AC to DC to AC

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Old 08-22-12, 10:10 AM
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AC to DC to AC

Hi
i have added a low voltage transformer to convert AC to DC but I have a requirement to run a UV light that requires a 110v due to Ballast that it has. How do I convert this AC to DC to AC again?

Thanks
 
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Old 08-22-12, 10:26 AM
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Welcome to the forums

Sounds horribly inefficient. Can't you pull a line prior to the transformer for the 120 AC you need?
 
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Old 08-22-12, 10:27 AM
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Use a power inverter. They are often used to run AC devices from your car or truck.

One thing to watch is there are different ways they create AC. The more expensive type creates a true sine wave like you have in your houses wiring. Less expensive inverters create a modified wave that looks more like stair steps. Some devices can work with the modified pattern while others can not.

 
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Old 08-22-12, 10:50 AM
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I know. To run a 110 live wires to my pond would cost about $2000 but I spent $60 for low voltage transformer and wire and I am all set to run foundation motor and few focus light but I need to add this UV filter but it requires 110v. I am stuck now.
 
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Old 08-22-12, 10:55 AM
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I tried to use car converter (DC to AC) but it was not working on the low voltage line. I am not sure why? It seems it works only on battery and not on AC to DC voltage
 
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Old 08-22-12, 12:16 PM
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i have added a low voltage transformer to convert AC to DC
A transformer will not convert AC to DC. Are you sure it is a DC power supply and not just a transformer?
I tried to use car converter (DC to AC) but it was not working on the low voltage line.
That would be consistent with having used a step down transformer not a DC power supply.

In addition the lower the voltage the greater the voltage drop unless you use very large gage wires. Have you measured the voltage under load at the end of the run?
Here's a calculator: Voltage Drop Calculator - for single and 3 phase ac systems and dc systems
 
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Old 08-22-12, 12:20 PM
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You don't have enough POWER at the end of the low voltage wiring to operate the inverter. Remember that for a step-up from 12 volts to 120 volts the lower voltage side will have to supply ten times the amperage required on the higher voltage side. Assuming your UV light is rated at 50 watts/120 volts that would be about 0.4 amperes on the high side but a full 4 amperes (plus to accommodate inverter inefficiency) on the low voltage side.

Sorry, you are just plain out of luck.
 
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Old 08-22-12, 01:00 PM
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Since the inverter works when connected to a battery I suspect Ray2047 is on the right track. If you have a transformer you may have 12 volts AC.

You mention that it's too expensive to run AC down to the pond but also mention that you are converting AC to DC??? So, where is the AC coming from to feed your transformer or DC power supply (whichever you have)?
 
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Old 08-22-12, 05:53 PM
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Let me try to explain how I did this. I have pond in my back yard about 100 ft from the AC 110v outlet. Since running a underground 110v
is expensive, I have added a low voltage transformer and a 16 gauge wire to run a 12v DC foundain motor. the motor is working fine. Now I have 110v UV light so wondering if there is a step up transformer for low voltage.
 
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Old 08-22-12, 06:13 PM
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I have added a low voltage transformer and a 16 gauge wire to run a 12v DC foundain motor.
And as said earlier a transformer does not provide DC only lower voltage AC. Is this a transformer or DC Power supply?

I have pond in my back yard about 100 ft from the AC 110v
Your house supply is 120v not 110 volts. Given such a small load assuming the receptacle has a 15 amp breaker you could use #14 UF for the run. That's only ~ $60* for the cable. Probably less then you have already spent and if the receptacle at the house is GFCI protected you only need to bury it one foot deep. In my opinion the way your trying to do it just doesn't make sense and is probably costing more then just running 120v to the pond.

I have added a low voltage transformer and a 16 gauge wire to run a 12v DC
It is unlikely even assuming you have DC not AC a 16 gauge wire 100 feet long could supply the necessary amperage for an inverter to power a 120v light.

*Price Source: 100 ft. 14-2 UF-B W/G Cable-13054223 at The Home Depot
 
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Old 08-22-12, 06:30 PM
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I just noticed the transformer produces 12VAC because the motor volts is 12VAC.
 
