120v to 240v transformer may be a solution

Roswell Bob

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Is anyone using a 120v-240v step up transformer?

I was fortunate to get a 30kW 3phase 240v-480v transformer from my boss when we built our home. I now have 3 transformers that are good for 120v-240v. I use one to run the other side of my panel when I run inverter or smaller inverter generator. I am thinking to run my panel at strictly 120v and using a smaller 120v-240v transformer for the well pump.

The point is that these transformers are easy to find and inexpensive. A buck-boost transformer can be wired for either 120v or 240v. You can ignore the secondary of these transformers and just use the split primary to get 240v. If you like the inverter generator but are confounded by the limited offering at 240v then take a look at a transformer to get to 240v. The transformer will also provide some leakage reactance which may limit the starting surge in a well pump situation. The transformer will have it's own surge so I say may. The transformer can be energized first, and then switch on the well pump.
 

Roswell Bob

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Warner, NH
Is anyone using a 120v-240v step up transformer?

I was fortunate to get a 30kW 3phase 240v-480v transformer from my boss when we built our home. I now have 3 transformers that are good for 120v-240v. I use one to run the other side of my panel when I run inverter or smaller inverter generator. I am thinking to run my panel at strictly 120v and using a smaller 120v-240v transformer for the well pump.

The point is that these transformers are easy to find and inexpensive. A buck-boost transformer can be wired for either 120v or 240v. You can ignore the secondary of these transformers and just use the split primary to get 240v. If you like the inverter generator but are confounded by the limited offering at 240v then take a look at a transformer to get to 240v. The transformer will also provide some leakage reactance which may limit the starting surge in a well pump situation. The transformer will have it's own surge so I say may. The transformer can be energized first, and then switch on the well pump.

Or one of these which Mr Snoobler pointed out :)
 

066logger

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I have been trying to figure out a way to go from 120v single phase inverter output to 240v (split?) phase output. My idea was to use a small 2000 watt inverter to keep my idle loads to a minimum. Currently using an aimes 6000 watt inverter but at 79 watts idle consumption it’s not an insignificant draw when figuring for 3 days. But my issue is I can’t find any small inverters that output 240v. That’s an issue because then I can’t power both legs of my breaker box... anybody else do this? Btw, first post here. Currently learning about diy lifepo4 batteries. Got 8 eve 280ah battery’s on order to test and determine if they will work for me. So hello! Thanks for the wealth of information so far!!
 

Roswell Bob

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I have been trying to figure out a way to go from 120v single phase inverter output to 240v (split?) phase output. My idea was to use a small 2000 watt inverter to keep my idle loads to a minimum. Currently using an aimes 6000 watt inverter but at 79 watts idle consumption it’s not an insignificant draw when figuring for 3 days. But my issue is I can’t find any small inverters that output 240v. That’s an issue because then I can’t power both legs of my breaker box... anybody else do this? Btw, first post here. Currently learning about diy lifepo4 batteries. Got 8 eve 280ah battery’s on order to test and determine if they will work for me. So hello! Thanks for the wealth of information so far!!
I have moved my critical loads to one side of box so when I run off of a small inverter generator I have everything I need. I understand the idle current problem with the Aims. You could possibly move your loads to one side as well. What do you have for 240v loads?
 

066logger

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I have moved my critical loads to one side of box so when I run off of a small inverter generator I have everything I need. I understand the idle current problem with the Aims. You could possibly move your loads to one side as well. What do you have for 240v loads?
I had considered doing that Bob. And if I couldn’t find any other solution that was my plan. My biggest issue with that would be I would still keep my 6000 watt inverter hooked up. Just with a battery buss bar for both inverters to be hooked up to the batteries, and on the ac side some sort of transfer switch, inverter 1/off/inverter 2. At times, especially summer when I have a surplus of power I would use the big inverter. But if all my loads are only on one leg in my breaker box then it’s going to be pretty unbalanced for the big inverter. As for my 240v loads currently I only have my well pump.
 

066logger

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In my digging I even thought maybe to use a euro spec 230v single phase inverter with an autotransformer and found victron could swap from 50hz to 60hz so that was covered. But i had one heck of a time figuring out what kind of models victron even has. Ended up talking to a dealer and he had a faint idea of what I was after. But then he said victrons smallest unit was 3000 watts. So then I was back up to about the same idle power consumption of the aimes after adding in the autotransformer. Does anyone have a good link to victrons inverters that breaks down all the specs?
 

Roswell Bob

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I would like to hear from others on what their idle currents are. I am running a larger Aims unit myself and seeing about 2amps for a 48v inverter. That of course translates to about 2.4kWh - which is a big chunk of the 6kWh load I use every day. When I opened up my inverter I found a shitload of fets in parallel on each corner. They are what are called pig fets. Old IR parts that take gobs of gate drive energy to get them to switch. My friends and I have used them for transmitters into the MHz regions. The other power hog it the transformer. They take some energy just magnetizing the core. I would be willing to bet a newer high frequency design would do quite a bit better with the idle current. If you are interested in connecting two inverters and switching between them then you may want to look at Fuji reversing contactors. They have a mechanical interlock so that you cannot connect two inverters together at the same time - tho any decent inverter should be able to trip on that kind of a condition before the smoke escapes.
 

