Control Damper Leakage
Control Damper Leakage
(OP)
Hello Everyone,
I am currently working on a project which utilizes two air handling units. One is for the main building and the other is a dedicated unit for a lab space. If the lab AHU were to go down the main building unit ramps up and opens a control damper in a crossover duct to feed the lab space. The system works great, the only problem is that during normal operation we are seeing 1500 CFM (around 23%) loss down 50 LF of duct from the air handler. We have done extensive duct sealing and the only potential source of leakage left is the control damper in the crossover duct (the lab AHU is at a greater static pressure than the main building AHU). Does anyone know how well a control damper seals when it is fully closed? Is there a better alternative than a control damper?
Thanks Guys
I am currently working on a project which utilizes two air handling units. One is for the main building and the other is a dedicated unit for a lab space. If the lab AHU were to go down the main building unit ramps up and opens a control damper in a crossover duct to feed the lab space. The system works great, the only problem is that during normal operation we are seeing 1500 CFM (around 23%) loss down 50 LF of duct from the air handler. We have done extensive duct sealing and the only potential source of leakage left is the control damper in the crossover duct (the lab AHU is at a greater static pressure than the main building AHU). Does anyone know how well a control damper seals when it is fully closed? Is there a better alternative than a control damper?
Thanks Guys





RE: Control Damper Leakage
rmw
RE: Control Damper Leakage
Another problem might be the lack of operator motor torque required to fully shut the damper. Also there can be slop in the linkages, loose brackets, control problems etc. that prevent full closure. Do you have pneumatic or electrical operators?
RE: Control Damper Leakage
If it is a new construction, check what type of damper was specified and then verify that that is indeed the type installed. In a system isolation situation it should be a low leakage type damper with blade seals and rated for the appropiate static pressure that it will need to contain.
Also check the damper for damage. Bent blades, torn or missing seals or debris stuck in the damper can impair it's function. If an access door was not installed in the ductwork to acess the damper, it isn't much of a job to cut a hole and install one to look at the damper.
RE: Control Damper Leakage
It is a louvered damper which is electrically operated. All the duct work is new and we have cut an access door to check the damper for any visible problems (we didn't see any).
I will have to check with our Sheetmetal contractor to see what was actually installed but the plans call for a motorized isolation damper to be installed at the cross over duct. From what you guys have said it sounds like they either installed the wrong damper or the one that was installed was not designed to prevent leakage (low leakage damper).
Looks like I have some more research to do.
Thanks again