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Brad Townsend
10-20-2010, 10:23 AM
This past summer I think my shore power cooked my Engel freezer. The voltage at the pole was 108 volts, not good i know, When I put a load on such as elect heater ac or stove it would go as low as 90 volts. I also have had to replace a 32" Phillips tv, Macbook laptop,
and the mid AC units compressor would not come on. Now at a new site on 220 volt the mid AC will run, thought the compressor was fried. What I would like to know is What takes place with low ac voltage and can low ac voltage hurt something like a laptop which runs on probably 18 volts. Can the Hertz change with low voltage? The freezer was 4 yrs old, Engel sent me another compressor which is basically all the inards as it is a sealed unit for $350 and thought it was odd that the compressor went out as they are a world class unit good for eons. The 110 line was on a 30 amp breaker but I would pop it around 20-25 amp draw according to the gages in the coach. I will probably go back to the same site next year and would like to go to the powers that be with some knowledgeable info as ammunition to get this rectified.

Thanks for your time.

Brad

Richard and Rhonda
10-20-2010, 11:27 PM
I am no electrical engineer, but I and many others on this site can answer the questions. So here's a laymans explanation.

One, in any live circuit when the voltage drops the amperage goes up. Ohm's law. More amperage generates a lot more heat, hence low voltage burns up motors since the windings and other motor innards are not designed to handle the heat.

Also when the voltage drops, the hertz or frequency does not change from a practical standpoint. If the power is coming from the national grid it will be 60 Hz. If it is coming from a private generator like your coach the frequency can be off.

If you are at a campground that is dropping to 90 volts you are going to burn up a lot of expensive electrical components.

Suggest you search on this site and others for voltage protection devices.

RussWhite
10-21-2010, 12:49 AM
Richard and Brad,

Well I slept in my Newell last night and I am an electrical engineer :-)

I have to take exception with Richard's explanation of ohm's law. As an example think of a heater. Imagine the voltage slowly going all the way to zero, what is the current at that point - zero right? So no, current does not always increase when voltage decreases, in fact they normally are going the same direction. There are exceptions. A load that is trying to deliver a constant amount of work is one of those. Imagine a motor which is trying to maintain its rated rpm's because it is related to the number of motor poles and the frequency of the applied AC power. As the voltage goes down in that case the only way to balance the input with the output is for the amperage to go up. So in the case of a motor home, devices with AC motors ( air conditioners, household refrigerators, air compressors,... ) are adversely affected by low voltage due to heating from increased currents. Other devices however are not. Lamps, heaters, and all the other resistive loads will not be harmed.

That all said, the single biggest reasons for massive electrical problems in a coach is a bad neutral connection on a 240vac system. Without a good solid low resistive neutral, the 240 or whatever voltage you have, will not be evenly divided 120 to 120 as expected. Depending upon what appliances you have turned on at the time of the defective neutral the voltage could divide very unevenly, 200 on one leg, and 40 on the other. All the devices on the 200 volt leg that are turned on will suffer serious damage.
There are system that can be added to your coach that attempt to detect and disconnect before damage is done. They are probably not perfect in all cases that could develop, but at least they give you a fighting chance.

I chose http://www.progressiveindustries.net/ems_hw50c.htm Progressive Industries EMS-HW50C. It does provide a very nice hand if you are trying to convince a campground they have a problem. If the EMS will not energize, they need to get their power post repaired. I have used mine for just that and had good results with getting the post brought up to specs.

Hope some of this helps.
Russ - EE #530

Brad Townsend
10-21-2010, 10:01 AM
Thanks guys.
Russ
The device you have, is it for 120 volt only? the description says it kicks out if it sees 220 volts.
Also what is left to do if you are at a bad power source and it shuts down, say you are at an rv park for a couple days.

Have you herd of the Autoformer? a transformer type device that boost power to a safe level.I have been reading about them but not sure how reliable they are.

Brad

RussWhite
10-21-2010, 11:05 AM
Brad,

The EMS ( Energy Management System ) I mentioned is designed to handle up to a 50 amp service. At an RV park that is actually two 50A breakers tied together, each with a nominal 50 amp rating. The EMS can be purchased with a remote mounted display that will show you the voltage of each line ( phase ) as well as the current being drawn from that line. If your loads were equally balanced one could actually draw 50 amps on each line for a total of 100 amps at 120 volts, or 12KW ( kilo-watts ).
The device will actually work on a single phase 30 amp circuit as well assuming you have adapters to convert from 50A to 30A like most all coaches have or can be purchased.
The EMS monitors the voltage of each phase, not the phase to phase voltage. That is important since that supports a good neutral and if each phase voltage is correct, then by definition, the total will be correct. The device only allows power into your RV if each phase is within the range of 104 to 132.
Now shifting gears to the "autoformer"... That is a device that is capable of increasing the voltage before it goes into your coach. It looks for a situation where the voltage is too low ( varies by vendor ) and boots that voltage by a nominal 10% ( also varies by vendor ). I think the name "autoformer" is a play on the transformer configuration called an "auto transformer" which is a single winding transfer that can change voltage level but provides no isolation. My experience with the Hughes "autoformer" was not too good as the relays they used were actually not rated high enough for full load and would weld closed eventually requiring replacement. When I moved up to a 50A, two phase, voltage booster I changed vendors and have had very good luck with my PowerMaster VC-50 http://tweetys.com/powermaster-vc-50.aspx . Now, it's time for orange juice!

