My old furnace responded to the Fan position on the thermostat by just leaving the fan on at all times, even when the furnace was heating.
My new furnace doesn't operate that way any more. When it gets ready to fire up the burner, it stops the main blower completely for quite a few seconds, then starts the blower again.
I have been told that this is so a two speed blower can switch speeds, or because the burner requires it. The latest news I've been told is that all modern computer controlled furnaces do this.
I liked it the old way and hoped I could get the installer to make it run the fan continuously.
The furnace is a Maytag RC-80 furnace.
The manual seems to say that the Fan position should cause the furnace to always run the blower. So who's right?
COMMUNITY FORUM
It's not right, the maytag furance--even the two stage furnace does not operate in the manor you described, nor does the variable speed two stage furnace.
When you turn your t-stat to fan on the fan will and should run constantly until turned back to auto selection.
Put your s-stat into heat--take the temperature all the way up to 90 degrees.
THe first thing that happens is the induced draft blower motor should come on, this is a small motor--a few moments later approx 90 seconds the pressure switch will close and the glow coil will begin to glow, a few seconds later the main gas valve should open and the burners should light. A few seconds later the glow coil will shut down and then about 90 seconds later the main blower will start. The furnace blower will continue to run in either low speed or 15 minutes later kick into high heat, and run until the thermnostat is satisfied. IF the blower is starting on an initial call for heat before the fire starts you ahve a problem in the unit.
I suggest that you get the installers guide and read the operation of your unit to verify what I am saying, it sounds like there is a problem with the pressure switch, possibly an inadequate flue pipe or something along those lines. On start up the ignition system looks to besure that all of the safety devices are set in the proper position, if there is a problem with one of the devices the blower motor will start without the burners.
Perhaps you should have the installer comeback out and check it, or get a maytag dealer in a different city to speak with you over the phone and listen to your description of whats wrong.
My bet is that its a pressure switch problem!
When you turn your t-stat to fan on the fan will and should run constantly until turned back to auto selection.
Put your s-stat into heat--take the temperature all the way up to 90 degrees.
THe first thing that happens is the induced draft blower motor should come on, this is a small motor--a few moments later approx 90 seconds the pressure switch will close and the glow coil will begin to glow, a few seconds later the main gas valve should open and the burners should light. A few seconds later the glow coil will shut down and then about 90 seconds later the main blower will start. The furnace blower will continue to run in either low speed or 15 minutes later kick into high heat, and run until the thermnostat is satisfied. IF the blower is starting on an initial call for heat before the fire starts you ahve a problem in the unit.
I suggest that you get the installers guide and read the operation of your unit to verify what I am saying, it sounds like there is a problem with the pressure switch, possibly an inadequate flue pipe or something along those lines. On start up the ignition system looks to besure that all of the safety devices are set in the proper position, if there is a problem with one of the devices the blower motor will start without the burners.
Perhaps you should have the installer comeback out and check it, or get a maytag dealer in a different city to speak with you over the phone and listen to your description of whats wrong.
My bet is that its a pressure switch problem!
Here's what the install manual says about Fan Mode:
1. On a call for fan operation, the thermostat applies 24 VAC to the G terminal on the furnace control board.
2. The circulating air blower is energized immediately on the heating speed.
3. If the furnace is operated in the continuous ON position at the thermostat and is then switched to Auto, the circulating blower will operate for a specified delay (factory set at 120 seconds).
1. On a call for fan operation, the thermostat applies 24 VAC to the G terminal on the furnace control board.
2. The circulating air blower is energized immediately on the heating speed.
3. If the furnace is operated in the continuous ON position at the thermostat and is then switched to Auto, the circulating blower will operate for a specified delay (factory set at 120 seconds).
WHen you select the fan on position on your t-stat the circuit board automatically selects high speed. When the furnace is set into heat and the blower comes on in heat, your system may be over riding the blower on call from the t-stat, and momentarily shutting down the blower, but I would suspect that the blower would not shut down for any signifigant time in this condition, and infact the shut down I would look to be mometary while the blower switches speeds through teh circuit board. I still think that you have a problem with the unit, but do this set the fan into fan on, then leave the heat selector off, then let the blower run the blower should continue to operate until shut off. Then put the unit in heat, turn the fan into auto, and let the blower operate in the heating circuit, turn the temperature all the way up as high as it goes. If the blower maintains a constant speed for more than a 30 minutes, the systme is most likely a sigle speed unit. If the blower seems to speed up and get louder after 15-20 minutes, you have ether a two stage furnace or a variable speed furnace. In either case I would not expect the fan to shut down until the call for heat was over and the system had run its course.
