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A few months back, I mentioned a tool recommendation, the kind of thing every handy homeowner should have. This month, we're going to talk about a tool that everybody should have, handy or not. It's suprising how few people have one of these, or know how useful it is.
The meat thermometer. Yup, just what you thought when you looked at the picture. Nothing fancy, just the basic $6 gadget found in the housewares section of any hardware store. I get mine at ACO and Damman. If you have one, you know how handy it is in the kitchen. Not only will it get the roast just right every time, but it can keep you from overheating the court boullion when poaching fish.
I hear you asking, "So what does this have to do with house management?" Ok, just be patient while I digress for a minute.
In many home inspections, if I notice the hot water at the faucet is too hot, I measure the temperature. I've made a habit of warning people that it should be turned down at the water heater if it's over about 130 degrees F. I found myself in disagreement with some people over how hot it should be. It seems there is no standard, but plenty of conflicting opinion. Years ago, some dishwasher makers suggested setting the water temp to 160F or so for cleaner dishes. Most modern dishwashers have on-board temp boosters to make that dangerous practice unnecessary, but some folks still are hung up on that old 160F figure. The National Safety Council says to keep it at 120F or so to avoid scald injuries, especially if you have kids in the house. Recently, I've seen several newspaper articles saying you should turn it down to 115F to save energy. How that saves energy, I don't know, because you will end up using more for the same cleaning effect. The amount of energy used by a water heater is so small in relation to the house's total energy load that saving 10% of it is not an issue with me. What's worse is that 115F isn't hot enough to effectively control bacteria in the tank, and you could end up getting sick from it. And to add to the confusion, the water heater makers refuse to calibrate their thermostats in real degrees, so we end up with a relative "warm-warmer-hot-really hot" spectrum on the control, and guesswork as to what it means. So here's where the meat thermometer comes in.
Regardless of the setting, the temperature of the water will vary a few degrees. To get a good measurement, you want to check it at the high and low ends of the cycle. In most homes you can hear the start of the water heater flame from somewhere that has a sink. Kitchen, laundry, basement bathroom, etc. Start running hot water, and when you hear the flame come on, immerse the end of the thermometer probe in the faucet stream. This is the low end of your heater's temp range. Shut off the faucet, and wait a few minutes for the burner to shut off. Then, run the faucet for about 20 seconds and take another measurement. This will give you the high reading.
So, what should the readings be? Well, here goes one more opinion. I am comfortable with anything between 120F and 130 degrees. If I had toddlers in the house, I would tend more toward the 120F end of the scale. If my dishwasher didn't have a temp booster, I would go toward the high end, (and think about replacing the dishwasher).
It may take several tries at adjusting that warm-warmer-hot control knob to get the result you want. Wait a few hours between adjusting and measuring, to let the water and the control come to equilibrium.
So, what else can you do with that thermometer? How about an easy test to determine how healthy your furnace is? You wouldn't believe how simple this is, and what kind of problems it can alert you to.
Nearly all furnaces built since 1965 have a specified temperature rise range. This is what the manufacturer thinks the furnace should do. Remove the front upper cover, and look for the data plate on the inside of the cabinet. (On a few later models, the data plate is in the lower compartment, mounted on the blower housing near the circuit board.) This is a text-heavy tag, giving the model and serial numbers, and other pertinent data. Somewhere on this plate the temp rise ("augmentacion de temperature de l'aire" on some units) will be given. It's expressed in a range, like 40-70 degrees, or 75-100. If you measure the temperature of the air as it leaves the furnace and subtract the room temperature, the difference should fall in this range.
To get the lower number you need, just let the thermometer sit in the living space for a while, away from heat registers, out of the sun, and up off the floor. The best place to get the higher number is just downstream from the furnace, inside a duct. The big box on top of the furnace, called the plenum, is not the best spot. Radiative heating from the exchanger may give you a false high, and you risk poking the thermometer probe into the delicate evaporator coil of the A/C unit at this point. Look for a register as near as possible to the furnace, and stick the probe in there. Sometimes the joints between pieces of ductwork are loose, and you can insert a probe between the sections. The fabric sleeves on the ducts are fair game, too. The 1/8" hole you make in it with the thermometer will not have any significant effect.
Let the furnace run for a few minutes, and watch the thermometer reading. It will climb steadily, then level off. If the burner shuts off while the temp is still rising, turn the thermostat up a few degrees to get a longer on-cycle. Write down the highest reading, and subtract what you got for room temp. If the result is in the specified range, your furnace is running properly.
But what if it isn't? Temperature rise on a furnace is like blood pressure on a person; if it's out of spec, it's telling you something is wrong, but not exactly what. If your reading is too high, the cause may simply be a dirty filter. Change or clean the filter, and try again. If it's still too high, or substantially too low, then it's time to call for service. Running a furnace too hot shortens its life by overstressing the heat exchanger. Running it too cool can cause condensation inside the exchanger, also shortening life. Efficiency is also ruined by running too cool. Minor adjustments, like gas pressure and blower speed, affect the temp rise. Fixing these is work for an experienced heating contractor. If the top reading is really high, like over 200F, you have a serious problem, and should get a professional evaluation right away.
Next spring, I'll talk about using this same technique to evaluate air conditioner performance. One more thing on thermometers. When you buy one, look at all the units hanging on the hook in the store. They should all agree within a degree or two. Don't buy the one that reads several degrees off!
Nag of the month: This is the sort of weather that keeps the furnace running, and therefore the humidifier should be on. If you have a rotating-drum type humidifier, do a mid-season cleaning of the pan and pad. Is the pad hard and crusty? Throw it out and get another one. They seldom last more than a year or two, but they're cheap and easy to replace. If the unit is dripping, you need to adjust or clean the float valve inside the unit. Most of what accumulates in the pad, the pan and the valve seat are mineral deposits that come in with the water. There are tablets that you can buy at the hardware store that prevent the minerals from crystallizing, but then they just remain suspended in the water, turning it brown and thick. Regular cleaning is a much better way to handle the minerals.
Enjoy the rest of winter, we ain't halfway through this thing yet!
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