Cascading Fan Application at Welding School, Portland Community College

Updated: Apr 12

The Ultimate & Most Energy-Efficient System

Power MASTER
Installed Ecogate Power MASTER VFDs at PCC Rock Creek Campus

While preparing for the new welding shop at Rock Creek Campus of Portland Community College in Oregon, College officials requested a project specification that called for the most energy-efficient system available for exhaust ventilation.


The desired system was to work with maximum efficiency even when only one welding booth would be in operation, and maintain that maximum efficiency up to all 75 booths working at the same time.



Ecogate Smart gates are installed in horizontal sections of the duct branches


Cascading Fans System


The best option to design a system with such a large range of air volumes is what is called a "cascading fans system". Cascading fans are commonly used in Europe, and you can see an example in our case study from Crystal Doors in the UK.


How the system works: When you use only one welding booth, only the first fan will start. As users get to use more welding booths, the fan will increase air volume by running at higher RPM. If the air volume of a single fan is not enough, a second fan will start, and so on.

Why is it better compared to one larger fan? Because at lower air volumes, a single fan is running at a higher speed and therefore generating enough pressure to overcome all system losses (by hoods and duct systems).


Each welding booth is equipped with a laser sensor (with a safe invisible beam) that detects the presence of the operator and starts/ stops the ventilation system automatically.

All fans used for cascading fan systems are the same, with the same fan curve. If you combine two fans with different speeds, they have different fan curves, and thus the combined efficiency significantly drops. Ecogate system is solving this issue by using the so-called “Optimized Cascading Fans mode”. This is very simple: if two or more fans are used together, the greenBOX MASTER control system will operate active fans at the same speed. This is combined with Ecogate Closed Loop mode where the fans are regulated to provide the exactly requested air volume (850 CFM per one booth, 1,700 CFM for two booths, etc).


Another advantage of the cascading fans is that if one or several fans/motors/VFDs fail, the greenBOX software will replace them automatically with the next available fan/motor/VFD – i.e. the system will continue to operate. Every day, the next fan will be the leading fan to maintain the same wear & tear on all fans/motors/VFDs in the array and to check that all VFDs and fans are operational.



Achieved Electricity Savings Compared to Traditional Ventilation System


Compared to baseline with ventilation running to all welding booths, this on-demand ventilation system achieved excellent results: when only one booth is in operation, savings are 96% of electricity, when ten booths are in operation electricity savings are 85%, with 20 booths in operation 72%, and with 30 booths 61%. Keep in mind that the traditional system is running all time while this system starts and stops automatically on-demand as triggered by operator presence. Additional savings are achieved by the reduction of make-up air, based proportionally on the number of booths in operation.


Ecogate Smart gates installed (top-right of image)


Honeywell Tridium Building Automation System


Control system greenBOX MASTER is connected to the Honeywell Tridium Building Automation System. Honeywell Tridium system reads all data from the Ecogate system for monitoring, energy use evaluation, and measured air volume of the ventilation system. The measured air volume is used to adjust the make-up air system.


Ecogate Power MASTER VFDs are visible at the top of the photo

Summary


The article describes a highly energy-efficient ventilation system for welding booths as installed at the welding shop of Portland Community College Rock Creek Campus in Portland Oregon.


Additional benefits to this design include make-up air savings (as less air is removed through the general ventilation system out of the building), automatic system start & stop, and reduced noise in the shop.



Project design: Opsis Architecture, LLP

Project management: Pence Construction, LLC

Welding exhaust system: Avani Environmental Intl. Inc.



Portland Community College | Welding Technology at PCC



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