How much CO2 released by tankless gas water heater?

[Home Improvement]

Hi all,

I'd like to know how much CO2 is produced by a tankless gas water heater?
I'm sure it's nowhere near danger level.
this is a Paloma PH-5RX, the flame is set to minimum. How much CO2 is being emitted per minute? just wants to know the estimate.
my folks are "concerned" about CO2 poisoning from water heater and I argued that everybody's still alive even when we cook using gas stove at max flame on all 2 burners for 15 minutes everyday for the past 30 years...but it's nice if I can give them some hard numbers.

thanks

 

[Dana]

CO2 isn't very toxic to humans, and has to reach fairly high concentrations to cause acute symptoms.

Natural gas combustion delivers ~13lbs of CO2 per 100,000 BTU. The Paloma PH-5RX runs 10.5kw at high fire, or ~36,000 BTU/hr, which is 600 BTU per minute. So at high fire it's delivering 13lb x 600/100,000 = 0.078lbs per minute. I don't know what it delivers at minimum fire.

A typical cooking range burner puts out about 7000 BTU/hr, quite a bit less per minute.

Any water heater needs to be vented to the outdoors. The PH5 series is naturally-drafted, and comes with a dilution air draft hood to be connected to the exhaust venting.

I suspect they're more concerned about CO, which binds to hemoglobin, locking out oxygen, making it lethal at fairly low concentrations.

 

[Sponsor]

 

[Home Improvement]

CO2 isn't very toxic to humans, and has to reach fairly high concentrations to cause acute symptoms.

Natural gas combustion delivers ~13lbs of CO2 per 100,000 BTU. The Paloma PH-5RX runs 10.5kw at high fire, or ~36,000 BTU/hr, which is 600 BTU per minute. So at high fire it's delivering 13lb x 600/100,000 = 0.078lbs per minute. I don't know what it delivers at minimum fire.

A typical cooking range burner puts out about 7000 BTU/hr, quite a bit less per minute.

Any water heater needs to be vented to the outdoors. The PH5 series is naturally-drafted, and comes with a dilution air draft hood to be connected to the exhaust venting.

I suspect they're more concerned about CO, which binds to hemoglobin, locking out oxygen, making it lethal at fairly low concentrations.

wow, that's surprising...never in a million years would I thought that water heater actually produces more CO2 than gas stove...a little over 5 times more.
this is very enlightening.
now, I just need to find out the level where CO2 starts to become nuisance, toxic and finally deadly.
as for CO, I'm not too concerned about it happening, because that would mean something's really wrong with the heater to pump out CO, and you should be able to know when the fire is not blue.
thanks

 

[Jadnashua]

https://www.co2meter.com/blogs/news/4418142-dangers-of-co2-what-you-need-to-know

It would take a very tight house and a lot of burner to drop the O2 and raise the CO2 levels to become dangerous. OTOH, it doesn't take all that much CO to kill you. FWIW, all typical burners will produce a little CO, and the bigger the burner, the more worry, but because low-level CO exposure is cumulative...even a low-level exposure over a long time can be as deadly as a higher level, shorter term. The burner doesn't have to be defective to still produce a little CO. Once the CO is bonded to your hemoglobin, it does NOT want to release, which is why a lower level, long-term can become an issue. The 'natural', current level of CO2 in the atmosphere is about 400ppm (o.o04% of air), i.e., not very high, but enough to warm our planet (unless you believe some who will not be named!), nowhere near enough to be toxic directly to humans.

In general, you don't want any burner exhausting directly into the house...the use of a real exhaust hood on a range is a good idea to help take care of both the gasses produced, which includes water vapor. No water heating appliance using a burner should exhaust into the home.

 

[BillTheEngineer]

Interesting topic, I was looking into CO detectors little while back and trying them out. My initial assumption that combustion of natural gas or propane produces CO was not true in most cases. The CO detectors I was trying out would rarely get a reading that was of concern and I was wondering if they were working or the warm gases were causing an issue. In doing some research and trying to recall some basic chemistry, as long as there is sufficient oxygen (air) natural gas and propane combustion does not produce much if any CO. The by products of natural gas and propane combustion are water, CO2 and heat. Oil and other fuels it is a different story since there are more chemicals in the fuels.

And as other have said, the dangerous levels of CO2 are pretty high. And any CO is not good.

 

[Jadnashua]

It's a rare burner that is perfect and doesn't produce at least a little CO. Ideally, yes, there is none. A high level of CO is a killer. But, a low level, long-term exposure can cause some nasty side-effects, that may not kill you, but will make your life miserable.

I've been happy with the Nest Protect CO/smoke detectors I put in. I put some in at my Mother's house as well. It's neat that you can monitor their health from remote. They also have a motion sensor in them, and I can tell when my Mother gets up at night! Most CO detectors I've owned previously required replacement after 5-years. These stop working after 10, and self-test themselves along the way. Mine are hardwired to acv...my mother's are battery operated. They create their own network, and talk to you before things get bad enough where it needs to activate the alarm, telling you what's going on, and announces WHICH one(s) are being affected through all of them, so you can know instantly that it's say the basement verses the bedroom detector that was 'tripped'.

