Lunos and range hoods
I am wondering if anyone might be able to help with a question that has come to my head. I am looking to use Lunos e2 fans for ventilation in my house, and I am also planning to install a 900 cfm range hood.
Here’s what I have been wondering about: When the range hood is on, is that going to be causing strain on the Lunos motors, possibly to the point of damaging them? Let’s say my house is about 1 ACH50, so fairly tight.
Maybe I am underestimating the amount of air that can leak its way into a tight house, or I am otherwise overthinking things. The hood will only occasionally be on at full speed, but I am imagining that if the amount of air being exhausted is more than cracks, etc, in the house then whichever Lunos fan is trying to pump air out of the house will be straining hard to get anything out, since the fan-holes are going to be one of the easiest sources of make up air for the range hood.
Anybody else think this might be a problem, or am I blowing it out of proportion? Will it just mean that we aren’t getting efficient, balanced, HRV when the range hood is on?
Thanks!
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Replies
900 CFM is a lot. I don't think you can count on leaks to provide that. A passive or active makeup air vent would be a good idea. If you don't do that, I think you are right that it will come through the lunos fans. My guess is that it won't damage them, and if you do it for a short enough time, you will recover some of the heat stored in their thermal mass. Even if you have a makeup air system, it might not always work, so you might be trying to force air through the Lunos. I imagine that happens regularly with those systems, and if it damaged the motor or its controls, we'd be hearing about reliability problems, so I guess it's OK, but it might be worth asking the manufacturer.
Depending on the size of the house, 900CFM could cause 50Pa pressure difference - mimicking the blowerdoor test conditions (high depressurization if the Lunos e2 weren't installed/sealed off).
You are correct that the openings though which the e2 fans ventilates, will be the easiest way in to supply the 900CFM exhaust hoods make up air, if your house is at 1ACH50. However as you had already guessed, this is not preferable and code (M1503.4 Makeup air required) requires you to have a dedicated make up air if the exhaust hood is over 400cfm. This would be one way to deal with you situation. But as noted, the kitchen at that time, no longer benefits from the Heat recovery of the Lunos e2.
The other solution is to install a smaller range hood - 100cfm is for most uses ranges sufficient and the e2 system will be able in those cases to provide that voume (again the heat recovery will be less or inactive at such times, depending on the number of e2 fans installed/tightness of the house/if windows&doors or opened). Please contact us athttp://www.foursevenfive.com/ 800-995-6329 if you have additional question regarding your setup.
Stephen,
I agree with Floris. Here are the facts:
1. Building codes require that a house with a range hood fan rated at 400 cfm or more include a makeup air system.
2. Because they tend to depressurize a building, large range hood fans are almost always problematic.
For more information on this issue, seeMakeup Air for Range Hoods.
Cook the stinky stuff outside. Anything that needs an exhaust vent that big shouldn't be happening in your house.
Ok, ok! I get what you guys are saying about range hoods and make-up air. The thing is, there is a lot of documentation on the polluting qualities of gas and fumes from range tops. I tried really hard to like induction and just couldn't do it, so we're stuck with gas. We usually will only be running the fan on 300 cfm or so, as that is sufficient for most of our cooking, but on occasion we use all the burners with several on high.
From everything I've read about sizing range hoods to remove pollutants - it's really not just about the smell - 900 cfm is appropriate for the range we are getting. Mind you, a blower rated at 900 cfm does not really move 900cfm of air at max speed. The pressure inside the house, length of ductwork, etc, will all affect your actual air movement.
We don't have any other non-electric appliances planned. Local code requires make-up air only when there are other combustion appliances in use in the home. It does require, however, that if a source for make-up air is installed, that the make-up air be heated. This is a big problem for us, as I don't want to have a spot heater for incoming makeup air, and all of our heating/cooling will be done through radiant, so no furnace or other ductwork.
James - as much as I appreciate an outdoor kitchen, it's not in our plans at the moment I'm afraid.