Would there be a way to use the heat that's being ventilated from the range hood to help pre-heat the incoming make-up air?

I think you just have to accept that you are exhausting it because it is bad air (for whatever reason) and live with it. You don't actually run the big hoods that much anyway. They are commonly only needed when there is an acute issue, and then only for a few minutes. One of those times is on the rare occasion that you are actually using the full capacity of your mega-range and need to get rid of the heat that is building up. In that case, you just plain want the heat....out.

Posted By ICFHybrid on 31 Jan 2012 01:16 AM

yet nowhere in their literature actually quantify just how quiet.

Vent-A-Hood actually publishes more noise info than most of the other major brands. If you look at the right documents there, you can find the noise info while I was never able to find comparable numbers for the others..... The conclusion I drew from that is obvious.....

However, during my shopping, I also visited a number of demonstration kitchens set up at appliance sales places and found that the other brands appeared to be louder than the Vent-A-Hood.

I don't know if you noticed, but I amended that post with the noise info I found on the Vent-A-Hood site.    I'd been relying on the AJMadison site for technical info.


John

So if I understand this correctly, most codes DO NOT require a vented hood if you have an electric range?

How much energy to you save by not having to poke a 5" hole in the roof?

Posted By ICFHybrid on 31 Jan 2012 01:25 AM

Would there be a way to use the heat that's being ventilated from the range hood to help pre-heat the incoming make-up air?

I think you just have to accept that you are exhausting it because it is bad air (for whatever reason) and live with it. You don't actually run the big hoods that much anyway. They are commonly only needed when there is an acute issue, and then only for a few minutes. One of those times is on the rare occasion that you are actually using the full capacity of your mega-range and need to get rid of the heat that is building up. In that case, you just plain want the heat....out.

I only ask because I'll be doing the same thing with recovering the free energy being flushed down a shower drain by using a GFX HeatXchanger.    I figure that I typically have a shower running for about as long as I've got a range hood running, and would need to preheat the incoming make-up air for only as long as I'd be venting the range top.    Why not try to use the free energy from one to pre-heat the other?


John

Shower water down the drain represents an appreciable amount of energy usage. Running your range hood shouldn't be anywhere near that much. There are heat recovery devices for large amounts of air, but I doubt they price out for residential use. You just won't use the hood as much as a commercial kitchen does.

I just wanted to make sure.    Thanks.


John

Over on the JLC online forum, Materials & Techniques subforum, there is a current thread on the subject of makeup air for a range hood:
http://forums.jlconline.com/forums/showthread.php?t=59287
that has some additional useful thoughts. That is a "professionals only" forum, and they ask that folks not in the construction business not post or reply.

Dick:

Thanks for the link. I'll check it out.


John

After reading all of the suggestions in this thread, I think I've pieced together an efficient system that will work in an air-tight house, be relatively silent and address the concerns I've got about filling a house with cold air when the range hood is operating. The components of it are as follows:

36" LP Gas Range Top: http://www.ajmadison.com/cgi-bin/aj...T366L.html   (I'd likely never be using it at a rate higher than 65,000 Btus)

42" Range Hood: http://www.ajmadison.com/cgi-bin/ajmadison/E64E42SS.html   (slightly wider than the range top for more effectiveness)

600 cfm Inline Blower for Range Hood: http://www.ajmadison.com/cgi-bin/ajmadison/HLB6.html   (located in basement to minimize noise from range hood)

600 cfm Make-Up Air Heater & Intake: http://www.electromn.com/pdf/EL007.pdf

Automatic Make-Up Air Damper w/Digital Control Module: http://www.broan.com/Catalogs/Broan_Makeup_Air_Dampers.pdf

It's not the cheapest direction to go, especially taking into account the Make-Up Air system with a built-in pre-heat, but it looks like it could be a terrific solution.

What am I overlooking here?  Any red flags?



John

What about the Lossnay ERV from Mitsubishi? 

Is there something about the Lossnay ERV that exceeds the capabilities of the UltimateAir model?   I'm unfamiliar with it.    I really like the fact that the UltimateAir requires very little energy to run.   I'll check out the Lossnay though . . .