066logger

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I would like to hear from others on what their idle currents are. I am running a larger Aims unit myself and seeing about 2amps for a 48v inverter. That of course translates to about 2.4kWh - which is a big chunk of the 6kWh load I use every day. When I opened up my inverter I found a shitload of fets in parallel on each corner. They are what are called pig fets. Old IR parts that take gobs of gate drive energy to get them to switch. My friends and I have used them for transmitters into the MHz regions. The other power hog it the transformer. They take some energy just magnetizing the core. I would be willing to bet a newer high frequency design would do quite a bit better with the idle current. If you are interested in connecting two inverters and switching between them then you may want to look at Fuji reversing contactors. They have a mechanical interlock so that you cannot connect two inverters together at the same time - tho any decent inverter should be able to trip on that kind of a condition before the smoke escapes.
Thanks Bob, I have dug and dug and not made a lot of headway. To be honest it is disappointing but either not a single solar supplier knows their products well enough or what I’m after simply doesn’t exist. Nobody makes a sub 3000watt split output inverter. Nobody. And as for buying another smaller inverter, I had the aimes 2000 watt inverter charger. Their flagship big blue model in mind. They say on their website surges up to 6000 watts for 20 seconds. Aimes tech support said my 2- deep freezes and a 300 watt buffer load for tv and lights 3060 watts total would kill that inverter 🤦🏼‍♂️. Even after explaining that it’s a deep freeze and after startup drops to 1.5A shortly and I’m figuring worst case both starting at exactly the same time. Nope, wolnt do it says the tech guy. Well why the heck does your website say it will then?? Ugh. I’m so fed up with bs and people flat out lying in this industry!
 

Roswell Bob

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Thanks Bob, I have dug and dug and not made a lot of headway. To be honest it is disappointing but either not a single solar supplier knows their products well enough or what I’m after simply doesn’t exist. Nobody makes a sub 3000watt split output inverter. Nobody. And as for buying another smaller inverter, I had the aimes 2000 watt inverter charger. Their flagship big blue model in mind. They say on their website surges up to 6000 watts for 20 seconds. Aimes tech support said my 2- deep freezes and a 300 watt buffer load for tv and lights 3060 watts total would kill that inverter 🤦🏼‍♂️. Even after explaining that it’s a deep freeze and after startup drops to 1.5A shortly and I’m figuring worst case both starting at exactly the same time. Nope, wolnt do it says the tech guy. Well why the heck does your website say it will then?? Ugh. I’m so fed up with bs and people flat out lying in this industry!
I find a lot of sales/apps guys are a little bit light on the technicial side. If you can measure starting current on the refer you should be able top make an assessment of whether or not inverter will start it. I don't suppose you have a storage scope. The likelyhood of two inverters starting at the same time are small unless the inverter has been off and you plug it back in. Then of course they will both try to start at the same time. Does the inverter have an auto-restart function? If it trips it will try and restart?
 

066logger

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Well Bob, guess what! With the help of this forum I found pretty much exactly what I was asking for! Even more annoying is it looks like it’s made by the same people that make aimes inverters!! What in the world! I seriously wonder if the entire solar industry is just a bunch of scammers! Anyway, drum roll! https://www.sigineer.com/product/30...240vac-dual-phase-pure-sine-inverter-charger/

3000 watts, a little bigger than I would like but I’ll take it. 120/240 output! Idle consumption is 37 watts. Half what the 6000 watt is as is to be expected. $659. Exactly what I’m after, reading some reviews they said they didn’t have a correct charge profile for lifepo4 but neither does my aimes and I have a separate charger that I use for my generator anyway as it only outputs 120v. Perfect! Only thing is I have messaged them a couple times on availability and haven’t heard anything yet. Any experience with this particular crew? I’m just about to pull the trigger and see what happens.
 

Hedges

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My SI-6048US is 5750W, 120V, 25W idle. I'm operating these 2s2p.
I have a 9000 VA 120/240V toroid transformer on an SI-5048.
But what SMA saves you in watts you'll pay in $$$. A bit more PV and battery may be the cheaper solution.
 

066logger

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Whew, yeah. $3800 is a lot for an inverter. I’m sure they’re great, but yeah in my application when the idle draw is my main concern I just don’t know if I could justify that kinda $$$. That’s half of what I have in my system to date 🤣
 

the_colorist

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Yeah here is the thing: Most installers or even dealers in the field tend to be electricians that are now installers. They aren't engineers per se. No offense intended to anyone of course! Most of them simply don't have the training or have time/need to get the training. I've had fellow installers/solar company owners tell me they can find electricians on every corner but to find trained technicians/engineers that can build large stand-alone microgrids from the ground up is a bit more tricky. There aren't nearly as many of us.

It's the same with the sales guys. It's unlikely you'll talk to someone who really knows design and engineering on the phone unless it's a small company with the owner answering etc.

