Runaround - HVAC and HWH proper venting/exhaust

yuri

As IN, NO CO poisoning for you or your family or carbonned up heat exchanger from lack of combustion air which then produces CO. Most cases of CO poisoning are from a lack of combustion air/ bad gas and air mixture or blocked chimney which fails to draft properly from a lack of combustion air. Cracked heat exchangers account for less than 20%.

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kenmac

Just to add to what been is saying. We're talking about free area. There is a Free area rating for wood lovers & 1 for metal. Just remember .Code is minimum safety requirments. Doesn't hurt to go beyond minimum

denemante

Let's hope it doesn't happen. But what are the worst case scenarios or medium case scenarios if things don't function well? I plan to have C02 detectors all around. Actually already have a few.

yuri

Slow poisoning of you and your family. CO detectors are NOT very accurate and 100% reliable at low levels as they cost less than $50. You would have to get very high grade ones and spend a lot more $$ to get accurate low level sensitivity. At the low price range they are meant for catastrophic failures like blocked chimneys etc. Natural draft appliances, especially the water heater have no safety devices for fumes spilling out and that long venting concerns me. I have seen chimney draft change with outdoor temp, barometric pressure changes, wind etc. It can lose its draft. That is why we try keep the venting within 6 feet and use a double wall B vent which stays warmer. All you can do is buy new ones and hope they work when needed. The days of long venting being safe in homes is over as there are more powerful exhaust fans, tighter houses and appliances drawing air out of the house. The only safe bet is a 6" insulated flex pipe from outside into the furnace room to provide combustion air. I had a chimney lose its draft this winter, was oversized and got too cold and fumes were spilling into the house. No spill switches on a water heater. Lady of the house smelled the moisture in them and fortunately called us. We changed it to a electric water heater and eliminated the chimney. Has a sealed combustion high efficiency furnace also.

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hvactech126

CO (carbon Monoxide) not CO2 (carbon dioxide) detectors are actually alarms. Alarms (good ones) willl use this criteria : In accordance with UL 2034, the CO sensor will not alarm to levels of CO below 30 ppm and will alarm in the following time range when exposed to the corresponding levels of CO.
70 ppm CO concentration 60 – 240 minutes
150 ppm CO concentration 10 – 50 minutes
400 ppm CO concentration 4 – 15 minutes

This means that you could still have a low level of CO present and never know.

sorry to get off on the tangent, but just a little education.

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yuri

I tell all my customers NOT to get a false sense of security with them. Negative pressures and venting problems are getting SERIOUS concern where I am. They are making a residential HVAC service and installers course and license here with a full apprenticeship and the sheet metal guys and installers have to take it and be certified soon. Pretty soon all our return duct joints will have to be airtight and foil taped/siliconed or sealed with duct sealer and the air filter opening sealed with a plate so no air can be sucked from the furnace room.

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Marty S.

That's good to know. If I remember correctly OSHA regs limit CO exposure to 50 ppm in a 8 hour period. Any idea if the CO detectors will alarm for that or is 70 ppm over 60-240 minutes low as they go?

hvactech126

that is as low as they go and yes you are correct it is still unsafe below the point that they alarm! some will alarm at 40 ppm but will not alarm at all below 30 ppm

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beenthere

Medium case, brain damage over time.

yuri

And a lot of people don't consider that small children have 1/4 the amount of blood in them that an adult does. Therefore the concentration may be incredibly higher for them and the consequences worse. Just like lead poisoning it may lead to learning disabilities etc.

They have smaller lungs but I would still not want to get them exposed to that stuff at all.

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