 

[Home Improvement]

I read in wikipedia that CO level should not be higher than 50 ppm over an 8 hour period. assume each shower takes around 10 minutes of water heater running at minimum flame settings, how much CO would it produce assuming it's all incomplete combustion?
and also, how long till CO dissipates? the WH is outside bathroom, but still inside the house. it is on the first floor directly under a void space all the way up to third floor.

 

[MACPLUMB]

But do you have a vent pipe out though the roof, or is venting into the house ?

 

[Jadnashua]

All gas fired water heaters, doesn't matter if it is a tank or tankless, should vent outside, so if you follow the rules, you'd never have CO or CO2 problems. One of the few flames that doesn't require a vent is a gas stove, but if that is not adjusted properly, it could kill you. As a product of combustion, if you vent into the house, you not only get CO, but CO2, and H2O, and those things can cause problems but the only one likely to make you sick is CO. CO2 is basically inert, as is water. Excess moisture in the house could lead to mold or other structural problems, but it won't directly be unhealthy. Too much CO2 decreases the amount of O2 we need to breath, but isn't, itself, poisonous until it is in too high of a concentration, limiting how much oxygen is available. our bodies expect and only work well when the percentage of O2 to other gasses is within a relatively narrow range. Disrupt that balance, and we'll have problems...

So, worrying about the CO from a tankless heater shouldn't be an issue. If you don't follow the installation instructions and have the exhaust where it could find its way back inside, then, yes, it could be an issue, but there are rules about how far from a window, door, or other opening in the dwelling that the exhaust must be. If you follow those rules, it won't be an issue. As with many things in life, break the rules, and there are consequences.

CO can be a health issue from either high dosages, that will tend to kill you, or long-term lower dosages that will make you sick, but not necessarily kill you...neither one is good. A good CO detector will detect both situations. A cheap one may not, and it doesn't matter WHAT burner is running...too much CO, and you could die - vent it outside!

 

[Home Improvement]

All gas fired water heaters, doesn't matter if it is a tank or tankless, should vent outside, so if you follow the rules, you'd never have CO or CO2 problems. One of the few flames that doesn't require a vent is a gas stove, but if that is not adjusted properly, it could kill you. As a product of combustion, if you vent into the house, you not only get CO, but CO2, and H2O, and those things can cause problems but the only one likely to make you sick is CO. CO2 is basically inert, as is water. Excess moisture in the house could lead to mold or other structural problems, but it won't directly be unhealthy. Too much CO2 decreases the amount of O2 we need to breath, but isn't, itself, poisonous until it is in too high of a concentration, limiting how much oxygen is available. our bodies expect and only work well when the percentage of O2 to other gasses is within a relatively narrow range. Disrupt that balance, and we'll have problems...

So, worrying about the CO from a tankless heater shouldn't be an issue. If you don't follow the installation instructions and have the exhaust where it could find its way back inside, then, yes, it could be an issue, but there are rules about how far from a window, door, or other opening in the dwelling that the exhaust must be. If you follow those rules, it won't be an issue. As with many things in life, break the rules, and there are consequences.

CO can be a health issue from either high dosages, that will tend to kill you, or long-term lower dosages that will make you sick, but not necessarily kill you...neither one is good. A good CO detector will detect both situations. A cheap one may not, and it doesn't matter WHAT burner is running...too much CO, and you could die - vent it outside!

you're using NEST for CO detector? they're good? you have any other alternative manufacturer? how about First Alert or Kidde?
thanks

 

[Jadnashua]

The Nest Protect is a smoke/CO detector. They're not inexpensive, but they are networkable, come in both wired and battery versions (probably only 120vac, though), and, for my installation, they network themselves together, so if one goes off, it talks to the others, and each one will set off its alarm. To get that networkability on the others, you need to have them wired with that trigger line, and then, you can't tell which one set things off easily. The Nest units will tell you what's going on and where. If it notices say the smoke level rising, it will say that, and only when it gets to a dangerous level will it actually sound the siren alarm. I think they are very well thought out. They talk...I do not know if they can be set to multiple languages. Their sensors are designed to last 10-years...many of the others on the market are designed to last 5, so figure that into the cost equation. I've used First Alert units in the past...I think the Nest product is better, but do not have scientific proof.

In my situation, there wasn't one in the basement, so it was not wired. If it went off, you'd be unlikely to hear it upstairs, especially if sleeping two floors above. Getting a trigger wire down there from the others in the house would have been a major pain. I switched them all over to the Nest Protect, and they instantly all became networked together. I put some in at my mother's house and used their battery version, since I wasn't going to try to wire power up through the plaster walls and ceilings. They function in the exact same manner, but have more batteries in them whereas the acv powered ones only have a couple for backup if the power goes out.