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Clocking a boiler

Tim Davis
Tim Davis Member Posts: 21
Can some one give me the formula clocking a boiler on natural gas.

Thanks in advance!


  • yeti
    yeti Member Posts: 3

  • John Williams, Jr.
    John Williams, Jr. Member Posts: 13
    do you mean...

    clocking the gas meter for fuel usage or burning rate?
  • yeti
    yeti Member Posts: 3
    clocking a meter

    For clocking gas input to an appliance (4 ounce) make sure all the other gas fired unit/appliances attached to the meter are shut off. Then the test hand on the as meter shall be timed for at least one revolution and the input determined by using this time for the smaller dials (1/4 and 1/2) allow at least two revolutions on the larger input appliances. test dials are generally marked 1/2, 1, 2, or 5 cubic feet per revolution. then check with your local gas supplier for converting the test hand readings to cubic feet per hour or

    (60 X 60 X dial size) divide by number of seconds for one revolution =total CFH
  • Clocking the burner

    1. Shut off all other equipment.

    2. Using a stop watch

    3. Look for the test dial on meter usually the 1/2 foot dial is best.

    4. Let the meter do two rotations of the 1/2 foot dial.

    5. Note the number of seconds it takes for the two revolutions of 1/2 foot dial.

    Example: 20 seconds for two revs

    Divide the number of seconds into 3600 (number of seconds in one hour)

    3600 divided by 20 = 180 cubic feet per hour

    Multiply 180 by the BTU content of gas in your area or use
    1,000 as a round number.

    180 x 1000 = 180,000 BTU's

    If you are interested I have a full procedure for measuring input available from our catalog.
  • Steve Paul
    Steve Paul Member Posts: 83
    clocking a boiler

    Measuring the Input of Gas to an Appliance

    Mr. Paul
    3rd Year Plumbing

    Sometimes we are called upon to service a gas water heater, furnace, boiler, range or other gas equipment that appears to be producing less energy than the customer feels is adequate. Some of these calls are unfounded but others are legitimate complaints. After exploring many of the possible conditions that might be causing this problem, we quite often still can’t come up with an accurate diagnosis.

    There are times that for various reasons the appliance in question may not be utilizing gas at the rate of input for which it was designed. Therefore we must determine if the burner is functioning at its designed rate of consumption or if it is burning at a level less than optimal. This can be accomplished simply, by utilizing the gas meter and a watch with a second hand. To understand how to perform this procedure, the following basic information must be understood by the servicing technician:

    1- Natural gas in this region has a heating value of approximately 1,000 British Thermal Units (BTU) per cubic foot (CF). This means that 1 CF of gas, when completely burned, will produce 1,000 BTUs of energy.

    2- Gas appliances are rated by their manufacturers as to their output per hour of BTUs they will produce (BTU/HR), or CF of gas they will consume for each hour the burner is in operation (CF/HR). This information will be found on the appliance’s rating plate and is usually stated as, “INPUT (number) BTU/HR”. Knowing that 1 CF of gas will produce 1,000 BTUs, we must be able to assure that we can supply 1 CF/HR of gas for each 1,000 BTU/HR of rating.

    To determine the actual input of gas being consumed by the appliance we can measure or “clock” the actual rate of input to the burner by reading the gas meter and timing the rate of gas consumption by the appliance.

    The gas meter has various dials that indicate the volume of gas in CF that has passed through it. For this procedure we are only concerned with the half (.5) CF dial.

    To clock an appliance, perform the following steps in the order listed:

    1- Shut all appliances and gas consuming devices except the one being tested.

    2- Raise the thermostat or heat control setting for the appliance to a point high enough to insure that it will burn continuously without shutting down until you shut it down.

    3- Start the appliance burning.

    4- At the gas meter, accurately count the number of revolutions turned on the .5 CF dial for exactly one minute (60 seconds). This will measure the revolutions per minute (RPM) of that dial. For example, the dial may have turned 2 times, or it may have turned 3.5 times, or 5.75 times, or any other reading higher or lower.

    5- Multiply this reading by 30.
    This is the volume of gas in CF/HR, actually being consumed by the appliance being tested. RPM X 30 = CF/HR.

    6- Multiply the number found in step 5 by 1000 to find the actual BTU/HR being produced by the burner. (CF/HR X 1000 = BTU/HR). If it is less than the manufacturer’s listed BTU rating, the burner is not being supplied with the proper volume of gas.

    For example:

    Let us assume that a boiler rated at 175,000 BTU/HR does not seem to be providing an adequate amount of heat. If we suspect that the input to the boiler is not what the manufacturer designed it to operate at, we have to determine the actual input that is being supplied to the burner.

    Following the above procedure, suppose the .5 CF dial in one minute’s time has revolved 4 revolutions (4 RPM). When we multiply, 4 X 30 = 120. Therefore, 120 CF/HR is the actual input being supplied to the burner. This is substantially below the 175 CF/HR input required to yield the 175,000 BTU/HR the boiler is rated to produce. Knowing this, we must look for the various reasons that may be causing this problem.

    Some of the explanations for this may be:

    1- Inadequate gas pressure from the gas supplier.

    2- Obstructions or debris in the gas piping, valves or pressure regulators.

    3- Undersized gas piping.

    4- A defective appliance gas valve.

    5- Clogged or improperly sized burner orifices.

    The final resolution to the problem will involve a careful, logical process of elimination and a step by step investigation into all of the possible reasons that could cause the problem. It is imperative that when working with gas, all due care and diligence be taken and adherence to all safety precautions be observed in every phase of servicing and troubleshooting. Only persons properly trained to work with gas should attempt to do so.

    It may be possible that the gas supplier will have to be called upon to correct the problem if it is found that the reduced input is caused by defects in the supplier’s equipment. Whatever the solution to the problem is, determining the rate of gas input is among the first important steps to take for properly troubleshooting gas equipment.
  • Clocking not that complicated....

    see my post for a much quicker and less complicated way. By the way when you use your method you have to determine the value of each increment of the test dial. However Steve the rest of your information is excellent. Thank you for a very detailed explanation.
  • Yeti what is

    4 ounce about I am not familar with that measurement as applied to gas.
  • Unknown
    simply written

    3600/(seconds in one revolution) times (hand size) times (BTUH value per cubic foot)

    72 seconds on a half foot hand with 1000 BTUH gas.......

    3600/72 X 1/2 X 1000

    50 X 500

    25,000 BTUH
  • rudy_2
    rudy_2 Member Posts: 135
    Gas meter timing charts

    We've got some info on clocking gas meters: http://www.bacharach-training.com/referpage/clocking_gas_meter.htm
  • rudy_2
    rudy_2 Member Posts: 135
    Gas meter timing charts

    We have info on clocking gas meters on the Bacharach training web site: http://www.bacharach-training.com/referpage/clocking_gas_meter.htm .
    We also have some 'wallet' sized timing charts available. If anyone wants some copies, just email me your address and I'll get them in the mail.
  • claudio
    claudio Member Posts: 1
    gas technician

    How do you clock a meter using a metric gas meter. I ve asked 2 guys from the gas company and neither knew how to do it  
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