Moved topic: Kaseki MUA

8 years ago

In a 2012 topic, http://ths.gardenweb.com/discussions/2243080/wall-mount-range-hood-or-under-cabinet-range-hood?n=4 juliano_moreira wrote today:

Hello Kaseki ! have you finished your project ? can you share what you ended up doing ?? :)

Because the answer to this question is off topic to the other thread, I have answered in this new topic.

-------

I just 98% finished a deck project, and finished (if that term ever
applies to gardening) some garden and lawn rearrangement projects, and
am engaged in some painting projects, but perhaps you are referring to
my kitchen ventilation MUA project, completion of which has been
deferred due to many other projects since 2012.

In the MUA case, without taking the space to
discriminate between completed, uncompleted, and yet-to-be-done aspects
of the project, the bullets below define the path from outside to
kitchen and control of water and air flow. Please note that every MUA
situation is unique, possibly requiring a unique solution, and that more
than one solution can be suitable for a given situation.

Due to
variability of ventilation flow among two kitchen blowers, and three
bathroom fans, while allowing operation of a fireplace, and avoiding oil
burner exhaust leakage (even with oil burner MUA), I need to keep the
internal house pressure near zero differential with the outside.

From the outside:

Empty
down-blast blower housing used as a air intake (looks like a big
mushroom) on roof over attic away from ventilation exhaust blower
housings
Ducting to an in-line blower in attic
In-line blower
Ducting to the air filter
Possible
motorized damper (the pressure drop across the air filter seems high
enough that household heat cannot flow upwards to the attic from natural
weak pressure changes
Pleated air filter in caddy
Hydronic to air heat exchanger (about 2 x 2 ft) (just above diffuser)
Ceiling diffuser (about 3 x 3 ft OD in hall leading to kitchen)

Control system for heat exchanger

A
larger version of the typical residential Taco hydronic circuit pump.
This is mounted with many other Taco hydronic pumps on a manifold
supplying heat to the house from an oil burner
One circuit from the two Taco multiple circuit control boxes in use
Taco
control for this circuit is established by the OR circuit made up of
two thermistor-driven relay modules (industrial thermostats). One
senses the temperature at the living area side between the diffuser and
heat exchanger and one senses the temperature of the heat exchanger
copper plumbing at the exchanger. The former is for air temperature
control and the latter is backup to avoid freezing. These have some
built-in hysteresis

Control system for the in-line blower

Differential
pressure is sensed between kitchen and attic. The attic is well
ventilated to the outside while protected from wind that would require a
very complex sensor to avoid erroneous pressure measurements.
Air lines from passive sensor housings lead to a pressure-to-current transducer within a control system
The
transducer generates a control loop current proportional to
differential pressure. This current is used to trigger relays for
enabling functionality, as well as drive a Fuji computer performing a
P-I-D control loop function
The computer in turn generates a control current to the MUA blower motor driver
Components for this loop (except the motor driver) are made up of DIN rail-mounted devices.

kas

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Comments (6)

avamom2012
8 years ago
I wouldn't expect anything but the best conceptualization as well as installation work from you, kas. Thank you for sharing the specific details of your heated MUA construction and implementation. I'm wondering if you might wish to share this for publication on http://www.greenbuildingadvisor.com, as so many of their readers as well as Martin Holladay would find this very helpful given the engineering complexity of residential heated MUA and green building of homes.

