October Q & A by Mark Polk

*NOTE: At Mark's discretion, material might be edited to suit a wide audience. Due to the large volume of material and correspondence we receive, individual replies might not be possible, nor can we acknowledge receipt of submitted material. Selected questions will be answered in future issues of our RV Education 101 newsletter and on our site. Thank-you for your understanding.

Q My RV has a 30-amp breaker box, and I just had two new a/c units installed (15,000 BTU Coleman’s). The tech told me that they cannot be run at the same time when I am hooked up to shore power because they will draw too much power, but that they can run at the same time when they're on generator power. Is it true that shore power won't work to power both? Thanks for your help!

Mark Says:This is a common problem with 30 amp systems. First of all, appliances require more power to start up than they require to run after starting. For example a 15,000 BTU AC can draw 14 to 16 amps to start and once the compressor engages it may only require 12 to 13 amps to run. So the first problem is two AC's could potentially require 32 amps from a 30 amp system. If you have anything else on at the time, like the refrigerator, coffee pot etc. you may only have 20 or 25 amps available.

For two roof AC’s to run and be able to use other appliances usually requires a 50 amp system. On 30 amp systems some manufacturers use energy management systems that will start one AC first and once it is up and running the second one will start. Then if you turn on another appliance and the system senses that there is an overload it automatically sheds one of the AC's until there is enough power available for it to start again.

If you attempted to run them both at the same time on shore power you would be using about 26 amps and depending on how many 12 volt devices you were using the converter itself could be using the remaining 4 amps which results in you not being able to use anything else in the RV. Another concern is if the campground voltage drops at all it can create additional problems. Usually if there is not enough power, damage to an AC unit will occur during initial start up.

I know this won't help much but a better solution for your RV would have been to use a 13,500 BTU unit in the front and a much smaller unit like an 8,300 BTU in the rear of the RV. Some of the new AC units require much less energy to run. An 8,300 BTU unit only uses 8 amps versus 13 or 14. This would allow 21,800 BTUs to cool the RV rather than one 15,000 BTU AC trying to cool the RV.

I wish I had better news, but properly managing the amps being used in your RV can extend the life of your electrical system and appliances.

Q I live in Lewisburg, PA. I'm ready to winterize and store our 28' TT. I've read that you should put wood under the tires when storing the RV. What's the purpose of the wood under the tires? Also, will the plastic leveling blocks (like Lynx Levelers) work just as well? Thanks!

Mark Says:Ideally you should attempt to get the weight off of tires when it will be in storage for a period of time. But, this is not always practical or possible. If the weight can't be removed, at a minimum you should try to move the RV every three months to prevent tire flat spots and ozone cracking at the tire sidewall flex point. Flat spots will usually disappear after the tires warm up and travel for a distance, unless the vehicle hasn't been moved for six months or more.

There are actually several reasons for blocking tires. The first step is to make sure the RV is as level as possible so more weight isn't on one tire than the others. The perfect scenario would be to store the RV and its tires in a cool dry, covered area, but as we all know this is not always possible either.

Storage surface areas can cause your tires to age prematurely. You don't want to leave the tires in contact to any heat producing material or petroleum based material like asphalt. You also don't want them exposed to constant cold or moisture, like sitting on the frozen ground. The wood acts as a barrier between the tires and the ground surface they are being stored on. The proper storage steps would be to clean the tires, cover them to protect them from harmful sunlight and UV rays and inflate them to the pressure indicated on the sidewall of the tires.

It is extremely important that the blocking you use is wider than the tires tread and longer than the tires overall footprint. If not the steel cables in the tires sidewall can be damaged which can also result in premature tire failure.

Yes you can use Lynx Levelers, just make sure you follow the directions above.

Q Hello, you guys have helped me before so I hope you do not mind me bothering you. I purchased a Wilderness Yukon Trailer 29' and I would like to purchase a generator, but I have no idea what size generator would be needed to run everything in my trailer. If you have any info I would appreciate the help!!

Mark Says:A trailer with a 30 amp electrical system is capable of using up to 3,600 watts before encountering any problems. 120 volts X 30 amps= 3,600 watts. Generators are rated in kilowatts. One kilowatt is equal to 1000 watts, so if you want to be able to use your trailers electrical system the way you normally do when you're plugged into a 30 amp service I would recommend a 4KW or 4,000 watt generator. 4,000 watts divided by 120 volts = 33.3 amps. Anything over this is probably overkill.

Try to find a generator that has a 30 amp outlet that uses a twist on type of plug. You can get an adapter that will go from the RV plug to the twist on generator receptacle. This way you have all 30 amps going through the RV power cord. Other generators might have two 15 amp household type receptacles. In this case if you plug into one receptacle you would only have 15 amps going to the trailer.

This is a sample of the adapter http://www.jackssmallengines.com/honda_gen_rvadapt.cfm

Here is a generator selector chart to help calculate the proper size generator http://www.funroads.com/gensets/ogGensetSelector.jhtml

You can go to www.rvuniversity.com to read a generator article: http://www.rvuniversity.com/staticpages/index.php/rvgens101

Q Hello Mark, I read your how to Buy an RV article, however I have a question not covered in the article. Can you please advise me on this question. How do I determine the price to pay when purchasing a used RV? Do I go by NADA value or the asking price? Help would be greatly appreciated, I don't want to make a big mistake. Thank you in advance,

Mark Says:Pricing for a used RV involves many factors. Just a few are the age of the unit, the condition, mileage if applicable and any options it is equipped with. Most importantly is the overall condition of the RV. The NADA is a good guide to go by and the pricing in the NADA is based on the RV being in good condition. Good condition means that there is no damage and everything on the RV is in proper working condition. You should be able to buy the RV and go right out and use it. If not the price goes down.

You didn't mention if this was a dealer or a private owner, but regardless make them show you that everything on the RV is working. Appliances in an RV are expensive to replace. Also, inspect the unit thoroughly looking for signs of damage that are sometimes hidden like water damage. If you're not sure what to look for take somebody with you who knows RVs.

If it's a motorized RV the mileage is one factor used to determine the price. Another is any optional equipment above and beyond a base model. You can go to nada.com and if you know the year, make, model, mileage if applicable and what options the RV has you can get an idea of a fair price. It will give you low retail and average retail. If it's a motorized RV you not only need to inspect the coach but the chassis too.

If the asking price is within a fair market price this doesn't mean you should just settle on paying that price. There is almost always room to negotiate on asking price, unless you run into a deal of the lifetime, in which case you pay the money and leave. Don't be afraid to make a ridiculous offer and just see what they say, in most cases you will meet somewhere in the middle of the road on pricing. I personally would not pay the high retail price unless it was in showroom condition. You should be able to get it close to the low retail price or less. Remember RV's depreciate they don't appreciate. In some cases RV owners are upside down meaning they owe more than the RV is worth and they want to pay off the loan, so their asking price is too much for the RV.

You need to know what you are looking at, know what a fair asking price is, inspect the unit thoroughly, verify everything works and then negotiate the selling price. Be patient, a good deal will always come along eventually.

Copyright 2007 by Mark J. Polk owner of RV Education 101

RV Expert Mark Polk, seen on TV, is the producer & host of America's most highly regarded series of DVD's, videos, books, and e-books. http://www.rveducation101.com/