two sump pumps

[steve66]

So there are two NEW sump pumps for sewage. One lead, one lag. a total of 4 circuits. each pump is 240 volts, 2 circuits each. when either is running the amperage is correct. However, when both run at the same time the amperage doubles, to 39-40amps.
When we got there the 30 amp fuses blew.
Any ideas as to why the amperage would double?

The well was not purged when the new pumps were installed. The old pumps were rated for only 15 amps.

Maybe I'm stating the obvious, but if two pumps are running, the amperage should double. I think we are all assuming you mean it quadruples, or draws 4 times the rating of a single motor.

But just to be sure: What size and voltage are the motors, and what is their current rating??

Most of these duplex pumps are made to be fed with 2 branch circuits. That's part of the redundancy. If one breaker (or fuse) trips, the other motor can still run off the other branch circuit.

 

[renosteinke]

I suppose it's a matter of definition, but I have never seen a duplex pump install that I would call "two circuits."

ONE circuit to the pump control panel. At the panel, there are separate breakers for each pump. While you can reason that these control OCPD's make for 'separate branch circuits,' I look at them as being 'supplimentary' OCPD's.

The control panel also usually breaks out the control power from the pump power.

 

[steve66]

I suppose it's a matter of definition, but I have never seen a duplex pump install that I would call "two circuits."

ONE circuit to the pump control panel. At the panel, there are separate breakers for each pump. While you can reason that these control OCPD's make for 'separate branch circuits,' I look at them as being 'supplimentary' OCPD's.

The control panel also usually breaks out the control power from the pump power.

Almost all the commercial ones I've seen take 2 separate branch circuits.

It doesn't make much sense to run duplex pumps from one branch circuit. If one shorts out, it will trip the circuit breaker, and the lag pump would be useless.

If the original pumps were 15 amps each, the new pumps could easily be 20 amps each. So the 40 amps the origional post mentioned would be completely normal. And if they fed that from a single 30A circuit, I think that is an obvious problem.

So my question stands: Is there one branch circuit for 2 pumps, and what size and voltage are the pumps??

 

[renosteinke]

What is a branch circuit? That's the question.

You're simply not going to find a pair of pumps, working together, that have individual circuits coming straight from the distribution panel.

No, you're going to have the distribution panel power a control panel. The control panel will act as a 'sub panel' and break up the feed from there. With breakers in the control panel, you could argue that each pump's individual feed was a 'branch circuit.'

That would make your circuit to the control panel a 'feeder' now. So, what you're asking is: how do you size the feeder?

Pump #1 FLA + Pump #2 FLA + Controls/alarms FLA = What you need. No need for 125% anywhere, as nothing runs continuously. Nor do you add up breakers.

So, let's say your pumps have FLA's of 7A. The control panel might very well have them on 20-A breakers (need to allow for starting current). That's 7 + 7 + 1 = 15. The whole installation might also be served by a 20-A feeder.

An alternative way to look at things is to cinsider the control panel your 'appliance.' The panel will have a sticker telling you the maximum size pumps it will control, and recommend a certain size circuit. Go with that information, and don't worry about the pumps.

Now ... for one of the finer points .... what is your pump's FLA? Haha- trick question. The pumps, and their nameplates, are down in the pit, covered with crap. Where is that apprentice when you need him?

No ... pumps often come with stickers that repeat the nameplate info. A smart installer will put those stickers inside the control panel. Or, at least, he'll use his Sharpie to write the info inside the panel. The nameplate on the pump will likely be impossible to read once you clean it off.

 

[steve66]

What is a branch circuit? That's the question.

You're simply not going to find a pair of pumps, working together, that have individual circuits coming straight from the distribution panel.

No, you're going to have the distribution panel power a control panel. The control panel will act as a 'sub panel' and break up the feed from there. With breakers in the control panel, you could argue that each pump's individual feed was a 'branch circuit.'

That would make your circuit to the control panel a 'feeder' now. So, what you're asking is: how do you size the feeder?

