complaints when using a hughes autoformer

Ralph Cramden wrote:
What it takes is for two RVs to be plugged into the common pedestal at the end of the circuit, and 4 or 5 RVs pulling high loads between said pedestal and the MDP in the middle of the circuit. They were unable to find what causes it, or correct it. It's not like they devoted a lot of time to it either. The voltage at the MDP read a constant 116 volts.

That doesn't quite make sense and without being there is hard to speculate. Yes, perhaps a bad/loose neutral connection. Occam's razor = simplest explanation is usually the correct one (I watch too much Dr. Phil). I sure wouldn't rely on a CG to understand electrical stuff.

In some cases a poco can have high voltage lines that are very long before getting to an area/neighborhood of concentrated loads like in a rural setting for ex. They may set the fixed taps on the local transformer higher at +2.5% (123V) or +5% (126V) to prop up the voltage drop for when demand gets high. Private property owners with their own onsite high voltage step-down transformers can sometimes set the fixed taps higher to compensate for large fluctuating demand loads. Commercial CGs (unless quite small) typically have a bunch of pad-mounted transformers spread around a property and it's possible sometimes taps are intentionally set above 120 volts because there are very large swings in demand from winter to summer peaks. I've yet to see over 120 volts. Choosing a site closer to a transformer can sometimes reduce voltage drop. I've seen voltage go up and down like a yo-yo from overnight to dinner time but only once have had the EMS cut us off but now use an autoformer if I know voltage is low when we first hook up. We mostly stay in older CGs (Thousand Trails) and low voltage is common in them and always a possibility. Best have been casinos with a spare-no-expense electrical system.

I once designed a major expansion of a dairy plant on Vancouver Island before they got natural gas. At the time, milk in pouches was in vogue and they had a new machine that sealed them with an electric element which was voltage sensitive to get the req'd temp. After they started up the new plant the machine was spilling milk everywhere on the floor and they wanted to blame me. Turned out the poco had a very long high voltage line to the dairy's new substation and everyone in the city was dragging down the voltage at dinner time from electric stoves and electric heating - they had to do a major transmission line upgrade pdq. I hate low voltage!

Ralph Cramden wrote:

Dutch_12078 wrote:

Ralph Cramden wrote:

No mention in this thread of high voltage conditions. I have experienced that at certain parks on occasion and have seen voltage beyond the PI cutoff point more than once, such as 146 volts. In that case an EMS is your only defense as 140 will instantly fry most microwave control circuits even if internally fused, and the fridge element will be toast along with the 5 amp fuse on the board itself, possibly even the entire board.

I've never seen a voltage higher than the 127 volt max Range B ANSI
utilization standard so far, and my SurgeGuard also cuts off for high voltage, although I don't recall off hand what the limit is for that.

The PI EMS high voltage threshold is 132. At one PA tate park with older wiring and shared pedestals, I have seen voltages higher than that threshold, and the park maintenance super and I can recreate it.

What it takes is for two RVs to be plugged into the common pedestal at the end of the circuit, and 4 or 5 RVs pulling high loads between said pedestal and the MDP in the middle of the circuit. They were unable to find what causes it, or correct it. It's not like they devoted a lot of time to it either. The voltage at the MDP read a constant 116 volts.

Sounds like a high resistance neutral, lets get Gil back in here to analyze that scenario.

Dutch_12078 wrote:

Ralph Cramden wrote:

No mention in this thread of high voltage conditions. I have experienced that at certain parks on occasion and have seen voltage beyond the PI cutoff point more than once, such as 146 volts. In that case an EMS is your only defense as 140 will instantly fry most microwave control circuits even if internally fused, and the fridge element will be toast along with the 5 amp fuse on the board itself, possibly even the entire board.

I've never seen a voltage higher than the 127 volt max Range B ANSI
utilization standard so far, and my SurgeGuard also cuts off for high voltage, although I don't recall off hand what the limit is for that.

The PI EMS high voltage threshold is 132. At one PA tate park with older wiring and shared pedestals, I have seen voltages higher than that threshold, and the park maintenance super and I can recreate it.

What it takes is for two RVs to be plugged into the common pedestal at the end of the circuit, and 4 or 5 RVs pulling high loads between said pedestal and the MDP in the middle of the circuit. They were unable to find what causes it, or correct it. It's not like they devoted a lot of time to it either. The voltage at the MDP read a constant 116 volts.

