Modern furnace CO safeties?

mixe1

In a modern 95 percent condensing furnace, what safeties are in place to detect a cracked heat exchanger or otherwise to prevent CO from entering the living space?

Jamie Hall

None, so far as I know. There are, however, safeties to prevent flue gas from entering the space. Spill switches, poor draught sensors, etc. That said, any building with a gas burning appliance in it -- from a gas stove up to a big boiler -- should have (and in many jurisdictions, must have) a CO detector. The ones from the big box and so on really aren't good enough; you should have a low level CO detector.

ChrisJ

Jamie Hall said:

None, so far as I know. There are, however, safeties to prevent flue gas from entering the space. Spill switches, poor draught sensors, etc. That said, any building with a gas burning appliance in it -- from a gas stove up to a big boiler -- should have (and in many jurisdictions, must have) a CO detector. The ones from the big box and so on really aren't good enough; you should have a low level CO detector.

Using the word furnace by definition, but against what many say here, I would say a good quality condensing system has a lot of pressurized water in the heat exchanger to prevent CO from entering the living space.

There's one hell of a huge selling feature over forced air and I think people need to start pushing it.

Grallert

I've found on warm air furnaces that the fan pressure will often lock out a burner if the heat exchanger is cracked. Over pressuring the combustion side of the unit. Not a safety by any means but often the first clue I would get in finding a faulty exchanger. a good quality co detector is a must.

mixe1

Would a cracked HE or a blocked flue become apparent because of a malfunction of the unit? (like maybe unable to fire, limit, soot, open pressure switch, erratic or orange flames etc)

Or could you see a cracked HE or blocked vent with no other signs of a problem?

Just looking for some piece of mind that a made in china CO detector is not my only fail safe.

captainco

New condensing equipment is less likely to spill into the space but it has happened even to the point that high efficiency boilers,water heaters and furnaces have been recalled. There have been deaths caused by re-infiltration from outdoors. There have been poisonings from leaky plastic flues because the pvc glue doesn't hold up.
Cracks in heat exchangers have almost never poisoned or killed anyone but holes have. Any time equipment is set up by sight or sound and not combustion testing it is potentially dangerous.
No contros on new equipment guarantee its venting or running safe!

pecmsg

mixe1 said:

Just looking for some piece of mind that a made in china CO detector is not my only fail safe.

You Uncle is confident that UL Approved CO detector is safe, Im Not.

I install a Low Level CO detector on all my installs. These will let you know "Something" is not right much earlier then the UL listed models!

mattmia2

So kidde makes a number of detectors with an led or lcd display that will indicate down to 10ppm, is there a problem with those models?

pecmsg

As long as they Alert at a low level.  

I prefer the Defender. 

Zman

I would say that redundant CO detectors are your best defense.
It is possible for a clever controls person to interlock a CO detector with the boiler controls so it shuts down when CO is detected.