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Matthew
Matthew, HVAC Technician
Category: HVAC
Satisfied Customers: 2014
Experience:  14 years experience in the HVAC field of service, installation, Manual J & D calculations
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The inducer moter and the blower moter run all the time on

This answer was rated:

The inducer moter and the blower moter run all the time on my rheem criterion II gas furnace the thermostae will not shut it down the flame is out .

Matthew :

Hello, My name is XXXXX XXXXX I will do my best to help you today.

Matthew :

You have an open limit device. This could be a roll out limit or the main limit.

Matthew :

Pictures to follow.

Matthew :

Full Size Image

Matthew :

This is the roll out limit you could have anywhere from 1-4 of these depending on the size furnace you have. They are mounted around the burner compartment where the flames would be. Each one has a small red button in the center this button is the reset button. If the limit is open the button is popped up and needs to be depressed to reset the limit and allow the furnace to start back up.

Matthew :

Full Size Image

Matthew :

This is the main limit and is located in the upper left corner behind the pressure switch of most rheem furnaces.

Matthew :

This limit senses the air temperature inside the furnace and if you have an air flow problem this limit will open because too much heat is built up inside the furnace. This limit is suppose to auto reset once the blower cools the inside of the furnace to a reset temperature on the limit. If the limit is not resetting then you need to pull it out and clean the little sensor disc on the end of it.

Matthew :

To test to see if this is the limit that is open you turn power off to the furnace and then pull the two wires off the limit and hook these two wires together. Turn power back on and if this limit is the one that is open then the furnace should start up with the wires hooked together.

Matthew :

Things that cause this limit to open in the first place is a dirty filter, dirty evaporator coil, blocked return or supply runs, malfunctioning blower motor, a bad control board, or a malfunctioning limit.

Matthew :

If you can't get this limit to reset then you will need a new one.

Customer:

I have cleaned the main limit, but have not checked the other limit switches at this time I will check them now

Matthew :

Could you get me the model number of the furnace and I'll look up and see if you have any aux limits. It will be a RG####.

Customer:

It is model RGPH 07EAUER I by passed the main limit and the furnace blower motor did not start up when the power was turned back on and the furnace did fire off as it should except the thermostate was not calling for heat.

Customer:

I have the furnace working with the main limit switch bypassed is it safe to operate this way until I can purchase a new one tomorrow?

Matthew :

no

Matthew :

This limit is what keeps the furnace from catching on fire if there is a problem. If you choose to run it with the limit bypassed do not leave it unattended.

Customer:

Do you have any suggestions

Matthew :

Take the limit out clean the sensor and tap it on the side of the cabinet a few times see if you can get it to reset.

Customer:

It did not work but you were a great help that is what I thought was wrong but was not sure. Thanks for your help

Matthew :

You can run the furnace but just keep a close eye on it. The limit opened for one reason or another and then just wouldn't reset so keep a close watch to make sure the furnace isn't overheating. Check your filter, make sure all registers are open and not runs are crushed, make sure the blower is running properly, and get the limit replaced as soon as possible. If it continues to trip the new limit you may need to get your evap coil cleaned. If you have a power zoned system make sure the dampers are opening properly.

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