Pump motor question

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no-mas

no-mas

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Jun 16, 2008
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FL
I had an engineer tell me he runs his pump around the clock because "the worst thing you can do for your pump is to turn it on." I get his point, namely the wear and tear of starting as opposed to continuous running, and he says he has replaced the pump 3 times in over 30 years. Seems impressive, but I've often thought "yeah, but you spend a fortune running that 2 hp pump around the clock." :roll:

My question: is this b.s., or does it really last longer? How long should a pump motor last? Is it more cost effective to run a two speed motor on low speed around the clock, and therefore not have to replace it as frequently??
 
Here's another thought, based on that statement: What if you only had a 1/2 HP pump (or a 2 speed/multi speed) pump and ran it 24/7? Now the cost to run drops immensely, and your water is never stagnant? I've posted many times before that I have a problem with short (2-3 Hour) run times, as pools sit stagnant for 20+ hours at a a time (which kinda grosses me out!).

His theory (to me) makes some sense. I like water to be in motion, I just don't like to pay too much to have it do that! I can see the value of it though.
 
simicrintz said:
His theory (to me) makes some sense. I like water to be in motion, I just don't like to pay too much to have it do that! I can see the value of it though.
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Yeah Bruce, this is exactly what I'm getting at. I run my pump longer than I have to, if only because when I'm home, I want to see the water moving. And, running on low I anticipate a cost savings, especially over the summer.

How long should a motor with 1 start/stop per day last, as opposed to running 24/7? Theoretically, is switching speeds causing the same wear as turning off and on?
 
Turning on and off a motor may shorten the life of the motor but the energy cost you save by turning it on and off will likely pay for several new motors over the life of the first motor.
 
What would the stress be like on a two speed pump that runs on high for pool cleaner/waterfall etc and then drops down to low for the rest of the time? Basically the pump would never stop but would cycle between the high/low speed.
 
I wouldn't expect much stress in either case. Is it more than not doing it? Yes., but not much. For higher HP motors > 10 HP, I think starting and stoping makes a much bigger difference but pool pump motors are quite small and the loads are not all that significant.
 
My new pump has only been in for a week; have had a 2.23 hp, one speed, for 23 years. When my old pump(s) started up it started with a surge. The Pentair Intelliflo VF, doesn't do that and primes it up slowly, so there is hardly any "jolt". You can set the prime time. Do any of the newer pumps, other than the Pentair VS/VF have that feature?

gg=alice
 
I think that can only be done with a variable frequency drive so all of the variable speeds should have it.
 

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mas985 said:
Turning on and off a motor may shorten the life of the motor but the energy cost you save by turning it on and off will likely pay for several new motors over the life of the first motor.
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No doubt this is true for a larger motor, but what about a low power (1/2, 1/3 or two speed on low) motor?
 
I have to wonder about whether the wear is that significant. I work in a garage, and our air compressor starts and stops all day long. I worked in the last shop for 14 years and we never changed the motor the whole time I worked there. It was capacitor start, if that makes a difference, but still, it had a rough life starting every ten minutes or so.
 
Most of the small pump motors are split phase, not permanent split capacitor. The start winding is controlled by a centrifugal acting, spring loaded switch. If the motor speed is modulated below the switch off speed the start winding will be toast pretty soon. Adapting a split phase motor to variable speed is not very practical.
 
Not anymore. Most of the pumps today are PSC motors. Look through the pump list on the CEC web site and close to 2/3rds are PSC.
 
Richard320 said:
I have to wonder about whether the wear is that significant. I work in a garage, and our air compressor starts and stops all day long. I worked in the last shop for 14 years and we never changed the motor the whole time I worked there. It was capacitor start, if that makes a difference, but still, it had a rough life starting every ten minutes or so.
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Good point, Richard.

Thanks to all...
 
Not to belabor a point, but having a start capacitor does not a psc motor make. It certainly improves starting torque, but if it is wired with the start windings without a corresponding run cap then odds are good it's a s/p. I would expect motors 1hp or less costing under $225.00 are likely to be s/p. (I was a small motor specialist for GE's largest fractional hp oem for many years.)
 
Snark said:
Not to belabor a point, but having a start capacitor does not a psc motor make. It certainly improves starting torque, but if it is wired with the start windings without a corresponding run cap then odds are good it's a s/p. I would expect motors 1hp or less costing under $225.00 are likely to be s/p. (I was a small motor specialist for GE's largest fractional hp oem for many years.)
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I wasn't talking about all motors just those used for residential pool pumps. They seem to be going the PSC route. If you don't believe me, check the California Energy Comission list of Title 20 pumps. They have each pump tested by a third party who supposedly is an expert in the field. Each pump motor is identified by it's type and performance. Nearly 70% of the pump motors are identified as permanent split capacitor motors. I haven't personally checked each pump but I'm pretty sure that the list is fairly accurate but if you have data indicating otherwise, I would interested to see it.

Here is the web site:

http://www.appliances.energy.ca.gov/AdvancedSearch.aspx
 
PSC's are generally more efficient than s/p's (for simple centrifugal pump applications) and certainly more compatible with motor controls. It doesn't surprise me that California would be emphasizing (if not requiring) psc's as well as full blown controllers. While I don't have current industry data, prices and efficiency awareness are two big factors in deciding which motors are actually being purchased. While California typically pushes industry simply because of market size it usually takes several years for the rest of the county to follow. $.08 per kwh provides less incentive than $.27+ per kwh plus additional demand charges and power factor penalties. There hasn't been a power plant built (or substantially increased) out there in 20 years. Certainly the future is in controlled psc's, or actually fully controlled rare earth permanent magnet dc motors. But it won't happen for a while yet. As for me, I'll stay over here close to the Atlantic.
 
If you look at the pump list on CEC web site, you will see that it contains nearly every pump currently marketed by Hayward, Jandy and Pentair/Sta-Rite so it isn't just the pumps "pushed" by California. There are currently ~194 pump models listed which I would say is pretty representative of the entire industry.
 
Swapped my single speed motor for a two speed this weekend; so far so good. The new motor is MUCH quieter on low speed, yet still moves enough water to sufficiently skim, run 3 sheer descent falls, run the heater and SWG. Easily the most difficult part of the switch was step 8 of this guide - installing the new seal to the seal plate. All the rest was as straightforward as could be.

Now my question: What are the possible results of the motor NOT being grounded? My new one is, previous one was not. The square flange was corroded quite badly after less than 3 years, and while I see evidence of a slight leak, I'm curious whether the lack of ground could have contributed to the corrosion.

Thoughts?
 

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