Voltage Too Low for an Autotransformer

[Jackm]

We're staying in a campground in Maine that has a 30 amp receptacle on the pedestal. Since the voltage appeared to be low (from a plug-in voltage meter we use), we hooked up our autotransformer to give the voltage a boost. However, the device keeps shutting down due to low voltage conditions (as it's designed to do). My guess is that the voltage is so inadequate here; even the autotransformer can't function.

We're only going to be here another 2 days so we're willing to put up with it. However, we can't use anything with a motor such as a washer/dryer, microwave, AC, or vacuum cleaner. My question is; has anyone else ever run into this problem? Thanks in advance.

Jack

[Kvtaylor]

Quote:

Originally Posted by Jackm We're staying in a campground in Maine that has a 30 amp receptacle on the pedestal. Since the voltage appeared to be low (from a plug-in voltage meter we use), we hooked up our autotransformer to give the voltage a boost. However, the device keeps shutting down due to low voltage conditions (as it's designed to do). My guess is that the voltage is so inadequate here; even the autotransformer can't function. We're only going to be here another 2 days so we're willing to put up with it. However, we can't use anything with a motor such as a washer/dryer, microwave, AC, or vacuum cleaner. My question is; has anyone else ever run into this problem? Thanks in advance. Jack

We have stayed as several places that the voltage was very low, but the autoformer stayed on. I normally place our 30 amp autoformer between the post and my power chord since it has a spike supressor. That park must have a very low voltage. I wouldn't use any appliances either with that low of voltage. That includes the ref. it could damage the circut board in it

[GaryKD]

Hi Jack,
I've been in way too many low voltage CGs. 30 or 50 AMP receptacle, if the CG does not have the AMPS coming into the park you will get the situation you are now in. Too many CGs have not purchased a large enough power service for the CG.

To be fair to the CG, I ask the manager if he will show me the main breaker panel for incoming power. It is easy to determine the size of the service. If the lack of incoming service is the problem, the only thing you can do is grin and bear it. Leave and put the CG on your never to return list. This is what I do.

I've been in CGs with 100 sites or less with between 800 to 1200 AMP service. The owner will not purchase a larger service. They will never see me again.

[Jackm]

The voltage here often drops to less than 100 volts under some circumstances. This place is currently for sale and represents a dying breed of privately-owned rural Maine campgrounds that simply can't keep up with the demands of the twenty-first century.

Thanks for the insight. One more night and it'll all be a distant memory. As you say, we probably won't be staying here again. On a positive note, the owner is nice, the sites are huge, and its in a pretty setting just 20 minutes from Portland. Appreciate the advice.

Jack

[wa8yxm]

There was a period of time when folks wired parks not with copper, but Aluminum. I've been in at least two parks wired (At least in part) that way. Several years ago my primary park was Grass Lake Resort (michigan) which is no longer a membership park.. This park had aluminum mains as well as branch circuits.. The transformer feeding the park had failed years earlier and the power company had installed a "Temp" replacement till they got one the right size.

Well... One of the mains failed (Burned clean through) so the manager spent Sunday pulling brand new mains cables (3 each copper cables around 1" in diamater for each of the legs,, L1-L2 and N) through the conduit to the master panel... The result of this new, better wire was the rigs got better voltage, drew more current and the temp transformer was finally replaced with a proper size unit.. The power company tech hooked it up wrong (The park was wired L1-L2-N he hooked it up L1-N-L2) and they ended up buying a lot of converters, televisions, microwaves and such when they fed the park 240 volts on the one leg instead of 120 (oops)

I was not there when that happened (I was there when the drop failed)

Another park I stay at the 30 amp sites are all aluminum. My Autoformer did not shut down.. but it could not make up the difference either, A/C kept tripping fuses.

[Jackm]

I know there's been a lot of discussion about having a surge protector but the odds of having a spike are infinitely less than the likelihood of running into inadequate power (as you describe). I'm not criticizing surge protectors. I'm simply suggesting that people are not as protected from "bad" power as they might think.

Jack

[Kvtaylor]

Quote:

Originally Posted by Jackm I know there's been a lot of discussion about having a surge protector but the odds of having a spike are infinitely less than the likelihood of running into inadequate power (as you describe). I'm not criticizing surge protectors. I'm simply suggesting that people are not as protected from "bad" power as they might think. Jack

Jack
I have witnesses two occasions where a surge protector would have saved a converter on a 5th wheel and a inverter on a motor home. A friend of ours tried to plug into a private pwer box in Florida where they stay for the winter. During the summer, some one replaced the plug and wired it wrong. The second time was in a campgrounds in Va where there was a power surge and it fried an inverter. Another friend of ours was parked right next to him and his autoformer saved his 5th wheel from any damage. For those reasons we use a surge protector on both 50 and 30 amps. Our 30 amp is built in the autoformer.
Now saying all that, in one campgrounds in Calif this summer, the owner would not let autoformers in his campgrounds. Granted, he had a power problem with his 30 amp (I was on 50 amp) and said autoformers pulled energy from the adjoining campsites on either side of the site using the autoformer. To me, its just another level of protection.

[mudpuppy]

Quote:

Now saying all that, in one campgrounds in Calif this summer, the owner would not let autoformers in his campgrounds. Granted, he had a power problem with his 30 amp (I was on 50 amp) and said autoformers pulled energy from the adjoining campsites on either side of the site using the autoformer. To me, its just another level of protection.

