I would think this is the last thing you want.. Typically in an exhaust scenario you want as much CFM as you can get (up to the limit set by the selection of the duct size) regardless of what the pressure balance is. All you're doing by adding a balancing valve, whether it adjusts electronically or however this thing adjusts, is throttling flow volume down.

Well, you need balancing or some form of flow control if you have multiple exhaust locations....

Note those analog-automatic balancers have a very narrow pressure range within they say they maintain a specific flow. If you want more control, you could use an air-valve, like the Accutrol. that way you also get a flow reading for verification. It all really depends on the application and how you want to operate the system.

Right. I was assuming this was in addition to a standard manual damper for balancing... ie it would only ever reduce flow. I'm missing why that would be a useful feature.

it would be useful in at least 2 ways:
- you don't depend on a balancer-person to manually set the flow and someone later inadvertently tempering with the balancing damper
- when system pressure changes (we don't know the rest of the system), you still would have the design flow.

Like if you have a VAV EA system and than tone zone needs constant flow. I never used one of those. To me they are a cheap replacement for using an airvalve. I would feel more comfortable with an airvalve since the BAS can show me the actual flow.

Quote (EnergyProfessional)

- you don't depend on a balancer-person to manually set the flow and someone later inadvertently tempering with the balancing damper

The device linked still has a manual setpoint adjustment, which must be set.

Quote (EnergyProfessional)

- when system pressure changes (we don't know the rest of the system), you still would have the design flow.

Fair point here.. but unless I'm misinterpreting OP's description, we're talking fart fans here, not main building exhaust. If adding another device in the duct, with all the associated costs and maintenance, actually worth it to prevent a toilet exhaust from pulling an extra 5 CFM for the half hour a day that someone is in the shower?

SwinnyGG:

But any idiot that can read numbers can set it. No need for an (often inaccurate) flow measurement. The flowhoods balancers use aren't accurate and if there is more than one grille, they are useless since the hood itself limits the flow. So having a factory-set device isn't the worst out of many bad options.

I wouldn't use such or other device in a single zone (1 fan for one room) setup. That would be like driving a car full throttle all the time and regulating speed by applying the brake.
For that one just sets the fan speed for the desired flow and uses zero dampers.

I don't know the product, so I don't know how well it actually works. One drawback I see is that you don't see the setting from outside the duct. It looks like it gets set before the duct is installed and then you don't see the scale anymore. So if the installer sets it wrong or not at all, I won't be able to verify without removing the duct. Maybe someone who ahs experience with it can chime in.

Thank you all for your answers.

As I mentioned in my original post, the discussion came about regarding our future hotel tower toilets' exhausts. These will be central exhaust fans located in the mechanical floor on the top of building, serving several risers each, so each fan might serve 50+ rooms.
As such, some sort of balancing needs to be done to avoid that the toilets nearest to the fan have excessive exhaust while the ones farther away have deficient exhaust.

In our existing tower this was done with manual VCDs by a commissioning team pressed by everyone in a rush to open the hotel, so the result were below average, to be nice...
So we were looking to a better and more person independent solution knowing that when we are talking about hundreds of rooms, the toilet exhaust is the least of the commissioning team's worries in a rush to open.

EP:
Accutrol valves would be a nice addition, but it seems a little bit of an overkill for an application like this one and budget wise, would be prohibitive.

I think Accutrol would be too expensive for just hotel toilets. We use them where we actually have varying exhaust (e.g. some zones scheduled times, or EA is based on some IAQ criteria). One large issue with manual balancers is they don't iterate the balance. Once you adjust one damper, it impacts flow of all others again because the system automatically re-balances once to change one flow. Technically they should have to go through multiple times to minimize that. But they never do. So if these automatic valves actually work, they would work well. I would inquire how they deal with dirt over many years of operation.

I think installing these in place of manual dampers and expecting you can commission an exhaust system that serves hundreds of rooms without manually balancing, or at least verifying the balancing, of each room individually as you normally would is pure fantasy. Best of luck.

You still have to verify the flow, IMHO. But you don't have to do the iterative (and they never iterate!) damper adjustment. You also still want to adjust the central fan speed to be able to operate at the lowest possible speed while still providing enough flow in the critical zone. If those valves work as advertised, I see large labor savings and better result.

