Foretravel Motorhome Forums => Foretravel Tech Talk => Topic started by: Peter & Beth on June 07, 2010, 01:54:20 pm
Title: Low Voltage and Appliance Performance
Post by: Peter & Beth on June 07, 2010, 01:54:20 pm
Can we discuss how the low voltage condition impacts A/C longevity & performance? Or, for that matter any other appliance as complex as an A/C unit?
1. Are the motor(s), its windings, wires (gauge), controls, etc. providing the power to the units the concern? 2. If so, then the power rating/design for each of these motors can be calculated by the formula: Power(watts)=Volts x I(Amps). 3. So, is the power rating of the motor(s) a constant? That is, the motor will draw sufficient amperage to get its rated power and thus the amperage is increased as the voltage decreases? Or does the power output of the motor (watts) drop off in some modality as the variable (volts) increases or decreases above or below some threshold estimate? 4. Or, is there some other relationship between the variables (P=V x I) that causes potential long term failures?
Title: Re: Low Voltage and Appliance Performance
Post by: Barry Beam on June 07, 2010, 06:18:58 pm
Low voltage causes higher current, overheating, higher demand reads, and thermal damage to equipment.
The most compelling reason is that replacing appliances is costly (not to mention inconvenient, a waste of time, and a hassle to get them replaced). And more often than not, you don't even realize there's a problem until you see the smoke!
Many AC motors will burn out when they draw too much current, which is what happens when there's insufficient voltage.
When the power supplied by the park is too is low for an appliance or group of appliances being operated (for example, if you're running both the air conditioning and the microwave), you generally can't run those appliances or any additional appliance without risk of damage.
Title: Re: Low Voltage and Appliance Performance
Post by: Tim Fiedler on June 07, 2010, 06:45:56 pm
My first post on the new site! Was in Windsor Fri - Sun for the Red Bull Air Races - Windsor RV Park had a 30 amp circuit (tried two different spots). Voltage was 109 - 115 on each leg. EMS system would cut off voltage if I tried to run one room air. Net, we weren't there during the day, and if I needed to cool off the interior of the unit I unplugged and ran the generator. Luckily the nights were cool and I dind't need the air at night. Lesson learned, if the panel doesn't show 120 volts per leg, I won't be trying to run the air. .
Title: Re: Low Voltage and Appliance Performance
Post by: Peter & Beth on June 07, 2010, 07:01:48 pm
Here's what I've learned after doing some research, and the best article can be found at the below link: http://ecmweb.com/design_engineering/electric_highs_lows_motor/ (http://ecmweb.com/design_engineering/electric_highs_lows_motor/) A motor rated at say 1500 watts will require 1500 watts to run. It will require this wattage regardless of the voltage. So a 1500 watt motor running on 105 volts will draw 14.3 amps. The operating amperage range is specified on the motor's plate as well as the voltage. If the operating range for the motor is 12 to 14 amps. You will burn up the motor prematurely by overheating for long periods of time. The motor may have safeguards built-in to cut off power when certain conditions are met. Of course, if the total amperage draw exceeds the circuit's rating, say 20 amps, then that safeguard will result in a tripped breaker at the panel.
I suppose that the A/C's manuals may contain the motor(s) ratings. I'll have to check this when I go to the storage facility.
Title: Re: Low Voltage and Appliance Performance
Post by: Neal Pillsbury on June 07, 2010, 09:19:34 pm
Can we discuss how the low voltage condition impacts A/C longevity & performance? Or, for that matter any other appliance as complex as an A/C unit?
1. Are the motor(s), its windings, wires (gauge), controls, etc. providing the power to the units the concern? 2. If so, then the power rating/design for each of these motors can be calculated by the formula: Power(watts)=Volts x I(Amps). 3. So, is the power rating of the motor(s) a constant? That is, the motor will draw sufficient amperage to get its rated power and thus the amperage is increased as the voltage decreases? Or does the power output of the motor (watts) drop off in some modality as the variable (volts) increases or decreases above or below some threshold estimate? 4. Or, is there some other relationship between the variables (P=V x I) that causes potential long term failures?