Ralph Cramden wrote:

No mention in this thread of high voltage conditions. I have experienced that at certain parks on occasion and have seen voltage beyond the PI cutoff point more than once, such as 146 volts. In that case an EMS is your only defense as 140 will instantly fry most microwave control circuits even if internally fused, and the fridge element will be toast along with the 5 amp fuse on the board itself, possibly even the entire board.

I've never seen a voltage higher than the 127 volt max Range B ANSI
utilization standard so far, and my SurgeGuard also cuts off for high voltage, although I don't recall off hand what the limit is for that.

myredracer wrote:


Curious what CGs/RV parks people stay at where you don't run into low voltage? Do you monitor voltage with a permanent voltmeter mounted inside?

I monitor voltage with a semi-permanently installed digital volt meter and also have a permanently installed SurgeGuard that cuts off power if the voltage drops too low. That's never happened, nor have I ever seen it low enough on the meter to be concerned even during peak usage hours. We were at multiple state and national parks in Florida, Georgia, and South Carolina all through January, February, and March and never saw a reading below 115, with 120-125 most of the time. All of the private parks we overnighted at while in transit showed similar voltage ranges. Where we are right now in upstate NY, we normally see ~120, although we're only seeing 114 right now. That's likely related to temporary sub-station load sharing while the power company folks are making permanent repairs due to a recent wind storm that left ~46,000 customers without power across the state for several days.

Ralph Cramden wrote:

myredracer wrote:


Note that the NEC only covers permanently installed electrical wiring & components installed within RVs by RV manufacturers.

Note that on a 30 amp RV the RV manufacturer uses a chunk of 10-2 Romex from the shore power connection to the main breaker. Also note that the entire system is installed by a bunch of hacks using the piecework method of compensation. If you look closely You'll probably find they over torqued all the breaker lugs stripping out the heads with a #2 square drive impact gun, and smashed the conductors so flat of you move them the slightest they'll snap right off. Also note the entire installation is backed up by RVIA certification........a nice shiny silver sticker......that is nothing more than a sticker LOL. If the installers did not over torque the connections, they probably left them loose.

No mention in this thread of high voltage conditions. I have experienced that at certain parks on occasion and have seen voltage beyond the PI cutoff point more than once, such as 146 volts. In that case an EMS is your only defense as 140 will instantly fry most microwave control circuits even if internally fused, and the fridge element will be toast along with the 5 amp fuse on the board itself, possibly even the entire board.

So you are saying STAY AWAY FROM RV'S because along with poor craftmanship you will get electrocuted.

myredracer wrote:


Note that the NEC only covers permanently installed electrical wiring & components installed within RVs by RV manufacturers.

Note that on a 30 amp RV the RV manufacturer uses a chunk of 10-2 Romex from the shore power connection to the main breaker. Also note that the entire system is installed by a bunch of hacks using the piecework method of compensation. If you look closely You'll probably find they over torqued all the breaker lugs stripping out the heads with a #2 square drive impact gun, and smashed the conductors so flat of you move them the slightest they'll snap right off. Also note the entire installation is backed up by RVIA certification........a nice shiny silver sticker......that is nothing more than a sticker LOL. If the installers did not over torque the connections, they probably left them loose.

No mention in this thread of high voltage conditions. I have experienced that at certain parks on occasion and have seen voltage beyond the PI cutoff point more than once, such as 146 volts. In that case an EMS is your only defense as 140 will instantly fry most microwave control circuits even if internally fused, and the fridge element will be toast along with the 5 amp fuse on the board itself, possibly even the entire board.

Lynnmor wrote:
Gil,
Could you give us a good estimate of power usage between an AC laboring on 100 volts, and an AC operating more efficiently on 110 volts boosted by an autoformer? Of course the one on low voltage may well burn up.

Excellent question and one I have tried to find the answer on in the past. Unfortunately, RV AC makers do not publish any data on current draw versus voltage so can't give a reasonable/accurate answer. Couldn't find a graph of some kind either that would demonstrate what happens, even on a generic residential air conditioner.

The mechanical load on a compressor motor stays basically the same so as the voltage drops, the current will increase as the motor works harder to produce enough power to drive the compressor. In approximation, I would say that there isn't a significant difference in power consumpution. I think the autoformer has an internal loss of something like 3-5%.

The big difference is in damage that occurs as voltage gets low. HP output of the compressor motor will go down as the square of the voltage (running condition). At initial startup, the torque will drop as the square of the voltage. Both of these cause overheating of the windings and damage to the insulation. At some point as voltage drops and current goes up, the 20 amp breaker can trip or the overload element will (due to overheating windings) and if either occurs you want to check voltage. Momentary startup current can be in the 60-70+ amp range depending on model/brand of AC unit which is around 5 times full load running amps. You *could* be at a reasonble but low voltage while running but the voltage can drop out of sight on startup due to how the CG is wired. You can't see what happens to the voltage on startup and will never know harm it is doing.

