Trane heat exchangers

[billygoat22]

Isn't there a "buy my book here" button on this site? sounds like one I saw yrs ago. Everyone is ripping you off, buy my book and I'll tell you what you want to hear, don't fix it.

He states static pressure as proof that furnaces can't leak @ hx, but total pressure is full picture. Also, not seeing employees of manufacturers telling the public about furnace hxs is not proof that cracked hxs are safe.

[pairajacks]

Total pressure is static plus velocity pressure. As the blower air sees restrictions, the velocity pressure gets backed up and INCREASES static pressure. The bulk pressure in the blower - house area is higher than the combustion chamber. The only way to get reverse air flow through a crack is to have local eddies where the venturi effect dominates, sucking CO into the house air. (Can this happen? Or is it designed to be fail-safe?). The sited reference did talk (slightly) about this.

My point is, if something is this unsafe, and potentially dangerous to just about everyone, wouldn't gas furnace heat exchangers be designed to be fail-safe? Does anyone KNOW that they are not designed to be fail-safe? Just about every other product under the sun IS fail-safe. Why isn't the un-attended roaring gas-fire in everyone's garage that we call a furnace fail-safe?

Given how likely furnaces are to have a crack (I read some posts where 3 year old Trane furnaces were being replaced for cracks), the market should be moving in the direction of making furnaces fail-safe, not relying on service guys to make judgements about hard to inspect areas.

[Chuck]

Total pressure is static plus velocity pressure. As the blower air sees restrictions, the velocity pressure gets backed up and INCREASES static pressure. The bulk pressure in the blower - house area is higher than the combustion chamber. The only way to get reverse air flow through a crack is to have local eddies where the venturi effect dominates, sucking CO into the house air. (Can this happen? Or is it designed to be fail-safe?). The sited reference did talk (slightly) about this.

My point is, if something is this unsafe, and potentially dangerous to just about everyone, wouldn't gas furnace heat exchangers be designed to be fail-safe? Does anyone KNOW that they are not designed to be fail-safe? Just about every other product under the sun IS fail-safe. Why isn't the un-attended roaring gas-fire in everyone's garage that we call a furnace fail-safe?

Given how likely furnaces are to have a crack (I read some posts where 3 year old Trane furnaces were being replaced for cracks), the market should be moving in the direction of making furnaces fail-safe, not relying on service guys to make judgements about hard to inspect areas.

When a crack gets to the point of leaking, it is hazardous to have air blowing into the HX. This affects the flame and can cause dangerous rollout and elevated CO levels. Wouldn't it be better to catch the crack before it gets to that point, even if it is not an immediate hazard?

In most cases, just a visible crack in a HX is not sufficient reason to red tag and disable a furnace. To shut down and red tag requires there to be a problem that poses an immediate danger to the occupants of the building. A barely visible crack does not qualify but needs to be brought to the owner's attention and repair recommendations made.

[Joehvac25]

I had one last week, hairline crack, no rollouts. I told the lady, it's under warranty so I ordered a primary and secondary, left it running.

[billygoat22]

Total pressure is static plus velocity pressure. As the blower air sees restrictions, the velocity pressure gets backed up and INCREASES static pressure. The bulk pressure in the blower - house area is higher than the combustion chamber. The only way to get reverse air flow through a crack is to have local eddies where the venturi effect dominates, sucking CO into the house air. (Can this happen? Or is it designed to be fail-safe?). The sited reference did talk (slightly) about this.

My point is, if something is this unsafe, and potentially dangerous to just about everyone, wouldn't gas furnace heat exchangers be designed to be fail-safe? Does anyone KNOW that they are not designed to be fail-safe? Just about every other product under the sun IS fail-safe. Why isn't the un-attended roaring gas-fire in everyone's garage that we call a furnace fail-safe?

Given how likely furnaces are to have a crack (I read some posts where 3 year old Trane furnaces were being replaced for cracks), the market should be moving in the direction of making furnaces fail-safe, not relying on service guys to make judgements about hard to inspect areas.

manuf manual says annual maintenance required, and as part of that hx inspection. GAMA standard is industry guidline for hx inspection, and is repeated as addendum in international code book. that seems to be the method for keeping and eye on hxs.

blocked flue switches are not hx hole detectors.

I've seen furnaces that were positive static pressure in the cabinent, but soot all around the crack/hole in hx and in house.

I'vbe tried contacting manufs/reps about the hx issue, how much too much crack, and they're rather evasive about giving straight answers. Have a Payne document about the steel secondary hxs that resulted in a class action lawsuit, and there was some spin on that.

[Hvac216]

Any crack and I condemn it. I won't make it unusable unless its really bad. A crack can lead to poor combustion which will lead to worse combustion. I'd rather err on the side of caution. I can see not doing anything and have it turn bad in a year or two and then come back on the last person who had their hands in it.

[LibertyTree]

This was a big reason I stopped selling Trane. Customers always ask me what is the best furnace to which I can answer with all sincerity that its all about the heat exchanger design. I now only sell brands with tubular heat exchangers, no more clamshell for me ever again. These companies need to sack up and move to a tube design. They aren't perfect, we've all seen cracked tube HX's but they are like a needle in a haystack compared to the daily cracked clamshells. Trane is going to learn the hard way like Carrier.