Oven more resilient than they think

kw: local events, observations, home maintenance

Replacing a burnt-out (partially melted) oven element from a forty-year-old range is no trivial undertaking. I'll forego a blow-by-blow rant on the five hour process. Just the facts I was faced with:

• Waste King has not made ranges for more than twenty years.
• The "book" (no web site had the model number) at the parts place showed about 100 WK oven elements, but none was even close to the one we brought in.
• We considered replacing the whole range, but it is 29.5 inches (75 cm) wide and all modern units are at least 30 inches (76.2 cm). The "hole" it needs to fit in is 29-5/8 inch (75.25 cm).
  
• It is also 24 inches (61 cm) deep, much shallower than modern units.
• Somebody needs to design an oven with the connections to the heating element in front. It took me two hours to get the element out.
  
• The heating element is marked 240V, 2700W. Most modern heating elements are 3000W or more. The guy at the parts store warned against using a different element.

OK, on that last point: I know physics. A 2700W element at 240V will use 10.8 Amps, so its resistance (hot) needs to be 22.2 Ohms. A 3000W element will use 12.5 Amps and resist at 19.2 Ohms. More on such figures anon.

The parts store manager got me in contact with a local repairman whom he called "the McGiver of appliances". Turns out this guy is a gem. He said the oven switch had plenty of capacity to handle 12 amps or more, because it was sized to run the oven and broiler both, and the broiler has a hotter element. He said it is worth a try with an element that hooks up the same (there are a lot of those).

His shop is one of those wonders of the lost art of mix-and-match repair work. He has a few dozen old ranges on the floor, plus hundreds of other used appliances. But most of his space contains parts from discarded units. Among a few thousand oven heater elements, he chose two (of many) that would fit the connections, though they are a bit smaller than the one being replaced. Others were clearly too large. He also found one clearly marked 1800W, so we had a standard to use for checking resistance.

1800W at 240V means 7.5 Amps and 32 Ohms. His Ohmmeter showed this one was 45 Ohms, cold. That makes sense; Nichrome wire loses a little resistance when it heats up, but not so much that it runs away with itself. So now we had a factor: 45/32 = 1.4. I needed a resistance between 1.4x22.2 = 31 and 1.4x19.2 = 27 (both rounded a bit), and I would not care much if it was a little higher than 31 Ohms.

Both the "near fits" came in about 33 Ohms, so I bought them. One was cleaner than the other, so I cleaned it some more and put it in. It heats up a bit more slowly than the oven used to, because I suspect it is a 2400W element. Fine by me.

Anyone out there whose oven element melts on them: find a place with used parts, and it is likely you can locate an element that will work well and extend the life of your range. I saved myself a kitchen remodel for $30 (plus five hours of my time).