soft starter for 10HP single phase 240V pump

[BrianMuir]

Hi,
I took over a project from another engineer, and on his drawing he is calling for a pair of starters to engage a pair of 10HP 230V water transfer pumps. I want to help the contractor order the right product, but all my local suppliers have been unable to identify a starter that can handle 10HP in single phase. For whatever reason whenever I get involved with motors larger than around 6HP they are always three phase, so I never had this issue before. I seem to recall some method of using a three phase starter for a one phase application, does anyone have any advice about this, or perhaps a specific recommendation for a unit well matched to the problem?

Activation is by PLC, at 24V, but of course we can add a relay and supply 120V activation.

thanks a bunch!

 

[texie]

Danfoss makes soft starts for single phase motors. Not sure if they go that big though, you'll have to check their site. Given the 10 HP size I wonder if it might pay to change the motors to 3 phase and use a VFD.

 

[Jraef]

Soft starters for single phase motors are becoming rare in general because you should not use them with capacitor start motors, which is 90% of single phase motors. They should only be used with PSC (Permanent Split Capacitor) and Shaded Pole motors, two types that generally are used in applications where you don't need soft starters very often. As a result, most mfrs have stopped making and supporting them.

Last I heard, Baldor was still selling a large 1 phase soft starter, but theirs jumped from 40A, which is only 7.5HP at 230V 1 phase, to 110A, which is serious overkill and expensive as a result. It also is not UL listed at that size. Baldor claimed it was because standard NEMA motor designs don't go above 7.5HP at 230V 1 phase, but I don't think that is true. But all of this was before ABB bought Baldor, and Baldor's soft starters were brand labeled from someone in the UK that is a competitor to ABB over there, so this arrangement might have had a bullet put in its head by now. I don't know of anyone else who makes a UL listed single phase soft starter that large.

And no, you cannot use a 3 phase soft starter for a single phase service and load, there is no way to "fool" it. Soft starters have to time the firing of the SCRs off of a Zero Cross point in the sine wave. A 3 phase unit will assume a 120 degree separation between phases to determine that timing. In a single phase application, you don't have that 120 degree separation so the SCR firing would be off and likely fry the SCRs and/or motor.

That's a lot of power to try to start with a single phase service, a soft starter may not even be enough. Figure that Across-the-line starting current will be 300A, so a soft starter may be able to limit that to 150A each, but even that is a lot to ask of a typical single phase distribution transformer. You would need a 75kVA transformer feeding these behemoths. If it were me, I'd buy a 20HP 230V VFD and feed it with the single phase, then use a 10HP 230V 3Ph motor. A VFD could start them at FLC, roughly 50A each. That would be a lot easier on your system.

 

[Cow]

My first call would be to the local utility. Some utilities won't allow you to start anything bigger than 7.5HP(single phase) across the line.

 

[BrianMuir]

Yikes. Thanks for the advice. The pumps are in the ground so swapping them out is going to be a bit of a problem. I'm just starting to look at this and I don't have specs for the pumps yet. 10HP seems huge for the application so I'm hoping it they are actually much smaller. Will post back when I know more.

 

[mbeatty]

To my knowledge, single phase motors are usually only designed up to 7.5 HP. One starter phase is jumpered to allow current through all 3 overload phases. I usually run incoming power to L1 and L2, on the starter, and jumper T2 to L3 for this application.

Regards,

Mark

Edited for clarity: It is not current through all 3 phases, but it makes it appear to be 3 phases of power available.

 

[BrianMuir]

Hello,
I have confirmed that the customer does indeed have 10HP pumps. They are ITT Goulds G&L series. As one poster suggests, no one seems to make a starter appropriate for this size in single phase. I note the last poster presents a method for using a three phase starter but Jraef presented a convincing argument about why this would not be possible.

I've asked the pump vendor to assist but the situation looks a bit grim.

 

[Rampage_Rick]

That's a lot of power to try to start with a single phase service, a soft starter may not even be enough. Figure that Across-the-line starting current will be 300A, so a soft starter may be able to limit that to 150A each, but even that is a lot to ask of a typical single phase distribution transformer. You would need a 75kVA transformer feeding these behemoths. If it were me, I'd buy a 20HP 230V VFD and feed it with the single phase, then use a 10HP 230V 3Ph motor. A VFD could start them at FLC, roughly 50A each. That would be a lot easier on your system.

I also recommend the use of a VFD, though it would neccesitate the replacement of the motor.

