He could - I was commenting on what was proposing, not what he could do.
Converting 220V to 110V without neutral conductor
- Thread starter Rick Barndt
- Start date
- Status
He could - I was commenting on what was proposing, not what he could do.
Birken Vogt
Senior Member
- Location
- Grass Valley, Ca
I have one, it is a lot of work but pretty good for long sidewalk bores, etc.
drcampbell
Senior Member
- Location
- The Motor City, Michigan USA
- Occupation
- Registered Professional Engineer
That's the way to control costs -- add the one-time purchase price of two 15 kVA* transformers, plus the eternal energy cost of transformer losses when powering the biggest load on the site, and the eternal cost of energizing the transformer cores when nobody's using them.
* (I'm assuming the use of 600-volt transformers ... why implement a bad idea halfway?)
Sberry
Senior Member
- Location
- Brethren, MI
- Occupation
- farmer electrician
What country are we in has "220" and "110" ?
Joethemechanic
Senior Member
- Location
- Hazleton Pa
- Occupation
- Electro-Mechanical Technician. Industrial machinery
Probably several. I was just suggesting that the original poster could use an autotransformer to fix his problem where ever it is.
winnie
Senior Member
- Location
- Springfield, MA, USA
- Occupation
- Electric motor research
You can't use an autotransformer to derive a grounded conductor in an already grounded system. At best you could derive a neutral which would have to be treated as ungrounded.
IMHO the installation proposed (convert existing supply to 240V then use an isolation transformer to derive a 120/240V) is not a hack if all codes are followed. However I would be beyond surprised if it was the best solution in a given situation.
Post #24 says it best. Your gut tells you that replacing the run under the concrete is not feasible.
But consider the costs of doing the transformer properly, the ongoing losses of the transformer, the improved capacity (50A or more at 240V) of a new run, the reliability issue of an old underground run, familiarity for future electricians, etc.
Once you consider the various factors, the transformer approach is much less attractive.
Jon
IMHO the installation proposed (convert existing supply to 240V then use an isolation transformer to derive a 120/240V) is not a hack if all codes are followed. However I would be beyond surprised if it was the best solution in a given situation.
Post #24 says it best. Your gut tells you that replacing the run under the concrete is not feasible.
But consider the costs of doing the transformer properly, the ongoing losses of the transformer, the improved capacity (50A or more at 240V) of a new run, the reliability issue of an old underground run, familiarity for future electricians, etc.
Once you consider the various factors, the transformer approach is much less attractive.
Jon
drcampbell
Senior Member
- Location
- The Motor City, Michigan USA
- Occupation
- Registered Professional Engineer
The Mister Mom clip is our own variation of Godwin's law, isn't it?
"As an online discussion grows longer, the probability of seeing the Mister Mom clip approaches 1."
(all due apologies to Mike Godwin)
en.wikipedia.org
"As an online discussion grows longer, the probability of seeing the Mister Mom clip approaches 1."
(all due apologies to Mike Godwin)
Godwin's law - Wikipedia
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
You can probably get a guy with an underground directional boring machine to route a conduit under the concrete for you that would cost less than you might think.
You might also find that getting someone in with a concrete saw to put in a trench is not real pricey, and fixing the concrete after is not horrible either. But you probably will need to get someone who does these things all the time to do it for you if you want it done well.
I think all the ideas you are going to come up with to do this on the cheap are either going to be "hack" or have code violations, and probably both.
IMO, your best bet is to see if you can run new wires in the existing conduit or do it overhead. If neither is acceptable for whatever reason, maybe it is time to just walk away if the customer just does not want to foot the bill to do it right.
You might also find that getting someone in with a concrete saw to put in a trench is not real pricey, and fixing the concrete after is not horrible either. But you probably will need to get someone who does these things all the time to do it for you if you want it done well.
I think all the ideas you are going to come up with to do this on the cheap are either going to be "hack" or have code violations, and probably both.
IMO, your best bet is to see if you can run new wires in the existing conduit or do it overhead. If neither is acceptable for whatever reason, maybe it is time to just walk away if the customer just does not want to foot the bill to do it right.
drcampbell
Senior Member
- Location
- The Motor City, Michigan USA
- Occupation
- Registered Professional Engineer
Sure you could.
It wouldn't be beneficial for this application -- while it would provide 240 volts, it wouldn't provide any more power.
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
BTW, I think this circuit would allow you to use the existing UG conductors with the existing colors and be code legal going the transformer route.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Agreed. This is an expense to which you add your mark-up and pass on to the customer like any other.
