Running pump in reverse?

[Greenmonster123]

i am hoping one of you guys can tell me what happened to this pump I was working on today. I went to start up an irrigation system today that I winterized last fall so it has been off for about 4-5 months. The 5hp 75 gpm pump tripped the reset as soon as I hit the disconnect on. I put my amp meter on it and tried again, it read overlimit. So I called my well service friend he told me to swap the black and red wires in the control box and bump the power a few times to make it run backwards to hopfully un-stick the pump. I did this and sure enough after a few bumps I put the wires back the right way, hit the power and it came to life running at the proper amperage. What do you think caused this to occur? And is this "trick" something that is often done by you guys?

 

[Valveman]

Yeah that is a common trick to un-stick a three phase pump/motor. It is not real common but it does happen. Usually is is on a fairly new pump (tight clearance), and usually one that uses cast iron bowls and brass impellers. After sitting for a length of time the cast iron will rust enough to stick the impellers. Switching two wires and bumping it the other direction will break it loose most of the time. I do not see this problem with some of the Stainless Steel type pumps like the Grundfos. The SS doesn't rust and they use runner wear rings that don't stick like the metal ones do. The cast iron bowls also won't do this as much after they are worn a little as the tolerances are no longer as close.

 

[Sponsor]

 

[Greenmonster123]

This was not a 3 phase pump

 

[LLigetfa]

I wish there was such a trick to get my old Goulds 1/2 HP sub unstuck. I had to pull it a few times when it ate so much sand that it locked the rotor. I put a pipewrench on the outlet of the pump and whacked it with a hammer to apply enough G-force to unstick it.

 

[Valveman]

I don't think swapping the red and black wires on a single phase motor will make it spin backwards. Just kept bumping it is probably what made it start. Sometimes you have to bump it multiple times. I also use the next larger control box on one like this as the extra start cap size helps.