Dutch_12078 wrote:
I don't use an autoformer, nor have I run across a park to date where I needed one, but in those that prohibit them in their rules, I've found the predominate reasons are that they believe the devices somehow "steal" power, although I've never found a park manager or owner that could logically explain how that happens. The other reason has been possible liability insurance issues because the NEC prohibits the use of auto(trans)formers in RV's, which it does. I have inquired of the NFPA what the reasoning is behind the prohibition a couple of times, but I've never gotten a response.

Note that the NEC only covers permanently installed electrical wiring & components installed within RVs by RV manufacturers. It is perfectly fine to use a plug-in autoformer. Oddly, extension cords and adapters aren't required to be UL listed (which is why CW sells non-listed ones). The Hughes autoformer as a complete unit isn't UL listed and only has internal components that are. You may not want a hardwired piece of equipment in an RV that isn't UL listed... I think I know why the NEC doesn't allow them but would be speculation on my part.

The autoformers do NOT steal power in any way, shape or form. It's scientifically impossible. If there were many users in a CG using autoformers, it is theoretically possible to increase current in feeders and the main service to the point that a section of a CG or the entire CG could be overloaded. When the current goes up, the voltage goes down so the power being used is the same or less. Plus, many autoformers would drag down the voltage throughout a CG. However, the reality is that there are very few RV-ers in CGs using autoformers.

Curious what CGs/RV parks people stay at where you don't run into low voltage? Do you monitor voltage with a permanent voltmeter mounted inside?

valhalla360 wrote:
Also, where is you surge guard mounted? If it's at the pedestal, you can easily have 50-60' of line with further voltage drop. Even the built in ones an have another 20' from the device to the air/con unit.

You must be confusing me with someone else as I never said I'm running a TRC Surge Guard. :R Several years ago I did have an early version portable TRC Surge Guard hard wired into the trailer just before the converter but replaced it with a hard wire Progressive EMS-HW30C which sits under the sofa and is likewise wired into the main service line that runs back to the converter. Like others I've found Progressive's meter calibration lacking and have re-calibrated mine so it does indeed disconnect at an indicated 104 vac. :B

valhalla360 wrote:
Kind of scary as the standard design voltage is typically 120v +-10%, so below 108v starts getting sketchy.

SoundGuy wrote:
Normal supply voltage in N America is sped'c to be 120 vac +/- 5%, meaning one should find unloaded source voltage no lower than 114 vac, no higher than 126 vac.

ANSI C84.1 is the standard in N. America that applies to power companies. 120 volts is the standard "nominal" voltage. There are two ranges, one is Range "A" of +/- 5% of nominal and range "B" which is +6% & -13%. A poco can supply 104.4 - 127.2 volts and still meet voltage delivery requirements. Range B is only to occur on an infrequent basis. PG&E has a good explanation here.

On top of that, there is voltage drop in feeders and branch circuits on private property. The NEC does not have a max. allowable voltage drop but has instead 6 recommendations which includes 5% total for a combined feeder and branch circuit.

Voltage can be as low as 99.2 (at the point of utilization) and still meet the ANSI standard and the NEC recommendations. Voltage drop can easily exceed 5% in older CGs/RV parks due to long runs of smaller gauge wire along with the higher demand of today's RVs.

Most electrical devices, equipment and appliances are designed and rated for 120 volt but some can be less like 110 or 115 volts (esp. motors) to account for presumed lower voltage at their terminals. AirXcel says "These air conditioners were designed to operate from a 115 VAC, 60 HZ, 1 Phase power supply" and couldn't find a min. voltage. Dometic states "The unit is a 115VAC, 60Hz appliance. The proper operating range is between 103 and 126.5 volts AC. " Just because they say the min. is 103 volts it doesn't mean that prolonged use at this voltage is perfectly okay. This is running voltage and during the momentary startup, the voltage can be waaay below what is good for the compressor & fan motors. Low voltage causes the motor windings to overheat and the damage is cumulative over time.

IMO, the SurgeGuard cutoff voltage of 102 is too low. I think even the PI 104 volts is too low and would prefer 105 or maybe a bit higher. Besides an EMS unit being highly recommended (as in almost mandatory), an digital/LED voltmeter permanently mounted inside is also highly recommended. Voltage can be rock solid at/near 120 or can go up & down like a yo-yo sometimes and down to near 104 where our EMS will cut out.