We lost our shore power

[Ray D]

I often get myself into a jam, taking a contrary approach. I have been biting my tongue, on this one. I decided, why should this be different? contrary opinion follows!

I see victims of a crime blaming each other, instead of the perpetrator, here. I think we are all in the same boat. The power company advertises that it has the power for sale. The RV Resort advertises full hookups. The RV enthusiast pays the tab, using his hard earned money, to stay at the resort. Shouldn't be a problem here!    :-\

However, we have RVers at each other's throats, because they are not getting what they paid for. It's not your neighbor's fault! 

The use of transformers? Baloney! The power company uses transformers, all along the line, to keep the service performing. The resort "buys" the power assuming that they are actually getting it. The probem is that they are not actually delivering. You are not getting what you paid for.

Without knowing more about the status of the resort's power system and the delivery from the power company, it's hard to tell which is responsible. One or the other should update.

It is not, however, the fault of the customer-victim. It is not the fault of equipment used on the individual RV. Maybe the supplier needs one more transformer in his system. Maybe the resort needs to update their electrical service equipment. I wouldn't be sniping at my neighbor. I'd be asking the campground management what they are doing to deliver what I paid for.  :

Sorry.  :'(   I'll go back in my hole and do penance, now.  :

Ray  D  ;D

 

[Tom]

Ray,

Given the power issue as a fact of life at many campgrounds, I'd prefer to understand how the autoformer works.

Last weekend we had an interesting issue when berthed with numerous other boats at a marina. Our boat requires 240V (2 separate legs of 120V), whereas the marina had only 30A 120V receptacles. I have a "smart Y" (a $400 adapter) that allows me to use a pair of 30A receptacles on different legs and to feed the 50A 240 cord going to the boat. Both 120V legs have to be present for anything to come out of the 50A end of the adapter (thus the name 'smart').

It was hot, so folks were running their air conditioners. The breaker feeding one of my 120V legs tripped a couple of times before we tracked it down to a neighbor on the same leg running two ACs and their water heater. Having them shed some load, we were back in business, for a while. Next time it tripped, by the time I got to the breaker panel in the marina's restaurant, someone was in there with a multimeter and a screwdriver.

Shortly thereafter, our neighbor had power, but I didn't. The only difference was that our neighbor's boat runs on 120V, so they only needed the one leg that we shared. Since that leg was good, I turned to my other neighbor who was plugged into the other leg and he had power. I was left thinking that my 'smart Y' adapter had been fried. I gave up for the evening, fired up the generator for a couple of hours, went to dinner and decided I'd figure it out in the morning.

A long story but, in the morning, I confirmed my adapter was fine and deduced that the marina staff had assumed the tripping circuit breaker was "bad" and rewired that circuit to a different leg, essentially supplying both circuits from the same 120V leg.

In reality, there really was too much load on the marina's power system with all these boats running their ACs and other appliances. The marina had implemented a temporary "fix" that, in their eyes, appeared to work. Everyone was a happy camper (boater) and, once I understood it, I really had no issue with it. Being without shore power for a night wasn't going to be the end of the world.

Actually, I wasn't without power. After I turned off the generator, I hooked up another adapter that allows me to power one leg of the boat from a single 30A receptacle. The ACs, stove and water heater require 240V, so they don't work, but the refrigerators, battery chargers and inverter/charger get powered along with the 120V receptacles on board.

 

[Ron]

I agree with Don's statement. I have never came out and said that the autoformer doesn't work it does but there is no free lunch and the price is paid by the rest of the occupants of the campground and the campground system is further downgraded.  I still recommend against the autoformer.  I guess some of us might just have more consideration for others.

 

[John From Detroit]

You should note that though I do, on occasion, use an autoformer, I fully agree with Ron that if I choose to boost to protect my delecate electronics, I do it at the cost of others not having enough power left over.  In this I"m being selfish. however if I suspect there is a problem I normally do shed loads to relieve it.

And as I said, the one time I did have a problem it was warm enough I did not need furnace, cool enough I did not need AC, all we were running is the television and sat receiver, default stuff (Converterfs) and the microwave sounded funny.

A check of line voltage showed a low voltage condition (Xantrex display)  I tripped the breaker feeding the xantrex (Forcing it to go into inverter mode) bridged the house and inverter batteries via a diode (thus floating the inverter batteries off the PD converter) and the Microwave worked normally.

