Author Topic: can I go too far with my engine drive?  (Read 2405 times)

icebox

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can I go too far with my engine drive?
« on: December 15, 2013, 01:42:22 pm »
We have a 2 plate seafrost system with an engine drive feeding thru one end of the 2 plates and a 12 volt system from the other end. The engine drive is on a simple timer and the 12 volt system has an electronic controller.

Are there any issues with running the engine drive a long time?
Can we make it TOO cold? Will this throw off the AEO setting on the 12 volt system?

Thanks

Richard

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Re: can I go too far with my engine drive?
« Reply #1 on: December 18, 2013, 11:09:25 am »
The best answer to your questions would be from Cleave president of SeaFrost. I can only give an opinion of how his system would perform based on similar systems I designed and tested.

First the engine drive systems I designed were protected from extreme low side temp/pressure by a low pressure switch. SeaFrost engine drive systems do not have low pressure switches but they do have a low temperature cut off switch inside the black control block, This switch may not protect compressor if it runs longer than it should. In addition to low flow/low pressure protection my designs included a low refrigerant switch. The question of holding plates getting too cold is not a problem it is compressor cooling and lubrication as refrigerant flow decreases at very low temp/pressures, I worry about.
 In conclusion I would advise against winding engine drive timer too often.

I believe Seafrost 12 volt system’s refrigerant flow is controlled by a low constant pressure regulator valve instead of cap tube or TXV, so extended running time should not cause a problem for compressor as long as condenser fan is operating.

The AEO module does not know what is happening with plate or box temperatures. The thermostat controls compressor starting and stopping based on where its temperature sense tube is located and where temp control is set. The AEO module provides safety function for voltage and amperage the same as all Danfoss electronic modules. In addition to protecting compressor AEO controls compressor speed automatically. Again the AEO does not see temperatures in box what it does is monitor how long compressor runs in a thermostat cycle. If compressor is cycling too often AEO will slow compressor speed to improve System Coefficient Of Performance (SCOP).  If thermostat setting is not satisfied in manufactured program time limit compressor speed will be increased.

If you understand at what temperature eutectic material in holding plate is set to freeze at  compressor needs to be capable of reaching a temperature 20 degrees below the eutectic point.