2-wire multi-voltage AC/DC pump... Now what?

[Francois Gamache]

Pump is Grundfos 6 SQF-2 has 1 ground, 1 neutral, 1 hot leg. Natively accepts and handles the following:
DC 30 to 300V or
AC 90 to 240V
Basic wiring diagram supplied in installation manual attached.
Maxes out at 8.4A and 1400W.

So.... If I want to get max flow on AC, I need to run it on 240V (or 167V if that was an option!)

How do I do that on regular north-american household electrical setup where normally a 240V appliance has 2 hot legs @ 120V each?

Do I splice 2x 120V circuits and connect to the pump's single hot leg??? Doesn't sound kosher.

Hints?

 

[WorthFlorida]

Without any transformers you can only run it on the ~120 volt. It looks like this motor unit is designed for worldwide use since the rest of the world except Japan uses single phase 220 v. Since this motor can accept DC or AC voltage it means to me that that there is probably some kind of regulator circuit in it. Google search "step up transformers". I'm not sure if these step ups will work well on these motors. You're are best to call Grundfos support and ask.

Your last question is exactly right, it makes no sense .

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[Sponsor]

 

[Reach4]

Do I splice 2x 120V circuits and connect to the pump's single hot leg??? Doesn't sound kosher.

You will use a 2 pole breaker, and deliver two hots to the pump. You will connect one hot to N and the other hot to L.

The green or bare wire will go to the terminal indicated by the ground symbol.

This is based on your attachment.

 

[WorthFlorida]

You will use a 2 pole breaker, and deliver two hots to the pump. You will connect one hot to N and the other hot to L. The green or bare wire will go to the terminal indicated by the ground symbol. This is based on your attachment.

This motor cannot be connected to two phase 240v. Just look at any small power supply laptops, tablets, etc. It will read 90-240v 50-60hz so it can be use worldwide. Usually the AC plug side it detachable so the North American or the European cord can be package with the unit depending on its destination.

This is from the Grundfos web site and the specs read 1 x 90-240v. That tells me it is not a two phase AC motor. This company is in Denmark and Euro companies will use the 1 in their specifications to indicate single phase. What really surprised me was that DC power can also be used which would be perfect for remote locations off the grid using solar panels.

http://product-selection.grundfos.c...mber=95027334&productrange=gma&qcid=230750887

Electrical data
Motor type MSF3
Power input - P1 1.4 kW
Rated voltage AC 1 x 90-240 V
Rated voltage DC 30-300 V
Rated current 8.4 A
Power factor 1,0
Rated speed 500-3600 rpm
Start. method direct-on-line
Enclosure class (IEC 34-5) IP68
Insulation class (IEC 85) F
Motor protection Y
Thermal protec internal
Length of cable 6.562 ft
Motor Number 98163731
Udc 300 V
Udc 30 V

 

[Reach4]

This motor cannot be connected to two phase 240v.

240VAC in a house is single phase. https://en.wikipedia.org/wiki/Split-phase_electric_power

 

[WorthFlorida]

It's named single phase in the US because one phase of the usually three phases (120 degrees apart) from the power plant is used. The single phase put throught a transformer creates two voltages whose sine waves are 180 degrees apart. For clarity I like to use the name two phase to indicate that each leg is ~120v out of phase. However, I'm not sure if this motor can be connected to hot 120v legs.

 

[Reach4]

For clarity I like to use the name two phase to indicate that each leg is ~120v out of phase.

I certainly agree that each leg out of phase with the other. There is something actually called 2 phase, but it is not used for public power distribution today, as far as I know. In that, the 2 phases are 90 degees out from each other.

You might find this amusing: https://terrylove.com/forums/index....asing-of-voltages-out-of-a-transformer.56003/

 

[Francois Gamache]

What really surprised me was that DC power can also be used which would be perfect for remote locations off the grid using solar panels.

