Burrah Boy
10-08-2010, 05:07 PM
Hi guys, I work at a site that has five of these units with 3 compressors per unit. Over the years I have done various repairs on these units where I have had to remove the refrigerant, carry out the repair, pressure test and vac (obviously). However, on nearly all ocassions that I have carried out this procedure I have had fuses blowing on me. Either one of the 250amp supply or all three of the 120amp fuses on the main bus bar(there are six fuses per compressor but only the three on the hard wired, not the soft start side). This has beaten me around the bush with various electrical checks and test, but to no avail. I happened to speaking to a bloke from carrier and mentioned this to him. He asked me if I electrical isolated the main supply BEFORE i pulled a vacuum and I said no. He said that was the fault but couldnt explain why. He said they at Carrier were issued a bulletin saying that pulling a vac without totally isolating the incomer would blow fuses but no technical explanation why. So once the system is in a vac state, BANG! I cant understand the reason behind this. I have never had issues like this on other chillers. The reason I dont isolate the system is to keep the oil seperator heaters on. I have spoken to other work mates who have also had this problem happen to them.
Any Sages out there willing to give me technical reason and explanation?:(
Thanks!
Any Sages out there willing to give me technical reason and explanation?:(
Thanks!