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Canada Blower [link widoczny dla zalogowanych] Company offers various models of Make-Up Air Units for larger industrial plants ventilation requirements.
Negative Air [link widoczny dla zalogowanych] Pressure in industrial manufacturing facilities can create problems such as:
* Exhaust fans losing performance, as [link widoczny dla zalogowanych] the building pressure becomes negative.
* Pilot light outages and exhaust system failure on natural draft gas equipment.
* Cold air drafts and infiltration of dirt and contamination from outside.
* Difficulty opening or closing exterior [link widoczny dla zalogowanych] between the building and the outside environment or from one building area to another. This may be accomplished in three ways:
- Constant air supply with variable-speed exhaust;
- Variable air supply with constant-speed exhaust;
- Variable Return-Air.
Constant air supply with variable-speed exhaust [link widoczny dla zalogowanych] is recommended where a hot or [link widoczny dla zalogowanych] contaminated environment [link widoczny dla zalogowanych] must be ventilated while maintaining room pressure. Unit may be interlocked to that it only operates with the exhaust system.
Variable Air Supply with constant-speed exhaust may be preferred where fume exhausters or fume hoods are used to provide critical ventilation of contaminants from a ?clean? environment while make-up air is used to maintain a positive pressure to prevent infiltration.
In either case, when the system is enabled, a pressure sensor in the building space monitors room pressure. When a high or low pressure reading is detected, the air supply or exhaust is adjusted to compensate.
When controlling [link widoczny dla zalogowanych] a Variable Air Supply unit (or VAV Unit - Variable Air [link widoczny dla zalogowanych] Volume), two methods are available:
- Damper Control - Unit discharge [link widoczny dla zalogowanych] damper is adjusted using the damper motor.
- VFD (Variable Frequency Drive) ? Controller adjusts the speed of the blower motor Discharge Damper adjustment is an older method of controlling discharge air volume. Its main advantage is that it only requires positional control of a small discharge damper motor. The major disadvantage is the wasted Horsepower of the blower motor at lower delivery rates.
In recent years, fan speed control using VFDs has become economical. In this application, a standard energy efficient motor is usually adequate down to 75% of normal [link widoczny dla zalogowanych] motor speeds. For a fan speed down to 25%, a premium efficiency motor is required. Inverter duty [link widoczny dla zalogowanych] motors are not usually necessary since at 25% of normal fan speed, air delivery is minimal.
Variable Frequency Drives are also programmable. They are used to provide soft starts and to ramp motor speed up or down in response to signals from the control system.
Finally, in a generally ?clean? environment without a critical need to remove large quantities of contaminants, a simple solution to [link widoczny dla zalogowanych] building pressurization is a Return Air Unit with the return air damper motor controlled by building a pressure sensor. When building pressure increases, more inside air is returned through the unit, relieving the pressure. [link widoczny dla zalogowanych] When building pressure falls, more outside air is supplied to the building in order to ?pump up the pressure?. Precise control of building pressure by a single piece of equipment can thus be achieved.
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Additional information can be found at the Canada Blower company web site Oleg CthetchelIndustrial Ventilation Systems DesignerCanada Blower Co.