My own Broan Universal Make-Up Air Damper installation project was much simpler: a hole cut through side of house exterior brick with 8" round rigid ducts connecting to our main HVAC return. A Braun MUA unit on the return connects via 24V wiring to our Wolf vent hood (900 cfm) such that when it is turned on, the Broan damper is opened to pull air into the return and distributed through the house. Exhaust from the Wolf vent hood is to roof exterior, driven by a compatible Wolf exhaust fan. I haven't had any kinks in two years, minus recent fixing of a small opening in the exterior MUA duct. The MUA duct are in a conditioned crawl space in which I have installed lighting, as well as easy access, so as to keep an eye on the system. I also have a remote hydrometer in the crawl MUA duct area and check every so often on consistency of humidity/dew point (this is how, I believe, I picked up there was a small exterior MUA rigid duct separation and went and closed it). As to the metal screening over the exterior intake duct hole, I check that every couple of months by visual inspection and it is fine without holes and firmly attached. And there is draw. No filter further down the line so not to mess with the airflow dynamics. All in all, while tempered MUA is preferable, I feel I did well working with my permit office, with Broan and my kitchen GC to get a substantial 900 CFM MUA system installed. Btw, thank you, kas, for all the knowledge you have offered us. I have enjoyed reading every morsel and am glad to see this post.
kaseki
Original Author
8 years ago
So when the hood is running, the air flow direction in the HVAC return is (potentially) reversed by the MUA flow and air flows out of the HVAC return registers? (This is a clarification question, not a thinly disguised criticism; the likely distribution of return registers through the house should greatly minimize any cross drafts near the hood. Not knowing what the air flow rate of the furnace is, net direction of flow when the furnace is running is unclear.)

Before considering any publication, completion and testing are required. In particular, the purported ability of the Fuji computer module to self-optimize its PID parameters (where the complex-plane poles and zeros of its transfer function are located) is yet to be demonstrated, at least in the context of my application.