 

[Tom]

I'm still curious and put a call in to the tech guy at Hughes. He's not available today, but hopefully we can connect tomorrow.

 

[carson]

Re the Auto (Trans) Former (A-F) controversy:

I have read the entire thread, sometimes with awe, inspiration, sadness and bewilderness.
Also having been in the biz for many years, perhaps I can give you my insight. Have also learned a lot.

I have constructed and calculated a small model using the typical RV situation using a Campground power pole with questionable voltage output.

The model assumes a load in the Rv being purely resistive (non-reactive in nature, i.e. no motors). The nominal voltage required is 115VAC.

It is also assumed the  Auto-former will supply a constant 115V  regardless of its input voltage from the pole; that is its function, within limits.

Without the A-F a 100 Watt load (lamps) will require 0.87 amps (R=132.25 ohms)
                              500 Watt load (coffee pot              4.35 amps (R= 26.45 ohms)
                              1000 Watt load (toaster) will require 8.70 amps (R=13.23 ohms)
                              2000 Watt load (Oven) will require 17.39 amps (R=6.61 ohms)

With A-F under varying pole voltages: (the internal RV consumption will be the same, (@115VAC).
If pole voltage is 90 VAC, the A-F will draw 1.11a for the 100 w load (vs 0.87a).
5.56a for the 500w (vs 4.35a), 11.11a for the 1000w (vs 8.7a)and 22.22a for the 2000w (vs 17.39a) load from the pole.

At 100V pole voltage, it will draw 1a for 100w load, 5a for the 500w load, 10a for the 1000w load and 20a for the 2000w load from the pole.

At 115V pole voltage, consumption will be the same as without the A-F.
There are losses in the A-F, which have been ignored in this model, it?ll only make it worse, as will reactive loads.

At 120 V pole voltage, it will draw .83a for the 100w load, 4.17a for the 500w load, 8.33a for the 1000w load and 16.67a for the 2000w load.

Conclusion: with low pole voltage, more amperage is drawn from the CG than required by the RV. At 115V it is neutral; at higher voltage it draws less.

All this is only my feeble attempt to us the KISS principle, by using the old OHMs Law, i.e. E=I x R  and P=E x I.  By sticking to non-reactive loads only, the calculations should be right on and be representative, on the conservative side.

This post is not a rebuttal to any other post but rather my thoughts on the subject.
After this thread dies, everybody shake hands.

carson in wet Florida today.

 

[Ned]

Carson, you are just saying what many of us have been saying all along.  When the voltage is low because of high current loads, the autoformer just increases the load on the campground electrical system, making the problem worse by increasing the current draw and further decreasing the voltage.  The RV with the autoformer benefits at the expense of everyone else until the campground main breaker trips.

 

[carson]

Guess I  was trying just to convince the skeptics bu putting a few numbers into the argument. Do you think I will be successful?

Remember the old adage: Change a person against his will, of the same opinion he will be still.

That seems to be human nature.

carson

 

[Gary RV_Wizard]

[Far too] many years ago I had an old physics professor who had a way of reducing complex problems to simple ones. His basic theory/formula was WORK = WORK, which is another way of saying there is no free lunch. It's also a paraphrase of the law of conservation of energy, meaning that the energy consumed in one act has to come from somewhere else as input, i.e. energy is neither created or lost.

Work is this case is measured in watt-hours. The autoformer really does nothing energy-wise except perhaps to consume a bit of energy as heat loss (probably that 1 amp that Tom referenced). If the RV is consuming 2000 watts, then 2000 watts has to come as input. Both Ron & Roland are saying the same thing in that regard.  On the consumption side the voltage goes up and the amperage goes down but the watts remain the same. On the input side, the source voltage is lower so the amps are higher than on the consumption side, but it is still the same watts. They have to be to deliver the required power. The A-F did not cause this - its a natural result of the power draw. In its simplest form, Power = Amps X Volts (usually shown as P = EI) That's probably not strictly accurate for AC power to a motor & compressor (an air conditioner, for example), but I think for our simple needs it is close enough.  So in our example, the RV is drawing 2000 watts and will draw it regardless of the voltage (up to the point where the motor stalls or burns up). The A-F dies not increase the amperage drawn from the source, but it enables the RV to utilize that amperage in a more healthy manner, increasing the voltage and reducing the current (amperage) on the consumption side while keeping the watt-hours (work) constant. There is some loss do to inefficiency and maybe some control circuitry, but at the bottom line WATT-HOURS = WATT HOURS, i.e. WORK = WORK.  If the voltage was not boosted, the RV would still be drawing the same watts and therefore the same input amperage. The amp draw would not be any less because the A-F was eliminated - the input and consumption voltage and amperage would be the identical.

