Question for electricians

[DarkBlack]

Nope. My well is even deeper, and I’m using a 3/4 hp pump.
Static level, and gpm desired are big factors

 

[WinterDeere]

Nope. My well is even deeper, and I’m using a 3/4 hp pump.

Interesting. I see lots of charts like this, courtesy of Google:



It seems to show the 3/4 hp pump petering out around 260 ft depth, and only delivering 5 gpm at 240 ft.

 

[DarkBlack]

The THD issue has to do with excess heat being created in electronic parts, due to the non-sinusoidal waveform, I have read. It all feels the same to me when it bites.

Heat, and harmonic distortion can mislead the power supply’s frequency timing.
It doesn’t matter if the supply supply is a switcher, or linear..If the product requires frequency over watching, such as a good UPS system would have, or timing circuits based off of phase angles,.. those devices are likely to see dirty input power as frequencies higher than 60hz. A single repetitive spike might give the UPS a measurement period indicating the input power is 120hz.

 

[DarkBlack]

Interesting. I see lots of charts like this, courtesy of Google:

View attachment 3744711

It seems to show the 3/4 hp pump petering out around 260 ft depth, and only delivering 5 gpm at 240 ft.

That’s a 15gpm pump chart.

 

[WinterDeere]

That’s a 15gpm pump chart.

True. But given the size of today's homes, I think that's a pretty standard size to specify.

 

[DarkBlack]

True. But given the size of today's homes, I think that's a pretty standard size to specify.

Maybe for people who like run lawn sprinklers everywhere.
7 gpm is more than enough for my house. Even if I somehow exceeded 7 gpm momentarily, which won’t happen, my pressure tank, that everyone has, would handle the brief excess demand .
Here’s a 5 gpm 4” pump chart:
3/4 hp circled

 

[WinterDeere]

That makes sense. I assume the big difference between nameplate pump capacities is the size and pitch of the impeller, effectively changing the mechanical advantage?

 

[DarkBlack]

That makes sense. I assume the big difference between nameplate pump capacities is the size and pitch of the impeller, effectively changing the mechanical advantage?

The interesting counterintuitive part, is that for a given hp, a lower gpm pump actually requires more stages and weight and size, than a higher gpm pump of the same series , using the same motor

 

[WinterDeere]

The interesting counterintuitive part, is that for a given hp, a lower gpm pump actually requires more stages and weight and size, than a higher gpm pump of the same series , using the same motor

Yeah, counterintuitive at first glance. But I guess it makes sense when you stop to think about the fact that the lower GPM trade-off is greater lift. You can achieve greater velocity with changing impeller size and pitch, but the greater lift pressure at a given input HP may require more stages to reduce blow-by at a given RPM.

 

[alexinPA]

Tested the power meter this morning. Works fine showing W, A, F. Even catches the surges. Interesting to see how actual W are different from tables provided. One thing I can't explain... My generator is running with low load-about 60w. Turning on ceiling fan and see 2w. Tried a few times.
How can it be? Any thoughts?

 

[DarkBlack]

Tested the power meter this morning. Works fine showing W, A, F. Even catches the surges. Interesting to see how actual W are different from tables provided. One thing I can't explain... My generator is running with low load-about 60w. Turning on ceiling fan and see 2w. Tried a few times.
How can it be? Any thoughts?

Watts will be calculated off of measurement volts, and amps.
The question is …. How many current donuts does it use? Can you switch the amp display to show each leg individually?
You can have leg 1 to neutral current.
You can have leg 2 to neutral current.
You can have leg 1 to leg 2 current.

The advertised photo only shows 1 current donut
I don’t know how they can give correct 120v amp readings for both legs, without a second donut to account for the neutral current.

 

[DarkBlack]

Did it come with a manual that explains what current path the amp display is actually displaying?

Running 2 of the wrong wires through a single current donut can cause an increase in load to incorrectly read as a decrease because of cancellation. Hopefully you don’t have that going on

 

[WinterDeere]

Running 2 of the wrong wires through a single current donut can cause an increase in load to incorrectly read as a decrease because of cancellation. Hopefully you don’t have that going on

They can run the two legs in opposite directions through the inductive loop, in order that they add despite being out of phase. But I agree, one ammeter on a two-leg system with split voltage leaves enormous room for ambiguity. I'm surprised there aren't two ammeters, one for each leg. Neutral current would be difference in two leg readings.

 

[DarkBlack]

They can run the two legs in opposite directions through the inductive loop, in order that they add despite being out of phase. But I agree, one ammeter on a two-leg system with split voltage leaves enormous room for ambiguity. I'm surprised there aren't two ammeters, one for each leg. Neutral current would be difference in two leg readings.

Problem with that setup, is the amp reading will only be correct for L1 to L2 flow. It’s totally wrong for 120v circuits.
Example:

1 amp flows L1 to L2. Meter “sees” 2 amps because of double wires through the donut.

1 amp flows through L1 to N meter only “”sees” 1 amp.

So first, the amp measurement is unreliable because the meter doesn’t know if the current to display should be as measured, or divided by 2.
Second, the meter’s wattage logic doesn’t know if the amp # should be 1/2, or a portion of 100% number to use based on the neutral current flow imbalance caused by the 120v circuit’s flow, that it is unaware of.

 

[WinterDeere]

Problem with that setup, is the amp reading will only be correct for L1 to L2 flow. It’s totally wrong for 120v circuits.
Example:

1 amp flows L1 to L2. Meter “sees” 2 amps because of double wires through the donut.

1 amp flows through L1 to N meter only “”sees” 1 amp.

Yep. Not a great setup, but really the only solution for a single meter on a split voltage system. It would at least show total current flow, with the overcurrent devices still being the only means of tripping an individual leg overcurrent.

Second, the meter’s wattage logic doesn’t know if the amp # should be 1/2, or a portion of 100% number to use based on the neutral current flow imbalance caused by the 120v circuit’s flow, that it is unaware of.

Agreed. Although unless wattmeter is actually accounting for power factor, it's mostly a useless frill feature, anyway.

Best would be two ammeters, one for each leg.

 

[alexinPA]

Not sure what it all means. To clarify, the voltage reading on power meter is ~120 volts all the time. Does it mean wattage I see is half of actual? The generator screen shows 240 v. How can turning on a ceiling fan can reduce total watts? And this is the only one appliance that does it.

 

[DarkBlack]

Not sure what it all means. To clarify, the voltage reading on power meter is ~120 volts all the time. Does it mean wattage I see is half of actual? The generator screen shows 240 v. How can turning on a ceiling fan can reduce total watts? And this is the only one appliance that does it.

All speculation till you post the schematic, or description of the amp/ watt screen from your owners manual

 

[grsthegreat]

Not sure how yours is setup. Mine has 2 separate meters and 2 separate CT’S set to read both phases. Mine reads Volts, Amps and frequency

 

[WinterDeere]

Not sure what it all means. To clarify, the voltage reading on power meter is ~120 volts all the time. Does it mean wattage I see is half of actual? The generator screen shows 240 v. How can turning on a ceiling fan can reduce total watts? And this is the only one appliance that does it.

It's mostly likely just an artifact of imbalance, sign of a floating neutral. It'd be interesting to see the neutral to ground voltage under both scenarios.

There's also a small chance it's the result of an auto-ranging meter with badly-differing resolution at two different amperage levels, such that one reading is just badly erroneous, but I really doubt that's the case.

 

[alexinPA]

All speculation till you post the schematic, or description of the amp/ watt screen from your owners manual

There's no owner manual