# Step Down Transformer Questions



## chocks141 (Nov 21, 2015)

Here is my question.

Using a step down transformer on my back-up generator, can I wire it to a 220/240 plug with 2-15a breakers and get 30a 110 out of it?


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## A Watchman (Sep 14, 2015)

Please provide a more concise view of how and with what you are wiring from the supply to load...... I am not clear.


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## azrancher (Dec 14, 2014)

chocks141 said:


> Here is my question.
> 
> Using a step down transformer on my back-up generator, can I wire it to a 220/240 plug with 2-15a breakers and get 30a 110 out of it?


OK, several questions come to mind, first just because the 240 VAC plug has 2 X 15A breakers doesn't mean it can provide that many Watts, and you realize that if this is a US based electrical generator that the 240 VAC plug is already 120 VAC on each leg of the plug when measured to ground, or neutral if you have a 120 VAC plug already. So you could split the 2X15 A breakers i.e. take out the strap that makes them both disconnect at the same time and then you have 2 120 VAC circuits at 15 Amps.

*Rancher*


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## A Watchman (Sep 14, 2015)

Are you splitting the circuit at an outlet or at the breaker? Remember 220/240 does not utilize a dedicated neutral wire, as does 110/120 volts. Of course a ground can be utilized by defeating its intended purpose.


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## dwight55 (Nov 9, 2012)

If you put a plug into the 220/240, . . . wire those two wires to the primary of a 2:1 stepdown transformer, . . . on the secondary side, . . . you will have 110 volts.

The power input being 15 amps, . . . yes, . . . you should get almost 30 amps out the other side.

That part of electricity is not for the over-thinkers, . . . it is 100% ABC simple.

Now, . . . there is a small loss in the conversion, . . . maybe only giving you 29.75 amps, . . . but generally speaking, . . . the volts and amps are inversely proportional.

May God bless,
Dwight


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## azrancher (Dec 14, 2014)

dwight55 said:


> If you put a plug into the 220/240, . . . wire those two wires to the primary of a 2:1 stepdown transformer, . . . on the secondary side, . . . you will have 110 volts.
> 
> The power input being 15 amps, . . . yes, . . . you should get almost 30 amps out the other side.
> 
> That part of electricity is not for the over-thinkers, . . . it is 100% ABC simple.


However that is one large, not huge stepdown transformer for... I guessing 4KW of power, it's not something you would do if you can do it otherwise.
*
Rancher
*


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## dwight55 (Nov 9, 2012)

azrancher said:


> However that is one large, not huge stepdown transformer for... I guessing 4KW of power, it's not something you would do if you can do it otherwise.
> *
> Rancher
> *


Correct, . . . 30 amps X 120 volts = 3600 watts, . . . shortly shy of 4KW, . . . and yessir, it would be a largish transformer.

But, . . . sometimes the simple way is the best way. I would have no problems at all using such a setup.

In fact, . . . I've used similar setups many times since my first electrical training that began in the spring of 1964........ compliments of of the US Navy in Great Lakes, ILL.

I really think the important point, though, in all the discussion here, is that the objective from the OP, is easily obtained, and the training for doing that is not complicated. This is something that "may" become of use to someone out there in the SHTF world of our future.

Knowing how simple it is may make the difference between having 110 volt electricity for life saving measures and not having it, . . . watching people die.

Even knowing that for example, . . . if the OP only had a 220 volt generator, . . . and 110 volt light bulbs, . . . it is good for him to know that if he wires two of those bulbs in series, . . . he can turn them both on with a single switch, . . . will get the required light from them, . . . and not burn them up as would happen if they were connected in parallel across the 220 source.

May God bless,
Dwight


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## chocks141 (Nov 21, 2015)

Thanks for the info. I know just enough about electricity to be dangerous.

Ok, here's the deal.
The incoming AC for my inverter in 110 only. It supplies the load for the house, then any extra goes through the charger to the batteries.
my backup is a Gererac 6500 portable generator. The 110 plug on the genny that I plug into has a 20a breaker, so I can only get about 65% out of the charger.
I know I can wire 1 leg of the 220 to get 110, but that plug has a 15a breaker on each legs, so that would be even less.
If I can get 30a 110 out of the 220 plug, I can turn my charger up.


