Stupid question about Amps

[litespeed]

I am rigging up a water pump. 12 volt water Pump that runs at 500 GPH at 1. 5 amps.



If I reverse the polarity the pump runs at half speed (approx 250 GPH). At this polarity and at this speed is the amp draw the same or does it drop?



I'm guessing that it remains the same because of the windings, wiring etc... . ?



I'm trying to draw as little amps as possible.



Thanks,



AJ

 

[MotleyCrueCab]

If you reverse the polarity, the pump will run the same speed, only backwards. Are you sure you have the specs of the pump correct, 1. 5 amps doesn't seem like enough power to flow 500 gph.

 

[TRAMPLINEMAN]

Not on a single phase motor. Swap two of the 120V legs on a three phase motor and it'll run backwards.

 

[MChildress]

I have to agree with Motley, a DC motor will run backwards if current is reversed. If your pump has a rubber impeller it probably got wasted when the pump motor ran in reverse.

 

[Kingsbury]

All right to answer your question. First I'll assume you are referring to DC, if you run a DC motor backwards it still takes the same amps. If it really is turing at half speed then it doesn't like trying to move the water in the wrong direction and may be working harder than it is designed for and drawing MANY more amps than it is designed for. It will not live long this way. Good luck but you need to keep the flow of coolant going in the correct direction.



Paul

I am rigging up a water pump. 12 volt water Pump that runs at 500 GPH at 1. 5 amps.



If I reverse the polarity the pump runs at half speed (approx 250 GPH). At this polarity and at this speed is the amp draw the same or does it drop?



I'm guessing that it remains the same because of the windings, wiring etc... . ?



I'm trying to draw as little amps as possible.



Thanks,



AJ

 

[Hoefler]

If the pump is a vane type pump, you would be building pressure against the intake check valve. That would make it appear to run at half speed when the polarity is reversed, the motor will run backwards.



To answer your question, dc motor, forward or bacwards, still same amps.

 

[litespeed]

The pump is a 12Volt "DC" pump. It is rated at 1. 5 amp load at 500 GPH. There is not rubber impeller and there are no parts to "damage". This is a very simple pump. No check valve and just a small nylon impeller. Pump is an Attwood A500 aerator pump and is not a self priming pump.



Here is the specs:



http://www.attwoodmarine.com/Products/pumps/aerator_pumps_charts.asp



The pump appears to be running the same direction when I reverse the polarity. I will check it to be sure. It is difficult to tell by looking at it. But by sound I would say that the RPM's have been cut in half and the water is still moving the same direction and not in reverse. It is also flowing at least half the amount of water.



My goal is to flow around 250 GPH with as little amp draw as possible.



Thanks for all the help..... But now I'm a little confused?



So is the amp draw going to be less or more?

 

[JApol]

When you reverse the polarity on a DC pump it will spin backwards. The reason it is not pumping as much is because the impeller is not designed to run in that direction.

How well will your turbo build boost if you plumb it backwards? Sure it will sorta work but not as effiencently as if it was plumbed right.



As far as amp dray wired backwards? Being that the motor is priobably working harder to move less liquid I would guess in the 5-15 amp range.

 

[jelag]

A brush type DC electric motor... . using standard field coils will run backwards only if you reverse the current in the field coils..... if it has magnets for field coils..... than reversing the connections will reverse the motor... . that said... .



The motor will draw a fixed amount of amp's based on no load conditions, and full load conditions... . at no load it will be less... as its doing no work... there is nothing you can do... . to change the current draw on this motor, no matter what direction you run it..... other than decrease the load..... that means decrease the head pressure..... or limit the input... os that it only pumps say 200 gph... . On the ohter hand... 1. 5 amps sounds like a very small amout of current... todays modern batteries... . like what is in our trucks... is, lets say a 150 amp hour battery. . that means it will supply 150 amps for one hour..... or 15 amps for 10 hours... . or 1. 5 amps for 100 hours... . or . 15 amps for 1000 hours... . simple ohm's law math here.....



Hope this helps...

 

[SBall]

The pump appears to be running the same direction when I reverse the polarity.

If your "DC motor" runs in the same direction regardless of the polarity of the connections, it sounds like it would be a series-wound motor, sometimes referred to as a "universal motor". The field would be a wound field (as opposed to permanant magnets or a shunt field), and connected in series with the armature.

These types of motors are usually used in high torque applications though and typically not used in small pumps so I'm confused. It would be nice to know the amp draw with both the positive and negative polarity wiring configurations.

 

[litespeed]

Thanks for the additional input!!



I am understanding what is happening now.



This little project wants me to take a class on electrics.



AJ