Water pump makes lights flicker

[Kamahele]

My Johnson WPS 3.6 water pump has always caused the "house" boat lights to flicker when it pulses. I did some rewiring and it got worse. I'm thinking of running a 10 gauge cable directly from the battery to the pump to power it exclusively. Any thoughts that could help with this? What about a capacitor on the pump that could smooth out the voltage fluctuations? Alternatively capacitors on the lighting circuits? I recently replaced the incandescent bulbs with LEDs, but (senior moment) I can't remember if the LEDs flicker more than the incandescents . Thanks for any help.

 

[GA_Boater]

You might consider running a dedicated ground also. Grounds need to be able to handle the same current as the power wiring and often the ground is not upgraded as more accessories are added.

 

[shrew]

If the pump is pulsing, then you should consider installing a Accumulator Tank right after the pressure pump. Both Jabsco and Shurflo make a small one that will fit in tight spots. The lights flickering are from voltage drops. This can occur with old batteries which are not holding sufficient charge. It can occur when there is oxidation on the common ground. corroded connections can also create unnecessary draw.

 

[Kamahele]

Thanks GA_Boater and shrew for your comments. I'll try running a new cable to the pump; the pump always pulses - it's how it works; the batteries are brand new and problem persists; there is an accumulator tank - maybe it's kaput (can it be tested?).
Anyone else have an idea?

 

[Texasmark]

Food for thought. Lighting circuits in your house are on a separate circuit from your receptacles so that when you plug in your vacuum cleaner and turn it on the lights don't wink at you. Things like refrigerators, freezers, electric AC/heating units and all surge equipments are fed by their own power-return wiring to prevent what you are experiencing. Actual wire gauge is sized for a 2% voltage drop at max load from the public utility, per my copy of the code. AWG sizing is for continuous current heating, not surges.

 

[DeepCMark58A]

How old is the pump? Windings in the motor may be delaminating due to wear and tear.

 

[Grub54891]

I have to agree with texasmark, dedicated circuits are a must, along with separate breakers. Some look to be separated, but run off a common feed which is to small for all the loads put on it. Once the wiring is in proper order, thing not only work better, they also last longer as they are getting the proper amperage for each device.
​And deepcmark is also on a good track, a failing device could do that, but you would think the breaker or fuse would blow, unless it's oversized for the device, Not a good thing. Good clean connections, proper wire sizes are pretty important.

 

[Kamahele]

Thanks guys, I'll keep working on it when I can get to it after winter...

 

[jbcurt00]

Texas, DeepC and Grub, you know Kam is talking about boat lights NOT residential house wiring, right?

Good luck Kam

 

[Grub54891]

Texas, DeepC and Grub, you know Kam is talking about boat lights NOT residential house wiring, right?

Good luck Kam

Yes I do.

 

[DeepCMark58A]

Yep 12 volt pump. The shaft can drop because of bearing or winding failure no matter the current or voltage.

 

[crazy charlie]

In every boat I can remember,the lights slightly dim while pump is on and when pressure is built up and the pump stops running the lights get noticable brighter.I kind of like it that way because it is easy to tell if the pump continues to run due to lack of water without standing over it or listening to the pump.Charlie

 

[Texasmark]

Doesn't matter what wiring it is. If you have a sizeable load on a conductor, you suck amps through it and amps x the resistance of the wire causes voltage drop. Voltage drop along the wire subtracts from the voltage available for the lights if connected to the same circuit....aka daisy chained....using one hot and one cold connected along your different load circuits. Thus the lights dim, just like when you use a dimmer, different principle of operation, but results are the same.

After that any dimming is the result of the source resistance. House power sources are essentially zero source resistance. Batteries are a different critter. If you want to know your batteries internal resistance, get a load tester and hook it up. Measure the terminal voltage at zero amps and then crank the amperage up to some value, might use the 150 amp spec for my 90 hp Merc. Record the terminal voltage again. (V1-V2)/150 amps is the internal resistance of the battery. Any load pulled from the battery will drop the output voltage by V = load current x that battery resistance if the engine is off. If on, if the load is greater than the alternator's output it will still wink, if less, it won't.

By using a separate hot and return to each function, you only have to deal with the source resistance as a determining factor for dimming lights.