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Return Ducting
- Thread starter hvacers
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- #3
hey willard,
could you explain your objection to ceiling plenum return. these are the most common return air paths here in australia for large office building, probably due to the ease of doing fit-out, no real problems in balancing that I have come accross. thanks
could you explain your objection to ceiling plenum return. these are the most common return air paths here in australia for large office building, probably due to the ease of doing fit-out, no real problems in balancing that I have come accross. thanks
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- #6
ChrisConley
Mechanical
Locate ceiling returns in every space that is seperated. Size the returns generously, based on the expected airflow. Use manufacturer's charts. Eggcrate style is typically acceptable.
We typically provide a return air 'boot' on the grille to minimize crosstalk, and for visuals. Double check your return air path, and provide transfer grilles as required to get the air back to your air handler.
We typically provide a return air 'boot' on the grille to minimize crosstalk, and for visuals. Double check your return air path, and provide transfer grilles as required to get the air back to your air handler.
Waramanga
I was retained to trouble-shoot a plenum return system that was less than a year old. I took the balance report which showed cfm readings that mimicked the contract documents. The balance contractor and I read all the diffusers and the actual reading variance was way above 50%. The balance report was obviously done without reference to the actually-measured cfm's. I have seen this many times.
We took down the ceilings and added a ducted return and variance was less than 10%. Any place where air delivery is important, as in an hospital, return plenums are a disaster.
I was retained to trouble-shoot a plenum return system that was less than a year old. I took the balance report which showed cfm readings that mimicked the contract documents. The balance contractor and I read all the diffusers and the actual reading variance was way above 50%. The balance report was obviously done without reference to the actually-measured cfm's. I have seen this many times.
We took down the ceilings and added a ducted return and variance was less than 10%. Any place where air delivery is important, as in an hospital, return plenums are a disaster.
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