I have a 2 stage gas furnace , How can I tell it is opening up the second stage gas when the stat is calling for it,, By temp increase in ducts?. I cannot see a Fire of the burner change , it is sealed , how does the teck check it. How do I check it, easily.
There is a definite change. For example, a low fire rate [40,000] a high fire rate [80,000]. There's a definite change.
"m Ransley" wrote
Call me a sicko, but when I first got my 2 stage variable a few years ago. I would sit down in the basement without any lights on the cold nights. I would wait until the 2nd stage would kick in, there is a definite roar when it kicks in, also you could see it get brighter around the furnace. Guess I was like a kid with a new toy. Pretty cool, huh?
Borg, prepare to be assimilated! LOL Couldn't resist with that name!!
yea well I hear the Blower go UP , but not the GAS
Those responses are Not Answers to proof of gas 2 stage
This is Turtle.
Get a temperature of the first stage while running and the blower is in low speed. Then turn it up to 90ºF temp on the thermostat and take a reading while the higher speed blower kicks in after 3 minutes. The higher speed blower is suppose to tell you the high burner is running. You may get a same temp. but never less temperature reading. If the Temperature of the low burner / lower speed blower you can get the same temp or a little higher reading when high kicks in, but if you get a lower temperature on the high speed blower running. Your second stage burner is not running and you high speed blower is.
Also you can go by the differencial temperature of the air going in the return and what is coming out the registers at each room. This is Called the TD by HVAC peoples and is very useful. Check the TD on low speed fan and then on high speed fan / high burner check the TD. The Low speed TD should be the same or a little less than the high speed / high burner running of the TD.
99.99% of the time if the high speed kicks in the high burner comes with it. Only about .01% of the time it will not. This is very rare.TURTLE
I'm guessing this furnace [ 2 stage ] is burning natural gas. If so, raise the thermostat to a ridiculous temperature of 90º and go outside to your gas meter. Check the gas floor by timing the half foot mark with your watch. The higher rate should burn more gas. The other way to check is to use a manometer and check the manifold pressure.
Actually, that's called the delta-T or dT, not the TD.
A delta-T is a change in temperature of a single thing. In this case it is the change in temperature of the air as it flows through the heat exchanger.
A TD is comparing the temperatures of two different things. An example would be comparing stack temperature to return air temperature.
Gary R. Lloyd CMS HVACR Troubleshooting Books/Software
This is Turtle.
OK The dT thing. What I'm looking for is the fan running high speed and the burner on low. The dT will drop a good bit if the furnace will not shift to high burners at high speed fan. The dT will drop and not stay the same or rise some. More Air and the same burner setting , you will get less dT. Just Logic Thinking.
TURTLE
This is Turtle.
This is a testing system by the customer and if you put a man-0-meter on it. You can just look at the burners to see it for you have it open to see. I can tell high from low by just looking.
TURTLE
Gary;
Not sure everyone is knows what 'CMS' stands for. Why don't ya clue in those that don't know. It might add credence to your comments, [Just a thought.]
It's a designation of Refrigeration Service Engineers Society, and stands for Certificate Member Specialist. Won't mean much to those outside the industry, but people in the trade know how difficult it is to attain.
I have a university degree also, and belong to a scholastic honor society, but who cares? In the HVACR industry CMS means something.
Gary R. Lloyd CMS HVACR Troubleshooting Books/Software
I agree. :)
Gary R. Lloyd CMS HVACR Troubleshooting Books/Software
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