chockwald
10-21-2010, 02:35 PM
Russ.....wow, very informative, and I think I actually get what you are saying. Between Richard, Tom, Steve and you I think I am beginning to unravel the mysteries of electricity, which up until this point have been complete mysteries to me. The biggest lesson I have learned is that, seemingly, most electrical issues in our coaches stem from a bad, or faulty neutral/ground. Personally, that has been my experience with my coach. Virtually every electrical issue I have had has eventually been traced to a "ground" issue.

I was going to suggest the PowerMaster to go in tandem with the Progressive Industries Energy Management System, but yo ubeat me to it! The cost for both is going to be around $1,000, but when I think of the damage that can result from low voltage I think these two items combine to make a good insurance policy.

Brad Townsend
10-21-2010, 02:51 PM
Russ.
Just been doing a lot of searching for feedback on the powermaster and found a site with some 1500 posts about the 3 different units and not one bad comment about the Power master.
In fact the powermaster has more of a surge protection built in than some individual surge protectors.
Good info!
I have seen prices as low as $609. free shipping. Seems that having one of these units should be a must with rvers. A practical insurance policy providing peace of mind.

Thanks Russ
Brad

Brad Townsend
10-21-2010, 02:59 PM
For those interested here is the post for the threads about the 3 units.
http://www.irv2.com/forums/f52/powermaster-voltage-booster-36629-3.html

prairieschooner
10-21-2010, 05:15 PM
Brad,
If you wait until you get to Arizona here is one for $40.00 savings but it may not be worth the wait and it is out in Welton. They may ship though;
http://www.arizonarvpartscenter.com/Power-Master-Voltage-Controller-VC-50-p/vc-50.htm

Brad Townsend
10-21-2010, 07:44 PM
Thanks Steve, Thats the one I had my eye on. I am not in a rush as we will be on the road come Sunday Arriving at Senator Wash sometime mid Nov and will be dry docking till ten.
Then we will be on solar and wind for the winter.

Brad

prairieschooner
10-21-2010, 09:29 PM
I'll have to give you a weather report. We will be in Yuma next week for a short visit. I should be able to stop by the Yuma Marketplace and check prices while we are there.

Brad Townsend
10-22-2010, 04:48 PM
Ok Steve do that. Looks like they received a lot of rain recently.

jwe648
10-22-2010, 05:02 PM
52` At La CASA this am in Scottsdale.. & I'm looking for my Rubber Duck!


Ok Steve do that. Looks like they received a lot of rain recently.

prairieschooner
10-23-2010, 12:31 AM
It has been raining since the beginning of the week and is still raining as we speak here at the Cabin. My Mom is in Yuma and she is bragging that they actually haven't got much more than drizzle. I should be there Thursday or Friday and I'll get back to you then.
We have also been building a fire in the wood burner at night. It will be good to get to a warmer climate, 70 degrees here I come! and I need to get into Algodones, Mexico to get my Shrimp Taco fix. I will most likely stop at the "purple place" a few doors from the border and taste the Tequila!

express1
10-23-2010, 12:59 AM
Steve, do you really feel comfortable going "that" south?
Mexico?
Notice many good deals on the pacific coast, just not sure about safety.:cool:

prairieschooner
10-23-2010, 04:18 AM
Actually we have decided to be cautious about going too far south. We feel that Algodones should be safe. The area only has Doctors and the miscellaneous jewelry in it. When Tricia asks "are we there yet?" I say "not yet, there are no Dentists".
I say you work your way to Yuma, AZ and we take you and Connie to shrimp tacos! The only difference between Mexican Shrimp and Louisianan Shrimp would be Hot Sauce and Cajun Sauce. I am sure after a few Cervezas no one would care.

encantotom
10-23-2010, 06:06 AM
darlene has taken her mom to algodones to have dental work done. i called the border patrol and they said it was totally safe. there are organized bus tours from mesa to just go down there for dental work. there are also a couple of good body shops that do compete rv work including paint for a fraction of the price. upholstery too. i talked to the owners and saw pictures of their work.

the dental work my wife said was very very good and offices were as nice as the one we go to. my mother in law had tons of dental work so it saved probably over 20k.

tom

Bill & Sonja
10-23-2010, 01:52 PM
Sonja had extensive dental work done in Algodones at 20% of the estimate in Calgary. Very pleased with the work. I'm interested in looking up that upholstery shop. We felt completely at ease there last winter.