Peter, It's a little more complicated than just P=IE(PF), but you are correct. However, especially with motors, overvoltage conditions should be regarded with even more respect than undervoltage conditions. In increasing orders of complexity, the following are some things that we would do well to remember: 1. Don't place stress on electric motors and other electrical equipment as a result of staying connected to any power system at or near the ends of voltage limits. The best life and most efficient operation occurs when you operate motors at voltages very close to the nameplate ratings. When supplying voltage to motors, stay as close as possible to 120 VAC ± 5% (114 to 126 VAC) and as far away from the "outer limits" of 120 ± roughly 10% VAC (104 to 132 VAC) however and whenever possible. 2. Rules of Thumb for High and Low Voltage · The amount of work (Power) required is dictated by the load. Thus, for a given cooling demand, a motor on a Rooftop AC has a FIXED Power demand at any instant. Then, if voltage goes down, current must go up (Power = Current x Voltage x (PF)). The Power Factor will only help a small bit in an under voltage condition. In an overvoltage condition, however, PF will increase exponentially once a motor core becomes saturated by the stronger flux lines. · Small motors, like ours in our FT motorcoaches, tend to be more sensitive to overvoltage and saturation than undervoltage conditions. · Single-phase motors like ours tend to be more sensitive to overvoltage than do large industrial motors. · Overvoltage can drive up amperage and temperature, even on lightly loaded motors. Thus, high voltage can drastically shorten motor life, even on lightly loaded motors. · Motor efficiency drops with either high or low voltage, and motors overheat more rapidly in the reduced efficiency condition. · Motor power factor improves (helps) with lower voltage, but drops sharply with higher voltage due to motor core saturation induced by the stronger magnetic flux . · Motor inrush current goes up rapidly with higher voltages. 3. Most of the time, unpredicted and/or unknown electrical power source faults do damage before we ever realize something is wrong. Therefore, because we frequently have the opportunity to experience damage, a high quality, automatic, electrical monitoring system is very cost effective. I installed a 50 amp, permanently wired EMS system to protect against both shore and Power Tech Gen faults (the '98 U270 had no EMS) and it has saved my bacon numerous times while coaches all around me, including FT's, had varying amounts of damage. IMHO it has been well worth the investment and only one or two times out of a dozen, did I know that something had gone wrong before the EMS told me.
Hope this is helpful. I've attached a good article that is aimed at non RV Industry, but is well written and informative with respect to your question. Neal
Oops! I see that you have already found the same article that I was trying to copy and attach to my above reply. You're too fast for me! Here's the link again; http://ecmweb.com/design_engineering/electric_highs_lows_motor/ (http://ecmweb.com/design_engineering/electric_highs_lows_motor/)
Title: Re: Low Voltage and Appliance Performance
Post by: Peter & Beth on June 07, 2010, 09:37:23 pm
Is the PF a constant that is specific to the Motor (Load)? And, is it found in the nameplate? It got a little beyond my experience when one of the articles I was reading began a discussion of torque and start-up loads. But I got the jist that high VAC is potentially more damaging than low VAC.
What I'd like to develop is a chart for my A/C's to establish the upper & lower VAC range. Although it is impossible to visually monitor for protection, it's better than nothing. I agree having an EMS is the best route as my 97 U270 did not come with one either.
Title: Re: Low Voltage and Appliance Performance
Post by: Dave Head on June 07, 2010, 09:43:33 pm
Even more. Power = current times voltage. Also, since voltage = current times resistance, Power also equals current (squared) times resistance. With current rising as a square function, power losses due to heat generation rise the same way.
Quote
Peter B. Martin wrote:
A reply has been posted to a topic you are watching by Peter B. Martin.
The text of the reply is shown below:
Here's what I've learned after doing some research, and the best article
A motor rated at say 1500 watts will require 1500 watts to run. It will
require this wattage regardless of the voltage. So a 1500 watt motor
running on 105 volts will draw 14.3 amps. The operating amperage range
is specified on the motor's plate as well as the voltage. If the
operating range for the motor is 12 to 14 amps. You will burn up the
motor prematurely by overheating for long periods of time. The motor may
have safeguards built-in to cut off power when certain conditions are
met. Of course, if the total amperage draw exceeds the circuit's rating,
say 20 amps, then that safeguard will result in a tripped breaker at the
panel.
