Determining inrush current on manufactured AC and DC Pumps

Thread Starter

coolro18

Joined Jul 10, 2020
17
I am using a couple pumps that are manufactured to be run from a standard wall outlet. I've learned that upon starting, both AC and DC motors can have inrush currents of several times the rated current, but I'm unsure how to determine if these pumps have any internal limiter on inrush current. Do wall plug pumps like these typically go much past their rated amperage? I ask because I'd like to control these pumps with solid state relays. I find it hard to imagine a company would expect the consumer to have a supply tolerating such heavy inrush currents.
 

Alec_t

Joined Sep 17, 2013
11,417
Welcome to AAC!
What are the current and voltage ratings of your wall outlet and the pumps?
Do the pumps have a voltage adapter/transformer or are they driven directly from the outlet?
 

Thread Starter

coolro18

Joined Jul 10, 2020
17
Welcome to AAC!
What are the current and voltage ratings of your wall outlet and the pumps?
Do the pumps have a voltage adapter/transformer or are they driven directly from the outlet?
Hi, I am running 12VDC pumps that are rated for a max of 17.0 amps, and I am also using 120VAC pumps with max amps ranging from 10 to 20 amps. They are driven directly from the outlet, and the DC ones will use a transformer.
 

Thread Starter

coolro18

Joined Jul 10, 2020
17
Hello!
Do you have the part numbers of the pumps you are driving? Also an idea of the schematic that you plan to use?
These are some of the pumps,
DC Pump:
https://www.amazon.com/Everflo-EF5500-Diaphragm-Boxed-Ports/dp/B007ZQZLJC/ref=sr_1_1?dchild=1&keywords=everflo+ef5500&qid=1594392280&sr=8-1

AC Pump:
https://www.amazon.com/Simer-3415P-Spinkler-System-Pump/dp/B009ZTV15U

I am operating the solid state relay with a 4-20 mA output from my controller, and mains voltage on the dry contacts.
 

KMoffett

Joined Dec 19, 2007
2,884
The stated AC pump data in your link is "230VAC" at 2208 watts (9.6A) Startup current for AC motors is up to 10X the run current.
 

KMoffett

Joined Dec 19, 2007
2,884
"I am also using 120VAC pumps with max amps ranging from 10 to 20 amps. They are driven directly from the outlet, and the DC ones will use a transformer. "

You can't drive that 230VAC pump from a 120VAC/15A outlet. You might be able to drive a 120VAC/1.5HP (9.3A) from a 120VAC/15A outlet, if there is nothing else on that circuit. Otherwise the breaker is likely to trip an startup.
 

nsaspook

Joined Aug 27, 2009
7,356
Why is the need to limit it?
It is generally only very momentary.!
Max.
If directly connected to mains with a mechanical contractor that's usually not a problem but power limited supplies like inverters or peak sensitive switching solid-state devices sometimes glitch with even short motor start overloads.
 

GetDeviceInfo

Joined Jun 7, 2009
1,729
I am using a couple pumps that are manufactured to be run from a standard wall outlet. I've learned that upon starting, both AC and DC motors can have inrush currents of several times the rated current, but I'm unsure how to determine if these pumps have any internal limiter on inrush current. Do wall plug pumps like these typically go much past their rated amperage? I ask because I'd like to control these pumps with solid state relays. I find it hard to imagine a company would expect the consumer to have a supply tolerating such heavy inrush currents.
I wouldn’t worry about it. Use beefier SSR or a horsepower rated relay.
 

nsaspook

Joined Aug 27, 2009
7,356
What about its effect on the supply? I plan on having a supply feed capable of 300A, and I believe such a high inrush current on a 20A motor will damage the supply.
That's very unlikely. Most problems with starting motors are from over-sensitive protection circuits causing hiccups.
 

GetDeviceInfo

Joined Jun 7, 2009
1,729
What about its effect on the supply? I plan on having a supply feed capable of 300A, and I believe such a high inrush current on a 20A motor will damage the supply.
In my experience, the greatest destructor of motors is extended start times. Load dynamics may require a ‘soft start’, to which many circuits have been implemented. In industry, you can find wye/delta, transformer, resistive,VFD, and dedicated soft starters. Generally speaking though, with induction motors, the faster you get to speed, the less destructive heat is generated. Most supplies are transformer sourced. The transformer by nature will source high currents required by starting motors, up until voltage droop causes stalling. That leaves you’re O/C device inline to limit the circuits draw. Along comes the time inverse breaker which mirrors a motors heat characteristics.

One of the challenges of motor circuits is bringing the motor up to speed while reducing heat generation. If the load allows, faster is better. Across the line, bang, go.
With that being said, I’ve worked on sites where very large motor starts have to be scheduled with neighbouring users to prevent line droop.
 
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MaxHeadRoom

Joined Jul 18, 2013
20,927
Your AC pump appears to be a radial impeller pump, inlet front, discharge at the top.
These type of motors draw less current when the outlet is throttled down, and max current when the 1-1/2" discharge is maximum flow.
If concerned, a throttle valve could also be used for the start up period.
Or for example if this were used in an irrigation system. ensure all valves OFF at start up. Also the pump will reach operating RPM much faster.
Max.
 
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Thread Starter

coolro18

Joined Jul 10, 2020
17
In my experience, the greatest destructor of motors is extended start times. Load dynamics may require a ‘soft start’, to which many circuits have been implemented. In industry, you can find wye/delta, transformer, resistive,VFD, and dedicated soft starters. Generally speaking though, with induction motors, the faster you get to speed, the less destructive heat is generated. Most supplies are transformer sourced. The transformer by nature will source high currents required by starting motors, up until voltage droop causes stalling. That leaves you’re O/C device inline to limit the circuits draw. Along comes the time inverse breaker which mirrors a motors heat characteristics.

One of the challenges of motor circuits is bringing the motor up to speed while reducing heat generation. If the load allows, faster is better. Across the line, bang, go.
With that being said, I’ve worked on sites where very large motor starts have to be scheduled with neighbouring users to prevent line droop.
Ok, and if I for example had 5 1-1/2 HP motors at 20A and a couple extra motors under 10A totaling close to the allowable amount by the 300A feed, do you see any potential problems with DOL starting in terms of inrush? I plan on using a HP rated power SSR
 

MaxHeadRoom

Joined Jul 18, 2013
20,927
I would set up some kind of sequencer start device, rather than place all on line at once, max 30sec between each should be ample.
Max.
 
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