Question for HVAC types

[Don Baer]

I had the house I am selling inspected and the inspector wrote down that the "knox rods" in the furnace are worn. What are knox rods and can I replace them my self ? Where would I look for them in the furnace ?

[Randy Moore]

Don,

I have done some residential work but mostly commercial HVAC. I have never heard of those rods.

Be interested in the responses

Randy

[Charlie Hans]

Here is a link that will tell you what you are asking I think.
www.nachi.org/bbsystem/viewtopic.php?p=103069
Charlie

[Ken Garlock]

Don, he must be really talking about the Johnson rods. Johnson rods are those imaginary parts of a car or machine that are always loose or just falling off. The important part is that they are only seen by teenage boys. The problem with Johnson rods are yelled at the vehicle driver in an attempt to get him to pull over and check his rig.

Otherise, I would get a second opinion.

[Frank Hagan]

Sounds like NOx rods ... as in Nitrogen Oxide. I'm assuming this is a house in Southern California (except for San Diego), the state of Texas or Clark County, NV? Smog regulations require lowered NOx emissions there from appliances.

NOx is formed when metal is heated, and when fossil fuels are burned. One way to lower NOx is to limit the amount of metal that gets heated in a furnace. Modern pressurized burners concentrate heat above the burner surface, whereas older atmospheric style burners had larger ports and the flame heated the burner metal quite a bit. The NOx rod simply dampens the flame and cools the burner, thereby producing less NOx.

NOx rods are problematic. There are better (read, "more expensive") ways to acheive the lowered NOx emissions, but the NOx rod was a quick fix when the regulations came into effect. I'm not sure if you have to have the furnace restored or not, but I'll bet the SCAQMD does require it with the sale of every house. It may be cheaper to replace the furnace.

First, check to see if the furnace is covered under a voluntary recall by the manufacturers and the CPSC (you may get the repair done for free ... see http://www.furnaceinspect.com/questions.shtml and the CPSC's notice at http://www.cpsc.gov/cpscpub/prerel/prhtml00/00190.html)

The recall covers only "horizontally fired" furnaces ... if the furnace is longer than it is tall, it is probably horizontally fired. Find the model and serial number to compare it to those listed on the websites above.

[Al Willits]

I'd go with NOx rods too, here in Minn we can just remove them when they rust out, unfortunately in Calif you don't have that option, if there's no recall on them, contact a parts supplier or the manuf of the furnace about replacements, not sure of the furnace you have, but most are replaceable parts that we've seen


Al