I had an irrigation pumphouse with 3x 10HP running off a 200A single phase service. They replaced a single 10HP, but nobody at the time noticed the pole pig was only 10kVA. Didn't last long before it went boom... The utility was going to replace it with another 10kVA, but I begged for something bigger and got a 25 kVA. Not ideal but it's survived 4 years.

 

[Cow]

Hello,
I have confirmed that the customer does indeed have 10HP pumps. They are ITT Goulds G&L series. As one poster suggests, no one seems to make a starter appropriate for this size in single phase. I note the last poster presents a method for using a three phase starter but Jraef presented a convincing argument about why this would not be possible.

I've asked the pump vendor to assist but the situation looks a bit grim.

Just what I'd do, we use AB starters, I'd look up a single phase NEMA starter(or IEC) and see if they make one. If not, I'd find one that could handle a 7.5 HP(either 2 pole or 3 pole), whatever I could find, and then take a look at a starter the next size up. Even if it didn't list 10HP single phase as an option on the starter, if I could find the right heaters to match the motor, I'd do it.

This is if the pump vendor couldn't recommend any alternatives or offer any advice on what's worked well in the past for his other customers using 10HP single phase pumps. If he says these are the first ones he's ever sold.......

Personally, I think 10HP is WAY to big on single phase. I'd rather feed a drive single phase to run a 3 phase motor.

 

[ptonsparky]

We work on 1 ph 10 hp grain fans frequently. Some will use 4 pole DP contactors with 2 poles per hot. These are not motors that cycle often however.

Not soft start.

 

[Jraef]

Just to be clear, I was referring to not being able to use a 3 phase soft starter on a single phase motor. No problem using a 3 phase across-the-line (electro-mechanical) motor starter on a single phase application.

You only have to loop power through all 3 phases if you are using the IEC style bimetal overload relays, because they will nuisance trip if there is not power on all three legs. But if you get one of the bigger NEMA style starters, they are not phase loss sensitive (unless you ask for that) so you can just run your motor circuit through 2 of the 3 legs. But like I said, starting those is going to be a real challenge.

 

[BrianMuir]

Hi, OP here...

I have an update. The pump motor data finally arrived. They are Baldor 37F838W578 units, with current listed at 284A, swell. See what happens when the plumber specs the pumps?
Yes, indeed I have been after a soft starter (see thread title). But finally some good news... I tracked down a Siemens soft start unit, rated for this size motor. Siemens makes a variant apparently designed for single phase operation (this is the 3RW30 series). It is something they are phasing out but it's not quite gone yet. I'm cross checking everything but it seems promising.

Thanks to everyone for the help, and I'll post back with a conclusion.

 

[ptonsparky]

Hi, OP here...

I have an update. The pump motor data finally arrived. They are Baldor 37F838W578 units, with current listed at 284A, swell. See what happens when the plumber specs the pumps?
Yes, indeed I have been after a soft starter (see thread title). But finally some good news... I tracked down a Siemens soft start unit, rated for this size motor. Siemens makes a variant apparently designed for single phase operation (this is the 3RW30 series). It is something they are phasing out but it's not quite gone yet. I'm cross checking everything but it seems promising.

Thanks to everyone for the help, and I'll post back with a conclusion.

I could not find the 37F838W578 at all. The 284 A is Locked Rotor, Startup, or ???

 

[Jraef]

I could not find the 37F838W578 at all. The 284 A is Locked Rotor, Startup, or ???

Couldn't find it either. But Baldor doesn't allow searching by Spec number (even though they say you can). I pulled up a 37F395W578 data sheet by searching for 10HP 230V single phase and got that number, then searched that number right off of their web page and it said it had zero results, so obviously there is some sort of disconnect there.

284A sounds like LRA to me though as well. The other 10HP 230V 1 phase motors are all around 40A. 600% is fairly typical LRA, so that would be 240A. Sometimes it's a little higher (or the FLA was a little higher).

3RW30 soft starters were made obsolete 6 years ago now. Did you find one in surplus somewhere? If so, make sure it has a part #3RW3045-1AA12, the last 5 digits being the thing that makes it single phase. Anything else would be a 3 phase soft starter that only uses 2 of the 3 phases, which people sometimes call "single phasing" soft starters but would not work for you. That 1AA12 was the ONLY version that would work. When I worked for Siemens 4 years ago we already could not get them, the factory that made them was shut down. So if you found them, better grab them quick.

 

[BrianMuir]

Yes, the part number is 3RW3045-1AA12, and my Siemens rep tells me that they are available on 3-4 weeks lead time. Hopefully he is right about this. The 284A is the starting current.

