Engineered Systems - February 2009 - (Page 29) COTTONWOOD FILTER SCREENS The supply air rh sensor needs py to be reliable or it will saturate one day when too much moisture hits it, and never recover. The high-limit rh l sensor should be a manually operated device that only provides a relay dry-contact c output to open the control t t circuit. The return or exhaust air rh sensor is probably the h bb most critical since it is the one d h tl d used for rh control in the end. As a consultant who looks at mainly retrofit projects in health care and other commercial and institutional buildings, I have seen numerous abandoned humidification systems that were either too difficult or too costly to maintain and control. ™ KEEP COOLING SYSTEMS CLEAN ALL SEASON LONG ”The Green Way to Keep HVAC and Cooling Tower Systems Clean and earn LEED Credits” Stops Airborne Debris Before It Can Become a Problem! Mount over Intake Openings (Stops debris at entry point) Low Static Pressure Impact (>1/10th w.g. drop @ 600 fpm) Clean with Broom, Brush, Shop Vac. or Garden Hose Doesn’t Require Removal for Cleaning Reduces / Eliminates Cleaning Chemicals (Eco-friendly) Saves Energy (Equipment operates clean all season long) Reduces Maintenance Time & Cost (up to 75%) Helps Attain LEED Credit Points (in multiple categories) Resists Mold, Mildew, UV and Flames (self-extinguishing) 15+ year service life For More Information Contact: Air Solution & Newway Company Tel 513-860-9784 or 248-676-9418 www.airsolutioncompany.com Input 193 at www.esmagazine.com/instantproductinfo AT THE VERY LEAST So if you plan to maintain acceptable control of temperature and rh in a critical space, at the same time controlling operating and maintenance ESM03084AirSol.indd 1 2/19/08 1:40:27 PM costs over the long term, then what do you need to do at minimum? The minimum number of control elements required are actually more than you may think or want. You need a reliable source of steam, a good control valve that is sized well to supply only the minimum The experts in stainless requirement at the peak conditions, and at least three and perhaps steel clean air systems four rh sensors — a supply air humidity duct sensor to ensure you don’t overspray the air, a high-limit rh sensor mechanically interfor waste water locked to the control valve to cut the humidity supply in case of a failure, a return or exhaust air duct sensor, and possibly a space rh sensor treatment facilities, to reset the supply rh. Figure 2 illustrates the required elements. plus: Of course, the whole thing will be controlled from the building • Custom fabrication control system, and appropriate failsafes and alarms need to be set up • Rush deliveries to capture potential problems. And naturally, each control element will have its own challenges during its lifetime (which needs to be as long as possible). The supply air rh sensor needs to be reliable or it will saturate A-J Manufacturing offers a complete line of custom one day when too much moisture hits it, and never recover. The highand standard stainless steel air distribution products, all limit rh sensor should be a manually operated device that only provides designed and manufactured to offer durable, dependable a relay dry-contact output to open the control circuit. The return or and low maintenance performance necessary for waste exhaust air rh sensor is probably the most critical since it is the one used water treatment facilities. for rh control in the end. Use a high-quality sensor for this — even if it What’s more, with our state-of-the-art manufacturing costs $1,000, it will pay for itself easily in a large system. capabilities, we can also offer you the industry’s shortest The supply air rh sensor is often used to control the steam valve, but lead times for custom orders. So for continuous linear, it is ultimately reset by the return/exhaust air element. Unless the OR security grilles, modular diffusers and much more, contact has independent humidity control, the rh sensor in that space will just A-J Manufacturing today! be an indicator of conditions. Keep in mind that if the space is cooler than average return air, the rh may be quite a lot higher, which is yet another reason to keep rh levels at minimum acceptable in the supply. The use of these systems is obviously very seasonal, so it is a good idea to isolate the whole system back at the source in early spring so 800-247-5746 • www.ajmfg.com that no heat is wasted. Just letting the control program shut the valve When it has to be stainless, it has to be A-J! A-J Manufacturing Input 13 at www.esmagazine.com/instantproductinfo w w w. esmag a zin e. c o m ES02084AJWasteWater.indd 1 29 12/13/07 2:37:23 PM http://www.airsolutioncompany.com http://www.esmagazine.com/instantproductinfo http://www.ajmfg.com http://www.esmagazine.com/instantproductinfo http://www.esmagazine.com
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