I would avoid Aims/Sigineer personally. That said, small split-phase inverters are hard to come by. Sacolar (Growatt) has some nice ones in the Sunrino lineup that are also Lithium compatible but I have yet to test the integration implementation. Victron with an autotransformer is super as long as you have a great dealer with good pricing. Idle on an MP II 48/3000 is 11W.

If you go with Victron, they have 230V Multiplus/Quattro inverters down to 500VA. Even in 48V. You could one of their autotransformers or you can use something like Solaredge's SEAUTO-TX-5000 5KW transformer. Solaris has a good price on them. I haven't used one of the Solaredge models personally yet (I will in a few weeks) but it should be fine. I wouldn't use it for over 22A or so (line-to-line transfer).

The other option is to get a 120V Victron unless you need 120/240V. If you do need 240V, at that point it's just a cost tossup between models/configurations although if you only have a 120V generator it can be tricky. I'm currently working on getting the pricing and availability for the new Multiplus II 48/3000/35-32 120V (PMP482305100). Could be a game-changer price-wise for 120V installs.

If you want to see Victron's full equipment list, just look at the price sheet:


PM me if you want pricing on anything.
 

066logger

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Back to the drawing board lol. So my main reason I would like to have 240v output is just for simplicity. My well pump is 240v, so I’m always going to have to have 240v in one form or another with enough juice to push a 1/2 hp pump. So trying to move all circuits to one leg of my breaker box complicates things. My loads on the average day minus pumping water come out to 3000-3200 watts worst case scenario. If Both deep freezes come on at the same time. My aimes has treated me well for 4 years, although their tech support definitely leaves something to be desired. But the idle draw, just kills me.

I had really looked hard at victron but the dealer I talked too said the smallest unit that could be paired up was 3000 watts? Maybe this isn’t the case? I will definitely look through your price list! Based on my specs 3000 watt 24v 240v split output would you have a particular one of their inverters in mind?
 

066logger

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Also, I do like the idea of two inverters for backup reasons. Two is one one is none kinda thing lol
 

Hedges

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Whew, yeah. $3800 is a lot for an inverter. I’m sure they’re great, but yeah in my application when the idle draw is my main concern I just don’t know if I could justify that kinda $$$. That’s half of what I have in my system to date 🤣

Closer to $5k msrp. But what matters is the deal you find.
Thanks to DC solar mine cost $1250 so I put in four. I bought on eBay from someone who probably paid $500 to $800?

Right now you can pay $2k plus shipping for an SI-5048 or $2k shipping included for an SI-6048



You'll still need a transformer for your 240V pump. But think 11,000W surge will help?
 

Bawk80

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Is anyone using a 120v-240v step up transformer?

I was fortunate to get a 30kW 3phase 240v-480v transformer from my boss when we built our home. I now have 3 transformers that are good for 120v-240v. I use one to run the other side of my panel when I run inverter or smaller inverter generator. I am thinking to run my panel at strictly 120v and using a smaller 120v-240v transformer for the well pump.

The point is that these transformers are easy to find and inexpensive. A buck-boost transformer can be wired for either 120v or 240v. You can ignore the secondary of these transformers and just use the split primary to get 240v. If you like the inverter generator but are confounded by the limited offering at 240v then take a look at a transformer to get to 240v. The transformer will also provide some leakage reactance which may limit the starting surge in a well pump situation. The transformer will have it's own surge so I say may. The transformer can be energized first, and then switch on the well pump.
Hello, I am using an inverter which powers my home except the dryer, refrigerator and hot water heater run at 240 volts. Can you tell me where to buy the transformer you use and will it work for me? My home runs on 200 amps.
 

Hedges

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Hello, I am using an inverter which powers my home except the dryer, refrigerator and hot water heater run at 240 volts. Can you tell me where to buy the transformer you use and will it work for me? My home runs on 200 amps.

Your home may have 200 amp service, but how many watts is your inverter? Is its output voltage 120V only, or 240V only?

Dryer 240V is common, probably 120V for motor & timer, 240V for heating element. Could be around 5kW. You can wire it to run on 120V and about 1250W if you prefer. A 5kW isolation transformer or a 2500W auto-transformer could converter 120V to 120/240V for the dryer.

Refrigerator is 240V? That's unusual. It's power is probably only a couple hundred watts for the compressor, 800W for defroster or ice maker. What are its ratings? (label may be in door frame or inside.)

Water heater - what are its ratings? Common to have up to 4800W elements. But it can be wired for 120V, would draw 1200W.

Need to know how many watts have to be converted from 120V to 240V to size the transformer. That would either be the maximum your inverter puts out, or the sum of all 240V appliances you want to run at once.
 

Hedges

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My inverter is 2000 watts with 6000 watt surge capability

120V I suppose.

If you use a 120/240V transformer, then it won't be able to power either the dryer or the water heater; they will overload it and it will shut off.
If you wire them for 120V, then you can power one at a time with the inverter.

How big a battery do you have?
How much PV?

For these heating loads, it would be best to enable them when battery is full, disable when battery drops to some reasonably high SoC like 80%. That leaves power for other loads.

(This is assuming a conventional resistance element water heater, not a hybrid with heat pump.)
 
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