Using PSU to Power Pump

[sullivnc]

I am trying to use an AC adapter to power a pump. The pump says it is rated for 12VDC at 7A. The PSU outputs 12VDC at up to 12.5A. The PSU works fine when not connected to the pump, i.e. it outputs 12VDC. However, when it is hooked up to the pump, my meter shows a variable voltage reading of between 0.5 and 1.5 VDC. I have pictures of both the pump and PSU, but had no way to upload them here. Email me if you want to see the pictures. Any help or answers as to what is going on here would be much appreciated. Thanks.

 

[Harvey]

The PSU outputs 12VDC at up to 12.5A, which is more than enough than the 7A required to power your pump, by itself. However, that would leave only 5.5A available for the rest of your system.

If you're water cooling, I'd guess the complete system is powerful enough to require more than 5.5A @ 12 VDC. In other words, your complete system, including the pump, is demanding more current than your PSU can provide and is shutting down when it exceeds its current limit.

Two solutions:

1. Buy a new PSU that can provide at least 7A above the current required for the rest of your system.

2. Buy a separate supply for the pump that can provide at least 7A at 12VDC.

Hope that helps.

 

[sullivnc]

Hi Harvey,

Thanks for your response. The pump is the only component in the system. I understand it might require extra current past 7A to start up, but that doesn't explain why it's drawing such a low, variable voltage. For clarification, this is a Shurflo diaphragm pump, P/N 8009-543-250.

 

[Harvey]

Hi Harvey,

Thanks for your response. The pump is the only component in the system. I understand it might require extra current past 7A to start up, but that doesn't explain why it's drawing such a low, variable voltage. For clarification, this is a Shurflo diaphragm pump, P/N 8009-543-250.

Thanks. I though you meant that you were trying to power it off of your computer's PSU.

As I said, it sounds like the PSU is going into current limiting. Assuming it's connected properly, the only reasons for that would be that the pump motor is stalling out or shorted internally, or the PSU is failing.

If you're trying to use an ATX computer PSU or other supply that has other outputs, it may not work if one or more of the other outputs has no load on it. If so, try a single output supply, or add a dummy load resistor from whichever output requires it to ground to draw enough current to keep it active.

 

[rgallant]

I am trying to use an AC adapter to power a pump

might not be pure dc , maybe list the model

-I'm in the process of powering my 2 pumps ,17 fans ,2 fan controllers off a second psu unit , but I picked up a cheap pc 500 watt psu

 

[Harvey]

I am trying to use an AC adapter to power a pump

might not be pure dc , maybe list the model

I understood that the OP's pump requires DC, and that's what his PSU puts out, but I could be wrong.

I design electronic hardware, and I know some things can run on DC or AC. I also know that it's a bad idea to try to run AC operated gear on DC or vice versa. It's just begging for some SED's (Smoke Emitting Devices).

 

[rgallant]

lol thats why I asked for the model to see if it's a pc part, I have tons of fairly good 3 amp 12v dc power supplies on hand ,but would not trust them for any pc equipment even fans , no mention of type of pump but most will have some sort of speed control if the 12v is not clean you have to wonder what its controller will do.

 

[bryanl]

You can post photos at imgur.com. The 0.5-1.5V reading under load indicates the PSU may have gone into current limiting mode, and positive displacement pumps, including diaphram pumps, tend to draw very high current at start-up. A rotary impeller or vane pump may be a better choice.