Venting gas water heaters vs. gas stoves.


Why do gas water heaters require external venting while gas stoves do not? Is there something fundamentally different in the combustions byproducts (CO vs. CO2) that need to be vented for the water heater and not the stove?
If the only reason is the volume (BTU rating) of byproducts, it doesn't make sense. For example, a moderate water heater can have a rating of 75,000 BTU, while a high end stove will have a total BTU rating over 100,000.
Worse case, think about cooking a Thanksgiving meal, oven is on for six hours and all the burners are going, all this is vented inside the house. While downstairs the water heater just has a pilot light going. Why is one required to have external venting while the other one doesn't?
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In Minnesota at least, a gas cook stove does indeed require ,by code, a vent which goes outside. I'm sure that's true of many other states as well. I have seen unvented stoves but they have never been seen by a building inspector, I bet.
Regardless of code, it is recommended and worthwhile to have a hood for your gas range. I don't always use mine but that is what is recommended by the safety pundits.
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I can tell you there are hundreds of thousands of gas ranges that have no vents. Not required in PA or CT but I don't know about other states. Yes, they have been seen by the building inspector.
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wrote in message

It's not an issue in NY, either.
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That's because Minnesota believes that all their residents are children who must be protected by government legislation.
<rj>
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before energy conservation, homes leaked so much it wasnt a big deal since stoves dont run continiously, and if your typical a 4 burner stove rarelky uses more than 2 burners at any time
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Minnesota is a very nice place to live and I don't ever want to leave. I will agree that the State can be a bit paternal at time, as most are.
We have long winters here where folk heat their homes continuously for many months of the year. Every year ordinary people are killed here by carbon monoxide poisoning. Its stuff like that that causes the legistature to pass such laws. Grieving relatives are very hard to say no to in a State like MN where even small things can make very big news.
I doubt if you can disagree that a hood is a good idea for any cook stove. Your state may be less restrictive than MN but that won't cause me to move there no matter where it is.
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snipped-for-privacy@gmail.com says...

Our stove has four 15,000 BTU burners. This is on the high side for residential cooktops. When I have all four burners running on max (60,000 BTU) for any length of time (a minute or two is all it takes), the kitchen gets hot enough that I have no choice but to open virtually all of the windows on the first floor, particularly with a houseful of guests, as likely would be the case with a big Thanksgiving dinner. I can't imagine how uncomfortable 100,000 BTU would be in that situation. The open windows are plenty of ventilation.

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But I'm guessing that such a large stove also has a vent hood??
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Making venting a requirement would require enormous amounts of work for many homes, especially those whose kitchen designs are defective. That's defined as "stove not on an outside wall".
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I think the difference is in the fact that the kitchen range generally operates while being observed and the water heater operates day and night where no one can observe whether the flame is burning at all, whether it is burning yellow and creating lots of carbon monoxide, or burning too high because of a regulator malfunction.
No one recommends leaving the kitchen range burning unattended all night while the house occupants are asleep, which is what the water heater does. People have been killed by improperly vented water heaters and by using gas ranges for heating the house but they are both very safe when properly installed and used.
Don Young
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Good answer! Logical and concise.
I live in an 8500 DD climate and hate to see my heating $ go to waste. So now I think I'll move the water heater to the kitchen/LR where I can keep an eye on it, and install a timer so it doesn't run at night :).
Actually I plan on looking into retrofitting a vent damper to isolate the water heater from the vent stack when it's just on pilot.
Thanks again.
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Actually a 4 burner plus over gas range creates very little CO when it's burning correctly. Also, as another poster mentioned, the stove can be observed wihile a semi hidden gas water heater can not.
I've run my unvented gas oven consistently and have a CO detector in the kitchen. My detector is one of those Nighhawk types that with a push button, can give low level reading below the alarm threshold. Rarely do I see even any trace CO from the range.
Occasionally during summer days, I've seen trace amounts of CO on the detector that come from outside air. The ambient air due to distant auto exhaust probably has more CO than a properly operating gas range.
I've never thought that range hood venting was even designed for CO elimination. They are more often designed for odor and smoke elimination. Many such range hoods are not even vented to the outside. They are vented within the home after having the gases pass thru multistage filters.
BTW, the standard gas water heater has a burner BTU rating of 35,000 BTU/hr, that's nowhere near 75K/hr. The only gas water heaters that I've seen with 75K or higher rated burners were commercial units used in apartment buildings.
Doug
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A good range hood vented to the outside WORLD to remove that oven heat is lots more efficient than your AC !!
whiteoak
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