Pump #1 FLA + Pump #2 FLA + Controls/alarms FLA = What you need. No need for 125% anywhere, as nothing runs continuously. Nor do you add up breakers.

So, let's say your pumps have FLA's of 7A. The control panel might very well have them on 20-A breakers (need to allow for starting current). That's 7 + 7 + 1 = 15. The whole installation might also be served by a 20-A feeder.

An alternative way to look at things is to cinsider the control panel your 'appliance.' The panel will have a sticker telling you the maximum size pumps it will control, and recommend a certain size circuit. Go with that information, and don't worry about the pumps.

Now ... for one of the finer points .... what is your pump's FLA? Haha- trick question. The pumps, and their nameplates, are down in the pit, covered with crap. Where is that apprentice when you need him?

No ... pumps often come with stickers that repeat the nameplate info. A smart installer will put those stickers inside the control panel. Or, at least, he'll use his Sharpie to write the info inside the panel. The nameplate on the pump will likely be impossible to read once you clean it off.

You are completely missing the point. Most duplex pumps are made to be supplied with two different circuits. Not one circuit that is split at the control panel, but two different circuits. Those two circuits could come from completely different panels. Or even different services. Or one from an emergency panel backed up by a generator, and another from a normal power just in case the ATS fails.

If you only run a single circuit to a duplex pump control panel, there is no redundancy for the power feed. Trip one breaker and you'll be knee deep in you know what.

Now ... for one of the finer points .... what is your pump's FLA? Haha- trick question. The pumps, and their nameplates, are down in the pit, covered with crap. Where is that apprentice when you need him?

No ... pumps often come with stickers that repeat the nameplate info. A smart installer will put those stickers inside the control panel. Or, at least, he'll use his Sharpie to write the info inside the panel. The nameplate on the pump will likely be impossible to read once you clean it off.

Only a hack would install two new pumps and never check to see what the motor size or FLA is. He said the original pumps were 15 amps each. Just based on that alone, it seems very likely a 30A circuit is too small to run 2 pumps.

That would make your circuit to the control panel a 'feeder' now. So, what you're asking is: how do you size the feeder?

Pump #1 FLA + Pump #2 FLA + Controls/alarms FLA = What you need. No need for 125% anywhere, as nothing runs continuously. Nor do you add up breakers.

I know how to size a feeder, and I never asked "how to size a feeder". Without knowing the motor size from the OP, there is no way to do any calculations.

 

[renosteinke]

"You are completely missing the point. Most duplex pumps are made to be supplied with two different circuits. Not one circuit that is split at the control panel, but two different circuits."

Yes, I am. I cannot imagine the arrangement you describe.

Mind you, I'm only familiar with the pump standard I helped write for a testing lab, the pump systems I designed/ quoted for a major pump manufacturer, the systems I've encountered industrially, and the systems I've encountered in service work. Sizes varied from 1/20 hp to 30 hp- which ought to cover just about anything we'll ever see. I just can't imagine two pumps working together without them running through a common control panel.

I suppose you could kludge something together, with floats operating separate contactors in different enclosures, but you wouldn't have any alternation. I suppose you could bring power in separately to each contactor. Sure seems like the hard way to do things.

Might be nice to see some catalog, somewhere, that describes such an arrangement. That folks here assert that such separate supplies are 'normal' has me scratching my head.

Still, there are millions of pumps out there, and I've only seen a few thousand.

 

[steve66]

Still, there are millions of pumps out there, and I've only seen a few thousand.

Well, obviouslly, if you haven't seen it, they don't make it.

Try Federal Pumps type PC-5 or PC-6 controllers. One 3 phase input for each pump (each with a separate fused disconnect/motor starter) and a third input for 120 V control power.

Perhaps more common, is a control panel that only has two 3 phase power inputs (again - one for each pump), and there is a control transformer from each input. So if one power input feed goes dead, control power automatically transfers to come from the other power input.

 

[renosteinke]

I search "Federal PC-5" and google thinks I want tax advice