 

[Cow]

I'd be thinking ahead on this one, when this softstarter takes a crap, will you be able to find parts for it? It doesn't sound good for you.

That's always my problem with electrical parts, especially lights, 2 mos. later you can't replace a damaged fixture because it's not in their system anymore. And the new replacement looks nothing like the old one....

 

[texie]

Unless I'm missing something here, it would seem prudent to just change the motors out to 3 phase and put in an oversized VFD and call it a day. Sounds like a better solution anyway as you will get better reliablity and others features to boot.

 

[mike_kilroy]

might there be any value in beginning with 460v instead? are 1ph 460v softstarts available? if so, might it help to use a 460v 1ph model and then run thru a 2:1 step down transformer to double the current and run ur 230v motor? I have no clue if 460v 1ph r available but it may be an idea if so....

 

[Jraef]

might there be any value in beginning with 460v instead? are 1ph 460v softstarts available? if so, might it help to use a 460v 1ph model and then run thru a 2:1 step down transformer to double the current and run ur 230v motor? I have no clue if 460v 1ph r available but it may be an idea if so....

No, no 480V 1 phase soft starters, because there are no 480V 1 phase motors either.

Seems to me the 3 phase motor issue was already addressed and rejected because it was part of the pump design or something? But now looking at the G&L line of pumps, there are multiple types but they are not submersibles, so the motors are all just standard C-Face designs. Surely there is a 3 phase version of the same motor available. I would still recommend that VFD / 3-phase motor option for long term reliability.

Still, if your goal is to finish the job and get paid for it, you found a solution. If I were you I'd talk them into a spare Soft Starter or two, because Cow is right, you won't be able to get a replacement soon (and that product was never known for being excpetionally robust).

Good luck.

 

[kwired]

My first call would be to the local utility. Some utilities won't allow you to start anything bigger than 7.5HP(single phase) across the line.

Done here all the time. We have farms with single phase services and they often have multiple 10 Hp and even larger crop drying fans. Not only do these have the typical instantaneous locked rotor current when energized but they are high inertia type loads and take several seconds to accelerate to full speed. Voltage drop only makes this worse whether it be from long conductors or small POCO transformers.

To my knowledge, single phase motors are usually only designed up to 7.5 HP. One starter phase is jumpered to allow current through all 3 overload phases. I usually run incoming power to L1 and L2, on the starter, and jumper T2 to L3 for this application.

Regards,

Mark

Edited for clarity: It is not current through all 3 phases, but it makes it appear to be 3 phases of power available.

I can show you several 16 Hp single phase motors that are currently in use.

Hello,
I have confirmed that the customer does indeed have 10HP pumps. They are ITT Goulds G&L series. As one poster suggests, no one seems to make a starter appropriate for this size in single phase. I note the last poster presents a method for using a three phase starter but Jraef presented a convincing argument about why this would not be possible.

I've asked the pump vendor to assist but the situation looks a bit grim.

If you find a starter like you are looking for it will be a three pole unit with parts missing in one pole. Will cost about same as three pole unit. If using thermal overload type starter you only need overload in one pole. If using phase loss sensitive three pole overload you have to run 2 lines through two poles and one of them from load side back through third pole or it will trip because of what it sees as apparent phase loss.

I also recommend the use of a VFD, though it would neccesitate the replacement of the motor.

I had an irrigation pumphouse with 3x 10HP running off a 200A single phase service. They replaced a single 10HP, but nobody at the time noticed the pole pig was only 10kVA. Didn't last long before it went boom... The utility was going to replace it with another 10kVA, but I begged for something bigger and got a 25 kVA. Not ideal but it's survived 4 years.

When you have only one 10 Hp motor on a 10kVA transformer you usually have horrible voltage drop problems unless the motor is the only load.

I'd be thinking ahead on this one, when this softstarter takes a crap, will you be able to find parts for it? It doesn't sound good for you.

That's always my problem with electrical parts, especially lights, 2 mos. later you can't replace a damaged fixture because it's not in their system anymore. And the new replacement looks nothing like the old one....

That was my thinking also. Why sell them something that has no replacement or at least is hard to replace.

No, no 480V 1 phase soft starters, because there are no 480V 1 phase motors either.

I can show you a few dual voltage 10 HP 240/480 volt single phase motors - they are hydraulic pump motors for hydraulically driven center pivot irrigation systems. The system usually uses three phase motors, but when three phase is not available they use this particular motor, fed from 480 volt single phase service.