Joined here in desperation, looking for independent thinking folks like you to weigh in:
My plumber replaced BOSC gas on demand hot water heater with a tankless in February 2018. He also told me to close 2 of 3 6"x13"to-the-house airflow vents in the sealed in-home, 2'x4.5' utility room to stop CO emission into house. CO had been coming in to the home from the utility room previously.
He also sealed one roof vent to the tankless to make it a closed, dedicated air supply for the new tankless.
He ran a taller PVC pipe through the existing 6" (?) roof vent which is now the only outside air vent for the LAARS minitherm gas boiler.
No more CO in house, however the boiler pilot has gone out 5 times this winter since the change out. Plumber replaced thermocouple. Pilot still goes out. Minitherm serviced, pilot still goes out. Plumber attests Minitherm operating correctly.
My small, very high altitude home is extremely air tight. My theory is that when I use the poor quality kitchen exhaust fan, some kind of vacuum may be created in the house, so there is not enough airflow for the Minitherm to run.
Maybe also some kind of air flow down or up from wind that snuffs the Minitherm pilot?

Rather than replacing the MInitherm with a closed system (multiple thousands of dollars, but probably a clean fix) can anybody else suggest a solution? I have photos and can provide dimensions roof venting. Thank you in advance.

my thinking is to open up (if possible) the old air intake vents to see if the pilot stays lit.
in other words, get some more make up air into the space..
if the pilot stays lit, problem solved.
if it goes out then close the vents and start troubleshooting the boiler..

Thanks packy--I thought the same thing.

I'd have doubts that the boiler is operating correctly. Did he leave a printout from a digital combustion analysis with the boiler?

paul, in a perfect world someone would do a combustion analysis on a piece of gas equipment.. i can honestly say that since the 1970's i have never seen one done. oil burners yes but gas no..

packy....In a world where there are CO emissions in the home? God forbid something happens....you better be able to prove the equipment was operating correctly when you left it.

i read you loud and clear, paul..

Guys, I assume! Thank you. I've never heard of a digital combustion printout. Where I live in NM things are a little less up to date. I wonder if anybody here even has the equipment to do one. Because I've had issues with CO I've got three different CO meters, two of which measure from 1 ppm and I'm hyper vigilant about monitoring CO.
I'll ask around to get a digital combustion reading with printout. Most recent plumber suggested replacing the whole system with a Navien closed combined boiler-water heater. Not sure I want to go that way, but trying to get an accurate read of the amount of air that is getting into the utility closet. Plumber told me there is a chart that will show air flow for pipes, vents given by size. My unit is a 75,000 input rate.

[www.pmengineer.com]

Thank you Packy! This is what I need.



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