Posts Categorized: Ask DAC

Ask Rick: Lab Exhaust Fans | Vibration Isolation for Strobic Air Tri-Stack Fans

Q.  We are recommending high plume dilution lab exhaust fans from Strobic Air for a project.  What would you recommend for vibration isolation?   A.  Strobic Air recommends that the Tri-Stack Fan be mounted on a 1½” wide strip of ¼” neoprene pad.  No further vibration isolation is required or recommended. Tri-Stack fans are balanced… Read more »

Ask Rick: Energy Recovery Wheel | Question on ANSI/ASHRAE Standard 62.1-2010

Q.  It appears that the ANSI/ASHRAE Standard 62.1-2010 restricts the use of wheels for lab use.  Is this the correct interpretation?   A.  As it stands ANSI/ASHRAE Standard 62.1-2010 is not clear on the question of Class 4 exhaust (which includes lab fume hood exhaust).  The standard reads as follows: Class 3 air shall… Read more »

Ask Rick: Glycol Run Around Loops | Why do we not use Ethylene Glycol in the USA?

Q.  Why do we not use Ethylene Glycol in the USA? A.  Great Question.  We use pumped glycol energy recovery systems all the time here in the United States.  Up until recently we have almost exclusively used Propylene Glycol.  Ethylene Glycol had not even been a choice.  The biggest reason for this is that Ethylene… Read more »

Ask Rick: Pumped Glycol Systems | Does Air in the Glycol impact performance?

Konvekta Pumpd Glycol Pumping Package

Q.  I have some questions about pumped glycol systems.  What happens if all the entrapped air is not removed from the glycol?   Should a closed loop have auto bleed? A.   Air bubbles entrapped in the glycol circuit are very detrimental to the thermal performance of the energy recovery system.  It causes the heat transfer… Read more »

Ask Rick: How does a high pressure atomizing humidifier work?

High Pressure Humidification Spray

Q.  How does a high pressure atomizing humidifier work? A.   Atomizing humidifiers like the Carel humiFog systems utilize a high pressure (1,000 psi) pumping system to pressurize treated water and pump it to atomizing nozzles.  The nozzles then reduce the water jet into a very fine water droplet (10-20 microns).  Due to the fine droplet… Read more »

Ask Rick: Pumped Glycol Energy Recovery | Pressure Drop for Konvekta Coils?

Q.  What is a typical pressure drop across the Konvekta coils? A.  The air pressure drop across the coils depends on several factors: number of rows, air face velocity, fin spacing and tube alignments. There is a trade-off between thermal efficiency and air pressure drop which will be one of the design considerations if we… Read more »

Ask Rick: Lab Exhaust Fans | Lab Exhaust Stack vs. Air Intake Location

Q.  The commissioning engineer has commented that the Heat Recovery Unit (HRU) does not meet the 25’ separation distance between the Intake hood and Exhaust Discharge requirement.  I believe that our design with the effective plume height of 44’ and the fan discharge 16’ above the inlet of the intake hood is better than a… Read more »

Ask Rick: Lab Exhaust Fans | What Standards to reference for Lab Exhaust Fan design?

Q.  I am designing a lab exhaust system and using Strobic fans. What standards, both ASHRAE and otherwise, should I be using as a reference? A.   Below are a list of standards related to laboratories and laboratory ventilation: NFPA-45 – Fire Protection for laboratories UL 705 – standard for Power Ventilators in accordance with the… Read more »

Ask Rick: High Performance Fume Hoods | Are Pass Thru Fume Hoods considered High Performance Hoods?

Q.  Are pass thru fume hoods considered ‘High Performance Hoods’?   A.  Pass Thru Fume Hoods are not high performance hoods.  Under good conditions, with one sash open between 12” and 18”,  the hoods can contain at lower velocities.   But, performance is different for each installation and dependent on lots of variables.   To achieve maximum… Read more »