![]() ![]() Static pressure testing can help reveal the answer to this intermittent issue. As the filter starts to load up with dirt or is replaced with a more restrictive media such as a pleated filter, the problem seems to mysteriously disappear. When the filter is new, there is more pressure in the return side causing ducts to “oil-can” each time the fan comes on. One of the most common variables in the oil-canning ducts is the air filter’s condition. Excessive static pressure can cause movement in metal duct as the blower in the air handling equipment begins to move air. One such condition is created when undersized ducts are installed. You can usually track down this problem with a good ear, but what about those times when the source isn’t as obvious? Many of us have dealt with panned floor joists making a “kerplunk” sound as they are walked on. When a duct system is subjected to certain changing pressure conditions, the noise sounds like pressing in on an oil can. You can also reference the manufacturers noise criteria (NC) rating of the grille or register in question. Design supply registers for a face velocity under 500 fpm and return grilles in the 300–500 fpm range to keep the system quiet. Pay attention to the desired airflow from a grille or register and make sure it’s within acceptable velocity limits to keep the hum from occurring. If the branch duct connection at a boot or can is out of alignment, sound levels can also increase as much as 12 dB due to the increased turbulence. As air passes though these vanes, a hum is produced. Poorly selected grilles and registers can cause excessive air velocities through the vanes. If it’s one of those days, you may need to cut into the duct system to isolate and repair the offending damper. If you’re lucky, the thumb screw on the damper assembly is loose and just needs tightening. The most common sources are typically associated with air noise made from balancing dampers, grilles, and registers.īalancing dampers that contact the inside of metal ducts are known to rattle as air passes across them. In the late 1980s, the band U2 released the album “Rattle and Hum.” While it was popular back then, it’s an unwelcome sound when coming from many HVAC systems. I hear that technicians place a bounty on the heads of those who mastic these panels shut. Whatever you do, don’t mastic the blower door or coil access panel. #Hvac trminal equipment definition install#You can install gaskets on any removeable service panels to minimize noise. In some instances, you may need to add return ducting to reduce fan generated noise.ĭuct leaks close to the equipment can also cause jet engine noise as air passes through panels. You can still have this problem on a properly sized duct system if the blower inlet is too close to the return grille. If you have a platform return, use sound-deadening materials like ductboard or internal liner inside the return cavity to absorb and deaden the noise. Otherwise, downsizing equipment can help lower decibels. If it’s a system you’re servicing or maintaining, duct upgrades may be in order if the equipment is sized correctly. The jet engine noise usually isn’t an issue when the duct system is sized correctly before installing ECM equipment. Duct leaks close to the blower assembly.Electronically commutated motor (ECM) blowers on undersized duct systems.If you find your customer turns up their television or yells during conversations, they might be dealing with “jet engine noise.” It’s often tied to fan-generated noise when the blower is on. ![]() While an HVAC system might not get that high, the same nuisance is often experienced. ![]() ![]() To keep it in context, a jet engine taking off from 200 feet away is equivalent to 130 dB. Most airplane passengers put on noise-cancelling headphones to avoid this nuisance. One of the obvious HVAC sounds that drives people crazy is jet engine noise. As you test, keep a look out for these annoying sounds an HVAC system makes. Try it out and give your customers a gauge on how loud their system is. #Hvac trminal equipment definition download#Introductory level sound meters are inexpensive, but if you have an iPhone, you can download the free NIOSH sound level meter app. I provided these examples for reference in case you decide to check them out.
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