Frequently Asked Questions

1. How do I set up an economizer to supply 10% fresh air ?
2. How can I verify that a gas appliance if firing at the rated input ?
3. What are the comfort zones ?
4. How do I set up capacity controls ?
5. What is ... ?
6. When is ... ?

How do I set up an economizer to supply 10% fresh air ?

"Just look at the opening and if it's close that's good enough. " That's the answer I was given when I first asked the question. " good enough " That bothered me, I knew the minimum allowed by law was 10 % and any more could  potentially be a waist of energy so I was determined to find an easy way to verify the setting. To set up an economizer to a given percentage all you need is a thermometer. With a thermometer in hand take the outdoor ( OA) and return air ( RA ) reading and multiply each by the percentage required. If we wanted 10% fresh air we would multiply 10% x OA =T1 and 90% x RA =T2 then we just add T1 + T2 =MA and get our mixed air temperature. If we had a 40^oF outdoor air reading and a 75^oF return air reading we should set up the minimum position on our economizer to a mixed air temperature of  71.5^oF.    ie.   0.10 x 40^oF = 4^oF,   0.90 x 75^oF = 67.5^oF,  4^oF + 67.5^oF = 71.5^oF    

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How can I verify that a gas appliance is firing at the rated input ?

The most common way to verify the input is to do what is referred to as clocking  the gas meter. Clocking the meter means we will take an exact reading of the consumption of fuel running through the meter.

1. Shut off the gas supply to any other appliances being fed off the same meter including any pilot lights.
2. Set the thermostat to it's highest setting and allow the unit to run for 15 minutes to verify the stability of the rating.
3. At the gas meter chose a dial that best suits the input of the appliance , The longer the duration the more accurate the reading. What you are looking for is a dial that takes approximately 1 or more minutes per revolution.
4. Find the number of seconds it takes for one revolution on the gas dial and divide this into the number of seconds in one hour then multiply it buy the dial itself. If it were to take 90 seconds for the 2 foot dial to make one complete revolution it would be, 3600 / 90  x 2 = 80  this gives you 80 cubic feet per hour. If the the gas supply in your area is 1000 Btu's per cubic foot then the appliance is running at 80 cu. ft/hr x 1000 Btuh/cu. ft = 80,000 BtuH 

Use the fallowing table as a guide 

Find the number of seconds for one revolution on the chart , read the matching cubic feet for the matching dial size.

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What are the comfort zones ?

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How do I set up capacity controls ?

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What is ... ?

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When is ... ?

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