# Gimmick or Progress? The Smart Vent by Keen.



## isipwater (Nov 20, 2015)

I recently came across a new company called Keen, selling an "innovative" product called the "Smart Vent."

Is it a Gimmick or Progress?

Others (perhaps the HVAC "establishment") are quick to point out that the smart vent may damage heating/AC systems.

Is this a classic case of the old guard trying to protect it's turf (not wanting to lose business of zoning systems)?

Or

Has Keen made a useful product?

You decide. I am curious to hear your thoughts?

Check it out here: http://www.keenhome.io/


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## Where2 (Nov 20, 2015)

Never going to work in my house. Replacements for my 12" round ceiling A/C vents (yes the Jetson's version from 1962) aren't offered.

Not sure how my central A/C and heat air handler would like having the duct output throttled like those vents are trying to do. In many cases, I can do the same thing by shutting the door to a particular room.


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## isipwater (Nov 20, 2015)

Where2 said:


> Never going to work in my house. Replacements for my 12" round ceiling A/C vents (yes the Jetson's version from 1962) aren't offered.
> 
> Not sure how my central A/C and heat air handler would like having the duct output throttled like those vents are trying to do. In many cases, I can do the same thing by shutting the door to a particular room.


Yes, the sizing won't work.

So, I do wonder if they will cause damage to an HVAC system.  They are not cheap.


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## woodgeek (Nov 20, 2015)

Studies have shown that doing zoning by closing registers on forced air systems doesn't decrease overall energy usage.  Many ducts leak enough that the increased back pressure causes more leakage, as well as more blower energy.

So if you want this to get comfort, sure, but don't expect it to pay for itself in energy savings.


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## isipwater (Nov 20, 2015)

woodgeek said:


> Studies have shown that doing zoning by closing registers on forced air systems doesn't decrease overall energy usage.  Many ducts leak enough that the increased back pressure causes more leakage, as well as more blower energy.
> 
> So if you want this to get comfort, sure, but don't expect it to pay for itself in energy savings.


Right, if it is going to exacerbate existing leaks, it makes no sense from a cost perspective.

Let's say you have no duct leaks, do we think it would decrease the heating and cooling bills?


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## woodgeek (Nov 20, 2015)

It might save a small amount, but how do you know you have no duct leakage?


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## isipwater (Nov 20, 2015)

woodgeek said:


> It might save a small amount, but how do you know you have no duct leakage?


That is what I am wondering.  I really don't know. I just moved into a house with ducts for the first time. My other two homes that I have owned had none.


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## woodgeek (Nov 21, 2015)

Don't waste your time or money.  There have been scam devices like these for years...and the verdict is NO.


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## velvetfoot (Nov 21, 2015)

Do modern furnaces have infinitely variable ECM fans now?  I can see the ECM fan varying its speed based on back pressure, like an auto pressure circ pump supplying zone valves.  Come to think of it, zoned hot air systems are now common, no, and wouldn't the furnace fan have to react similarly?  I admit, I don't know how they work.


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## isipwater (Nov 21, 2015)

woodgeek said:


> Don't waste your time or money.  There have been scam devices like these for years...and the verdict is NO.


Have there been products like this before that are Smart?  Each vent talks to each other and are controlled by sophisticated temperature and pressure sensor algorithms.

If the Keen system is a gimmick I am ready to recognize that. However, perhaps this is progress and a clever way of tackling this heating and cooling problem.


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## isipwater (Nov 21, 2015)

velvetfoot said:


> Do modern furnaces have infinitely variable ECM fans now?  I can see the ECM fan varying its speed based on back pressure, like an auto pressure circ pump supplying zone valves.  Come to think of it, zoned hot air systems are now common, no, and wouldn't the furnace fan have to react similarly?  I admit, I don't know how they work.


Yes, exactly, this is what I am wondering. 

