Low Running Amp of Pump

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bwchoo Active Contributor Join Date: Jan 2009 Posts: 18	Low Running Amp of Pump 03/31/2010 4:27 AM
	Dear sir, Our chilled water system consists of primary and secondary system. We have 7 nos of same capacity primary chilled water pumps (end suction pump)which are installed parallel. The pump operation is 5 running + 2 stand-by. The problem is one of the pump is running at low amp compared to other running pumps (4 running at same amp & one is different). As I understand if this particular pump running at low amp, it indicates that the pump's operating point is at low flow high head compare to other pumps. Why this happen? Please advise. For your info, six out of seven is running at same amp only that particular pump is different. Regards Choo
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Kaisan Power-User Join Date: Nov 2009 Posts: 296 Good Answers: 27	#1 Re: Low Running Amp of Pump 03/31/2010 5:06 AM
	Your understanding is correct. Low amperage in parrallel running pumps is nearly always due to low flow due to one pump not achieveing as high a differentail head as the others. However, can I state the obvious first - have you checked the ammeter reading. Also are the motors identical? After that you have to look at things that will negatively affect the head of this pump. Look at suction restriction, discharge restriction (NRV etc), impeller diameter, motor speed (unlikely), impeller damage, direction of rotation (very obvious but often overlooked). It is also possible that this pump is more efficient than the others due to good clearances etc. __________________ I have no special talent. I am only passionately curious. Albert E
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Abner Active Contributor Join Date: Jan 2010 Location: Rochester, NY - USA Posts: 21 Good Answers: 1	#2 In reply to #1 Re: Low Running Amp of Pump 04/01/2010 8:26 AM
	Kaisan, Vote 1 for GA. bwchoo, I would just add along the same line of thought to check the impeller itself for a foreign object lodged within the impeller vanes. Also when checking diameter of the impeller also check thickness of the impeller. __________________ Abner
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