Using a 110 to 220 step up converter

MainelyTom

Hi, have an off-grid 110 volt solar system. Need to add a well pump to the system (previously gravity fed surface water). Problem is that the well head is 120 feet from the house (septic system set back requirements) and about 230 feet deep (with about 40 feet to the top of the water). Plan is to place the pump at about 210 feet. But that gives a run of at least 330 feet and the pump installer is figuring a 3/4 hp pump. Likely a Grundfos 5SQ07-270. Because it has built in soft-start, we are hoping to avoid the usual motor start up surge. But still, that's 600 watts. At 330 feet I'm not sure what wiring to run. I've done the calculations and it should be able to handle 12/3wg the whole distance. Just don't want to get caught having to move up to 10/3 for the higher amps over that distance. Luckily the pump has a wide voltage range so It should be able to handle even a 20 volt drop at 220. Any thoughts? Go with the 110 volt without a step up converter? or go with the 220 with a step up converter. And do the step up converters use power when not in use? couldn't find an answer to that.
Thanks.

Estragon

FWIW, I had a similar issue with a submersible (lake) pump.  I ended up going 240v (my only 240v load) with an autotransformer.  The autoformer doesn't use much just being on (a few watts).  If power is tight, I turn it off at night, as water in the pressure tanks is usually enough.  The inverter search probe makes the autoformer a bit noisy, but it's almost silent just being on.   

I also found if the autoformer is turned on with the pump pressure switch closed, the gfi opens, but if the autoformer is powered first, no problem.  A well pump likely wouldn't have gfi though, so likely not an issue.

mike95490

Your 3/4 hp pump will consume more than 600w    My inverter logs my 1/2 hp at 1,000 watts, because of losses and power factor.

A DC or integral inverter pump may be less and if you starve the pump for power with small 12ga wire, your pump rate will decrease. for that distance, I'd suggest the 10ga if you can swing it.

freddieoliveras

Hi, what step up transformer dis you use?

NANOcontrol

You still have losses in the step up transformer.  Besides the core loss, there is all the wire resistance of the windings. Transformer should be way oversized to make those losses minimal.

Mike_in_PA

Question.  Can I use a transformer to step up 120 volt (SI 6048) to 240 volt for the well instead of an autotransfomer?  The only load on the output side would be the 240 volt well.  I have one of the  PSX-240s autotransformers at work, so I do understand how that works to balance loads. Wondering if I could use a cheaper 3 KVA transformer for the new back up system at home. I realize the well needs split phase--just don't if you can get that out of of step up transformer somehow. Also, can a 3 KVA transformer handle the higher well start up power?  Its a typical 3 wire 1/2 hp well pump, head is less than 80 feet. TIA.

mike95490

It's nice to have some overhead in the transformer, once the core saturates, it simply cannot supply any more power.

here's a chart of well pumps with LRA specs.

 Have you tried your pump on your PSX-240 ?  is it able to start the pump ?

 And watch for the load of the transformer magnetics stabilizing as the pump comes on.  you may need a 5 second delay, so the transformer is going, before the pump starts.  Both inductive loads at the same time may overload the inverter.

softdown

Gut feeling is 220 volt pump wanting 8 AWG wiring and consuming over 1000 watts. Well pumps are huge energy hogs. Water is heavy and pushing it 230' high then another 150' or so... 
Just guessing though. My 1/2 hp pump is an energy hog at 100'. And 12 AWG was barely enough - voltage sinks to ~108 under use. 

softdown

This may sound dumb but I don't understand how a step up converter from 110 can replicate American 220. European 220 - sure. 

Mike_in_PA

Not dumb.  I think you would need two step up transformers out of phase to each other somehow, just wondering if anyone has tried it. I will be replacing the well with the Grundfos SQ when it finally goes, so just need a solution till then.  Pump is 27 years old now.

softdown

Mike_in_PA said:

Not dumb.  I think you would need two step up transformers out of phase to each other somehow, just wondering if anyone has tried it. I will be replacing the well with the Grundfos SQ when it finally goes, so just need a solution till then.  Pump is 27 years old now.

It is the out of phase part that seems kind of impossible to me. People don't use two inverters to make 220 volts for the fun of it. 