I suppose that the A/C's manuals may contain the motor(s) ratings. I'll
have to check this when I go to the storage facility.
Title: Re: Low Voltage and Appliance Performance
Post by: Dave Head on June 07, 2010, 09:51:07 pm
Darn, Neal - you almost sound like a nuke! Oh wait, you were one! High voltage, you will cause insulation breakdown and short circuits. Low voltage will create excessive heat. The excessive heat will get you faster than the insulation breakdown. The older the equipment, the stronger the possibility of insulation breakdown due to insulator aging (assuming the newer equipment is built to the same standards!).
Quote
Neal Pillsbury wrote:
A reply has been posted to a topic you are watching by Neal Pillsbury.
The text of the reply is shown below:
Quote from: Peter B. Martin on Today at 01:54:20 PM
Can we discuss how the low voltage condition impacts A/C longevity &
performance? Or, for that matter any other appliance as complex as an
A/C unit?
1. Are the motor(s), its windings, wires (gauge), controls, etc.
providing the power to the units the concern?
2. If so, then the power rating/design for each of these motors can be
calculated by the formula: Power(watts)=Volts x I(Amps).
3. So, is the power rating of the motor(s) a constant? That is, the
motor will draw sufficient amperage to get its rated power and thus the
amperage is increased as the voltage decreases? Or does the power output
of the motor (watts) drop off in some modality as the variable (volts)
increases or decreases above or below some threshold estimate?
4. Or, is there some other relationship between the variables (P=V x I)
that causes potential long term failures?
Peter,
It's a little more complicated than just P=IE(PF), but you are on the
right track. However, especially with motors, over voltage conditions
should be regarded with even more respect than under voltage conditions.
In increasing orders of complexity, the following are some things that
we would do well to remember:
1. Don't place stress on electric motors and other electrical
equipmentas a result of staying connected to any power system at or near
the ends of our design voltage limits. The best life and most efficient
operation occurs when you operate motors and other electrical equipment
at voltages very close to the design or nameplate ratings.
[/color]Especially when supplying voltage to motors, stay as close as
possible to 120 VAC ± 5% (114 to 126 VAC) and as far away from the
"outer limits" of 120 ± roughly 10% VAC (104 to 132 VAC) however and
whenever possible.[/font]
2. Rules of Thumb for High and Low Voltage[/b][/font]
· The amount of work (Power) required is dictated by the load. Thus, for
a given cooling demand, a motor on a Rooftop AC has a FIXED Power demand
at any instant. Then, if voltage goes down, current must go up (Power =
Current x Voltage x (PF)). The Power Factor will only help a small bit
in an under voltage condition. In an over voltage condition, however, PF
will increase exponentially once a motor core becomes saturated by the
stronger flux lines (Higher Voltage).
· Small motors, like ours in our FT motor coaches, tend to be more
sensitive to over voltage and saturation than under voltage conditions.
· Single-phase motors like ours tend to be more sensitive to over
voltage than do large industrial motors.
· Over voltage can drive up amperage and temperature, even on lightly
loaded motors. Thus, high voltage can drastically shorten motor life,
even on lightly loaded motors.
· Motor efficiency drops with either high or low voltage, and motors
overheat more rapidly in the reduced efficiency condition.
· Motor power factor improves (helps) with lower voltage, but drops
sharply with higher voltage due to motor core saturation induced by the
stronger magnetic flux .
· Motor inrush current goes up rapidly with higher voltages.
3. Most of the time, unpredicted and/or unknown electrical power source
faults do damage before we ever realize something is wrong. Therefore,
because we frequently have the opportunity to experience damage, a high
quality, automatic, electrical monitoring system is very cost effective.
I installed a 50 amp, permanently wired EMS system to protect against
both shore and Power Tech Gen faults (the '98 U270 had no EMS) and it
has saved my bacon numerous times while coaches all around me, including
FT's, had varying amounts of damage. IMHO it has been well worth the
investment and only one or two times out of a dozen, did I know that
something had gone wrong before the EMS told me.
http://www.viprv.com/ems/ems.html#about
Hope this is helpful. I've tried to attach a good article that is aimed
at non RV Industry, but I keep running into MS Word 2007 formatting
problems. I'll try to get it to you in another Post.
