FTS airjet

[Gary S]

hello all,
FTS MODEL:317-00079-000
I had a quick look at a unit yesterday and dont know much about these units and wondered if anyone on here did.

Its a precision temperature system used for testing purposes. it basically can be set at all temperatures as low as -75c for testing components at high/low temps. it has a wide hose that supplies air into a test box and the temp can be set by users. it has 2 condensing units in a cascade system set up as far as i can see. the lower compressor runs on r404a and the top one is marked R290 (propane). Think its a american unit as refrigerant quantity is in pounds and the default temp is farenheit.

Unit would not cool when i looked at it. the controls are quite complicated with lots of different controllers pcbs and touchscreen panel. put gauges on R404a and pressures were a little unusual. low back pressure and high pressure. low was less than 1 bar and high about 15 bar although adding some refrigerant made no difference. maybe the system on propane is short as both units run with no cooling. Maybe there is a control software issue?

anyway any input from someone who works on these units would be greatfully received.

thanks

[Peter_1]

R290 will not be the refrigerant for the low side, only some R290 to flush the capillary. R290 has +/- the same properties as R404a. As long as the low trap isn't running the high trap isn't loaded and LP will be low on the R404a.
R404a must first cool down deep enough before the low trap can and will start.
What's the brand of this freezer. Try to energize once the low trap manually or force it electrically while monitoring pressure. Be careful, these units run mostly under vacuum, so avoid entering air in the system. Vacuum your hoses very well