PM ---------- Previous Post was at 09:35 AM ----------

Next test, as all of the folks I spoke to think your heaters are toast, lift the leads on L1, L2, and L3 and wire them directly to the input side of the starter. See if the starter then holds. If so, it's the heaters for sure.

 

[Vieques Arnaud]

wow Frank, I owe you big time....thanks for making all these calls for me.

Yep motor is single phase 7.5hp Baldor. Don't know that I will be able to get electrician to run tests today unfortunately.

 

[Wookie]

You can do this. I can walk you through it.

 

[Vieques Arnaud]

Sorry saw this too late was out diving...thanks again for the help. Air pressure switch is fine and I believe oil pressure switch is fine too.
I do get a read of 138v on the out of AC-AC coil, isn't that high maybe that's what caused the fuse to blow originally ?
I should be at it again tomorrow and will test the heaters on the mag.

 

[frogman62]

Guys, Most of these use a 3 phase starter because that is less expensive/ The 3 phase works for 1 phase with the jumper connecting across the overload for one of the electrical legs
IF single phase it should be L1 and L2 input of 230, Jumper from T2 to L3 and motor connections from T1 and T3
Hope this helps
Jim Shelden

 

[Vieques Arnaud]

So the motor control is fine and so are both pressure switches. The little coil on the electronic board is fried and I get a read of 138V on the ac-ac transformer which would probably explain why the fuse blew in the first place and why the coil on the small board got fried....
btw heaters are fine too.
Input power is fine (a bit on the high side) but I don't understand why the ac-ac is putting out 138V, I know it's old (1988).
Do these just get tired and don't work properly or should I be looking somewhere else ?

@jim thanks for that input, my electrician who is not a compressor specialist was just a little nervous about it and so was Wookie...