UL Listed CO Detectors are virtually worthless. 70 PPM needs to be meet and exceed for up to 3 hours before alarming. You could be dead!
Drop to 69 and the clock resets to zero!

Get a Low Level nonUL Listed alarm. 1 near the boiler / Furnace 1 outside the bedrooms.

 

Ugh! So you are pretty much confirming what the first gentleman said at the inspection. I'm definitely going to look into a low level alarm.

What about the gap in the connection? Is that normal? The second guy said that is was normal and said something about the 'flow of the air going out,' so it isn't a problem.

Thanks@

 

I don’t have issues with it. A smoke pen
Will tell you.

 

To focus on your question about the gap in the FLUE pipe, you will be just fine, that is acceptable...absolutely nothing to worry about there...absolutely normal and A-OKAY.

 

the flue pipe should be under a slight vacuum due to the chimney draft, so any leakage would be good air into the pipe, rather than bad air leaking out.

A smoke test would tell if the chimney is drafting, or a draft test on the flue pipe. there is something called a "combustion air zone" test that would ensure not only draft, but will continue to draft when door to room is closed and all appliances in room operating.

 

Not being sarcastic here, but if that small opening in the vent is of concern, why isn't the one large hole on top the water heater a concern to you?

The draft hood on a water heater will spill more flue gasses than any small opening in the vent pipe connection.

 

Haha.... No worries. Be sarcastic

Truthfully, I didn't see the water heater until you pointed it out (thanks for that. Ha :gah...

It was the fact that the first HVAC guy went on this tirade about how dangerous my old system was because of small fissures (??) in that particular duct, which I couldn't really see... So when I saw the gap, it made me paranoid.

I appreciate everyone's advice. I turned my heater on last night and won't worry.

 

I had a whole new AC, HVAC and duct work installed.

Did you register each section including the coil, as if not the manufacturer warranty drops. You need the serial number from each section.

Did they bother to do a startup/commissioning report on your new system, things like checking static pressures, setting CFM, temperature rise across HX ( Heat Exchanger ) check gas pressures, final field refrigerant charge, etc. etc. are within manufacturer guidelines?

Here is one guide.

https://www.energystar.gov/sites/default/files/National HVAC Commissioning Checklist _Rev 11.pdf

 

hvac guy was likely referring to the heat exchanger, internal to the furnace.

 

That's how flue pipe is supposed to go together.

Your chimney should be under negative pressure so air would be drawn in the tiny gaps instead of leak out.

Don't try sealing the pipe with duct or foil tape. The heat from the pipe can burn cheap tape.

 

Looks to me like just tightening that screw in the picture would close up that gap some. As said that small gap is not a major concern.