Abbaka vs Greenheck - Rooftop Range Hood Blower

jjinbrooklynJuly 16, 2014

Thanks so much to all of you who share your knowledge with this group. It�s an amazing resource!
We are at the tail end of a renovation of our 1905 attached brownstone in Brooklyn, NYC. At the very beginning of the project (before I even knew what CFM was!) we decided to convert our re-circulating range hood (a big c. 1961 stainless steel hood that sits over our similarly great 1961 Crown range) to one that would exhaust outside through the flat roof of our building. Converting the hood was a snap. Finding room for ducts and pipes without disturbing the architecture of the home was not! Between the architects and contractor, we figured a way to get the air out, but only had room for a 6-inch duct with two elbows over a 35 foot run. (First elbow is right out of the hood � duct goes horizontally about 10 feet through a soffit, then makes another turn and goes up about 25 feet to the roof). I didn�t realize how problematic this would be until now, when everything is done and we�re just looking for the blower for the roof.
My electrician worked with his supplier to spec a Greenheck blower (CUE-099-VG http://www.greenheck.com/products/detail/2) and meanwhile, my own research turned up the Abbaka HyEx 1.0 (http://www.dvorsons.com/Abbaka/pdf/HyEx.pdf). I�m now trying to decide between the two.
The Greenheck assembly costs about $500 more than the Abbaka. And, the warranty on the Abbaka is 7 years and the Greenheck only 1 year. But, my electrician feels much more comfortable going with the Greenheck as it was recommended by his supplier. My architects and contractor don�t have enough experience with these brands to offer an opinion. But I�m sure you guys do! Does anyone have an opinion on this? Pros? Cons? etc.? Thanks very much!
p.s. A little more detail: We are a family of 4. Our 40-inch range has 6 burners (don�t know the BTUs) but we rarely use more than 2 burners at a time. We don�t do a lot of high fat or smelly/smoky cooking, but occasionally like to make some bacon or pan fry a piece of fish.

This post was edited by jjinbrooklyn on Fri, Jul 18, 14 at 7:11

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hvtech42

Greenheck is more often used in commercial applications, which make up the vast majority of outdoor exhaust fan orders. This is probably why the supplier is more comfortable with it. It also explains the shorter warranty; warranties for commercial products tend to be much less generous. Abbaka is more of a residential brand. Both are quality products and will last a long time if applied and installed properly.

It comes down to aesthetics. The Abbaka is a much more low profile unit designed to blend in with the roof of a house. The Greenheck is designed to be put on the roof of restaurants and schools where looks won't matter as much, and there will be plenty of other HVAC equipment up there anyway.

    Bookmark   July 16, 2014 at 1:20PM
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kaseki

The Abbaka is designed, as illustrated in the link, to exhaust down-slope on a slanted roof, typical of most residences. I don't think it would be good on a flat roof. My Wolf uses the same approach, and my roof slope is around 22 degrees.

The upblast style shown at Greenheck's link can be used on a flat roof, and is probably the most efficient as it is standard for restaurants. A flat roof should be difficult to see from the street so the configuration shouldn't be subject to criticism from passing observers.

What is difficult here is the tiny straw you want to move the exhaust through. For any decent air flow, the blower will have to be sized to meet its flow rate working against a significant pressure loss. If your HVAC guy can estimated the pressure loss (including losses in the baffles and hood transitions), Greenheck can probably choose a blower and motor combination to meet your need. Greenheck may even be able to perform the estimate from the duct length. Just don't expect significant flow in a six-inch duct to be silent.

I would plan on insulating the duct to reduce noise.

kas

    Bookmark   July 16, 2014 at 6:27PM
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hvtech42

Abbaka works fine on a flat roof provided you install it on a curb. I am able to see equipment on top of commercial buildings with flat roofs from the ground all the time.

    Bookmark   July 16, 2014 at 6:56PM
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kaseki

hvtech42 wrote: "Abbaka works fine on a flat roof provided you install it on a curb." This is a good idea for adaptation of that configuration, however it could defeat the configuration's purpose -- low observability. Curbs that are both strong and rust resistant may not be inexpensive.

hvtech42 wrote: "I am able to see equipment on top of commercial buildings with flat roofs from the ground all the time." I won't argue with that, but the OP is in Brooklyn and observers on the street looking at the OP's brownstone while having a line of sight to the roof edge may not have a line of sight to the blower unit if it is back from the edge.

The point is that both approaches need to be considered in context of where they need to fit, how they fit, and what compromises are needed to utilize them. Abbaka's blower is likely sized for up to a few tens of feet of 10-inch duct. Abbaka may not have a motor/blade option for high pressure loss six-inch-duct configurations. This can be answered, of course, by contacting Abbaka and asking.

For reference, the fan curve for the Wolf Model 336 "1500 cfm" external blower (same configuration as the Abbaka) has zero flow rate when the static pressure reaches 2.2 inches of water column. I likely use up 1.2 inches w.c. with baffles, transitions, duct length bends, and a Fantech silencer, all ten-inch duct, which is why I have routinely reported here my estimate of 900 actual cfm given minimal added MUA loss.

With 35 feet of six-inch duct, my blower (and Abbaka's) might find its operating point to be only at 200 cfm at full power. This is why blowers intended for high static pressure operation are configured differently. It may be that even Greenheck is not prepared to deal with the losses of a long six-inch duct. In such a case, an in-line vane-axial fan such as Rotron makes (or possibly Fantech) may be needed. A silencer would be recommended for high speed six-inch fans, as they will likely be loud even when pulling only a few hundred cfm through the duct. Fantech may make silencers as small as 6-inch duct size.

kas

    Bookmark   July 17, 2014 at 10:42AM
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jjinbrooklyn

Kas and Hvtech42 - Thank you so much for all the information. I'm feeling so much better having some educated opinions on this!
So, this blower will be installed on the roof behind some really ugly and big central air conditioning equipment.I can't see any of it from the street, so, aesthetics aren't really an issue. The abbaka I'm looking at is for an 8-inch duct - closer to my situation than any of the fantech or broan solutions. The abbaka engineers thought it would be okay putting it on a 6-inch - I would of course lose efficiency and cfm, but it was looking like my best/only option in the residential range.
Given that aesthetics are not important, it may be worth the extra $500 to go with the Greenheck, as the professionals on my project are most comfortable with it. Though I think I should probably speak to the engineers over at the supplier one more time to make sure that they've considered all the complexities which you guys have outlined so well here. I'd hate to pay the premium only to find that it didn't do the job as well as the abbaka would - that's really my fear here.
The advice is much appreciated! Thanks!

This post was edited by jjinbrooklyn on Thu, Jul 17, 14 at 11:47

    Bookmark   July 17, 2014 at 11:45AM
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kaseki

You will also need to ensure that the kitchen exhaust is not within 10 ft of an A/C air intake, although there might be exceptions depending on how the exhaust is directed. Local code should be consulted before cutting holes in the roof.

kas

    Bookmark   July 17, 2014 at 7:37PM
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jjinbrooklyn

My hood is about 13 feet from the intake (on paper, but air would have to travel around a wall making it about 20 feet) but only about 12 feet from a fireplace (which has draw problems so we are putting a fan on top of that too). Hoping this won't cause any problems...

    Bookmark   July 18, 2014 at 7:28AM
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kaseki

As far as I know, there is no problem with exhausts being near each other, although if they nearly abutted each other various low-probability scenarios could be imagined, such as fireplace sparks interacting with greasy effluent.

kas

    Bookmark   July 18, 2014 at 10:12AM
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