Boost AC circuit

[Emesine]

I have a 1500' 12 gauge wire leading to a power panel. I am running a 1/3 horse power motor off this panel continuously (air pump for my lake) and a 1/2 horse power motor intermittently (my well pump, which kicks on for about 5 minutes about 6 times per day.) Both motors are 220 VAC.

The problem is, when my well pump kicks on, the AC voltage drops significantly, which kills my air pump, which eventually burned out the motor.

I would like to install some batteries at this panel with synchronous inverter that would kick on when the well pump kicks on, keeping the AC voltage high enough to run both motors. Can anyone suggest a product that would do this, or another strategy that would work?

Thanks!

Andrew

 

[BobK]

Would there be any problem with just turning off the air pump while the well pump was running? This would be far simpler.

Bob

 

[Emesine]

Hi Bob, Thanks for the reply! I did try this for a time. The air pump develops about 15 PSI, which continues even when the pump shuts down. It is capable of running at 15 PSI, but it is not capable of starting against 15 PSI. Bottom line, the air pump was unable to start after having been switched off, and sat for about a day powered but unable to start. I think this did damage to the pump motor.

I then put a small bleed in the pressure line, allowing the pressure to fall back down to zero so that the pump could restart against zero PSI instead of 15 PSI. This worked for a week or so, then I found the motor again powered and unable to start- but this time the motor was permanently damaged.

Ideally I'd like to build a system whereby the air pump runs continuously, but one option would be to replace the air pump motor, and see if the system works with an undamaged motor. Again, thanks!

Andrew

 

[AnalogKid]

Another strategy: a DC powered air pump motor. A universal input AC/DC power supply would ride through brownout sags down to 90 Vrms. And, you could add a battery stack with simple diode OR-ing for deep dips.

ak

 

[Alec_t]

How about use a solenoid valve which opens to release air when the well pump turns on, then closes when the well pump turns off?

 

[Minder]

If it were me I would be interested in finding out why? Not patch it up unless there are other circumstances.
If the supply for the circuits is wired in 12g 220v it should normally be capable of around 4.5Kw!
There is no way a fractional HP motor should cause the voltage to collapse, even the starting in-rush.
Does the voltage collapse at the source power panel?
M.

 

[BobK]

Or, based on your original idea. Use a relay to switch power to on an ordinary inverter. No need for a grid tie one.

Also, you could add a separate power cable to avoid the voltage drop, assuming most of it comes from the 1500 ft cable.

Bob

 

[Minder]

A 1500ft 12g cable run will drop ~4v when the pump is running, allowing for a 10a inrush at start, for a very brief time it would drop by 23v-25v should be no concern, as I said find out where the drop is happening?
If at all.
M.

 

[Minder]

Another strategy is to turn the Air motor off very briefly when the 1/2hp kicks in, it is fairly infrequent.
Once the pump is running, bring the air motor back on line.
M.

 

[davenn]

as I said find out where the drop is happening?
If at all.

he said it was ... so presumably he measured it

@Emesine did you REALLY measure a V-drop ??

Once the pump is running, bring the air motor back on line.

he said that doesn't work cuz once the air pump stops it wont start pumping again against the air pressure

Hi Bob, Thanks for the reply! I did try this for a time. The air pump develops about 15 PSI, which continues even when the pump shuts down. It is capable of running at 15 PSI, but it is not capable of starting against 15 PSI. Bottom line, the air pump was unable to start after having been switched off, and sat for about a day powered but unable to start. I think this did damage to the pump motor.

 

[Emesine]

The voltage drop at the panel is very significant. The wire is 1881 feet (3762 there and back) for a total of about 6 ohms of resistance (12g wire is 1.588 ohms per 1000') I have calculated and measured voltage drops in the range of 30 to 45 volts while both motors are running.

 

[Minder]

Can you use the method in #9 but use a method of unloading the air pump until up to speed?
Unload valve e.g..
Or can it be off for just the 30min/day ?
M.

 

[davenn]

Can you use the method in #9 but use a method of unloading the air pump until up to speed?
Unload valve e.g..
Or can it be off for just the 30min/day ?
M.

Minder please read the thread properly

he had already tried that as well

I then put a small bleed in the pressure line, allowing the pressure to fall back down to zero so that the pump could restart against zero PSI instead of 15 PSI. This worked for a week or so, then I found the motor again powered and unable to start- but this time the motor was permanently damaged.

 

[Minder]

The problem is, when my well pump kicks on, the AC voltage drops significantly, which kills my air pump, which eventually burned out the motor.

Andrew

Did you actually wire every thing in properly interlocked to switch off the air pump, dump the air when the 1/2hp starts, and restart the air pump at the end of the well pump interval?
I can see no reason why this would not work? Unless you relied on manual intervention?
M.

 

[Emesine]

Hi Minder,

Yes, it was wired and setup perfectly. I put both the well pump and the air pump on the same relay such that the one would turn on when the other turned off. I then made sure that the pressure would bleed off completely before the air pump turned on. However, this was all wired with a pump that had been previously been damaged. The system might work with a fresh pump.

 

[Emesine]

AK, that is an interesting solution. Bob, your solution is along the same lines, just using an inverter and an AC pump instead of a DC pump. Would any AC/DC converter work for this application? There is a large range of quality/price, etc... Thanks all for your help!

Andrew

 

[Bluejets]

35 to 40v drop while both motors are "running" is some serious Vd. I would hazard a guess that if this was a multimeter measurement then the inrush is much higher. Something seriously wrong as Minder says, it should be no where near this with info supplied. How far from your supply authority entry point? Is the final sub-circuit copper or aluminium? Perhaps one or the other motors have been damaged trying to start against an already crook motor.

 

[AnalogKid]

Would any AC/DC converter work for this application?

Something with active power factor correction, sometimes called a universal input. Better than autoranging, these will run on any AC input voltage between 85 and 260 Vrms. -ish - the exact range varies with manufacturer. A true industrial-grade multi hundred watt unit will cost $1-$2 per watt in ones. Chinese stuff on ebay will be much less. MeanWell is a good Chinese manufacturer.

ak

 

[Bluejets]

Maybe just run out some 10 sq mm copper cable. ️

 

[davenn]

35 to 40v drop while both motors are "running" is some serious Vd. I would hazard a guess that if this was a multimeter measurement then the inrush is much higher. Something seriously wrong as Minder says, it should be no where near this with info supplied. How far from your supply authority entry point? Is the final sub-circuit copper or aluminium? Perhaps one or the other motors have been damaged trying to start against an already crook motor.

way back in post #11 he said it was 1881 ft
So I'm not surprised there is a signif. V-drop