UPDATE:    The power of the Lossnay is impressive (they've even got a 1,200 cfm whole house model) but the energy to run it is quite high.    If I were to go with the 600 cfm model, it would require around 440 kWh/month to run--or so it appears--which would be equivalent to the energy needed to run about 10 large capacity refrigerator/freezers.      The UltimateAir RecoupAerator 200DX, although it's only about 1/3 the capacity of the 600 cfm Lossnay, requires only about 25 kWh/month to run.    I guess I'd need to crunch some numbers to see just how much electricity I'd be using to run the Make-Up Air system to be able to make a good comparison.   I'll talk with a technical person at Mitsubishi tomorrow and clarify things.


John

Posted By Litawyn on 31 Jan 2012 11:16 PM
Is there something about the Lossnay ERV that exceeds the capabilities of the UltimateAir model?   I'm unfamiliar with it.    I really like the fact that the UltimateAir requires very little energy to run.   I'll check out the Lossnay though . . .

UPDATE:    The power of the Lossnay is impressive (they've even got a 1,200 cfm whole house model) but the energy to run it is quite high.    If I were to go with the 600 cfm model, it would require around 440 kWh/month to run--or so it appears--which would be equivalent to the energy needed to run about 10 large capacity refrigerator/freezers.      The UltimateAir RecoupAerator 200DX, although it's only about 1/3 the capacity of the 600 cfm Lossnay, requires only about 25 kWh/month to run.    I guess I'd need to crunch some numbers to see just how much electricity I'd be using to run the Make-Up Air system to be able to make a good comparison.   I'll talk with a technical person at Mitsubishi tomorrow and clarify things.


John

Please let us know what you find out.

With that type of power use (10 large freezers), it would be better to just build a leaky drafty home and avoid paying the high utility bills that an ERV uses.

My question before you jump into the fire is how did you determine the exhaust hood cfm.

The manufacturers of the exhaust hoods list the info. Often, the blowers are sold separately from the hood, so you can choose the cfm for the unit you're purchasing. Just go here and look around. They carry nearly 1,100 models of hoods (and list the corresponding specs for each.)


John

acwizard - if what you were asking is "how did you determine the REQUIRED exhaust hood cfm, that is detailed the the range manufacturer based on the btu rating of the burners.

Posted By FBBP on 01 Feb 2012 01:46 PM
acwizard - if what you were asking is "how did you determine the REQUIRED exhaust hood cfm, that is detailed the the range manufacturer based on the btu rating of the burners.

ACWizard:

If that was what you meant by your question, I simply chose the hood and blower size based upon 1) maximum Btus I'm anticipating producing on the rangetop at a given time, and 2) the specs for the blower as listed on the website I referenced.    Knowing how I cook, I'm not expecting to ever have the range top producing more than 65,000 Btu/h.    According to the specs for the 600 cfm inline blower I'm considering, it handles a maximum of 65,000 Btu/h.

Hope this helps,


John

Posted By Lbear on 01 Feb 2012 03:43 AM

Please let us know what you find out.

With that type of power use (10 large freezers), it would be better to just build a leaky drafty home and avoid paying the high utility bills that an ERV uses.

Lbear:

What I found out--and I hope I understood everything correctly--is that an ERV is not a solution for bringing in air to offset a range hood, regardless of how strong it is.     The reason being that the ERV doesn't simply bring air into house when it's required; it does so by displacing an equivalent amount, ensuring that the movement of air doesn't affect the pressure in the house.   The range hood however only removes air, leaving the house in a negative pressure situation, especially if the house is airtight.     If I simply used an ERV in an attempt to counteract the air displaced by the range hood, I'd still need a separate source of incoming air to balance things out.    If I relied on a basic air intake vent to do this, I'd find the house filled with a blast of cold air every time I used the range hood in the colder months.    The temperature of that incoming air really should be adjusted, depending upon the time of the year and the outdoor temps.