So I don't see how using an autoformer costs anybody anything. The only way I can effect the park power grid to to turn an appliance on or off, thus increasing or decreasing the workload on the park grid.

 

[carson]

Gary, what am I missing.

Amperage, not volts, cause circuit breakers to trip. That's probably the point we are missing. The power cost for the park may stay the same, but the breakers will eventually trip no matter what the voltage supplied. I agree fully that Work=Work, but with a blown circuit breaker nothing Works.  Oh, well. Or something like that.

carson

 

[Gary RV_Wizard]

Carson,
I don't think tripping circuit breakers is the issue here, is it? The contention is that use of an autoformer reduces the power available to other customers in the park.

 

[John From Detroit]

All this is only my feeble attempt to us the KISS principle, by using the old OHMs Law, i.e. E=I x R  and P=E x I.  By sticking to non-reactive loads only, the calculations should be right on and be representative, on the conservative side.

This post is not a rebuttal to any other post but rather my thoughts on the subject.
After this thread dies, everybody shake hands.

carson in wet Florida today.

There is a problem with the KISS principle in that it's only good for RESISTIVE loads, that includes the fridge, water heater, toaster, and such,  For reactive loads like the Air Conditioner other rules apply.  and for regulated loads like radios and televisions still other rules apple.

Plus the auto-former does not supply a constant voltage,  It is a "Stepped" device, basically it monitors the voltage and if it's in a pre-set range (I'm going to assume 110 to 125) it does nothing.  If it drops below the lower limit then both a hughes and a franks will "Buck" by a fixed percentage. (I'm not sure without reading the manual what the percentage or limits are)

So as line voltage drops output voltage drops... Drops... GOES UP drops drops drops.

When the upper limit is reached a FRANKS auto-former will also drop the voltage

So as line voltage drops you might see  120, 119.....111.110.109. 125.124.123.122

with either unit.. NOTE: numbers are not accurate

However, in Resistive or DC circuit (either one) Watts = volts times amps.

In a reactive (AC only) circuit watts = volts * Amps * Power factor

The power factor of a motor increases as voltage drops However the motor also tries to keep the same wattage

This gets into math that is way more complex that I feel comfortable with (And I majored in math) but
the bottom line is this

Current does indeed increase when you use an autoformer... But not as fast as your KISS chart suggests.

 

[Tom]

Talked with Hughes Autoformer this afternoon and here's scoop, or what they could tell me ...

Hughes AF was sold a few years ago to the current owner, but the company name was retained. Unfortunately, it appears that the technical knowledge left with Bob Hughes when he sold the business. The current tech support was very helpful, but admitted that he's not really an autoformer expert.

Operation of the AF is simply a step-up/down transformer, using combinations of the 2 primary and 3 secondary windings mentioned in my earlier message (aka simple turns ratio). There is some voltage sensing circuitry that decides when to select the various combinations. Nothing new here.

The tech guy felt that, contrary to what their web site says, there is a penalty to the campground, although he wasn't able to quantify it or explain why. FWIW he's an RVer himself and feels that, if he needed to protect an investment, he'd use an AF.

I'm now going to bow out of this discussion, although I haven't received the explanation I was hoping for, either here or elsewhere. Nothing to do with being skeptical, just unfulfilled curiosity.

 

[homebrew2]

Well Tom I'm kinda like you, in that this subject got me thinking.  So just 'cause your
a nice guy I'll share what I know.

If you're curious how these things work go here;

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

Seems your local utility Co has been using these things forever.

Now actually, everyone here has been sayin just about the same thing....they
just don't seem to realize it.

While the "there ain't no free lunch" camp are quite correct, it does as Gary and others
pointed out cut both ways.

As an example my Coleman A/C uses app 1435 Watts while running. If the Camp line voltage is
115v, that would mean around 12.48 Amps.

  If the camp voltage drops to 91 volts (chosen cause thats where a "Franks" autoformer would drop out) my A/C would still want its 1435 Watts, so the amperage draw to the camp would increase to around 16 amps. No free lunch..right?