Yes, that was the selling point: we are in a rural location and will be going solar off-grid when we build (but on a generator for now...) The ability to connect DC directly from panels or batteries without having to worry about inverter tripping is, hopefully, worth the hefty price tag of this pump!

 

[Jadnashua]

If you can picture it...the power coming into your (typical, US) home is single phase. If you look at a transformer, the output is 240vac, but it has a tap in the middle of that secondary - i.e., halfway across it, which functionally equates to zero relative to ground. To get 120vac, they reference from one end of the secondary to the neutral tap in the middle, so you get two 'sections' of that output. If you need 240vac, you go from one end of the transformer to the other. In a transformer, across the secondary, the phases are opposite when one side is high, the other side is low. You can find out lots more if you Google it. As long as the ground is isolated from the neutral, it should probably work. Safest is to ask them.

FWIW, if you have a problem in your neutral coming into the house...without that lead...what would normally be 120vac, can become 240vac, creating all sorts of havoc!

 

[Francois Gamache]

Thanks for the info... I will need to review my phases and sine waves

It took 3 days to get a reply, but Grundfos technical support advises that the SQFlex pumps can in-fact take 2X 120V AC hots and a ground. I'll admit I'm still a bit leery and not convinced I wanna try it!

It must have a pretty sophisticated controller to accept all these possible connections...

fg

 

[Reach4]

It must have a pretty sophisticated controller to accept all these possible connections...

Imagine a 4-diode bridge rectifier feeding a capacitor. Then imagine the capacitor as the input to a switching power supply.

The input, on the left, can be provided with AC or either polarity of DC. Either way, you get DC across the capacitor.

 

[Jadnashua]

As I said earlier...in a typical US home, you don't really have 120vac coming in...you have 240vac. If you put a lead half-way across the transformer, the potential to either end is 120vac, and that's how you achieve a 120vac...you've halved the 240vac output by intercepting it half-way across the secondary of the transformer. 240vac does not use the neutral, 120vac does because that is what we call the midpoint, or neutral (since it's half way between a high and a low at either end of the transformer's coil). The ground point is also referenced to that neutral, but is only needed as a safety feature. Except in a fault mode, ground should NEVER have any current or voltage on it.

In places like Europe, where 220-240vac is the norm, they have a simpler transformer without the extra wire, the neutral, since they don't need it!

This shows a fairly common hookup from the higher voltage lines at the street, to your home's tap providing single phase, 120/240vac power.

http://constructionmanuals.tpub.com...0-volt-three-wire-single-phase-service-75.htm

 

[Francois Gamache]

You lost me after "Imagine..."
But thanks for the pretty picture ;-)

 

[DonL]

You lost me after "Imagine..."
But thanks for the pretty picture ;-)

It is really simple.

If you connect for 120VAC you use 1 Line and Neutral. (a or b and N above)

If you connect to 240VAC you use L1 and L2 (a and b in the picture above) and do not use the neutral.

Good Luck. Be safe use proper PPE and a fuse.

 

[Francois Gamache]

It is really simple...

Ah yes, that part I got.... I was puzzled by the previous response re: Imagine a 4-diode bridge rectifier.

Anywho, sometimes it's good to keep a bit of magic alive ;-)

 

[Francois Gamache]

So..... In conclusion, these SQFLEX pumps take whatever you throw at them.
Rewired to two 120V hot + one ground and it purrs like a kitten!

 

[Jadnashua]

The ground is for safety...it is not 'needed' for operation. A safety ground wire should never have any current on it except when there's a fault. But, it does provide safety for the pump and you, so should not be omitted. While you can think of the two legs of the 120vac as being separate things...they're really just 240vac when there's no neutral involved. The neutral is just 'half-way' between the sinewave between one leg and the other...thus the neutral designation.

If you could move the neutral connection along the secondary transformer, and were measuring from either L1 or L2 to it, you would get a varying voltage of zero to 240vac as that moved from one end to the other...that's how a variac works. You could think of it like a rheostat or volume control. It's just that neutral is fixed at half, and not moveable.