Bohn McDonalds Beacon cooler

[rango]

Whoops, started this thread accidently in res hvac........Now let's put it where it belongs.

The facts as I know them minus a couple

Box temp 43
r404 system
evap split 2 degrees
41 degree temp exiting evap
38 degree suction line temp at compressor
suction = 80+/-
high side 250
ambient = 85
Cose suction and system takes approx 3 minutes to pull down to 0 psig. Lock down high and leaks back to 20 psig in about 2 min. Changed one condensor motor. Evap and condensor both clean. Dang thing acts like overcharge but nothing been added. Been running for 4 years till this. System is a Bohn with the beacon system attached. Small box (8x10), w/15 ft of line. Overnite, will not go below 39.

Any thoughts? I got pulled off for some A/C while boss went to look at this one after I had started. He's baffled, but as a result I don't have info on subcool and condensor splitt, etc


Thanks

Rango

[codgy]

Is compressor running constantly? Superheat readings are taken directly off of beacon board located in box on front of evap.. Superheat should be running 8-10 deg. Instructions for board are inside cover. This board is somewhat self diagnostic and may be flashing an error code(probably a bad sensor). Make sure if you replace sensor(s) you use the latest version from beacon. These sensors are prone to water intrusion and failure. These units are tricky to diagnose if your not familar with them, as they try to refrigerate even when they sense a problem, rather than shutting down w/total loss of refrigeration.

[jhd1234]

You can download a service manual from Heatcraft's website.

[R12rules]

If your getting no real split across the unit cooler ... then your not feeding any freon.
And if your not feeding freon, your NOT refrigerating.

Hmmmmm.... bad powerhead on TX?
Totally pluged screen on inlet to TX?

[R12rules]

..and ..... if this sucker is running and not refrigerating ... why hasnt the low pressure control opened up and stoped the unit from running?

[rango]

This thing has an eletronic expansion valve on it as per the Bohn website. Stepper motor regulates superheat based on superheat sensor mounted on suction line and inputting to logic control. Are definetly getting some refreration effect as when you raise box temp to say 50 degrees, you will get a small split. Unit will cool (excruciatingly slowly). Boss walked into it this morn and it was 37 degrees after working all night. That's the setpoint and unit still would not pump down and cycle off. No solenoid valve on this systm. When box gets down to temp, stepper motor shuts off refrigerant supply through EV. Gotta be the electronic expansion valve stuck and not moving or weak compressor will not move refrigerant throught the system and pump down when through. I'm leaning towards the latter as the compressor takes approx. 2 min just to pull accumulator to 0 Psig.

[clavej2]

hello friend; you said the suction be back in 2 min, ok what time take to be in 35psig

[rango]

LPCO set at 0 psig with 20 psig diff. Close suction valve and pulls dow3n to cut out. Takes app. 2 min +/-. At cutout, close liq valve. Leaks back to cut in press (20) within a couple of min.

[clavej2]

hello friend; you better be sure,about the liq-valve is worlking,(that valve receive volt dc or ac) example 120volt 220volt or 0 to 10volt,dc

[rango]

No liqid solenoid valve. I'm talking about the liqiud dervice valve.

[clavej2]

hello friend; the valve that you tell me,use or not use voltage.

[rango]

Sory Clave, thought you were talking about the service valve. Expansion valve is O-5v.

[clavej2]

hello friend; maybe you has problem between (exp val, some sensor or board) do a visual check in wires loose by some vibration.

[rango]

Changed out compressor this morning. Coolin like a champ. Thanks all for the pointers.

[R12rules]

Now the question remaining is this; what killed the old compressor?

It sounds like you had a broken piston or rod. It sounds like it could pump only on one side and not the other.

You dont have to question why it went down. We just do so here cause this leads to making the system right ... rather than just making the system run!

A hack can often times make a system run, but not ever make any system right.

We all know and have met waaaay too many hacks. That's one of the best parts about this forum community. We can share information.

I exhort you to dig in and learn the reasons behind the murder of your last compressor. Seriously.
Unless of course, you already know.

[refer dude 2479]

is the suction pressure really 80 psi or am i reading your info wrong.???

[refer dude 2479]

sorry did not read page 2 of the posted thread. dumb a** me.

I agree with R12. you need to find the cause for the dead comp. could be bad sensors and or control on the electric txv. that is where i would start.

[John Grim]

Having serviced the MacBeacon units regularly for the last 15 years, I would like to give you guys a heads up. Any service on these units should start with removal and ohm the thermistors in ice water. 32,650 ohm. Promise this is where most of the problems start, goes double with the Beacon 1. The condensers are very hard to clean. Keep after it from the inside, ain't no fun, I know. If the boxes Mac unit gets shut off at the breaker, for delivery or inventory, the EEV remains open, liquid migrates to evap, then when power is returned the undersized accumulator is overwhelmed slugging the compressor. On the low-temp scrolls, liquid washes the oil from edges of scroll and scores the plates that seal the edges. If turning off at breaker, turn back on right after turning off. This closes the EEV, doesn't pump down, but at least the valve is closed...

[VTP99]

Hi John and welcome to the site. You might want to introduce yourself in the new member forum. Get your post count up and apply for PRO membership.
Vince

[John Grim]

Why is superheat 1 degree at coil and colder at the condensing unit. Sight glass might normally show a few bubbles in this case under normal conditions. Is Compressor should be pulling rated load. These units will reduce super heat to counter for high compressor discharge sensor reading.