Warmth Exchanger Cracks In Furnaces And Security Issues

Matthew Showers is an HVAC service technician, performing work in each the residential and business fields.  His specialty is in inverter and speaking methods.  Observe Matt on Instagram 

As heating season will get underway for many people, we’ll inevitably discover warmth exchanger cracks in furnaces, whether or not in somebody’s residence or on a business RTU at an workplace constructing.  Many, if not all, of us have been instructed {that a} cracked warmth exchanger is a hazard to individuals from a carbon monoxide standpoint. However is that this true? What are the precise security hazards of permitting a furnace to function with a compromised warmth exchanger?

Try three cracked Service warmth exchangers on the identical roof

This practice of thought started on a latest service name. I used to be requested by my boss to research a problem, after one other firm had condemned a warmth exchanger. I used to be requested to report again the mannequin and serial numbers, so we might give the constructing house owners one other quote for alternative. I used to be additionally instructed that the opposite firm had “repaired” the cracked warmth exchanger, so I needed to truly discover the defect for myself. What I discovered disgusted me: the opposite firm had merely utilized some RTV silicone to the opening and put it again into operation. Earlier than I left, I turned the gasoline provide off as a result of I didn’t need to be held liable ought to somebody endure and I used to be the final one on web site.

Sadly, there should not many assets relating to security and cracked warmth exchangers. From a basic physics standpoint, if a crack is massive sufficient, it is going to disrupt the burner flame as soon as the blower begins up.  This occurs as a result of the optimistic strain of the blower fan pressurizes the warmth exchanger, the added strain forces the flame to roll out of the burner part. Additionally, we are able to discover potential cracks by way of combustion evaluation based mostly on how readings change with the blower on in comparison with when the blower is off. I encourage anybody who works with flamable home equipment to obtain and browse Jim Bergmann’s free information, discovered at TruTech Instruments’ web site (https://www.trutechtools.com/Downloads) for extra info on this matter.

You can too take heed to Jim focus on combustion evaluation on this episode of the HVAC Know It All Podcast

There may be one article I discovered written in Oct. 2004 from Contracting Enterprise speaking about CO myths (https://www.contractingbusiness.com/archive/article/20864508/carbon-monoxide-lets-stop-the-insanity). The principle fable that the creator desires to dispel is that warmth exchanger cracks trigger CO. This, from a scientific standpoint, will not be true as a result of the surplus air from the blower provides combustion air which dilutes the flue gasses. From the expertise of a variety of technicians, most CO points come from improper venting, whether or not it’s blocked vents, recirculation of flue gasses, or spillage attributable to a number of home equipment sharing a typical vent.

Try Matt’s put up from Instagram discovering a cracked warmth exchanger

There may be one notable exception relating to burner assemblies: gun sort burners. Most combustion home equipment make the most of inducer motors which pull by means of the warmth exchanger meeting, whereas gun sort gasoline burners, much like normal oil burners, push by means of the warmth exchanger. Probably the most notable instance of those in my expertise is Trane’s Voyager RTU line. The warmth exchangers on these have a single massive header which then splits into particular person tubes, which is the other of what we sometimes see with “normal” burner assemblies. On this case, the warmth exchanger is definitely in a optimistic strain, so a crack might permit flue gasses to then be pushed into the air stream.

Trane Voyager burner diagram from the Trane 360 App

Right here’s a pair residential tales from my very own expertise:  Years in the past, once I was simply beginning within the area, I went out to a house to do a warmth upkeep for a brand new buyer.  Shortly after I began my inspection, I decided there was a crack within the warmth exchanger of the furnace, which was positioned within the attic. After I talked to the client about this, he talked about that his two youthful daughters, who have been between 2 and 6, had been complaining of getting complications. This was a telltale signal of CO poisoning, as kids and pets are extra prone to its results. Whether or not this was brought on by the warmth exchanger or another means I’m not sure, since I used to be nonetheless a greenhorn. 

One other time, about 2-3 years in the past, I went to an individual’s home who additionally complained of getting CO signs. I examined the furnace and located no points there, however upon inspecting the fireside upstairs, there was a noticeable “stain” on the steel curtain, which indicated that the chimney was blocked, inflicting the combustion gasses to spill into the house from simply the pilot! As technicians, we want to pay attention to any and all combustion home equipment even when we’re there primarily to examine the furnace for a routine upkeep.

In my view, any time I come throughout a cracked warmth exchanger, I flip off the gasoline and in houses, I flip off the change. I then inform the client concerning the state of affairs and that the warmth has been turned off as a result of it poses a possible CO downside. With business RTUs, I don’t flip off the disconnect simply in case the realm warms up and AC is then requested. To me, that is the most secure and finest apply for you, your organization, and the client. There are too many potential dangers, most particularly, well being to the client and legal responsibility on you.

Notice from the Gary McCreadie…

If a technician has any concern {that a} buyer might probably flip the gasoline again on, the tech can electrical disable the equipment from inside the cupboard.  Some areas require that purple tags are added to the equipment and likewise reported.  These steps will to assist to make sure the tech has offered due diligence.  

Matthew Showers

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