Thursday, December 16, 2010

Life's Better When You Know How Things Work

...In which Nathan struggles with a left-handed thermocouple and wins, then gets to school a doomsayer for his encore.

As a short-term fix, he'd duct-taped the critter in place, which provoked this response:
"Geez. When the water heater blows and launches through your roof, I wonder if it will look like the contrail in LA last month."

Nathan for the win: "It can't blow. [...] See, a thermocouple is a dielectric generator that puts out a couple of millivolts of electricity when it is heated (e.g., by the pilot light). It is connected to and holds open a normally-closed solenoid valve. If the pilot light goes out, the electricity stops, and the valve snaps shut, cutting off the gas. It does, in fact, fail safely, which is what happened when the thermocouple went bad[...]."

Yep. No moving parts. No external source of juice. Heat it up, it makes electricity; cool it down, it doesn't. This is true no matter if the lack of heat is from the pilot light going out or the thermocouple falling out of its awkward, backward threads. (And if you think that's fun, the ancient coal-converted-to-gas furnace in my house in Collegetown even ran the thermostat on the thermocouple voltage; talk about failsafe! And it would run and heat the house, albeit without forced air, even when the power was out.)

I don't know when it became popular to assume that all household appliances are monsters teetering on the brink of explosion and that all American men are hapless boobs when it comes to fixing them, but it's not true. It's funny in sitcoms because it's not true.
______________________
For the record, I vote with Nathan: left-hand threads on a common thermocouple is just stupid. I'd be very tempted to note the backwards threading on the water heater with a Sharpie or a paint pen.

20 comments:

Stranger said...

Hmm. Since Whirlpool makes darn near everything you can buy in household appliances, a sinister thermocouple is - sinister.

The more so when the seven appliances in the house all have different labels but were all made by Whirlpool.

At least there is an almost local, 30 miles each way, branch of Appliance Parts.

Stranger

perlhaqr said...

I wonder what the reasoning on using left-handed threads there was.

I know that the standard on gas welding apparatus is to have the fuel side connections be in left handed threads. One might almost think that reasoning was used here, in that the thermocouple is part of the fuel gas control system--except I've worked on household gas appliances, and their piping all runs regular old right hand pipe threads on their feed lines.

I'm with you on the "marker" idea, though. I had an older Chrysler at one point that had the left handed threads on the lugs on one side of the car. Spray painted all the lug-stud faces bright red on that side to remind me not to tighten them further when I was trying to pull a wheel off.

Nathan said...

I think I'm beginning to understand the left-hand thread thing. Apparently there is a fusible link inline between the thermocouple and the connector, which is set to blow when the temperature in the sealed combustion chamber gets too high (i.e., when the inlet for combustion air gets clogged). The left-hand thread prevents Joe Random Homeowner from replacing it with a standard 'couple that doesn't have the fusible link.

The fact that it has that fusible link, and that it was not made clear that the air inlet (which is on the bottom of the water heater, out of sight, out of mind) needed to be cleaned on a regular basis, is what caused so many people to have trouble with this model, and is why Whirlpool had to agree to a class-action settlement to get out of a massive defective product lawsuit. And they apparently modified the heater so that it now has a reset button on the combustion chamber door instead of a one-time fusible link in the thermocouple. (Mine, of course, does not have that feature. So the next time it goes bad, the water heater gets replaced.)

Nathan said...

FWIW I will not be replacing it with a Whirlpool (or any of the ones made by American Water Heater). It will probably be replaced with a Rheem or an A.O. Smith. Or maybe even one of those cool Bosch on-demand heaters...

Joanna said...

"I don't know when it became popular to assume that all household appliances are monsters teetering on the brink of explosion [...]"

I have florescent lights in my kitchen. My godmother is terrified of the bulbs, convinced that the slightest little bump will shatter them and send pieces flying. It's so bad that when I had to replace one last spring, I almost couldn't cut away the packaging because she insisted on holding them while I worked -- even though I had a firm, tight grip on them already.

Nathan said...

I should add that:

1) In Whirlpool's defense, the thermocouple did have a little label on it that said, "Caution: Left-Handed Threads". What confused me about that was that I haven't even had to think about thermocouples for a number of years, and I honestly couldn't remember if that was normal or not till I went to install the replacement :)

2) My friend who posted about the correlation between my fix and the contrail in LA has good reason to be concerned about natural gas appliances. As it happens, I saved his wife's life one time when I arrived at their rented house one afternoon and found her about as woozy as one can be without being completely unconscious. The first thing I did was run downstairs and look at the brand-new furnace, where I discovered that some idiot had not actually hooked the thing up to the flue before walking away from the job. I shut it off and they called the landlord and gave him a right chewing out.

I've been working on furnaces and air conditioners since I was 11. Thermocouples and thermopiles (the correct name for the one on your old gravity furnace that provided voltage for the thermostat) have always fascinated me. They're so standard that it was a real cognitive dissonance moment when I ran up against this one.

