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peytonrose1015

Modernaire PS-26 hood help

ILoveRed
6 years ago

My kitchen designer has never used a modernaire hood and is working with a source that I'm not totally confident in? It is the PS-26 that is popular here and I have always loved.

My stacked cabinets are inset and the uppers are 13" deep vs. 12" deep. KD thinks we may need to make the top of the hood custom at 13" instead of standard at 12" to accommodate the 13" deep uppers. I will if it is needed, but I just want to make sure.

If a customer has 13" deep uppers, does that require the custom hood in this style be made at 13" depth vs the standard 12"?

How do other customers handle this dilemma?

Here is my wall.

please check this for me if you know. Thank you.

Here is the hood

Featured Answer
  • kaseki
    6 years ago

    You can calculate nominal blower flow rate (CFM) yourself by doing the following arithmetic.

    First, calculate the required maximum CFM for hot cooking by multiplying the hood entrance aperture by 90 CFM/sq. ft. (We can slightly overstate this by using the outside dimensions of the hood 26 x 42 = 1092 sq. in. = 7.6 sq. ft. This requires around 700 CFM.

    Second, (ideally), round up all the pressure losses getting the air out the vent and getting make-up air into the house as a function of flow rate and see where this pressure loss curve intersects the blower's fan curve. Or, (roughly) assume nominal baffle loss, duct loss, MUA pressure loss, etc., and multiply Step 1's result by 1.5 and hope for the best. This yields around 1000 CFM. So a 1200 CFM internal blower will be suitable; the alternative 600 CFM internal blower will not be suitable. The external 1000 CFM blower can also work.

    There are a lot of assumptions here, and when dealing with MUA one has to know whether there are local municipal or state requirements, know what the safety requirements are in any case, and have a plan for how it is ducted (and possibly filtered and powered) to the kitchen, including heating if necessary.

    Comments (15)

    • ILoveRed
      Original Author
      6 years ago

      I just realized I posted an older version of this wall that specs the hood (which we had originally planned as wood) at 45" wide over 36" rangetop.

      It is changed to 42" wide. Sorry for the confusion.



    • PRO
      Trevor Lawson (Eurostoves Inc)
      6 years ago

      As retailer and distributor for ModernAire hoods on the east coast. Functionally it makes no difference at all. Visual wise 13" depth would be better. I would say that 90% of customers who have a 13" + top cabinet depth go with the extra depth. having said that to answer your actual question "its not needed".

    • ILoveRed
      Original Author
      6 years ago

      Hi Trevor. Thank you for responding.

      We are considering customization of the top of the hood.

      This may seem like a silly question.

      if we increase the top of the hood from 12" to 13 " depth to accommodate the 13" deep cabinets (without changing the depth of the rest of the hood), does that slight change in radius change the appearance of the hood?


    • ILoveRed
      Original Author
      6 years ago

      Also Trevor is 1200 CFM correct for a 36" Wolf rangetop? Again, thank you.

    • PRO
      Trevor Lawson (Eurostoves Inc)
      6 years ago

      If you go from 12" depth to 13" you wont notice the difference. I would always go with a 1200 cfm Blower.

      ILoveRed thanked Trevor Lawson (Eurostoves Inc)
    • ILoveRed
      Original Author
      6 years ago

      Kaseki...thank you for the great explanation. It seems both you and Trevor agree with my kd and hood person that 1200 is correct. We live in the boonies so no one is checking on these things but I would like to get it right.

    • ILoveRed
      Original Author
      6 years ago

      Trevor...so 1200 cfm it is.

      I hate to beat a dead horse but may I ask two more questions?

      -if I'm going to do a custom hood anyway, and I'm adjusting the length of the hood as well.....minimum above rangetop is 30" and maximum is 36" according to the Modernaire website. What height above rangetop do you think is ideal?

      -is it a backdraft damper that keeps cold air from blowing back into the kitchen? Is that standard or something I need to make sure I am getting?

      thank you for sharing your expertise.


    • kaseki
      6 years ago

      I suggest that you draw to scale a side view of the range top and hood with a stick figure cook in front of the range. Observe sight lines to the pans at the back. Observe the effect of the (tallest) cook's bending forward on his head intersection with the hood. If the hood is drawn on a separate piece of paper, it can be moved up and down to see the effect of placement.

      Mine is at 34.5 inches. While the hood should in principle grow in aperture area as the aperture is placed higher and higher over the range to maintain capture percentage, this is not usually bothered with in the region of 30 to 36 inches, particularly if you have already addressed hood overlap with the pan bases.

      Note that commercial hoods typically are at seven feet from the floor, i.e., 4 ft above the cooktop. A typical size is 4 ft front to back and significantly longer than the cooking zone. This deals with the expanding rising plumes, and also with cross drafts, which should no be neglected from consideration in residential applications.

    • kaseki
      6 years ago

      Forgot the damper question: "is it a backdraft damper that keeps cold air from blowing back into the kitchen?" Yes, that is its purpose, and I would recommend one at each end of the duct. Some hoods will include a damper. I don't know how standard it is to do so. Dampers and other duct components may be available from local HVAC distributors, or can be ordered from Fantech.

    • ILoveRed
      Original Author
      6 years ago

      Thank you Kaseki for sharing all of your knowledge regarding both questions I asked here. DH is 6'2" and I am 5'6". So I am thinking it needs to go up. I will follow your advice and make sure it is at the right height.

      i will also make sure that we have a backdraft damper at both ends.

      thank you for the source fanteck

      if my duct is round and 9 7/8 then I need a 10" like this one? Or two I should say. Thank you.

      http://www.fantech.net/products/air-distribution-products/airflow-control-devices/backdraft-air-dampers/rsk/rsk-10-backdraft-damper/

    • kaseki
      6 years ago

      Yes, that damper is typical. Note that neither side is shown crimped. Either one side has to be crimped (the one to be closest to the hood), or you need a band clamp such as Fantech sells for such purposes as attaching duct to their silencers.

    • ILoveRed
      Original Author
      6 years ago

      Why the crimping?

    • kaseki
      6 years ago

      Duct sections are typically crimped at one end so the section fits into another section. By crimping I do not mean mashing the entire end together, but effectively corrugating the sheet metal with the effect of making its diameter smaller. A typical do-it-yourself crimp tool:

      A dual crimped duct union

      ILoveRed thanked kaseki
    • ILoveRed
      Original Author
      6 years ago

      Thanks Kasecki...found out the hood I'm using has a backdraft damper. Thought I would let you know since you have been so helpful.

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