Blowing Fuses

I just moved to a house with a hot tub. It was drained when I moved. I recently filled it, and the jet/pump fuse blew in a few minutes. They are self-priming pumps, but i may have started the jets before that was done. I also read that they could have been airlocked, so I cracked the seal, blead the air out, replaced the fuse and fired it up again. This time it self-primed and ran good. I added the chemicals that I purchased from you, and everything was looking good. I went to check it before adding the last of the chlorine and noticed the jets/ozone were off, and the fuse had blown again. it ran good for 3-4 days. any suggestions on why this would happen, what I can check and what I can do to prevent it? thanks