Nathan said...

Joanna, the interesting thing about fluorescent tubes is that they are strong as heck until they break...at which point they continue to shatter even if you just look at them funny.

I don't like fluorescent tubes one little bit and I've had to replace thousands of them in my life; one of life's little ironies, that :)

Joanna said...

Nathan: It's the "strong as heck" part she seemed to be struggling with. It was like she thought they were made of spun sugar and I was working with asbestos oven mitts.

Stranger said...

Anyone who needs to replace a water heater should seriously consider a tankless demand heater. My Rennai cut my gas bill almost $40 a month, and paid the difference between it and the "high efficiency 40 Gal" I replaced in just over a year.

Stranger

Jeffro said...

Yeah, but - but....

Cars and trucks and planes all blow up - I've seen it on the boob tube so it must be true!

Jim said...

I'd file this beside Dell computers with the goofy pin-out on the power supply connector: Unnecessary, and easy enough to work around. For the heater, drill the goofy thread, and either use a larger thermocouple in the new thread or put a bushing in with normal-people threads.

For contrast mobile phone makers have banded together to standardize on MicroUSB for connectivity. I don't understand why, but I appreciate it.

Jim

Roberta X said...

Jim: Nope, not, read back up the comments and you'll see why. This thermocouple is special. Hmpf.

Nathan, with all due deference and I'm glad you were able to save him and his, did your friend not even check on the furnace work? --I'd fire that HVAC firm. It didn't happen to be A:rm@ster, did it?

D.W. Drang said...

I don't know when it became popular to assume that all household appliances are monsters teetering on the brink of explosion and that all American men are hapless boobs when it comes to fixing them, but it's not true.
"It's not up to code." And thus the .gov and the professionals conspire to ensure I call an electrician instead of doing the work myself. Honestly, the electrician does a better job, runs neater runs, etc. And technology now requires some specialized equipment and knowledge.

Roberta X said...

It always did, D.W. It always has.

Phillip said...

I grew up in the hills of WV, son of an appliance repairman. I learned early the value of knowing how anything I depended on worked, how to fix it if possible, and how to replace it if it wasn't.

I call specialists for some things nowadays, but there's a lot of things I won't let anyone else touch in my house unless I already know I can trust their work. Electrical issues are first and foremost of those, and if I had natural gas that would be another.

It always amazes me when I talk to someone and they haven't any clue how their car, computer, hot water heater, or much of anything else works. To me, these people live in a world of magic and those of us who can work on stuff are sorcerers.

Nathan said...

Bobbi -- Apparently it was like that when they moved in, or was done right after that, but it was all taken care of by the landlord. If I recall correctly it was a big duplex or quad in Chatham Arch that had recently been "renovated" by the owner. They also discovered the next summer that the brand new airconditioning unit outside was a hollow shell...

They did not live there very long. Between problems with the house and the generally crappy neighborhood, they hied away for Broad Ripple the next year.

I could not honestly tell you after all these years who the contractor was. I doubt if it was one of the big names. It was probably Sumdood that the landlord had on his speed-dial. He probably wasn't even licensed. (He certainly wasn't particularly skilled.)

Nathan said...

FWIW I would not use Broad Ripple's eponymous HVAC contractor, either; not on a bet. I've had experience with them and it was not good. Overpriced and undertalented in my book.

(They once put a 2-1/2 ton unit in a commercial space I had specced at 3 tons minimum and then acted surprised when it didn't work, and tried to blame it on us not telling them the space wasn't well insulated -- as if they hadn't gone over it when they were getting up their bid and didn't know that from the get-go. They ended up replacing it with the larger unit pretty much at cost.)

Nowayoutbutup said...

Even electric waterheaters can be fun.
About a month after buying the Mountain Shack I came home to about a 4 foot hole in the kitchen wall and a nice waterfall emiting from said hole.
Seems the thermostat as well as the tank popoff valve had chosen the same moment to fail.
While raking pine needles about a year later I found the popoff about 100 yards away.

Even though the mess was huge I am very glad I was not home for that event.
Plus the home inspection company paid for my kitchen remodel......

Ian Argent said...

@Jim: Oddly enough, you can thank the EU for the sudden standardization on MicroUSB for most phones. The eurocrats made noises about driving a Fiat over to the phone manufacturers and dictating a "standard" (for the environment, so that all those wallwarts could be re-used, basically). The manufacturers essentially standardized on MicroUSB (which had just been thought of) in self-defense.

WV: dulloom - much better for weaving than an exciting one, I suppose.

John B said...

Only 'cos we paid just under $600/year for insurance. We average a new appliance a year out of the arrangement. Furnace, dishwasher, water heater, none are jobs I'd want to do. Even back when I had my health. I may be building a modified tumbleweed house soon though. I love the idea of owning a house, instead of the other way around.