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## jdbushcraft (Mar 26, 2015)

Confused.. AC into an inverter? Inverters convert DC to AC. So you are converting DC to AC then converting again back to DC to charge batteries? Seems wasteful. I'm lost.. Sorry. Guess I don't understand your setup.


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## azrancher (Dec 14, 2014)

chocks141 said:


> The incoming AC for my inverter in 110 only. It supplies the load for the house, then any extra goes through the charger to the batteries.
> my backup is a Gererac 6500 portable generator. *The 110 plug on the genny that I plug into has a 20a breaker, so I can only get about 65% out of the charger.*
> I know I can wire 1 leg of the 220 to get 110, but that plug has a 15a breaker on each legs, so that would be even less.
> If I can get 30a 110 out of the 220 plug, I can turn my charger up.


OK I see where the confusion is, ... I think? Is this inverter+battery system part of a *Solar* system?

Your inverter that provides power to the house from the charged battery bank, it also charges the batteries either from solar panels or the generator. Your inverter/charger is rated in watts, it will only use as many Amps X Volts = Watts as it is rated for. OK so you currently have the inverter/charger plugged into the 6500 watt generator on the 20A plug (breaker), and the breaker is what protects the wiring to your inverter/charger, it doesn't limit the charging power of your inverter/charger, if that 20A breaker is not tripping then that is as good as you are going to get.

You could replace the 20A breaker with a 30A breaker but you don't get more Amps by doing so. So that brings up a question, why do you not have a split phase 240VAC inverter/charger in your system, do you not have any 240 volt appliances being powered by this battery backup system?

*Rancher*


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## paraquack (Mar 1, 2013)

Need lots more info.


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## chocks141 (Nov 21, 2015)

It is part of my solar system.
I have an Outback 3524 inverter/charger with a built in 85 amp charger and internal switching.
Everything in the house is either 110 volt or 12 volt (with 24v to 12v converter)
The inverter has 24v input from batteries, 110v input from the generator and 110v output to the house. If you need the power or to charge the batteries, you just start the generator.
you set the inverter to limit the incoming current, right now I have it set at 18 amps, if I set it any higher, it trips the 20 amp breaker.
so, it sends what is needed to run the house then the balance is converted to 24 volt and sent to the batteries for charging.
Normally I get about 65 amps from the 85 amp charger. 65 amps into 20- 205ah batteries is not much more than a trickle charge. So my thoughts are, if I can use the 30 amp circuit, I can up the incoming power from around 2000 watts to 3100, thus, more power to the charger = less run time on the generator.

That is why I am here asking, I'm not sure if this is something that is feasible or even worth the time to mess with.


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## azrancher (Dec 14, 2014)

chocks141 said:


> That is why I am here asking, I'm not sure if this is something that is feasible or even worth the time to mess with.


Have you priced a step down transformer at 6,500 watts (a 10KW is in the thousands)? Call Generac and ask if both of those 2-duplex outlets are phased the same, I suspect that they are separate legs of the 240 volt generator winding's and therefore could not be combined for 40 Amps. Even if they are the same phase, I suspect that Generac will tell you no you cannot do that.

*Rancher*


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## Will2 (Mar 20, 2013)

Law of Conservation of energy?

What are the specs of the step down transformer you are using.

The simple answer is yes more or less.

however you would only draw a maximum of 15A on each breaker if you drew more than 15 amps on any line then it would trip.
It may not be up to your local safety code though, check with your local electric safety authority to see if you are able to do any sort of home elctrical in your jurisdiction.

|||||||||||stepdown-220Vto110vline 1 _____ 15A breaker output up to 15A 110VAC
MAIN30A[
||||||||||stepdown220vto110vline 2 _____ 15A breaker output up to 15A 110VAC

Bear in mind though you could only draw a maximum of 15A on either line so if you wanted to hook up something with 30A on either of the 15A lines independently it would trip either of the 15A breakers.

What exactly do you want to use the two 15A breakers to power?

f
http://www.edrenzi.com/Code/Trans (1p).pdf


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## Slippy (Nov 14, 2013)

Will,

I'm going out on a limb here and saying that I doubt you have ever done any electrical work EVER.