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Old 08-22-12, 06:46 PM
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Looking online all but the small solar pumps are 12 volt AC (not DC).

If you do have 12 volt AC than you basically could use another transformer like at your house, but wired backwards to convert back up to 120 volts. I'm not saying it will work well though. Each transformer looses a percentage of the energy during the conversion and tie the two of them together with a hundred feet of 16 ga wire at 12 volts and you're sending power though a soda straw. It's a complex Rube Goldberg solution to a simple problem.

For what you will spend on another transformer and a inverter I think you would be much better to just bite the bullet and run AC power to the pond. I would even consider running #12 UF even if you just feed it with a 15 amp circuit. Since you also have to consider with wire length inside your house plus the 100 feet outside the larger wire will minimize the voltage drop over the long run and since you are going to the trouble to bury cable it's already a size larger if you decide to upgrade to a 20 amp circuit in the future.
 
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Old 08-22-12, 07:43 PM
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The outside receptacle may already be on a 20 amp breaker. I was just trying to gently lead him to the correct solution. Even 12-2 would only be about $70 (price source Amazon).
 
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Old 08-23-12, 03:52 PM
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I think I do not have any other option other than running a 110v. :-(

the UV light has 110v ballast but the light consumes only 12v so wondering if I can add low voltage ballast to the UV light. would that work? if it works then I don not need to run a 110v and I can use the low voltage line to the UV light.
 
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Old 08-23-12, 04:45 PM
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I think I do not have any other option other than running a 110v. :-(
Actually you can't and don't want to. Your house is supplied with 120 volts and that is almost certainly what your light works on.

the UV light has 110v ballast but the light consumes only 12v
Where did you get that info. A 120 volt ballast normally outputs around 600 volts. Maybe 1.2 amps or 12 watts but not volts.
 
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Old 08-24-12, 06:27 AM
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I am sorry not good at terminology. Let me type what is on the product.

Ballast Input 120v 60hz .24a for sure
uv light is 9 watt so 12v?
Since output is llow volts, can I replace existing ballast ffrom the unit to low voltage ballast that runs on 12vac?
 
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Old 08-24-12, 07:06 AM
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I don't know how you keep making the assumption/jump to 12 volts? What math is leading you to that conclusion? .24 amps at 120 volts is 28.8 watts. 9 watts at 12 volts is .75 amp. 9 watts at 120 volts is .075 amp. I just can't come up with any combination of math to get 12 as the answer.

Here is a link for a high output UV sterilizer bulb which lists 120 VAC for starting and 54 VAC for running. Notice that they specify two voltages which is very common. It takes more to jump the arc to start a bulb than it takes to keep it running. This also tells you that a ballast is more than just a transformer. They include starters or starting circuits. Here is a .pdf for Philips brand UV bulbs. You can see that the many different bulbs operate at different AC voltages and none are 12 volt.
 
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Old 08-24-12, 11:07 AM
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I am sorry it doesn't have output details but my question is, is there a low voltage (AC) ballast out there that supports 9w germical uv light? If you know could you please share me the store or URL details?
 
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Old 08-24-12, 11:43 AM
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No. I think they are all designed for higher voltage since that is what all countries provide, either 110/120 or 220/240 volts.
 
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Old 08-24-12, 12:40 PM
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There are 12 volt DC fluorescent lights for RVs. Can't say if your bulb would work. You are making this a lot harder by not just doing it the simple way. Run a 120 volt line to the pond. Simple, easy, and almost certainly cheaper. Apologies for a Dutch Uncle comment but you dug your hole when you went with low voltage AC. Don't keep digging it deeper.
 
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Old 08-24-12, 02:46 PM
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Yea, UV bulbs are an odd lot. There doesn't seem to be much standardization. If you found a RV type, 12 volt fluorescent light, got it's specs for starting and running voltage then you could shop for a bulb to match. Again, difficult solution to a simple problem.
 
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