I'm not sure what gensets do to make 220 volts. That may yield the answer. 

mike95490

Here's 2 articles about autotransformers (& regular CT transformers would work the same)

https://en.wikipedia.org/wiki/Autotransformer

https://canadatransformers.com/what-is-autotransformer/

And, many generators over 5Kw have a split phase winding to produce both 120 & 240VAC

softdown

^^^ If I read this correctly then autotransformers are used for reducing voltage. Useful for steeping down grid voltage (ex - 660) to neighborhood voltage (ex-440). Then another transformer around the back yard steps it down to 220 for household/commercial use. 

Highly simplified becaause thats how I roll. 

Estragon

Autoformers can be used either way. 

My X240 can step up from 120v source to 240v load (which I do to run a pump), or step down from 240v source to 120v load. 

Step down might be used, for example, on a split phase 120/240v generator to load balance L1/L2 where a big 120v load taken directly off one leg can cause issues for the genny.

mike95490

I use my autotransformer as a step up, from 120 to 240VAC,
or no step at all, but simply for load balance, because many 240VAC inverters need balanced loading to operate most efficiently.
I am using the 240V windings only.

freddieoliveras

That’s a 480v to 240v (split phase), how did you connect it?
120 in one leg?

mike95490

I only used the 240V winding.  The 120v generator went to x4 x3 .  Jumper x2 & x3 and the 240 comes out of x4  x1

totally ignore the 480V winding.

So to do this, you really need to understand how transformers and electricity work and should be wired.  Make a mistake, and you will be looking at the charred stump where your hand was.

softdown

mike95490 said:

I only used the 240V winding.  The 120v generator went to x4 x3 .  Jumper x2 & x3 and the 240 comes out of x4  x1

totally ignore the 480V winding.

So to do this, you really need to understand how transformers and electricity work and should be wired.  Make a mistake, and you will be looking at the charred stump where your hand was.

Sounds to be a different level than a typical 120 volt pop. 

jonr

It's also perfectly fine to treat a 480V:240V transformer as a 240V:120V transformer (ie, you can the 480V winding if you want to).

But I'd avoid the issue and use a 115V well pump.    No need for 3/4 HP when water is at 40' (+ draw down).

12 gauge copper is fine for the Grundfos 5SQ07-270 (8.4 amps, 2000 watts).

softdown

jonr said:

It's also perfectly fine to treat a 480V:240V transformer as a 240V:120V transformer (ie, you can the 480V winding if you want to).

But I'd avoid the issue and use a 115V well pump.    No need for 3/4 HP when water is at 40' (+ draw down).

He might be saying the water level is 190'. I can't hardly see doing 230' when water is hit at 40'. Many stop as soon as they hit water. I'd go another 30' or so myself - and I'm no expert on this. 

Mike_in_PA

Yes the 120 v SQ is the correct solution, but then I have to pull the existing pump.  Have to work up to that.  Around here, the well drillers do that...

Pump is set at 120', but water depth is about 35' below the pressure tank, and I run low PSI in the systems, so pumping head is low.

Neat use of the secondary windings to make an autotransformer Mike.

MichaelK

He might be saying the water level is 190'. I can't hardly see doing 230' when water is hit at 40'. Many stop as soon as they hit water. I'd go another 30' or so myself - and I'm no expert on this. 

An important parameter with drilled wells is the "refresh rate", that is how fast water enters the bore hole.  There may be more than one underground aquifer passing through his property.  If the one at -40 feet has a refresh rate of 2 gallons per minute, and the pump pushes out 5 gallons per minute, then the borehole will run dry.  By drilling the borehole deeper than necessary, you are both likely to drill through additional aquifers producing more water, and also increasing the available collumn of water available if the refresh rate still isn't high enough

wellbuilt

Most of the time the guys drill in to the aquifer and the water pops up almost to ground level.
then they set the pump 20’ off the bottom .
  You may have water up at 40’ but they had to drill down to 400’ to get it . 

Mike_in_PA

Wow, here it is 2025 and I still don't have the home backup system finished. 

I am still looking to use an inexpensive transformer to make 240 volt for the well.  I bought a 2 kVA Acme T-3-53042-S transformer, built as shown in the first figure below.  I want to take 120 from the SMA 6048 SI and have the transformer make the other half of the split phase.  Together, both legs should add up to a 4 kVA rating.  I would also like to use the same transformer to AC-couple some Enphase microinverters with the 6048. 

The second figure below is how I believe it should be connected.   

Any help is greatly appreciated!