kas
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Thanks for your input kaseki. I wish I were an engineer and could give an actual figure on how leaky the house is, best I can say is VERY :). Along with the hole out the roof for the swamp cooler there are also (6) 8"X5" openings to the crawl space. The other gas combustion appliances (boiler and H2O heater) are in the utility room which accesses the crawl space. The utility room is also below the kitchen. As for the source of their make up air I'm unsure... kinda makes me wish I'd asked the tech. who installed the new boiler last year a lot more questions. So, thinking this through if we were to go with the 1200 cfm hood and connected a damper to a fresh air inlet (hole) to the outside and to nothing on the inside (as we have no forced air and therefore no ducting), the damper would open when I used the range vent and let in MUA for the time the range vent was in use, and close when it wasn't. Realistically, how much more air could it be pulling in than the 6 other holes in the crawl space and the one in the roof? hmmm. I'm probably missing something in my logic but it seems silly to have only 1 of 8 openings controlled unless it's absolutely necessary to have that 8th hole and it's in a location that I want to be able to shut is my thinking. Currently I have a non-functioning electric range with OTR MW recirculation hood (the catalyst for the whole remodel). Needless-to-say I'm excited to have proper range ventilation and want to do it right, but I'm starting to think that a damper for additional MAU might not be needed. I do know this, the 3 times a year my DH takes the time to get me a really good fire going, I'm sitting in front of it and am no where near the range. :)
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I suspect the 0.4 factor is intended to account for the fan/blower performance in realistic conditions, particularly conditions that correspond to the small amount of MUA that the formula requires. My comments here have usually assumed a factor of 0.67, but that approximation assumes that imperfect MUA won't lower the interior pressure more than 0.1 inch w.c., there is another tenth lost in the baffles, and a commensurate amount in the hood ducting. One-tenth negative pressure, however, is too much for combustion appliances with air intakes that aren't isolated from the kitchen, or for fireplaces. Note that the Wisconsin formula listed by the OP is for cases without such combustion appliances. If there is an intent to filter the MUA duct for anything smaller than a bat, I would at least taper out to a largish filter so the filter pressure loss will be minimal. A smaller sized furnace filter would do, or a window screen if large enough (perhaps two square feet). When arguing for a four-inch duct because it can move X CFM, one has to consider what pressure loss will occur at that CFM. I think six-inch would be better in this case unless the duct length will be very short. kas
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This is what makes MUA such "fun." If the air is conditioned, it can be introduced distant from the kitchen or at least distant from the hood and have the best chance of not disrupting the rising effluent plume. If the air is unconditioned and cold, then close proximity is called for (although it is unlikely to be so close as to not chill-out the cook. This could have long-term ramifications. :) Insertion under the range is a good approximation of proximate, but might have these deficiencies: o Some ranges may not like this. Someone on this forum in the last year, I think, pointed out that high-end Brand X gas range instructions prohibited it. I don't recall who X was. I do not know what the basis of the manufacturer's objection was. o For cooktops, cabinets will be in the way. A grill at the feet may be used instead of a cabinet base, and for peninsulas and islands, another on the other side is plausible. Keep in mind that the grill will have to have a rather strong air velocity unless the grill is as large as the hood. Alternatively from floor insertion, a slotted counter top design around the cooktop would provide an ideal air feed location, but inadequate area for the flow rate. Also, it could be an opportunity for difficult cleaning. Pop-up vent systems run backwards come to mind. The air flow onto the cooktop could be disruptive to the flame pattern, so probably should be aimed outward. Flow would likely be too low without a very large pop-up. kas
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Thank you so much, kaseki,colbran, and weedmeister for your very helpful responses. Kaseki, the education you provided was phenomenal, and I really appreciate the time you took to explain the science behind the decisions. I had read the forums fairly extensively, but you have added new depth to the discussions. It is interesting - came home to read these responses after a 2 hour meeting with our contractor. One member of the team is urging me to get a hood that is 450 CFM and is dubious about the need for MUA. They also indicated that I didn't need the 36" hood for the 30" cooktop. (This is a very good company - considered to be one the best in town (I won't say where) and I know we don't have a commercial kitchen. On the other hand, we do use high heat to sear meats and to stir-fry. The person doing the construction diagrams did indicate that the information I presented and the questions I was asking were in fact consistent with safety standards (why you want a wider hood, MUA concerns etc). . It is an induction cooktop, which does reduce combustibles compared to our current gas stove, but I still want to make sure that we remove odors and smoke adequately. Because we live in a cold climate, we would need to address heating the air from MUA. From reading other forums, I get the sense that if I am running the a lower CFM hood at its highest setting, noise is likely to be greater than if I am running a more powerful unit at a lower setting. (Don't know if that's correct or just someone's opinion) I'll continue to read the sources you suggested to see if that is true. So far I can't find any dB information on spec sheets. Again, thanks to all of you for your responses.
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daisychain Zn3b
8 years ago
OMG. you are so hard core. I only understood about a tenth of that.

Don't need the info, but it somehow makes my day to know it is out there and that someone understands it.
kitchengirl
8 years ago
kas: I had my CS prof spouse review your post and he said it was "beyond my abilities to comprehend"! Wow.

We will be needing MUA in the kitchen, but before that, I need to pick an external blower with continuously variable speed for max 600 cfm (36" induction cooktop). Could you please suggest best options or point me in some direction? Thanks very much!
kaseki
Original Author
8 years ago
Continuously variable external blowers are available from Broan/NuTone, Wolf (probably a spec'd Broan), abbaka, Prestige, Fantech, and others. A global search on "kitchen hood roof blower" or similar phrases will yield many options. What you want to select will depend on what your roof is like, your preference for efficiency vs. low visibility, and how the fan curve versus the pressure losses in your system yields the desired air flow.

Noise could also be a factor. In this case, large and slow beats small and fast.

You need to ensure that the control on the hood is compatible with the fan. For those not wanting a research project, this requirement is most easily met by choosing a roof blower that the hood manufacturer has selected for use with the hood. (See the Wolf design guide for an example of designating blowers compatible with hoods.)

In general, I do not recommend particular products unless I have used them.

kas
kitchengirl
8 years ago
kas: Thanks very much -- VERY helpful "laundry list" of points to consider. Much appreciated!

Moved topic: Kaseki MUA

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