But thats not the end of the story, cause the heat of the wiring and the motors go up due to the increased CURRENT FLOW.  As the heat goes up resistance goes up and efficiency comes down. That 16 amps is probably over the ampacity of the wiring and real close to the starting amperage of the motor.

So when Hughs states on the page you linked to, that there is no detrimental effect on park
power by using their product I'm inclined to go along with 'em.

Now the rub to the "No free lunch" crew seems to be that Hughs says their unit draws from
500ma...no load...to 1.5 amp full load (which is common to any xfmr).

The Franks unit didn't specify but since theirs is designed to Bypass at over 115v it should be 0 at no load and 1.5 at full load .  So yes there is some additional load. All xfrmrs have flux leakage ect. so they are not 100% efficient.

Now here comes the fun part ;D......putting that loss into some kind of perspective that even
I can understand.

Autoformer no load = 2.8 nokia cell phone chargers. Or 1 electric fan.

Autoformer full load = .88 of the powerbrick of my laptop(1.7 amp) or less than 1/5 of the
8 amps of a 330w desktop PSU.

So the moral of this story seems to be that Gary was correct when he said that if you're
concerned about your neighbor, you've got to shed some load.

So I believe I'll buy one and sit in air conditioned comfort...and if my conscience gets
to naggin me I'll sleep like a baby knowing that I'm doin 5 times more to help my power
starved neighbor out than the guy next door who's using his desktop on the dadblamed internet.

 

[Tom]

Thanks for the "analysis" Denny.

I understand what an autotransformer is, but that's not the same as an autoformer. The latter has separate windings, providing isolation between primary and secondary windings, while the autotransformer doesn't. From the first line of that WiKi:

"An autotransformer is an electrical transformer with only one winding."

So I believe I'll buy one and sit in air conditioned comfort...and if my conscience gets to naggin me I'll sleep like a baby .....

That's kinda how the Hughes guy felt, except his version went something like "I'll do what I need to protect my coach".

Oh my, I wasn't going to post further in this topic 

 

[Roland]

Looking for some additional insight to this question, from some folks who "Don't have a dog in this fight", one provided the following thought. I enjoyed the logic and brevity.

"Hi Roland
I am not an engineer, but do consider myself a pretty well trained electrician.
This is my opinion:

I don't think the autoformer steals electricity from your neighbor any more than
putting a filter or booster pump on your hose would steal his water.
..."

The writer is a retired licenced electrician and contractor, an avid RV'er and does not own an Autoformer. Jack doesn't stay in parks with less than 108 VAC at the pedestal and therefore does not consider an Autoformer to be worth the money or hassle.

Green lights and soft breezes,

 

[Tom]

I don't think the autoformer steals electricity from your neighbor any more thanputting a filter or booster pump on your hose would steal his water.

That's a good analogy, especially since water pressure and flow are used as analogies to voltage and current in very basic electricity classes.

Don't have a dog in this fight

Not sure about that analogy to what seems to be a civilized discussion  ;D

 

[Ned]

It only becomes a problem when enough autoformers are put in use to increase the amperage beyond what the campground (or that feeder) can supply, then everyone goes dark, autoformer or not.

 

[Ron]

It only becomes a problem when enough autoformers are put in use to increase the amperage beyond what the campground (or that feeder) can supply, then everyone goes dark, autoformer or not.

I think you are correct Ned.  I think I will just drop out of this topic.

 

[John From Detroit]

There is another set of forums www.rv.net, where one of the members has the necessary hardware to test theories about auto-formers with.

I don't have his findings handy so I can not provide specific numbers but.....

He hooked up his RV via an auto-former a pair of ammeters (one either side of the auto-former) and a varacator to the mains, This allowed him to artifically lower the voltage and cause the autoformer to kick in and out.

He found that true to expecations the current drawn by the motors went up as voltage went down, however it was not a simple

Watts=amps*Volts  (That is only true in DC or resistive systems) it was watts = Volt-Amps * Power Factor.  (Volt-Amps = volts * amps)

And as the voltage lowered (to a point) the power factor wen tup. 

However below that point current in the motors increased greatly, and motor efficency also suffered (Not as much cold air)

This is about where the auto-formers kicked in.

He found though that the total watts consumed, and the total amps comming out of his varacator went up when the auto-former kicked in.  Thus there is a penality to the campground. and there is indeed less of the pie for others.

Still: I don't like taking chances with my air conditioners