Ice machines compressor runs extremely hot.

Hi, first make sure the switch is not in the clean position but to on. If it is in the on position and the water is circulating over evaporator plate and is running back into the water sump tray and compressor is running as you stated then check to make sure the hot gas valve is not letting hot gas leak through during freeze cycle, the way you can check is after start up wait about 5 minutes and check the temp entering the hot gas valve and the temp on the other side of the valve if temp is the same then valve is bad. The next thing to check is the refrigerant level this only can be done by adding service valves and weighing out the charge to see if it is low, if low then there is a leak. The freeze cycle is as follows. The compressor, fan motor and water pump are all operating and stay in a freeze cycle until the evaporator thermistor reaches 6.5 deg F. That signals the control board to place the unit into a harvest cycle.

Is the wiring correct? Fan runs when condenser is hot / high pressure not just when compressor runs so check condenser sensor.

These unit time freeze time and harvest times and keeps track of them. If your freeze time exceeds 35 minutes or harvest time exceeds 3 minutes, it will place unit in lockout. The biggest cause for excessive time to harvest is the harvest valve not functioning properly, and undercharged unit or a dirty condenser. The most probable cause is a dirty condenser. Under charged units can be determined by checking compressor outlet temperature while running, it should be 150 to 190 degrees depending on atmospheric conditions present. If it is harvest valve, the downstream temperature will stay at or near compressor discharge temperature. It should cool down to ambient temperature in a few minutes after freeze cycle begins.

Is the compressor overheating when this happens? Feel the top of the compressor when this is happening and tell me if the top of the compressor becomes extremely hot to the point that you cannot keep your hand on the compressor. Reason I ask you to do this is that it is possible that the compressor is short cycling because of a defective start relay and/or run capacitor. Let me know if the compressor is overheating of simply turning itself off. I will post a service manual if interested but would like to e-mail you the service manual for your Hoshizaki KM-255BAH because of copyright issues. You may contact me HERE if you like. Thanks Sea Breeze

The QYO604A uses r404A with a 28 oz. charge. The fan cycles for a couple different reasons. First, when the unit goes into harvest mode, it is the hot gas that allows the surface tension of the ice to plate to be broken allowing the sheet of ice to drop. It does not have the required btu capacity to do this in a timely manner with the fan running, and cycling it off allows the machine to provide a greater heat capacity to the evaporator. Second, in a properly charged machine WITH A GOOD COMPRESSOR, meaning the valves are not shot, unless it is extremely cold the fan will stay on and if it is that cold the machine is probably in a poor location. The fan cycler is a 200 psi open and 250 psi close. There are reasons the fan is intermittent also and usually this is due to a faulty switch, which after 10 years or so can fail from an electrical mechanical standpoint. I have seen the switch terminals loose and very tricky on diagnosing due to the nature of the symptoms. If your reading 200 off and 250 on then the switch is good and look at low charge, starving tev, bad compressor valves. You failed to mention what the state of production is. Normal rated, low or almost non existent. This also is part of the diagnosis. Good luck.

dirty filters in the indoor unit.As the ambient temperature rises the unit will work harder and longer,its fine when its just a normal day because the evaporator coil wont have time to ice up as the compressor will cycle off before the coil freezes totally,but during extreme ambient temperatures the coil will ice up as the compressor will continue running to reach set-point causing the coil to ice up

Possible causes are many
Things to check

• If air cooled, is the condenser coil clean and is the condenser fan running when in ice production ? Is the area extremely hot where the ice machine is located? If water cooled, is there adequate water pressure and is the water regulating valve set properly?
  

• When the system switch is in the off position is there any water running ( if so the inlet water valve may be stuck open)

• When in ice production, is the small tube that feeds from the hot gas solenoid hot? This tube comes from a valve at the back of the unit and feeds over the compressor and into a tee near the insulated Tx valve. This line should be hot during harvest and cool shortly after harvest.
• Has the float switch assembly been cleaned. this is a cylindrical unit beside the water pump,It can get plugged with minerals and not initiate harvest
• The system may have a refrigerant charge problem (short) or the compressor may be weak, at which point diagnosis would need to be done by a refrigeration tech

Hope this helps

this indicates that the backup freeze timer terminated the freeze cycle. Stayed in freeze cycle 60 minutes. Causes can be: stuck float switch, water valve leaking incoming water, and the more extreme can be hot gas valve leaking, txv not feed properly, low refrigerant charge, or bad compressor. Usually one of the first 2 items are the root cause.

if the ice production is slow first try to set it on a warmer temperature. Now if its frosted up then you will need to defrost it. Also check the fan to see if its running. if yes is the condensor clean? If yes then check temperature in bucket. 10 to 15 degrees is ideal for this model.

There is no rule of thumb for this. It involves exacting numbers based on specific density of product, starting and ending temps., and quite a bit other stuff. Condensing unit info can be gotten from any HVAC/R supply house. If you have a specific in mind, let me know and I'll get info for the specific.