Title: Re: Low Voltage and Appliance Performance
Post by: George Stoltz on June 07, 2010, 10:10:50 pm
Yikes. My head hurts. I barely understand all of this, but this is what I've learned to do by reading the Yahoo Foretravel Forum and the Escapees Discussion Forum:
1) Use a Progressive Industries EMS 2) Keep the blades on our 50 amp shore power cable clean and shiny 3) Always and only touch the power pedestal on first contact with the back of my hand. Then use the pedestal power tester built for me by George Hatfield. It tests to see if the circuit is 50 amps, reads the voltage on each leg, checks for an open ground and more. Neat device. 4) Turn off AC, fridge, microwave or toaster oven before disonnnecting or connecting to shore power. 5 Set the breaker on our Xantrex inverter based on whether we have 50, 30 or 20 amp service (thanks to Gary Omel for this one)
Title: Re: Low Voltage and Appliance Performance
Post by: Neal Pillsbury on June 07, 2010, 11:08:32 pm
Dang, Dave, I told you way too much! Peter, Power Factor (PF) may or may not be stated on the appliance nameplate or design documents. It is a given for a given appliance, but only at it's rated voltage and current. Stray from that V & I and PF shifts, especially in over voltage conditions. PF is near, but usually less than 1.0 for inductive and capacitive loads such as motors, fluorescent lights and transformers. PF is 1.0 for resistive loads (incandescent and LED lights, appliances with a heating elements, etc.) . Think of PF as a measure of current leakage. It is real current that flows through appliances, that generates heat, aging and reduced life without doing any real work that benefits us or the appliance. In inexpensive, poorly designed appliances, it can be as bad as 0.6 or so. It can be modified, but almost exclusively, not by us. Only by design in the generation and distribution of electricity or in the appliance design process. Our only reasonable choice is to purchase high efficiency appliances, especially when we replace high energy use appliances. I apologize for the horrible format problems in my previous post. The ForeForum conversion of documents, that I compose offline, is not WYSIWYG. I've got to find a more consistent way! Thanks for your patience, Neal
Title: Re: Low Voltage and Appliance Performance
Post by: Peter & Beth on June 08, 2010, 07:59:19 pm
I'm convinced that voltage variability above or below the Min./Max. limits on an appliance's nameplate is most detrimental to our high cost appliances, like the electrical motor driven A/C's. And, plugging into an EMS device is the best way to monitor and in some cases (Brands) modify the voltage delivered to the motorhome so extreme low/high voltages are minimized or cut-off before serious damage can occur.
But, what about the generator voltage variability and/or spikes? Is the generator's voltage reliably steady assuming the maintenance of the unit is performed per the manufacturer's specifications?
Can an EMS unit be wired to monitor the genset's performance?
Title: Re: Low Voltage and Appliance Performance
Post by: Rudy on June 08, 2010, 08:21:50 pm
Peter,
I wired my Progressive Industries HW50C w/remote between the transfer switch and the panel the transfer switch feeds. That way I not only have protection of all incoming AC sources, I can see the leg by leg Volts, Amps, and Hertz of shorepower and gen power.
Title: Re: Low Voltage and Appliance Performance
Post by: Peter & Beth on June 08, 2010, 08:28:31 pm
Rudy, can you provide more details on your installation? Where is the EMS located, what is the wiring required? The run from the ATS to the panel is rather short, but I guess you can install a box to contain the splicing, etc. in the area under the bed. Can the EMS be installed in the same area as the ATS?
Thanks,
Title: Re: Low Voltage and Appliance Performance
Post by: George Stoltz on June 08, 2010, 08:52:31 pm
Rudy, can you provide more details on your installation? Where is the EMS located, what is the wiring required? The run from the ATS to the panel is rather short, but I guess you can install a box to contain the splicing, etc. in the area under the bed. Can the EMS be installed in the same area as the ATS?
Thanks,
And, how much time did this take?
Title: Re: Low Voltage and Appliance Performance
Post by: Rudy on June 08, 2010, 09:32:24 pm
Peter,
I mounted the EMS in the bed where the transfer switch and panel are mounted. I ran the remote display wire under the floor in an existing chase to the drawer, VCR and TV cabinet. Then up to the hole for the VCR and out to the adjacent mounted remote display. Pull out a drawer or two to access the area.
