Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.
The irriating questions i just dont know!!! but i should!
tangled in wires
Member Posts: 23
Why on "newer" furnaces do the blowers no longer come on due to temperature. Instead they come on with a timer. they use a 60- 90 seconds delay or are told when to come on by an integrated fan control. Why is this? I know it must be due to the higher resistances in the new heat exchangers. My question is does the fan no longer operate based off temperature??
0
Comments
-
Design
All of the newer furnaces are fired in a counterflow fashion: the flow of combustion is counter to the airflow. Ther burners are at the top and air flow goes up. If you attempted to use an electromechanical fan control inserted midway in the air stream, the upper portion of the heat exchanger would over-heat before the control responded.
Carrier has used electronic boards since the 70's to control the fan.
**** Smith was the engineer for Carrier who basically invented the first 90% furnace. After that, York hired him to do one for them. He spec'd the old style electromechanical fan control with an internal warp switch wired parallel to the gas valve to time on the fan. Some knuckle head in purchasing ordered the standard fan control and the first generation of those furnaces came through that way. The all had early heat exchanger failures.Bob Boan
You can choose to do what you want, but you cannot choose the consequences.0 -
Timed on, timed off...
has been the rule for quite awhile now on the forced air end of things. I think it's less troublesome. Multiple fan speeds as always to dial in temperature rise and dip switches that gives flexibility on the "fan off" settings.Steve Minnich0 -
It's all
About the money. less wiring in the furnace.0 -
NFN but i got rid of the plenum temp switch before modern furnaces
cause i couldn't rub two nickles together and my house had a cracked heat exchanger, but you would only get that sooty thing when the house fan wasn't running. when the house fan was running, the air pressure in the plenum was plenty to exceed that in the fire chamber so no exhaust leakage.
not something i'd recommend for clients but getting rid of the temp. sense bought be 4 years on that furnace . . . .
brian0
Categories
- All Categories
- 86.3K THE MAIN WALL
- 3.1K A-C, Heat Pumps & Refrigeration
- 53 Biomass
- 422 Carbon Monoxide Awareness
- 90 Chimneys & Flues
- 2K Domestic Hot Water
- 5.4K Gas Heating
- 100 Geothermal
- 156 Indoor-Air Quality
- 3.4K Oil Heating
- 63 Pipe Deterioration
- 917 Plumbing
- 6.1K Radiant Heating
- 381 Solar
- 14.9K Strictly Steam
- 3.3K Thermostats and Controls
- 54 Water Quality
- 41 Industry Classes
- 47 Job Opportunities
- 17 Recall Announcements