This is why mine stays inside the storage compartment out of site. As far as I am concerned it is just another part of my power management system. When i pay for a site I am paying for 30 amps at an acceptable mimimum voltage. If I need to boost the incoming voltage so be it. As long as I do not trip the 30 amp breaker on the pole I am good to go.

[GaryKD]

Transformers (any brand name) do not rob power from the CG or anybody else. You can win a bar bet on this. My transformer, when at full power, takes 1 AMP of power. 30 or 50 AMP plug, if I want to use 1 AMP to run my transformer, that's my decision. The formula is WATTS = AMPS X Volts. The only way to adjust the WATTS side is to turn stuff off. An appliance will try to draw the WATTS it is rated for or die trying. If Volts go down, then AMPS must go up. That is the problem. All the transformer does is adjust the AMPS/Volts side of the formula as needed by the coach and only as power passes the transformer.

Like others, I keep my transformer inside the electric bay. There are too many people who believe what they do not understand. And I gave up changing their minds years ago.

[azloafer]

Progressive Industries 50 Amp RV Portable Surge Protector from tweetys.com

[RVDude]

Just a point of clarification about autoformers to reinforce gary's point. The "argument" about current consumption when autoformers are discussed depends on what side - the input or the output side of the autoformer - you are looking at. The argument often arises by not clarifying (or understanding) there is a difference based on which side of the autoformer one is talking about.

An example: (we can all easily agree that the ultimate governing factor is the volts and amps available at the pedestal)

Assume a pedestal voltage = 100VAC and draw the full breaker amps of 30amp and you have only (100*30) = 3000watts available at the pedestal (also assuming the voltage will maintain 100VAC at the full load). Hence you have a maximum of 3000 watts available at the pedestal for the autoformer (or anything else) to draw from. (note1 - unfortunately as the load on the pedestal increases, undoubtedly the voltage will also drop meaning less than 3000 watts is available) (note2 - IF the pedestal were at 120V the 30amp means 3600watts would be available, quite a loss)

On the coach or output side of the autoformer this means you can only draw 25amps at the boosted 120VAC (25*120=3000) before you blow the pedestal breaker. Exceeding 25amps on the autoformer output will in turn demand more current from the pedestal thus exceeding the pedestal breaker and trip it. So yes, you can not draw more than the pedestal 30amps but on the boosted side that also means yeas again that only 25amps is available - in this example. (amperage is a measure of "energy" while watts is a measure of "work" and are not interchangeable though in common lingo they are and create even more arguments)

The common misconception is that if you have up to 30amps feeding the autoformer you'll also have up to 30amps available from the autoformer boosted output which is not correct. Hence the argument - it all depends on which side (input or output) you are talking about and is seldom stated.

[Todd Coffelt]

All of the above posts talk about the amount of watts available for use by the RVer for voltages that vary from 100v to 120v. I have always been of the opinion that the circuit breaker at the pedistal was in place to allow a set amount of amperes to pass thru. I do not think that wattage has any bearing on the breaker.
Appliances in the RV that are inductive power users such as A/Cs or power supplies in microwave ovens, or any motor are set to operate on a given amount of watts. If the voltage drops to the 100v level, amperage consumption can and will increase by up to 25% to maintain the neccessary wattage.
Now, if the RVer is using a device that utilizes a transformer such as a Powermaster Voltage Controller or Autoformer and his incoming voltage is in the 100v range, the cost of raising the voltage is less than 1 amp (.7). His consumption of amperes of any inductive appliance will be up to 25% less than without a voltage controller. Of course, he has a front ;oaded cost of the .7 amp.
The breaker at the pedistal will see only the amperes being consumed. That is why I can operate two A/Cs off of a 30 amp pedistal if I can maintain a voltage of 117v minimum.

[RVDude]

todd - you are right, the breaker breaks due to amps. BTW wattage is directly tied to amps by (keeping things simple) volts * amps = watts.

Because we are talking different volts on either side of the autoformer (a simple transformer) we have to normalize the data by converting to watts to do the comparison between pedestal (100v) and autoformer (120v).

30 amps blows the breaker.
30 amps at 100v (pedestal) = 25amps at 120v (autoformer supply max).

Hence, if you try to draw more than 25amps (actually less due to transformer inefficienies which are in the 80% range) at the RV (autoformer output) side the autoformer will in turn draw MORE than 30amps from the pedestal and thus blow the breaker.

Converting to and comparing watts gives us apples to apples.

[Todd Coffelt]

RV Dude,
This is a test that I ran at a RV Park outside of Maumee, Ohio in August of this year.
RV= Royals International 5th Wheel
Power= 50A
A/Cs = (2) Coleman 13,500 BTU
Pedistal = 30A
Park voltage= 104v-108v
Transformer= VC-50 PowerMaster Voltage Controller (Installed)
Test Equipment Used = Universal Amp Meter, Beckman Volt Meter
At the start of the test, the voltage was in the 108v range at the pedistal. Total amperage draw was a little over 1 amp measured after the PowerMaster. Voltage leaving the PowerMaster was 121v (12% boost).
One A/C was started and the voltage dropped to 106v at the post and 117v after the PowerMaster. Total amps used = 15.3 A
The second A/C was turned on. Post voltage read 104v, after the PM it was 116.1v. Total amperage draw was 29.4A
We then unplugged the PM and then repeated the test. With one A/C on the incoming voltage was 106v and the total amperage recorded was 17.4 amps. We could not run the second A/C without tripping the breaker.
These results are quite different than your description.