The Fireside by Don & Glenda Hargrove A simple but effective test that will save you BTUs! Last issue I discussed various definitions of heat and the ways it moves around us. Heat can be moved, stored, contained, or wasted without us realizing what is happening. A case in point is the propane fired water heater. I have one, and many are in use in AE households. Do you know the BTU rating of this most important appliance? Do you know whether it actually delivers the amount of heat it is supposed to? How many of those precious BTUs are being lost through your vent pipe and heater casing? I want to tell you about a simple performance test you can run on your hot water heater to test its efficiency. You will need a thermometer that registers at least 150¡F., an accurate watch, a vacuum and a good stiff wire brush. Turn the hot water heater control to the pilot position. Allow the water heater to cool, or drain the heater and let it refill with cold water. Now turn on any hot water faucet and record the temperature of the water. I started my test with a water temperature of 60¡F. Make a notation of the time, and immediately turn the hot water heater ON. When all the water in the heater reaches the temperature you have set on your thermostat, the burner will go out. Immediately make a note of the time and turn the water heater off. Take another temperature reading at the same hot water faucet you used before. Some lucky person in your household now has the luxury of an entire tank of hot water while you continue on with the dirty part of the test. Allow the burner to cool off for at least 20 minutes. Cover the burner unit completely with a plastic bag. Using the wire brush and/or sandpaper, clean all the rust and scale from the bottom of the tank. It's rather a tight fit through the small door, but perseverance will pay its rewards. Be sure to wear gloves and a long sleeved shirt. For extra safety, wear goggles. A flashlight helps a lot. After the bottom of the tank has been thoroughly cleaned, remove the vent pipe from the top of the heater. Pull any baffle inside the heater up and out of the heater. Using a wire brush taped to a handle, clean rust and scale from the tube through the heater's tank. Take a little time and clean this tube well. The result of your efforts may be an impressive pile of gunk in the bottom of the heater. Vacuum all the rust and scale from the bottom of the heater. After I cleaned mine out, I lined the area under the burner with aluminum foil. This will help reflect radiant heat onto the tank. By now the lucky household member has probably used up all the hot water. If not, you get to use the hot water, but only until its temperature reaches the temperature reading at the very start of the test. In my case 60¡F. Now relight the pilot, turn the heater on, and immediately note the time. Wait until the water reaches the same thermostat setting as before and the burner shuts off. Note the time and temperature of the hot water at the same faucet you have been using. If your heater needed a good cleaning, it should take less time to reheat to the thermostat setting. I was able to reduce burner operating time in my case by 12 minutes. If you don't realize any change after you have cleaned your heater, your water may have high mineral content. This will cause mineral build up inside the tank and insulates the water from the burner's heat. Replacement is the only solution for tanks coated on the inside. What does all this data we've collected mean in terms of efficiency and BTUs saved? Subtract the start temperature from the final heated temperature for both data runs, one with the dirty heater and the other clean. Subtract the time figures from each other as well for each run. We now have two sets of data about how long it took to heat the water a known number of degrees. Look on the heater and find the manufacturer's info on tank capacity in gallons and burner size in BTUs. My heater has a 40 gallon tank, and is rated to deliver 38,000 BTU per hour. 38,000 BTUs per hr. Ö 60 min. per hr. = 633.33 BTUs per min. 40 gal. X 8.33 lbs. per gal. = 333.2 lbs. of water in the tank. 1 BTU = 1¡F. temperature rise in 1 lb. of water. Here is the data from my test runs: BEFORE Temperature Increase = 72¡F. Heating Time = 72 minutes AFTER Temperature Increase = 72¡F. Heating Time = 60 minutes It took 72 minutes to warm the water up before cleaning the heater and 60 minutes to do the same job after cleaning. Since my burner produces 633.33 BTUs per minute, its operation for 72 minutes produces 45,600 BTUs of heat (633.33 times 72). Its operation for 60 minutes produces 38,000 BTUs. The amount of heat it takes to raise the temperature of 333.2 lbs. of water (40 gallons- my tank size) 72¡F. is 23,990 BTUs (333.2 times 72). This is the amount of usable heat I have gotten from my water heater. If we subtract the amount of heat we have put into the water from the amount of heat we produced on each test run, we can calculate heat lost and the efficiency of the heater. In my case, I lost 21,610 BTUs before the heater was cleaned (45,600 minus 23,990). After cleaning the heater I lost 14,010 BTUs. This can be calculated as efficiency. Before cleaning, efficiency of the heater was 52.6% (23,990 BTUs of heat into the water divided by 45,600 BTUs used in the burner). After cleaning, the heater is 63.1% efficient. The 7,600 BTUs of heat I saved by cleaning the heater amounts to an efficiency increase of 10.5 %. Not bad for an hours work. There are 91,500 BTUs in one gallon of propane. This means we have saved about 0.08 gallons of propane per tank full of hot water. Assuming that we use 50 tanks of hot water monthly and a local propane price of $1.20 per gallon, we save $4.98 per month. If I keep the heater clean all the time, then we save $59.76 yearly. If your fuel source is natural gas, there are 100,000 BTUs in one therm (100 cubic feet) of natural gas. Your natural gas meter reads in cubic feet. You can use the same and similar experiments to check heater efficiency. Try it after adding an insulating blanket to your water heater. Now that you've cleaned your heater and saved some BTUs for future use, use your imagination and go enjoy that full tank of hot water!