Will a modern variable speed system adapt and work in harmony with the Keen system or will it end up creating bigger problems than it solves.  I have read lots of reviews and comments on the reviews for the Keen system and can't make up my mind. Those who are against this new system seem to come from the old HVAC establishment and come wiht a bias for their businesses not to be disrupted by new technological advancements such as this.

For me, I am still undecided


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## semipro (Nov 21, 2015)

I can't see how they would work well give that the temp sensor is on the register itself.  You need to know room temp not register temp.  I think hysteresis would be a problem.  Maybe if they included wireless temp sensors for each room that could be placed on a far wall.
I don't think the air handler would be an issue especially if a variable speed unit.  Otherwise, all the vents could be programmed to maintain a threshold overall flow.  Duct leakage is a problem but if ducts are within the living space not so much.
There's another system that uses inflatable bladders that can be placed inside ducts just off of trunk lines.  The supply air hoses are routed back through the ductwork to the air handler.  Each bladder is inflated/deflated by a central controller to change zone flow.  This makes more sense to me since it minimizes duct pressurization and related losses.
There are, of course, inline dampers with motorized doors that can be centrally controlled also.

Just shutting the door to a room results in room pressurization and increased leakage.  Makeup air coming in elsewhere needs to be heated/cooled. It would be better to shut off flow to the room using a damper located as close to the air handler as possible.


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## isipwater (Nov 21, 2015)

semipro said:


> I can't see how they would work well give that the temp sensor is on the register itself.  You need to know room temp not register temp.  I think hysteresis would be a problem.  Maybe if they included wireless temp sensors for each room that could be placed on a far wall.
> I don't think the air handler would be an issue especially if a variable speed unit.  Otherwise, all the vents could be programmed to maintain a threshold overall flow.  Duct leakage is a problem but if ducts are within the living space not so much.
> There's another system that uses inflatable bladders that can be placed inside ducts just off of trunk lines.  The supply air hoses are routed back through the ductwork to the air handler.  Each bladder is inflated/deflated by a central controller to change zone flow.  This makes more sense to me since it minimizes duct pressurization and related losses.
> There are, of course, inline dampers with motorized doors that can be centrally controlled also.
> ...


Well said. I think the attraction of the keen system is the simple install, but it probably not the best designed solution for this particular problem.


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## woodgeek (Nov 21, 2015)

ECM blowers have nearly constant CFM as a function of back pressure compared to the older type.  So, the cfm in other vents goes up when you close some, as does the power consumption of the blower.
The many other devices I saw that did this were not 'smart'.
If you have a good thermal envelope on the house, cutting off the heat to one room should not decrease its temp very much, and thus won't result in much savings even in principle.
If you have comfort issues...like some rooms are always too hot, or balance across house is bad, have an HVAC tech balance the system properly.
Of course,, there will always be some weird situations where this is handy, like a chilly three season room with a tie-in to the central HVAC that gets opened and closed manually, and takes a long time to warm up.  The smart functionality (presumably including timing) could allow it to be warmed up when needed.


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## begreen (Nov 21, 2015)

A properly installed HVAC system is balanced. Artificially closing off vents can upset that balance and cause the blower to race. Reduced blower life may happen in this case.


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## velvetfoot (Nov 21, 2015)

I have a friend who has like, 5, zones in his Carrier Infinity system.  It wouldn't seem logical that the ECM motor would target a constant system CFM.


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## woodgeek (Nov 22, 2015)

A zoned system would have a blower speed control board that ramped the ECM up and down depending on how many zones were open.


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## velvetfoot (Nov 22, 2015)

Exactly.  Perhaps these things could play nicely with a new system.


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## woodgeek (Nov 22, 2015)

The high end products from the HVAC cos all use custom controls that often don't work standard 24VAC thermostats.  I think it highly unlikely the Infinity system would interface with a third party gizmo.  If carrier wanted this funtionality, they would sell their own smart vents.

IOW, I assume the zoned systems have a central control board that commands the zone dampers and ramps the cfm through wired connections, all configured at install.  I don't think the blower is simply configured with a pressure sensor to regulate the cfm, decoupled from the zone control board.


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