| I think most RVers understand the importance of | | | | rating of a vehicle engine is only accurate at a higher |
| maintaining proper tire inflation pressure. The problem | | | | RPM range (usually 5000 to 6,000 RPM's), but rarely |
| is if you wait until you're on the road to check tire | | | | do you drive at 5,500 RPM's. As for the air |
| pressure the tires are too hot for correct evaluation. | | | | compressor it would require more amps, from a 240 |
| Checking the inflation pressure when you stop to | | | | volt circuit, to produce this peak HP rating. |
| refuel doesn't make sense; you will get higher | | | | The Cubic Feet per Minute (CFM) is an important |
| pressure readings and if you let air out the tires they | | | | rating when it comes to portable air compressors. |
| are underinflated when they are cold. Another | | | | CFM is basically a measurement of the rate a |
| problem is when you are at the campground, and | | | | compressor can deliver a volume of air. CFM varies |
| you want to check the tire pressure, there is no | | | | with atmospheric pressure. It also varies with the |
| available air support to do it. | | | | temperature and humidity of the air. Air compressor |
| This is why you might want to consider purchasing a | | | | manufacturers calculate Standard Cubic Feet per |
| portable air compressor. But, air compressors can be | | | | Minute (SCFM) as CFM at sea level with 68 degrees |
| confusing to understand, especially if you are trying | | | | F, at 36% relative humidity. |
| to find one that is capable of increasing the inflation | | | | Note: CFM ratings can be skewed by the |
| pressure in large motorhome tires. | | | | manufacturer too. Let me explain |
| Air compressors have 3 main ratings associated with | | | | Let's talk about our third rating, Pounds per Square |
| them, horsepower (HP), Cubic Feet per Minute (CFM) | | | | Inch (PSI). For air compressors the CFM ratings are |
| and Pounds per Square Inch (PSI). Understanding | | | | given at a specific PSI. In other words an air |
| these 3 functions of an air compressor can help us | | | | compressor rated at 3 CFM @ 90 PSI should be |
| select the right compressor for the job. | | | | capable of delivering the 3 CFM at 90 PSI. The |
| We'll start with horsepower. Unfortunately when it | | | | problem is air compressor manufacturers can |
| comes to air compressors, manufacturers don't do a | | | | advertise a higher CFM at a specific pressure because |
| great job of explaining it to the consumer, almost to | | | | the air compressor is capable of delivering the rated |
| the point some would consider false advertising. | | | | CFM going from 0 to 90 PSI, but what is the true |
| Manufacturers tend to over-inflate HP ratings, | | | | CFM delivered at 90 PSI. If your air tools or RV tires |
| assuming if the consumer see's 6 HP advertised, | | | | require a specific CFM rating at 90 PSI you more |
| rather than 2 HP, they are more apt to purchase the | | | | than likely won't get it based on the advertised CFM |
| higher HP rated compressor. This is true in many | | | | @ a specific pressure. What this translates too is that |
| situations. If you're a muscle car enthusiast you | | | | it will take a long time to inflate some larger RV tires, |
| would definitely consider the HP rating of a vehicle | | | | if the compressor is in fact capable of inflating the |
| before buying it, right? But if we take a closer look | | | | tires at all. |
| at horsepower, as it relates to air compressors, we | | | | When shopping for a portable air compressor the |
| can seek out the truth. | | | | key is to try and find one that can deliver about 4 |
| Horsepower was invented by an engineer by the | | | | REAL CFM based on the REAL HP rating at 90 to 100 |
| name of James Watt. The same watt you think | | | | PSI. |
| about when buying a light bulb. Watt is used as a | | | | If you have the storage room available, and you will |
| measure of electrical and mechanical power. When | | | | have access to electricity, you can find some reliable |
| we apply watts to HP, one HP is equivalent to 746 | | | | pancake style portable compressors that will do a |
| watts. So if you buy an air compressor rated at 6 HP | | | | good job inflating tires and performing other small |
| and it operates on 120 volts it is, in a sense, a false | | | | household jobs. If you prefer a battery operated |
| rating. If you plug the compressor into a standard 15 | | | | portable air compressor I came across a model that |
| amp, 120 volt circuit it would only produce about 2HP | | | | looks like it can handle the job, while I was |
| (voltage X amps = watts). The higher HP rating | | | | researching the topic. It's by VIAIR and it was |
| advertised is commonly referred to as peak HP, | | | | designed specifically for RV and other large tire |
| similar to a vehicles engine HP rating. The peak HP | | | | inflation jobs. |