The Standard for Degree-Day Measurement

NOTICE – FACTORY REPAIRS ON THE  F-90 AND F-90H WILL END ON DEC. 31, 2009

Johnson Degree Day has been meeting the demand for an accurate way to calculate heating degree days for over 50 years. Our fuel demand meters measure combined effects of temperature, wind, and sun to give you "effective" degree days!

 

We have four generations of Degree Day Meters. The first generation is the model ZZW. The ZZW was built in the late 50's to late 70's, and a large number of these meters are still in operation. The second generation of Johnson Fuel Demand Meters is the D-10 and the FD-50.  These meters were built in the late 70's to late 80's. Most of these meters are still in operation today also. The third generation of Fuel Demand Meters were the F-90 and the F-90H. The current models all have the Daywatcher designation.


Because of the advances in electronics, many of the components used in the earlier models are no longer available.  The ZZW, D-10, FD-50 are no longer able to be repaired.  Some, later model F-90 & F-90H units can be repaired, depending on the components affected.  Call our office for more information.


First, we need to identify what kind of model you have. All our meters have the model number D-10, FD-50, F-90, or F-90H on them except for our oldest meters - the ZZW's. The ZZW's have a serial number rather than a model number. The F-90 and F-90H are gray colored, the D-10 and FD-50 are either cream, black, or blue colored, and the ZZW's are a brown color.  If you have a D-10 or FD-50, there are no tests that you can do for it.

TROUBLESHOOTING the F-90 MODELS

When troubleshooting, it is very important NOT to assume there is a problem after only one occurrence.
Get two or three readings that indicate that there is a problem with the meter before making an effort to troubleshoot your meter. The more occurrences you have on record, the easier it will be to single out the problem.


To determine that there is a problem with your meter, compare your degree day readings with the readings of either the local weather service or a company in your area that has a Johnson Degree Day Meter. Due to the method of calculation it is better to compare your readings with a degree day meter rather than the weather service. For the best results compare with more than one other source of degree days. For help finding a company in your area with a meter, please call our service center.


Once you have determined there is a definite problem, you can use the following three steps to help you single out the cause of the false readings.

POSSIBLE PROBLEMS WITH YOUR F-90 WITH HEAT ONLY

 

POSSIBLE PROBLEMS WITH YOUR F-90H WITH HEAT AND HOT WATER

 

TEST 1

TEST RESULT

TEST RESULT INDICATIONS

TEST 2

TEST RESULT

 

TEST RESULT INDICATIONS


TEST 3

TEST RESULT

 

TEST RESULT INDICATIONS

 

OPERATION OF F-90 UNITS
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After your meter has been installed and plugged into the power outlet, it will begin to calculate degree days. The degree days will be slightly off the first day of operation due to the time of hook up and the temperature of the outside box when it is hooked up. The following is a brief explanation and instruction of the use of each component of the inside unit.

COUNTERS
There is a 'heat only' counter on both the F-90 and F-90H. This displays the degree days for your customers who use fuel oil, propane, or gas only for the purpose of operating their furnace. These degree days are determined by the length of time that the outside unit is calling for heat. The outside unit will call for heat more often the colder it gets outside, which means there will be more degree days accumulated. The F-90H also has a heat & hot water counter. This takes the 'heat only' degree days and adds additional counts for the fuel used to operate the hot water heater. The additional hot water degree days are determined by the length of time the outside unit is not calling for heat. The more 'heat only' degree days that are calculated the less additional hot water degree days are added. Once the outdoor temperature gets cold enough to produce more than 30 degree days on the heat only counter, only one or two extra counts will be added to the heat & hot water counter. It is not unusual for the heat only and the heat & hot water counters to be the same when more than 30 degree days have been calculated. On each of the counters there is a button to the left of where the degree days are displayed. This button is used to clear the degree days. When this button is pushed the counter will return to a setting of zero. Some software programs require you to set your degree day meter back to zero in the early fall. When the reset button is not being used slide it downward into the locked position. With the button in this position, your meter cannot be accidentally set back to zero.  The number of degree days will stay displayed on the counter if the meter is unplugged or if the power shuts off. It will add one count to the heat & hot water counter every time the meter loses power.

ADD BUTTONS
Underneath and to the left of each counter, there is an 'add button' which is covered by a grey rubber boot. The add button under the heat only counter will add one count to both counters on the F-90H. It will add one count to the 'heat only' counter on the F-90. The add button under the heat & hot water counter on the F-90H will add one count to the heat & hot water counter only. The meter must be plugged into an outlet for these operations to be executed. However, if you need to add counts to only your heat counter and not the hot water counter, you can accomplish this by simply pushing the add button under the heat only counter when the meter is unplugged from the outlet. There is a period of operation in which no counts can be added to the meter. If the add buttons do not add counts wait about 10 minutes and try again, or perform TEST 1 for 3-4 minutes.

INDICATOR LIGHTS
There are three indicator lights on the F-90H. There is a red indicator light on the bottom right corner of the unit. This light indicates that the unit has power being supplied to it. Under the 'heat only' counter there is an orange indicator light. This indicates when the unit is in the process of calculating a heat degree day. The meter will not add a count every time the light comes on. Under the heat & hot water counter, there is an orange indicator light which indicates when the unit is in the process of calculating a hot water degree day. There will be a period of operation when neither of the orange indicator lights will be lit.
 
RESET THE COUNTER
The counter that is used in your meter is an Omron H7EC counter. When you receive your meter, you will not be able to use the reset button on the front of the counter to reset the number display back to zero because the key protect switch is on. The reason we factory set the key protect switch on, is so that the number of degree days on the number display won't be accidentally reset to zero. This would cause havoc in the middle of the heating season. But if you want the reset button active, follow the given procedures below:
 


INSTALLATION

Select a location for the meter. The inside unitis designed to be mounted on the wall using two screws 8.5'' apart. The unit needs to be mounted within five feet of a AC power outlet. It is recommended that the unit not be mounted in high traffic areas, as someone may be tempted to press the ADD or RESET buttons "Just to see what happens." The RESET button has a protection switch and the ADD button is covered with a rubber boot to help protect against this from happening.

Select a location for the outside unit. Proper location should be at least three feet above and one foot away from any heated surface. In addition the location should be at least three feet away from chimneys, vents, or hot air exhaust. When placing the unit in the vicinity of a chimney, vent, or hot air exhaust, take into account the prevailing wind direction. It is recommended, but not mandatory, to place the unit on the prevailing wind side of the building.
Plan the routing of the cable.  The cable path should run from the outside unit to the meter as directly as possible. Try to keep the length of cable exposed to the elements as short as possible. The cable used is a common 3 ply 18 gauge cable. The cable may be cut or spliced as long as the connections are clean and protected.