I believe the system I laid out a few posts back that utilized the make-up air heater is the way to go.    I'd still have an UltimateAir ERV running 24/7 on medium (approx 80 cfm all the time,) but it would work completely independently from the range hood system.    Its purpose would be to function as the lungs for the house and always keep a steady stream of clean, outside air coming and going from the house.    With a house the size of what I'll be building (1,197 sq ft,) an ERV running on medium would perform a whole-house air exchange every two hours,  for a total of 12 full air exchanges every day passing through high density MERV 12 air filters.    This would have the ERV using about 40 watts per hour, or a total of around 29 kWh/month of electricity ($3.92/month in Mid-Coast Maine.) 

The range hood on the other hand would work in conjunction with a 600 cfm in-line blower to exhaust hot air, smoke and odors from the house when the range hood is being used and would be balanced by a 600 cfm make-up air heater in the basement that would be pulling in an equivalent amount of preheated air from the outside to keep the pressure and the temperature of the house in balance.    It would require virtually no electricity except when the range hood, clothes dryer or bath ventilation fan were running and caused the air pressure in the house to get out of balance.   The make-up air system would kick in automatically and not only bring in the needed air, but heat it to a preset temperature if necessary.    The system would utilize an automatic air damper that would keep any air from filtering into the house until it was called for, helping to keep keep the structure as air-tight and energy-efficient as possible.    In the dead of a cold Maine winter, the entire structure should require no more than 11,000 Btu/h to keep the indoor temp at 72F, plus whatever juice the make-up air system may require to preheat any incoming air when the range hood, dryer and/or bath ventilation fan are in use.

I'll be using an efficient wood pellet stove as the primary source for space heating, and a pair of condensing tankless water heaters, but they'll each be closed loop systems which will pull in the air they require and exhaust it as well.    Neither should affect the air pressure in the house.

Make sense?



John

If recommendations are for .3 ACH, is .5 ACH overkill or is more better?

-Rosalinda

You had stated earlier that you had a six burner rated at 23000 btus each. The total far exceeds the rated fan spec for the Broan fan selected. Residential kitchen makeup and exhaust is a huge grey area. We do commercial kitchens all the time and do occasional start ups for a well known makeup air mfg.The point I was trying to make is 600 cfm is shy on performance for your rated cooktop.Unlike commercial , residential codes allow great room for misgivings. Almost all of the custom homes that I'vebeen involved with have had elaborate kitchens. Unlike tract residential home , the equipment is commercial quality and welded grease ducts should be installed as per the commercial codes. 138000 btus is possible with your scenario and the hood and exhaust rate should be calculated correctly.

Posted By acwizard on 02 Feb 2012 01:53 AM
You had stated earlier that you had a six burner rated at 23000 btus each. The total far exceeds the rated fan spec for the Broan fan selected.  138000 btus is possible with your scenario and the hood and exhaust rate should be calculated correctly.

ACWizard:


Out of curiosity, have you ever seen someone in a residential kitchen with all six burners on a six burner stove running full blast ? 

If I felt there would ever be such a scenario in my own kitchen, I'd agree with you about sizing the hood.     But as I said previously, this will never be the case, so I've sized the system accordingly.     My maximum scenario would be using a wok at full power (23,000 btus) plus 3 other burners on medium (3 x 12,000 btus) for a total of 59,000 btus at a given time.    Even that is an extreme for me.    I look at it much like someone who calculates heatload requirements for a home.   They don't look at a worse case scenario of just how cold it could possibly get outdoors; they calculate things on the basis of historical averages.    Sizing a system based on some anomaly forces you into a system that is complete overkill.    A 1400 cfm range hood** in an airtight 1200 sq ft home would be a bit nuts.    Moreover, the cost of the Make-Up Air system required for such a hood in this situation would be prohibitive.    I'm also willing to bet that few if any residential installations of this range top have been paired with a 1400 cfm range hood either, nor have they been required to do so by code.   If it indeed were a necessity, code would have mandated it.

Again, I've sized this system based upon my known usage of a range top, not upon some extreme scenario that will never take place.



John


**This number was estimated based upon the most powerful Broan In-Line blower, which is 1100 cfm and claims it's sized for Maximum Cooktop Btus of 110,000.