I pulled the wires running from the transfer switch to the panel out of the transfer switch. I attached those wires to the output of the EMS. I then ran new wires from the transfer switch to the EMS. No separate splice box is necessary.
I used same color and size wire (#6 is my memory from Lowe's) as was between the transfer switch and panel. I connected them the same as per instructions that came with the EMS. I disconnected/connected one wire at a time to avoid confusing myself and helping to be sure Leg 1 stayed Leg 1 after all was said and done. Less than two feet of each color is needed.
I work slow and took about 1.5 hours. I'll bet others could half that time.
Well, I took a picture, but could not figure out how to insert in the message. But I was able to attach the picture. The silver box is the transfer switch, the black box is the EMS with colored wires entering from the transfer switch on the left side. The black cable on the right side of the EMS are the wires removed from the transfer switch and connected to the output side of the EMS.
Peter, you can do this. Feel free to message me a phone number if you would like help that way.
Title: Re: Low Voltage and Appliance Performance
Post by: Barry Beam on June 08, 2010, 09:51:31 pm
Don Hay did a built in EMS. It took about 4 1/2 hours. Photos and instructions http://beamalarm.com/Documents/progressive_ems.htm (http://beamalarm.com/Documents/progressive_ems.htm)
Title: Re: Low Voltage and Appliance Performance
Post by: Peter & Beth on June 08, 2010, 10:13:49 pm
Thanks Rudy & Barry:
Can someone discuss the differences performance-wise of the HW50C and the Franks Electronics EMS unit? I recall someone discussing the Franks unit as generating heat requiring a fan if installed in the ATS under bed location.
Is any humming sound generated by these units? (yes I know, it didn't forget the words ;D)
Title: Re: Low Voltage and Appliance Performance
Post by: Barry & Cindy on June 09, 2010, 12:49:53 am
Remove the cable from the transfer switch to the main panel at the main panel end. Then connect the removed end and connect it to the input side of the EMS. Buy a new #6 cable and connect it from output of EMS to the main panel.
Gen & shore will be protected and reported. Transfer switch will not be protected.
EMS can be place anywhere convient to the wiring.
Running the remote panel wiring just takes ingenuity, depending where you want to mount it.
Title: Re: Low Voltage and Appliance Performance
Post by: Rick on June 10, 2010, 07:33:52 am
Can someone discuss the differences performance-wise of the HW50C and the Franks Electronics EMS unit? I recall someone discussing the Franks unit as generating heat requiring a fan if installed in the ATS under bed location.
Is any humming sound generated by these units? (yes I know, it didn't forget the words ;D)
The HW50 is a hummer. Hums like a cheap AC-DC converter I once had in a travel trailer. I called Progressive and they confirm that they do hum. If mounted under the bed near the transfer switch it quickly becomes an annoying hum in a quiet area.
Title: Re: Low Voltage and Appliance Performance
Post by: Rudy on June 10, 2010, 09:04:50 am
In my case, the HW50C mounted under the bed is very quiet.
My wife hears better than I do and she can not hear it either.
Title: Re: Low Voltage and Appliance Performance
Post by: Neal Pillsbury on June 10, 2010, 10:28:35 pm
Peter, I don't care for Autoformers because there is no such thing as free power to you without impacting others on the grid. I'd be happy to walk you through the mathematics of that, if you would like to see the technical proof. But, essentially, if you are able to use more current (because you have an Autoformer) and you are running more appliances, there is less available current and voltage for your neighbors in an already overstressed power grid in any improperly or poorly designed park power grid situation. I feel that it is better to just ask Campground Management to be moved to better power or for relief from any noise abatement rules (and for the right to run my generator through the night) at a reduced park fee. I have only been refused this request once and we haven't felt the need to return to that park since. We have absolutely no humming noise out of our Progressive EMS HW 50C. Also, IMHO, the Progressive Inc. owner and sales staff are exceptionally ethical and customer oriented. I'm late to the party - but here is another EMS option. I wanted to protect the coach from both Shore and Diesel Gen set faults. I also wanted to have Utility Bay indication of what the EMS was doing as soon as I plugged into shore power (I still meter the power prior plugging in). Therefore (PHOTOS attached below), I: Mounted EMS under foot of bed, adjacent to ATS Ran data cable in split loom to Utility bay over Reels Mounted display selector switch and local display there Ran remote display (telephone wire) in split loom across black/gray tank bay, up through U-line floor (Sealed after) and up through false inner/outer wall to Utility /Power panel above Dining table. Total time about 5-6 hours Works extremely well and, as previously mentioned, it has protected me on more than a dozen unlikely and unanticipated occasions over the past 5-6 years. Neal
Title: Re: Low Voltage and Appliance Performance
Post by: Peter & Beth on June 10, 2010, 10:47:18 pm
Neal, thanks for the details. It looks like a very professional installation. Did you use a fish tape to bring the wires through to the dining room power display cabinet?
