Medium pressure ductwork

[Kmann444]

How do you lower medium pressure ductwork to low pressure ductwork

 

[zeusfaber]

Would you like to clarify what you want to do?

Connect a low pressure service to a medium pressure supply, using a suitable pressure reducer?

Redesign a system so it doesn't need medium pressure ductwork any more?

Recertify ductwork that was originally designed for medium pressure service for use at low pressure (perhaps with revised maintenance and inspection regime)?

Something else?

Suggest you also put numbers to your pressures and say what part of the world you're in - this is an international forum and terminology and rules both vary widely around the world.

A.

 

[Kmann444]

Hi
I am a job to relocate ductwork for an office alteration in New Jersey. The ductwork is supplied from a large rtu. There no plans I field measured the existing duct layout and saw two duct runs. The branches from primary duct went through a pneumatic air valve to reduce the pressure. The secondary ductwork was duct board and flex to offices
They need to add some more zones from primary duct. I was looking for information on how to do it. The system is 40 years old

 

[MJCronin]

Relocate and redesign 40 year old ductwork ???

In New Jersey ???

.... and it appears that you have never done this before ???

Does your Project Manager have an MBA ?

MJCronin
Sr. Process Engineer

 

[drawoh]

Kmann444,

Make the duct bigger, reducing the air velocity and the head losses. This is very basic fluid mechanics.

--
JHG

 

[Kmann444]

Above not the answer
Pneumatic air valves are reducing the air pressure to low pressure .
Does a vac box do the same thing

 

[drawoh]

Kmann444,

How do pneumatic air valves reduce pressure other than by reducing airflow?

--
JHG

 

[FacEngrPE]

There are all sorts of ways to get in trouble with this.

Pneumatic regulator can be used to drop pressure so the ductboard is not over pressurized. Self contained pneumatic regulators for HVAC systems are very old school, for the most part obsolete no parts available. You should attempt to verify the devices function before designing a system around it. If you are adding zones replacing the pneumatic regulator (if it is needed at all) should become part of the Controls Contractors scope of supply.

I would not be too surprised to find self contained duct pressure powered drop in air terminal units were originally used to zone the system. The repair parts for these are also hard to find.

Fibrous Glass Duct Construction Standards, 8th Edition has the information that will allow understanding what the pressure limit of your duct board system is, and will show if stiffeners are needed.

You should consult with the Air Balancing expert that will be involved in tuning the system after it is modified. He likely needs information that does not exist yet that you will need to create to get the duct system changes sized correctly.

 

[Kmann444]

a company called tek-air that can supply the air valves . they said special order
i added notes for operation of existing valves to be verified and system during renovation
you are right about it being an old system. they are planning to reuse as much as possible
can Vav box be used instead of air valve.