VCD installation

[jacob2017]

Please any one help me on this .

AS shown in attached file, if i have two branch duct; is it required to install VCD in both branch or one is enough.??

Thank you in advance.

Just for info- the selected Diffuser has damper and a equaliser

 

[dbill74]

No file attached.

 

[willard3]

To start with, is a VCD a volume control damper?

 

[Ziggypump]

Required, probably not. To make life easier for the balancer, YES.

 

[lilliput1]

Know that the system to be balanced must have the pressure drop from the fan discharge to each branch outlet equal the worst case duct run pressure drop. All of the runs terminate at the space essentially at the same atmospheric pressure. Thus volume dampers are required to kill the excess pressure available in each run. Throttling the air would be noisy if large pressure drop is required. So it is not good to just use the volume damper at the supply register or diffuser. Typically it is good to provide volume damper at each branch connection to the supply and return air riser. They would allow isolation of a floor for renovation. Also it provide a good boundary reference to designate duct pressure class construction. For example it can be scheduled that supply duct portion from the air handler to the bottom of the riser and to the volume damper at each floor level would be 6"wg pressure class. Branch main supply air duct from volume damper at riser branch to variable volume box to be 3"wg pressure class. Supply duct downstream of variable volume box to be 1"wg construction. Now since VAV boxes are rated up to 3" you have to check their noise. If to noisy put a volume damper upstream of the VAV box so the VAV box would only need to throttle say 1" wg.