Offer the customer prices for each viable option and let them choose cost, damage, and final results.
winnie
Senior Member
- Location
- Springfield, MA, USA
- Occupation
- Electric motor research
1) If you violate code it is a hack.
2) If you do something normal, don't violate code, and provide the utility the customer needs, you have a solution.
3) If you do something weird but don't violate code and save money, then it is an unorthodox solution.
4) If you do something weird but don't violate code, cost more money and deliver poorer performance, then it is a stupid solution.
A professional will never do 1, will aim for 2 but be open to 3.
It is an exercise for the reader if the OP is 3 or 4. I assert that what the OP is proposing is _not_ 1.
-Jon
2) If you do something normal, don't violate code, and provide the utility the customer needs, you have a solution.
3) If you do something weird but don't violate code and save money, then it is an unorthodox solution.
4) If you do something weird but don't violate code, cost more money and deliver poorer performance, then it is a stupid solution.
A professional will never do 1, will aim for 2 but be open to 3.
It is an exercise for the reader if the OP is 3 or 4. I assert that what the OP is proposing is _not_ 1.
-Jon
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Of course, any transformer usage will only reduce the final available current.
hbiss
EC, Westchester, New York NEC: 2014
- Location
- Hawthorne, New York NEC: 2014
- Occupation
- EC
Probably should have thought about this before buying that EV...
-Hal
-Hal
winnie
Senior Member
- Location
- Springfield, MA, USA
- Occupation
- Electric motor research
Fair enough, and if you combine that with the approach is post 33 (two transformers in an autotransformer configuration, getting up to 600V) you could deliver 12kVA to the garage using the existing cable.
Who wants to take bets on how long the cable would last underground at 600V?
-Jon
Joethemechanic
Senior Member
- Location
- Hazleton Pa
- Occupation
- Electro-Mechanical Technician. Industrial machinery
EE HitlerThe Mister Mom clip is our own variation of Godwin's law, isn't it?
"As an online discussion grows longer, the probability of seeing the Mister Mom clip approaches 1."
(all due apologies to Mike Godwin)
Godwin's law - Wikipedia
Autotransformer, if you're like me and have a basement full of takeout transformers, you (may be able to) use a standard 120 / 240 primary 16 / 32 secondary autotransformer. Ignore the secondary winding completely. Feed the 240 V primary and pick up the 120 from the midpoint.
I have done that with that transformer going the other way, Feeding 120 to the 120 half of the primary winding and picking up the 240 from the 240 point on the primary winding, ignoring the 16 / 32 secondary completely. A friend had a 240 well pump and was running from a 120 generator. I did it and tested it working perfectly but I would *never* sell it. I took it back out when he got a 240 generator, which was years later.
Generally there is only a very small list of (general case) simple rules that one needs to follow to survive with some confidence over the long term. It's obvious to everyone this case violates one or more of the very simple need to follow rule set.
Do it right the first time.
If the install is going to be there for the long term, your work should be expected to survive effortlessly over that expected lifetime. If you just want something for six months, you can use a free autotransformer from your basement.
If you expect the work to serve well for 20+ years, the feeder size could include capacity for a second EV fast charging, could be 40kW of future load. I think everyone agrees, do the feeder now. Question is just, how big is the future load.
Also, if the load is only lighting, skip the transformer and throw in some multivoltage ballast flourescents or multivoltage leds, call it a day.
I have done that with that transformer going the other way, Feeding 120 to the 120 half of the primary winding and picking up the 240 from the 240 point on the primary winding, ignoring the 16 / 32 secondary completely. A friend had a 240 well pump and was running from a 120 generator. I did it and tested it working perfectly but I would *never* sell it. I took it back out when he got a 240 generator, which was years later.
Generally there is only a very small list of (general case) simple rules that one needs to follow to survive with some confidence over the long term. It's obvious to everyone this case violates one or more of the very simple need to follow rule set.
Do it right the first time.
If the install is going to be there for the long term, your work should be expected to survive effortlessly over that expected lifetime. If you just want something for six months, you can use a free autotransformer from your basement.
If you expect the work to serve well for 20+ years, the feeder size could include capacity for a second EV fast charging, could be 40kW of future load. I think everyone agrees, do the feeder now. Question is just, how big is the future load.
Also, if the load is only lighting, skip the transformer and throw in some multivoltage ballast flourescents or multivoltage leds, call it a day.
Last edited:
- Status