It appears that Progressive's EMS is the way to go. I also see that you still have the OEM ATS 100. Very soon I'll be replacing it with the Lyght LPT50BRD, and when I do, I'll install the Progressive unit.
Many thanks,
Title: Re: Low Voltage and Appliance Performance
Post by: Neal Pillsbury on June 10, 2010, 11:21:01 pm
Peter, Once you pull out the U-Line, and have the EMS data (telephone cord) wire in the bottom of the Pantry, all that is needed is a straightened out coat hanger to fish a pull cord up to the Power/Utility display panel cabinet rear corner. The most difficult task may have been learning how to use the telephone cord plug crimping tool successfully. Radio Shack sells the crimper and the EMS can tolerate an adequate number of feet of data cable to get from either the foot of the bed or the utility bay (I don't remember the maximum length allowed - it's probably on their web site - or, just give them a call). One of the best features is the "memory" of what last caused a protective trip of the EMS. That design feature has been worth its weight in Gold to me in convincing recalcitrant Park managers and/or utility technicians that something is really wrong, especially when the problem is intermittent, as it often is. Neal
Title: Re: Low Voltage and Appliance Performance
Post by: Barry Beam on June 10, 2010, 11:26:45 pm
I'd be happy to walk you through the mathematics of that, if you would like to see the technical proof. But, essentially, if you are able to use more current (because you have an Autoformer) and you are running more appliances, there is less available current and voltage for your neighbors in an already overstressed power grid in any improperly or poorly designed park power grid situation. Neal
Hi Neal, I have heard this before but never understood how it creates more amps. My understanding has been it increases your voltage but decreases the amperage. Can you elaborate as I would like to understand how it gets more amperage. .
Autoformer claims: The Autoformer DOES NOT take power from the park. It does not affect the park or input voltage, or make electricity.
What it is doing is changing the voltage - amperage relationship, lowering the amperage and raising the voltage. Since appliances run better on higher voltage, lower amperage, less overall power is used from the park, and better service is enjoyed from your RV
An Autoformer running at full output (50amps) will use 1 amp, but will cause appliances to cycle more often and run cooler. This will use less total power from the park.
Title: Re: Low Voltage and Appliance Performance
Post by: Raymond Jordan on June 11, 2010, 12:05:10 am
Hi Neal, You sure have a clean utility bay!! And your 50 hardwire installation is well done.
Raymond & Babette Jordan 1997 U 320
Title: Re: Low Voltage and Appliance Performance
Post by: Dwayne on June 11, 2010, 09:18:30 am
Wow. I thought I was prepared with the 50 amp portable Surge Guard.
Title: Re: Low Voltage and Appliance Performance
Post by: Mike Baldacchino on June 11, 2010, 09:47:40 am
I don't quite understand the physics of it. If a device works to change something, it is still work! Work uses energy, so, a device that takes something in and changes it, uses energy. This means that less comes out, whether the device makes heat, or there is a coil in it, or something. Otherwise we have the proverbial "perpetual motion" thing going. If you have, say, 30 amps coming in at 100 VAC, and put it through a device, it is hard for me to believe that you can get 25 amps at 120 VAC. This then limits what you can use on the line. Use near the 25 amps (if the device lives up to their claim) and the voltage will drop anyway and you will still burn up the appliance. When I used to teach troubleshooting, I used a water hose as an example with pressure being voltage and volume being water flow. Put your finger over the end of the hose and you get pressure, but the volume reduces. There is no free lunch. Anything you do to the hose, whether you make it longer or stick a valve somewhere in the line or make it do work, it lowers something, either the pressure or volume. So it is, I believe, with electricity. Watts=Volts X Amps. Do I have a distorted view of it? Is the device snake oil?