Will2 said:


> Law of Conservation of energy?
> 
> What are the specs of the step down transformer you are using.
> 
> ...


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## Will2 (Mar 20, 2013)

Slippy said:


> Will,
> 
> I'm going out on a limb here and saying that I doubt you have ever done any electrical work EVER.


As usual you are totally wrong and out of touch with reality.

I have no need to explain myself to you but in addition to having an advanced radio certification enabling me to build transceivers legally up to 1500 watts and operate remote, I have also been enrolled in an Electrical Engineering Technology program for which I am in good standing. Of course this is relatively basic physics of which I had A's in my highschool physics courses which included the types of windings for energy conversions. I have insured my own home passed electrical safety inspections, for which it did. I have set up my own off grid electrical systems etc.. I have worked with step down transformers.

Do you not have anything better to do with your life than hound my posts, don't you find your life pathetic and aspire for more than nagging people?

None of this matters though as the OP should do nothing unless they understand the link I posted unless it is a life and death emergency.


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## Slippy (Nov 14, 2013)

Well now, an "A" in highschool physics AND an advanced radio certification? Why didn't you say so in the first place, snowflake? 
A bonus would most certainly be a Little Orphan Annie Secret Decoder Ring!
Carry on with more advice on ELECTRICITY! I'm sure nothing can go wrong...:whew:



Will2 said:


> As usual you are totally wrong and out of touch with reality.
> 
> I have no need to explain myself to you but in addition to having an advanced radio certification enabling me to build transceivers legally up to 1500 watts and operate remote, I have also been enrolled in an Electrical Engineering Technology program for which I am in good standing. Of course this is relatively basic physics of which I had A's in my highschool physics courses which included the types of windings for energy conversions. I have insured my own home passed electrical safety inspections, for which it did. I have set up my own off grid electrical systems etc.. I have worked with step down transformers.
> 
> ...


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## Will2 (Mar 20, 2013)

Slippy said:


> Carry on with more advice on ELECTRICITY! I'm sure nothing can go wrong...:whew:


As long as you are no where near an electrical source.


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## Slippy (Nov 14, 2013)

Will2 said:


> As long as you are no where near an electrical source.


Another excellent comeback!


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## dwight55 (Nov 9, 2012)

IF the primary side of the transformer, . . . having 230 volts input going into it, . . . is protected by a 2 pole / 15 amp circuit breaker, . . . 

You can use it to power a 4KW / 2:1 ratio / step down tranformer, . . . on the primary side.

On the secondary side of that transformer, . . . you will only get 110 volts, . . . but you will receive almost 30 amps.

That side should also be protected by a 2 pole / 30 amp circuit breaker. 

The reason you are using a 2 pole on the 110 volt side, . . . there is no neutral as is in most commercial electricity today. The transformer itself has eliminated the need for a neutral, . . . but has produced two live wires instead of the usual one.

It therefore needs both legs protected, . . . and you do that with a 2 pole circuit breaker.

May God bless,
Dwight


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## Will2 (Mar 20, 2013)

dwight55 said:


> IF the primary side of the transformer, . . . having 230 volts input going into it, . . . is protected by a 2 pole / 15 amp circuit breaker, . . .
> 
> You can use it to power a 4KW / 2:1 ratio / step down tranformer, . . . on the primary side.
> 
> ...


Well your answer is more intuitive however they originally asked

Using a step down transformer on my back-up generator, can I wire it to a 220/240 plug with 2-15a breakers and get 30a 110 out of it?

This had me think they had a breaker box with two breaker switchers to run branches off of. Meaning the 110 output would need to be split to two separate branches. Since the breaker is maxed to 15A it would trip at anything more than 15 amps on either branch since both branches are regulated by a 15A breaker.

you can't draw more than the rating on a breaker without it tripping the gate if it is maintained for that time rating.

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

Although it seems you may have gave him info for what he wants to do perhaps, or that he is seeking to run 110v at 30 amps, but my guess is perhaps he doesn't have a 30amp breaker switch..

This inclines they have an output on their generator, and they do not have normal access to their primary winding, as output is normally through the secondary winding not the primary on commercial devices. I could be msitaken though in this case.


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