McQuay AGZ 055

[joegrind]

agz 055 S# stnu0111001100
cct 1 down due to a defective suct press transducer. Is there a way to get the circuit back up temporarily until I can procure the oem part ( i have a biomed dept at my disposal and the have allsorts of resistors and electronic gadgets)

[Edited by joegrind on 08-19-2004 at 05:01 PM]

[lwarren]

Just started a 100 ton AGZ the other day, but I am not that familiar with them. I noticed in the microtech controller that circuit one and two had a low suction pressure cutout programmed at 55 psi. Enter the manager password and see if you can change the setting to get it going.

[lew2]

I don't know of a safe way around the transducers. The program in the controller uses them for the control of the compressors, and condenser fans, as well as safety settings.

The program in Microtech 2 does allow you to offset a transducer that is out of calibration to some extent.

They don't fail a lot of tranducers from my experience, however, that doesn't help you though.

[clydemule]

I don't know jack about McQuay stuff, but I have used hundreds of the Carel pco2 (peeko-two) controllers, which is exactly what the Microtech controller is.

The pco2-small (I think that is what is used on the AGZ) has 5 analog inputs, B1 through B5. The sensor is probably hooked to B1-B3, since B4 and B5 are reserved for NTC temp sensors.

The controller can be programmed to accept either 0-10 VDC or 4-20ma analog inputs. The Carel pressure transducers are 4-20ma, but McQuay could have bought them from someone else.

If the guys in this lab where you are working have a bunch of gizmos, see if they have a loop calibrator. It is a device used to calibrate sensors. You can either hook the sensor up to the calibrator, or hook the calibrator up to a controller. If you hook it up to the input point for the bum sensor you can send a fake signal to the controller. Just flip the calibrator to send a 4-20ma signal, and look at the suction pressure screen. As you move the dial you should see the pressure display change.

You can just leave the thing there until you get the right sensor. The only wrinkle I can think of is if the loop calibrator has an auto off feature to save battery power. Chances are if it does it will shut off just after you get home.

I hope this helps, even though it was kinda long.

Good Luck,

Clyde

[johnnyc]

Based on your S# the unit has a MicroTech 1 controller,and the txdr is used for pump downs and as an lp control and refrigerant freeze prot. You probably should not bypass the device,it should be available within a day or two from McQuay parts.The Microtech 1 and 2 use the same transducer,and send out a 0-5 vdc signal. If you had to you could tempoarily hook up a potentiometer or resistor and create the correct psi reading,but you may get alarms and will lose the freeze function.

[joegrind]

Originally posted by johnnyc
Based on your S# the unit has a MicroTech 1 controller,and the txdr is used for pump downs and as an lp control and refrigerant freeze prot. You probably should not bypass the device,it should be available within a day or two from McQuay parts.The Microtech 1 and 2 use the same transducer,and send out a 0-5 vdc signal. If you had to you could tempoarily hook up a potentiometer or resistor and create the correct psi reading,but you may get alarms and will lose the freeze function.

thats kind or what i was thinking! how about if i put a var adj resistor accross the red and white at the plug to provide about 2 volts( thats about what the other cct runs at) I only need the 1st cct during the day as cct2 will carry it through the night

[johnnyc]

You have to be careful how you wire in a resisitor,etc, the txdr takes 24vac to power it up and sends out 0-5v ,sharing the ground/common.You may need a separate 5vdc supply and then use a resistor or pot.But ,remember this should only be for a temp fix, DO NOT leave it this way,or you will be back for bigger problems

[joegrind]

Originally posted by johnnyc
You have to be careful how you wire in a resisitor,etc, the txdr takes 24vac to power it up and sends out 0-5v ,sharing the ground/common.You may need a separate 5vdc supply and then use a resistor or pot.But ,remember this should only be for a temp fix, DO NOT leave it this way,or you will be back for bigger problems I'm a little confused????according to the dia, red is fed from a regulated 5 vdc supply, wht goes to "s" and blk goes to "g" on the analogue imputs, I can't find 24v anywhere in the cct. I was also thinking of jumping the wht siignal wire from cct 2 over to cct 1 on the input board to fool cct 1 into thinking its running at the press of cc2 any thoughts

[787 Guy]

I dont know for sure but I think even if you do use a resistor to give you a fixed suction pressure when that circuit attempts to pump off it will generate a can't pump down alarm wich may require manual reset. I dont have any resistor information but 2.5dcv should be about 65#