# 606.2.2 Common supply and return air systems.



## mtlogcabin (Mar 9, 2015)

Designer is asking the following

"I have a project with a number of  heat pump units that are typically less than 2,000 cfm; but, they share a common ventilation duct connected to the return air inlet on the heat pumps.  Would this arrangement constitute a common supply or return air system per 606.2.2?"

The concern is if the ventilation unit on the roof is not running then smoke from one area served by one heat pump could be drawn through the common ventilation ducts connected to the other return ducts and be in violation of the intent of 606.2.2.

What do you think?

2012 IMC

606.2.2 Common supply and return air systems.

Where multiple air-handling systems share common supply or return air ducts or plenums with a combined design capacity greater than 2,000 cfm (0.9 m3/s), the return air system shall be provided with smoke detectors in accordance with Section 606.2.1.

Exception: Individual smoke detectors shall not be required for each fan-powered terminal unit, provided that such units do not have an individual design capacity greater than 2,000 cfm (0.9 m3/s) and will be shut down by activation of one of the following:

1.	Smoke detectors required by Sections 606.2.1 and 606.2.3.

2.	An approved area smoke detector system located in the return air plenum serving such units.

3.	An area smoke detector system as prescribed in the exception to Section 606.2.1.

In all cases, the smoke detectors shall comply with Sections 606.4 and 606.4.1.


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## cda (Mar 9, 2015)

Looks like they need shut down

If you have a commentary it kind of shows what you are looking at


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## north star (Mar 9, 2015)

*& = & = & = &*



I agree with ***cda***........I believe that you DO have a Common Supply &

Return system.

One of the Exceptions that provides "shut down" to each unit should provide

you with a compliant solution.



*& ~ & ~ & ~ &*


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