Broan make up air damper?

cottonpennyJanuary 2, 2012

I was doing some research to see if make up air would be required in my area...We are in PA and from what I can tell, make up air is required over 400 CFM. So, yes.

Found this system: Broan make up air damper. One website says the cost is between $125-$300 which seems really reasonable - much more than this site had led me to believe? I guess it only works with Broan hoods though?

Am I missing something here?

Here's the Broan website: http://broan.com/display/router.asp?ProductID=100744 (sorry, I don't know how to make it clickable)

And below the appliance site that talks about cost.

Here is a link that might be useful: Appliance site quoting cost

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colin3

The simple direct-wired versions of this damper just need standard household AC to work (they come with a step-down transformer). So they will work with any hood as long as you can get whatever turns on the blower to turn on the damper at the same time. It's a switch question.

The fancier "LinkLogic" versions looks proprietary to Broan.

The 6" and 8" damper units themselves are available for less than $100 online.

    Bookmark   January 2, 2012 at 12:45PM
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cottonpenny

So why is make up air considered so expensive then?

    Bookmark   January 2, 2012 at 1:34PM
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colin3

Other forum participants know much more than I do. But until they show up:
1. Unless you're DIYing it, you'll still have design and installation costs.
2. Commercial MUA systems are typically active: a blower to pump in as much air as is being pulled out, and often a heater to warm that air when it's cold. This runs to thousands of dollars. The Broan units are passive: just a vent that opens to the outside. Broan seems confident these meet new residential codes. Some HVAC professionals are skeptical that passive units are effective.

    Bookmark   January 2, 2012 at 2:23PM
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cottonpenny

Interesting. Maybe that explains why my builder sort of said NBD when I brought up MUA.

    Bookmark   January 2, 2012 at 3:36PM
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kaseki

The goal of such codes is to keep the house pressure from falling too much (relative to the outside) for proper combustion appliance exhaust flow. For some such appliances, the pressure drop that causes backdrafting is quite small.

The Broan unit may meet code because such codes are generally written without addressing the actual issue nor considering all of the factors involved in meeting the goal.

One could, for example, have no combustion appliances, say by using electric heat and dryer. Then the Broan meets code at a very low cost and is effectively irrelevant to the backdraft issue.

One could also have combustion appliances in a sealed room with its own source of air from the outside. MUA is again irrelevant to the backdraft issue. It would potentially be relevant to avoiding MUA by wall leakage.

A passive system will have a pressure drop. Whether this drop has any backdrafting effect on combustion appliances has to be evaluated. In general, filtering the MUA will cause a pressure drop that would, by itself, cause backdrafting in some combustion appliances. However, blower augmented oil burner furnaces can perhaps operate at this pressure loss if not too large (hood cfm is modest). Even oil furnaces will backdraft with passive MUA at higher hood cfm levels.

Where complexity (and cost) really become manifest is where the hood cfm is large and variable, there may be a second exhaust that is large and variable, some number of bathroom exhaust fans that may be on or off, window opening variability, fireplace in use or not, etc. Such conditions make the correspondence of primary hood motor drive and actual MUA required relatively weakly correlated. Then closed-loop active control of MUA is needed via electrical or pneumatic components.

kas

    Bookmark   January 2, 2012 at 7:08PM
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lori_inthenw_gw

Kaseki, are you saying this type of system might be adequate in a tight house with an open floor plan if it is all-electric? (We will have a woodstove, however).

    Bookmark   June 29, 2013 at 1:08PM
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