Energy Saving Technologies for Paint Spray Booths

There are six energy saving strategies used in the spray booth industry.

1. Direct fired and indirect fired heating systems

2. 100% fresh air control systems

3. Bake Mode recirculation

4. Prep Mode

5. Spray Mode recirculation

6. Pulse control system

1. Indirect Fired vs. Direct Fired

Some spray booths have indirect fired heating systems.  This means that the burner fires into a stainless steel box, the heat exchanger.  The burner heats the heat exchanger and the heat exchanger heats the air flowing over it.  The burner indirectly heats the air. 

Combustion fumes the inside of the heat exchanger are vented to the outside through a ventilation duct.  Since we are venting to the outside, 10%-15% of the heat is lost.  The system looses about another 5%-10% because the temperature will go up at a much slower rate inside the booth then when you are using a direct fired heating system.  The system wastes fuel and electricity because you have to operate it longer to reach the same temperature.  Altogether, indirect fired heaters are at least 20% less efficient than direct fired heaters.  They are seldom used in the finishing industry.

Direct fired heaters fire the burner in the intake air path.  They directly heat the air that is moved into the spray booth.  Their efficiency is almost 100%.  Direct fired heating systems are the dominant systems used in the finishing industry today.  They are at least 20% more efficient than indirect fired units. 

As their name states these systems exhaust all the air that they take into the booth.  These systems generally slow down the air flow through the heater in the Bake Mode but these systems do not recirculate.  They are the simplest and the least expensive.  They are also extremely inefficient.  Please see cost of operation table. 

Many spray booth come with a recirculation system.  These are generally 80/20 systems.  This means that in Bake Mode 80% of the air is recirculated and 20% of the air is exhausted.  You only have to take in and heat 20% fresh air.  Buying an 80/20 recirculation system is one of the best investments you can make.  In general, they save about 45% of the operating costs over a 100% fresh air system! 

Many high end spray booths have a Prep Mode.  Spray booths with Prep Mode keep the ventilation system at a reduced air flow rate when the painter is not spraying.  At the beginning of the finishing cycle, the Prep Mode supplies warm air to be able to prepare the car for painting.  A sensor detects when the spray gun trigger is pulled and the ventilation system ramps up to Spray Mode speed.  A few minutes after the trigger is released, and provided that the trigger is not pulled again, the ventilation system returns to the Prep Mode to save energy.  The system will stay in Prep Mode until the painter pulls the trigger again or switches the system into Bake Mode.

Prep Mode can be implemented in two different ways:

A.  Non Recirculating Prep Mode

Since you don’t need Spray Mode air flow while you are prepping a car,  some booths slow down the air flow in Prep Mode.  The logic is pretty simple.  If you reduce the air flow rate by 75%, you will reduce energy consumption by about 75%.

B. Recirculating Prep Mode

Systems that recirculate in Prep Mode generally exhaust only 20% of the air they move in the booth.  Prep Mode is an 80/20 recirc mode. 

In Canada, recirculation with a direct fired heater in an occupied space is not allowed.  Recirculating Prep Mode may only be used in the US.

Significant savings can be realized by recirculating a percentage of the Spray Mode air flow.  However, Spray Mode recirculation introduces some industrial hygiene issues.  These systems have to be designed to make sure that air contaminants are kept within acceptable levels. 

Rammstein Air developed a control system that incorporates all of the traditional energy saving methods AND adds several new technologies for additional savings. 

Predicting spray booth operating costs is a complex task.  To make an accurate prediction you have to take about 50-60 different spray booth parameters into account.  Some of the most important ones to consider are the size of the booth, local climate, cycle times and temperature set points.   The only way to achieve accuracy is to use a software model of the spay booth operation.  We created such a software model to make sure we can give you quick and accurate estimates of the savings you will realize by incorporating various control methods.