Cleveland 24-CSM steam oven

DHS125

I have been troubleshooting a problematic Cleveland 24-CSM steam coil generator convection oven for several weeks now and haven't found a solution.

Basic operation: The convection oven has a steam coil generator in the bottom cabinet. Building steam enters the water tank in a coil @ approx. 40 PSI. Potable water in the tank is heated by the coil and food grade steam is created which rises into the two compartments above heating the food as it swirls around it (convection).

Problem: After 3 1/2 to 4 hours of what appears to be proper operation the water supply valve stops operating on a consistent basis but the steam valve continues to cycle on and off. The water level in the sight glass drops slowly until it reaches the bottom of the tube. This takes about 20 mins. I have noticed that the water supply valve has opened at least once before shut down and supplied a small amount of water as observed by the level in the sight glass. Ultimately the sight glass level continues to drop until finally the water is at the bottom and the appliance shuts down on LLCO. It then resets and the water is restored to proper level, according to the sight glass, within 20-30 seconds. At this point a manual reset is necessary.

FYI
- this unit is not equipped with a auto blowdown feature - it is manual only
- the troubleshooting guide in the manual was followed and all specifications checked out as given
- there is a second appliance that is identical to the first that has begun to shut down in the same manner
- the only common connection between the two is that they both use building steam to heat the potable water
- the differences between the two is that the first has been gone over completely and has numerous new parts both mechanical, plumbing and electrical. The second machine has not been maintained, mostly original parts including control circuit board
- both units operation pressure is set @ 5 PSI with a differential setting of 1.5. The pressure rises to about 7 PSI and then drops to about 3.5 PSI.
- the steam coil pressure comes in @ 40 PSI but the gauge has shown drops in pressure as low as 25 PSI
- using the first appliance DMM's were used to monitor the voltages for the high probe, low probe, and WF valve (all brand new). During normal operation the probes and valve operated in accordance with the sight glass water level. After the 3 1/2 to 4 hours of normal operation, when the water level dropped below probe levels (according the sight glass) no voltage change appeared on meter. DMM read-out showed both probes were satisfied with water despite the low level in the sight glass. Interior of tank has been inspected and there are no signs of excessive corrosion and the baffle covering the probes is 100% solid. As soon the shut down occurs, seconds later the tank refills with fresh water and the probe voltage is shown as 12 volts until level is restored and then once again the probes show 0 volts which is normal readings during normal operation. This to me rules out any possibility of a electrical error, circuit board failure, or faulty probe issue.

How is it possible the water level in the sight glass can be nearly at the bottom and yet the probes show that they are covered in water?

This is the model I am discussing:
http://www.garlandcanada.ca/products/cook/steamers/convection/convection-6-pan-models/electric/24csm-classic-series-convection-steamer-with-steam-coil-15-psi-boiler

blee597

You say that you have another unit next to the problem unit that has the same problems. Do both units shutdown at the same time or do both units shut down after the same running duration? Also, you said that the unit goes down after 3-1/2 to 4 hours of operation. Have you measured that time to see if it is exact (as if a timer was shutting it down)?

JStar

My first impression is that the tank is the same or greater pressure than the feed-water pressure, causing an equilibirum and lack of positive movement. I'll look more into that unit and see what else could make sense.

Is the building steam coil leaking?