thanks for the advice and feedbacks (esp. concerns)...much appreciated.
Fact is as follows:
(1) ever since we have our AO Smith "skinny" 40gal natural gas water tank replaced with GE (it was 3 yrs ago in the month of November), this problem started to appear.
(2) This problem of backdrafting only occured in a very-specific condition. While during the past 2 years when that (backdrafting) happened it was haphazardly dealt with (happened in the morning hours when we started prepping our kids for school, getting out of the door for work, etc.) and it never happened throughout the duration of the winter (cold) months.
This year when this happened (that's during the transition between summer heat and first couple of seasonal cool-downs which would bring the interior of the house down to approx. 16C or so, and when my wife begins to complain about headaches, etc.), I took the day off to investigate (and also called on a serviceman to look into this matter). I recalled that the outside temp was around 8C, and was somewhat foggy. 15mins after turning on the heat mode on thermostat (to call on the boiler to start boiling full-power), that's when our CO detector starts to register with readings past 160ppm or higher....opening up that closet and when I felt on the angled exhaust pipe (the one that exhaust the boiler), the piping was not warm but rather cold (room temp). Immediately, I realised that there's not enough heat inside that 4" exhaust pipe to cause the exhaust gas to rise properly, so w/o hesitation: I crank up the GE hot water tank temp to kick-start that side (left side) of the exhaust piping temp.
3~5 mins into that, I can tell (from the CO detector reading) that the CO reading level no longer increases but begin to drop gradually (with window cracked opened of course)....
Over the next 30mins to 1hr as the hydronic in-floor heating boiler is in full action, the CO reading returned to zero and stayed there.
Such phenomenon would only happened once during the start of the hydronic heating season, and no longer appears throughout the rest of the cold months...
This leads me to believe that there's some exhaust issues on the boiler side only, and may have attributed by the fact that I replaced a relatively inefficient hot water tank (with bigger pilot light? or more frequent boiling cycles (because of less insulation(?), as opposed to the more efficient (3" insulation, and smaller pilot light that I can see) GE I replaced it with), causing the upper section of the chimney pipe to be somewhat colder than previously...
Anyways, I do appreciate all the advice and feedbacks in this case. I'm not going to replace it with all-electric ones, but to investigate and rectify the current situation with the boiler side of the exhaust instead.
Cheers,
Q
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