Title: Re: Low Voltage and Appliance Performance
Post by: Neal Pillsbury on June 13, 2010, 03:04:58 pm
Hi Again, Barry, We just had a family reunion and I was helping the DW with all the good reunion stuff. As the teenagers said, it was "Wicked Awesome", . Now back to the Autoformer issue. Let me apologize up front, because it will take a bit of explanation, so please bear with me. I'll post this because several others have expressed interest and I know that Autoformers are like AGM Vs. Gel Cells. These (among other technical topics) are highly polarizing and there are no absolutely correct or incorrect final answers. But everyone deserves quality input in order to be able to reach reasonable conclusions that apply to them I wasn't clear , I guess, in what I was trying to say.
I said: "I don't care for Autoformers because there is no such thing as free power to you without impacting others on the grid. I'd be happy to walk you through the mathematics of that, if you would like to see the technical proof. But, essentially, if you are able to use more current (because you have an Autoformer) and you are running more appliances, there is less available current and voltage for your neighbors in an already overstressed power grid in any improperly or poorly designed park power grid situation."
Like any step up or step down transformers, Autoformers, indeed change the input to output current and voltage ratios in proportion to the ratio of their primary to secondary transformer windings . And those relationships, in the simplest transformer form are: If Np = the number of turns in a primary transformer winding Ns= the number of turns in a secondary transformer winding Ep = Voltage applied to a primary winding in Volts AC Es = Voltage measured across a secondary winding in Volts AC Ip = the current in a primary winding Ep = the current induced into a secondary winding Then: Np/Ns = Ep/Es (directly proportional) Np/Ns = Is/Ip (inversely proportional) And therefore, Ep/Es = Is/Ip (inversely proportional) Thus, if you decrease the input voltage going into a step up transformer and you then build circuitry that senses that the transformer output voltage is also decreasing (because the input to output windings ratio determines the output voltage) and you then build circuitry that automatically changes the number of turns of secondary windings available, thus adding secondary windings to bring the voltage back up to the desired target voltage, you have built yourself an "Autoformer" (they actually do it in a few electronically controlled step increases, not in analog fashion). And yes, mathematically, as the input voltage decreased, output current increased, but you added secondary turns and brought the output voltage (and therefore current) back to the desired target, so input current has not now been appreciably changed. And all that you have to pay for is the "50 Amp Autoformer" itself ($500 or $600 maybe?) and the transformer "losses" which are advertised to be "1 amp at 50 amps of rated output load". It's good that the Autoformer Owner has used one of several options that has protected his inductive loads (anything with windings) by raising the operating voltage while keeping the current drawn from his power pole nearly the same, but let's look practically at what he has really saved in terms of the park grid and his neighbors. The figure attached below is a well accepted set of graphs that shows (in general terms) the relationship of supply voltage to various small induction motor characteristics (like for our AC compressor and fan motors). For a Penguin, DuoTherm, 13,500 BTU AC compressor and fan motor at full load at rated design voltage (115VAC, 60 HZ, 1PH) : PF = 0.88 (from Dometic online literature) Power = 1570 Watts Current = 15.500 amps (for two motors, 12.4 amps for the compressor, 3.1 amps for the fan)
At 10 % low VAC at the power pole (104 VAC, 60 HZ, 1PH) PF = 0.924 (From Graphs) Current = 16.323 amps (a 0.823 amp increase, which equals roughly one 95 Watt light bulb)
At 15 % High VAC at the power pole (132 VAS, 60 HZ, 1PH) PF = .748 (From Graphs) Current = 15.887 amps (a 0.387 amp increase, which equals roughly one 45 Watt light bulb)
Now to the crux of my distaste for Autoformers. If I am on a power source that, for whatever reason, is low or high in voltage, I am made aware of that condition by the EMS protective device that I have chosen. If the voltage is low, then I look for ways to reduce my load, use the generator or move to another site, as appropriate and I may use the equivalent of one, or at worst two, 95 Watt light bulbs more energy for a while in doing so. However, if I were on an Autoformer, it appears to me that I might not even know that I'm on a struggling, or poorly designed grid. And worse, because I'm unaware, I may be using additional appliances that I don't really have to use, just because I don't know, thereby drawing more current through the fixed resistance wiring of the park, creating more voltage drop and making the problem worse, or even much worse for my neighbors. Then if I'm a really bad neighbor and want to make things really, really worse, when someone comes to my door and asks me to consider shedding some loads or to consider stopping the use of my Autoformer, I'll tell them that I paid for the site and the power and I'll go out of my way to make their problem even worse.
