Question
QUESTION: I have a 1.5 hp beta flow pump drawing from my lake.  The lake has a very gradual slope and I have a 2" suction line that is probably 100' long, but depth from intake to pump only about 6'.  The pump feeds 6 Rain Bird pop-up impacts in each zone (total 4 zones).  I have a 20 psi well saver tank and pressure when the pump operates is 30 psi.  I have checked for a clog, debris in the system, and everything is clean, but it continues to thermal out, I assume it's the thermal protector.  The fella who advised me on the pump and system said he was very client friendly prior to my purchase, but when I called him for advice  with my problem he rather abruptly said the pump must have run dry, the warr. is void, and I need a new pump as the impeller is nearly impossible to remove from the motor.  If I need a new pump, fine, but it is only 2.5 years old and I just want to be sure it is not something simple.  Thanks for any help.

ANSWER: Sorry to hear you adviser was so rude and un informed.
Pumps will thermal shut-off for a few reasons. The reason the thermal shuts down happens is from excessive amps. High amps cause heat.
One reason. You are asking too much of it. Essentially, asking for 2 hp of water out of a 1-1/2 hp pump. The 6 Rainbird heads are well within a 1-1/2hp flow range unless you drilled out the nozzles and I doubt that.
Second possibility, it is running under voltage. This is caused from too small of wire running to the pump. If you have a voltmeter and are familiar with electricity, check the voltage while the pump is running, at the pump terminals. If it's under 110v per leg (I'm assuming it's running on 230 volt) this is a problem. You'll need larger wire to it.
Third, you have a bad motor and bad luck. Motors normally don't go bad.
If the pump ran dry at some point the impeller would normally melt into a distorted disc. In this case it wouldn't draw more amp it would draw less. It is the action of pumping excessive water that draws high amperage and causes motors to heat and thermal shut down. I believe you advisor was ill-advised.
Since the pump isn't working now anyway, I would open the pump casing and check the impeller. If it's melted then your probably not getting warranty. However, it the impeller is fine then you have a warranty claim. Assuming the warranty period is 3 years.
Good luck with this one.If you don't mind let me know how this turns out.

Matt

---------- FOLLOW-UP ----------

QUESTION: Thank you so much for the reply.  I have a Betta-Flo SFH 150 1.5 hp pump wired at 220V with 10/2  wire about 30 feet from a circuit breaker box at the rear of the house.  I paid extra for a brass impeller so I don't think it is melted as the pump runs and pumps if I didn't make that clear.  The pump will irrigate each zone, but only one zone per day the way my timer is set up.  I can't water longer than 30 -35 minutes as the pump shuts down, I assume the thermal protector.  I am pretty sure it is not the pressure switch. I'm sorry for the confusion. The Rain Birds are not drilled out, but they come with a bag of color coded interchangeable nozzles that allow you to adjust head pressure. I thought the larger nozzles would be easier on the pump so I put the larger ones in.  Maybe my mistake is here. I do not know how to check the amps at the pump, but I'm pretty handy.I have a feeling I am missing something elementary because I seem to be out of my element.  If I do need higher hp or the pump is bad, is getting the brass impeller off tough?  I've replaced my pool pump motor is it that much different?  Maybe just a motor swap?  Thank you so much for your help.

Answer
Thanks for the additional info.
The wiring if fine, 10/2 is more than adequate. The impeller would be in good shape since it is brass.
Though I couldn't find a specific pump flow chart (GPM) for your pump. They are all generally the same. The HP required to pump water is the same no matter what pump it goes through. If you are using either of the two largest nozzles in your Maxi-paws that could be the problem. This put the flow rate above 30 GPM, which is on the max of the pumps ability. Sorry to go back to amps, but it requires energy (Amps) to move water. The more water the more energy. Amps cause heat, heat shuts-off the thermal protector. Try re-nozzling to a mid size nozzle. I think you may fine the problem stops.
One thing which could have brought this on is wear. The nozzles do get larger with use. Especially, with lake, stream, pond water. What started as a 6.2GPM nozzle may now be a 6.8GPM nozzle. Normally, this isn't a problem, but if you started with a maximum and are now 10% higher, well.... you see the problem.
I haven't worked with Betta-Flo pumps so I don't know how the impeller is installed. I generally assume, if it was assembled it can be disassembled. This isn't always the case though.
I would try reducing the nozzles before anything else.

Matt