EP:
You hit the nail in the head. The iterative balancing is never done in a system like this, so after the first run, if there is one, the system stays like that for basically ever or when there is a problem in s specific area/room.

That is why this ABV system piqued my interest, as it seems fairly dumb-proof, maintenance "free" and eventually at a budget that the owner is willing to accept.
If in the limit after a few years it gets stuck with dirt and so on, providing it is installed in an accessible place, it might be fairly easy to clean/replace

Another thing that never gets done.... every few years you should re-commission the building and verify the flows. that way you find dirty/broken devices that over time change flowrates.

You have so little faith in your contractor that they won't balance a brand new HVAC installation that you're willing to install a brand new device, but you trust that they're going to correctly set up and install this device x500?

Well... ok.

You must be new to construction .... they do balance. But never to the standard SMACNA or other bodies require.
the more tasks you can take away from field staff, the better.

I can't list all the examples where the "balancer" didn't understand the difference between the geothermal loop and the hot water loop they were to balance because they didn't understand one device can be connected to multiple independent loops. Don't count on them knowing viscosity and density differences between water and glycol. Or standard air.

With balancers it isn't "trust, but verify". It is "don't trust and do verify"

It sounds like you've had to adapt to contractors who don't care much about the quality of their work. That's unfortunate for you.

I guess I'm coming from the standpoint of someone whose primary construction experience is in healthcare and critical industrial markets where balancing matters a lot, and we do it correctly. We iterate until every single location matches the design, without exception. This little device would save me nothing; if I used this in a healthcare environment I would still be required to manually verify every single grill flow rate, whether the product data on this thing says it's reliable against the device setpoint or not.

Are you a balancing contractor?

I don't work in healthcare and hope level of quality is higher there.

The sad thing about such balancing valves is, they save labor but cost more upfront. but the TAB contractor still will bid them the same way and the bid price for TAB won't be lower. So depending on what bid environment you are in, you should verify if the contractor actually accounts for potential savings. I'm in design-bid-build environment. So my design is completely done and reviewed by JHA before it goes out to bid and that is the first time contractors see it, and i have no choice in contractor besides whatever qualifications I require in the specs. In addition, I'm in a medium sized County with 500K capita. So I get to see the same contractors over and over. If your bid conditions or the market are different, everything can be different for YOU. I sometimes run "new idea" by some contractors i know to hear if they see it as a positive. but if you ask 5 contractors, you get 6 opinions.

I did state flow still needs to be verified (also for fan speed optimization). I also stated flow should be re-verified after a period of time (that applies to all systems)

SwinnyGG:

Now I understand better some of your comments.
You cannot compare the level of T&C required for healthcare, semiconductors, and other critical industries with hospitality.
I've worked in pharma industry many moons ago and even nowadays, many moons later, the T&C level on hospitality compared with what I was doing on pharma (which I would expect that became even more stringent since the time that I left) is like comparing a Wright brothers plane with an A380...

Apologize to you both if I came across as a dick in the thread..

But yes, the world I operate in is one where we don't half-ass balance the building and leave. For us the bone stock standard process is one where we extensively balance flows after equipment is commissioned in order to get CO for whatever building or space we're constructing, and then we spend a period of time after that (minimum is usually a couple of weeks but the length of this period scales with the size of the building) verifying, after end users are moved and and the building is operating, that all systems are functioning as they should under their actual live operating loads.

While I wouldn't expect contractors on hospitality projects to have that level of attention to detail, I would expect them to at least ensure they meet design. Overly optimistic on my part, I guess.

Obviously there are exceptions... but as designers we have to fight against a declining ability of field personnel. It seems systems get more sophisticated and field people less so. It is the same for cars etc. We went from repair to randomly replacing parts till the warning light stops.

With he decline of education (and willingness to learn) and retirement of many experienced techs this just will get worse no matter the industry. All we can do is move more work from the field to the factory. I'm not saying factory workers are more skilled than field workers. But at least they do the same thing all day and in a specifically designed environment. On the other hand, there is more crap coming out of factories nowadays as well. You can't win....

A hotel tower is actually a wonderful application for these automatic balancing dampers because the building pressure changes as the seasons change (stack effect) and the CFM required for hotel rooms is typically pretty low (about 30 CFM). If you just have manual balancing dampers then they would get out of balance between the lower and upper floors as the temperatures and wind changes outside.