Ice damage?

Hi guys, I have a blast freezer (-35°C) evap with some damage on it and would appreciate if I could get some ideas on what may have caused it?

There are numerous pockets of damage that seem to have 'blown' out from along the electric defrost bars (you can see the heater bar in the middle of the photo), taking the fins and copper pipes with it. I have been told it is from ice damage but my understanding is that ice build up would be randomly distributed. All of these pockets (about 8) have radiated from the heaters.

I hope you can see the damage clearly, if not I can try and get some other photos if that would help.

Thanks in advance,

Gareth

Attachment 11757

Too short defrost times letting the ice nearest the heater melt but not fully warming the evaporator and therefore not melting the ice further away from the heater rod.
When the system then restart the meltwater is trapped inside the outer ice with nowhere to expand to....

Anyway, that is my best guess.

:cool:

This looks like what is known as "Ice Balls" its caused by poor defrosting. It appears that during the defrost cycle ice that has frozen around the evaporator tubes melts but doesn't fully drain off the coil in certain areas. This ice tube which is still full of water lays around the pipe then re -freezes when the system restarts and crushes the coil tubes and often crushes the tube to the point where it splits and leaks. I have seen this on several different makes of coolers. I have even seen this on a Mitsi split heat pump on the outdoor coil which has frozen during the heating cycle.
In all cases the copper tubes are flattened as if done by a machine a very neat flattened finish with curved ends to the flattened tubes occurs with a neat split along the tube side.
Increaseing the defrost cycle time and the drip time
In most cases this cures the problem , sometimes extra heaters may be needed in the coil due to cold spots during defrost.
Its a strange phenomena why it occurs , I think its a combination of poor liquid distribution , and air flow which gives localised heavy ice formation plus over ambitious defrost settings.
Hope that helps ICE is a very destuctive force

Thank you both for your help. I had seen ice damage before, but not quite as this. As you said Glenn, almost like a machine had done it.