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Pressure washers in their simplest form can be broken down into two primary styles of units:

1. Cold Units
2. Heated Units

The difference between these two styles of units is the addition of a heating system for the water.

The heated units also have three primary categories associated with them. They are:

A. Hot Pressure Washers
B. Steam Cleaners
C. Combination Units

Before continuing on the differences between the different units, a description and understanding of how cleaning results are achieved is necessary.

Four Elements of Cleaning

There are four basic elements necessary for efficient cleaning no matter what method or what type of machine is used. They are:

1. Pressure
2. Water Volume
3. Cleaning Chemical or Soap
4. Heat

Varying any one of these four elements will change the cleaning characteristics. Because of this, compensation can be made for deficiencies in any element. In other words, if you were to use a small amount of chemical, or a weak one, then by adding more heat, pressure or volume effective cleaning could be attained. However, for any type of cleaning, there is always one combination of these elements, which produces the best results from a standpoint of time required, thoroughness and cost. Washing one's hands is an example of the four "elements of cleaning" at work. When hands are simply coated with a dried non-greasy deposit, water alone will wash it away. A high volume of free flowing water will speed the process because the impinging force loosens the dirt and the volume floats or flows it away. When dirt contains an oil, or grease, a chemical must be used. In hand-washing the chemical is commonly referred to as soap. Because soap is an emulsifier, the hands can be cleaned, to some degree, using cold water. After the soap is applied, the hands are rubbed briskly together. The friction creates heat plus an abrasive action, which help to break down and loosen the dirt particles. Using hot free-flowing water will result in faster cleaning as the soap and heat will emulsify the dirt more effectively, while the impingement of the pressure loosens it and the volume carries it away.

Ultimately, cleaning boils down to breaking the bond between the dirt and the surface that it is holding on to. Understanding the four components of cleaning and how they work can demonstrate the differences between the two primary styles of units. It is necessary to remember that most cleaning chemicals (soaps) become more aggressive and better emulsifiers as the temperature increases.

In a cold unit, cleaning is achieved using pressure, volume and soap. The water temperature remains at whatever comes out of the supply system since the unit does not have a heating system. The typical range is somewhere between 40 ƒ to 70 ƒF, although in some areas, it may be significantly higher or lower. Since soaps typically work better at higher temperatures, a deficiency exists. This must be overcome by increasing at least one of the other three components: increasing the pressure, increasing the volume, and/or using a more aggressive soap.

In a heated unit, cleaning is achieved using pressure, volume, soap, and heat. With the addition of heat, pressure, volume, and/or soap can be reduced some in order to achieve the same cleaning result.

Since heated units come in two primary categories, it is necessary to discuss the differences between these units.

Hot pressure washers and Steam Cleaners are similar yet different. They both share many of the same components. For example, they both have pumping systems, combustion systems, electrical systems, and solution systems, and may even share many of the same parts and components. The primary difference is in the pressure, volume and mostly the temperature of the two types of cleaners.

How a Steam Jenny Works...

It should be made clear at this point that a steam cleaner does not generate steam in the true sense of the word. The name of the machine is a gross misnomer. It is actually a CHEMICAL VAPOR SPRAY CLEANER!

The reason the name has persisted is because the vapor spray directed through a cleaning gun does resemble steam. Actually it consists of 85-90% solid water. The remaining steam is a by-product of creating pressure through heat. Because the name steam cleaner is synonymous with this type of cleaning device we will continue to refer to the machine as such.

At normal atmospheric pressures, water heated in an open pan boils at 212ƒ F. However, if the pan is covered, such as in the case of a pressure cooker, the water can be heated to temperatures above 212ƒF before boiling. Much the same happens in a Jenny Steam Cleaner. The heating coil located within the combustion chamber of a steam cleaner is subjected to intense heat. As cold water is pumped through the heating coil an orifice, or restriction, placed at the discharge end impedes its flow. As the water is heated it cannot expand, nor convert to steam, because of the "artificial atmosphere" created by the restriction. Because this condition exists the water reaches a temperature of 325ƒF., and yet remains in liquid form. Once past the restriction the water does have a chance to partially vaporize and when finally escaping to atmosphere the temperature immediately drops to its atmospheric boiling point (212ƒF). As this happens the spray bursts into millions of tiny droplets of water having a great impingement force (the expansion of the water when it hits the atmosphere can be up to 170 times).

Pressure Washers do not create steam at 325ƒF and subsequently do not achieve their impingement forces the same way as do steam cleaners. Pressure washers achieve their impingement force through the use of higher pressures and volumes since the temperatures produced are below the boiling point of water, somewhere between 180ƒ-200ƒF, and do not cause a vapor expansion like a steam cleaner. Pressure Washer pressures can reach upward of 5000 pounds per square inch (PSI) and the volumes can be as great as 10 gallons per minute (GPM). This allows pressure washers to achieve similar cleaning results as steam cleaners since the increased pressures and volumes will compensate for the temperature differences.

It must be noted at this time, that every type and style of pressure washer and steam cleaner has certain applications in which they will produce the best overall cleaning result based on the application, specified criteria, time required, cost, and thoroughness of the job. Not any one machine is the best overall at every application. There is continually a trade off of effective versus efficient cleaning.

This continual trade-off led to the idea of the Combination machine. Combination machines combine the cold pressure washer, hot pressure washer and steam cleaner into the same unit, hence, the name Combination Machine. With this types of unit, you get the versatility of 3 cleaners in 1. As easy as flipping a switch, the machine can go from a cold pressure washer to hot pressure washer. Change the tip in the gun and flip the machine selector switch, and the machine becomes a 325ƒF steam cleaner.