We had that happen in a Buffalo NY park. We woke up in the night to our single AC (I only had one turned on) going on and off because the EMS was tripping on low voltage. The EMS would reset and then trip off again a few minutes later. I suspected Autoformers since the park had had a low voltage earlier on in the evening (106 VAC) and two high end SOB's, with four AC's each (as well as Autoformers), had moved in after dark, one on either side of us. Outside, at the power pole, I watched my power dip well below 104 VAC for minutes at a time as their various AC compressors cut in and out in the 90 degree heat and humidity of the middle of the night. Since it seemed as though each was using three if not all four AC's, I tried their doorbells and, through their intercoms, got immediate and very angry responses from each neighbor. I eventually asked for assistance from park management, after working up through several levels of park staff. Management agreed that I had a problem but wouldn't help me out because their rules forbid me from using my generator, my neighbors were part of a larger Rally and they weren't about to irritate the $$$$$'s, the park had no other 30 or 50 amp sites (that they could fit us into) and, by this time, both Autoformer coaches had made it very clear to both of us that they were perfectly entitled to run all eight AC's if they wanted to, whether they were creating a problem or not. TOUGH S--T! Along with the grandchildren, we had a very sleepless night and a very sleepy next day at Niagara Falls. We won't patronize the park again, not even to inquire if it is under new management/ownership.
So under one scenario, I could keep it simple (as well as less expensive, by the cost of one Autoformer) and use maybe one extra 100 watt bulb for a bit, while I sort things out. Under the other (Autoformer) scenario I could potentially use 3 or more, 15,000 BTU AC's than I don't actually need to use (roughly equal to fifty-five, unneeded 100 Watt light bulbs, or 50 unnecessary TV sets simultaneously, or five or six coffee makers and/or microwaves ovens at the same time............. "just because" I'm not interested in the Golden Rule or in being a Team Player or in just plain using common sense conservation ).
I'm not at all adverse to anyone using an Autoformer to protect his/her appliances, as long as they conserve and try their best to be good neighbors. But, several times I have found that Autoformer owners have no idea whatsoever that they are having even the slightest impact on their neighbors (for example, just by running one AC that their neighbors can't) and they are generally the same ones that brag loudly about how many additional excesses they are able to enjoy, "just because they have an Autoformer, and their neighbors don't". Thus my distaste.
Hope this sheds some technical light, Barry. Pardon my emotional excesses. Neal
Title: Re: Low Voltage and Appliance Performance
Post by: Barry Beam on June 14, 2010, 08:18:11 pm
Quote
I'm not at all adverse to anyone using an Autoformer to protect his/her appliances, as long as they conserve and try their best to be good neighbors. But, several times I have found that Autoformer owners have no idea whatsoever that they are having even the slightest impact on their neighbors (for example, just by running one AC that their neighbors can't) and they are generally the same ones that brag loudly about how many additional excesses they are able to enjoy, "just because they have an Autoformer, and their neighbors don't". Thus my distaste.
Hope this sheds some technical light, Barry. Pardon my emotional excesses. Neal
Thanks Neal for that explanation. I 'll admit it will take me a little while to absorb it. It appears the answer means going deeper than what is on the surface. I will dig deeper into this now so I can have a better understanding. It is great to have such a wide range of expertise on the Forum.
I do use the Autoformer when necessary if I am paying for a 50amp site and my transfer switch is going on & off and it means no power at all. I came back from a hike with that situation. I don't know how long it was doing it. I think my transfer relay will need to be replaced due to the arcing. I can't go without at least 1 A/C. But I do agree in minimizing my use to and not exploit the situation. Thanks again for the thorough explanation.