Electric Furnace Problems (Please Read)
Electric Furnace Problems
Every year we field 1000's of tech calls for electric furnace not working properly or my fan quit working and my heater blows only cool or luke warm air.
The MAIN BRAIN to your electric furnace is the sequencer! It controls when to bring on the electric heat elements in sequence along with controlling the blower motor in the heating mode.
With this electric furnace sequencer replacement guide, you will be able to diagnose, select a suitable replacement, and replace a faulty electric heat relay / sequencer / contactor
**NOTE** ONLY YOU CAN ASSESS YOUR ABILITY TO PERFORM THIS TASK. THIS IS A GUIDE AND CANNOT PROVIDE ALL OF THE DETAILS FOR EVERY SITUATION.
An electric furnace sequencer is a device that turns one or more heating elements on and off. This is necessary to limit the electric current spike that occurs when an electrical device is energized. If all the elements in a unit were energized at the same time, the current surge would probably cause the breaker to trip or the fuse to blow. If all the elements in a unit were energized at the same time, the current surge would probably cause the breaker to trip or the fuse to blow.
In order to tell whether a part is broken or not, we must know how it normally works. The heat relay consists of a heater coil, a bimetal switch, and connections for wires. The heater coil on modern units is powered by 24 volts from the furnace control board. On older units, some of the coils were powered by 120 or 240 volt power. When power is supplied to the heater coil, electric current flows and produces heat in the relay. This heat causes a small piece of metal in the bimetal switch to deform and close the contacts of the switch. When the contacts close, power is supplied to the electric elements. When the power to the heater coil is interrupted, the small piece of metal cools off and goes back to it's original shape. This causes the contacts to open and interrupts power to the elements.
Testing A Sequencer
If you suspect that a sequencer is bad, you should test it before replacing it. To do this, you should begin by shutting off the power to the furnace and verifying that it is off with an electric test meter. Then, you should disconnect the wires from the coil terminals and measure the resistance of the coil. This will normally be around 20 ohms. If the reading is zero or considerably higher than 20, you should continue with electric furnace sequencer replacement.
Electric Furnace Sequencer Replacement
To select a replacement, you should obtain an exact replacement if possible. The relay will have a manufacturer's part number on it. If there is not a part number on it, you should match the heater voltage, the length of on/off timings, and the number of switches. The on timing will normally look something like H1-20 which means that the switch will close between 1 and 20 seconds after power is applied to the heater. The off timing will usually look similar to C40-110 which means that the switch will open between 40 and 110 seconds after power is removed from the heater coil. To remove the old unit, start by labeling all of the wires that are connected to it and where they are connected. (take your cell phone and take pictures) Then, removal is usually accomplished by removing a mounting screw. To install the new relay, you simply mount the switch and reconnect the wires. Then, you can turn the power back on to the unit. To complete your electric furnace sequencer replacement, you should observe a complete heating cycle to verify proper unit operation.
If you need help or a wire diagram Don’t Panic! Just send us an email email@example.com and we can look up a wire diagram for most models.
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Sequencer Cross Reference Chart
HS33247 SPDT HEAT SEQUENCER, 1 TIMING, 1 SWITCH (1 element or 3KW - 5KW)
HS24A341 SPST Heat Sequencer, 1 Timing, 1 Switches (1 element or 3KW - 5KW)
Industry No. 60000A0M
Interstate Electric IES24A34-1
A1 Components TDR10
HS24A342 SPST HEAT SEQUENCER, 1 TIMING, 1 SWITCHES (1 element or 3KW - 5KW)
Interstate Electric IES24A34-2
A1 Components TDR15
HS24A343 DPST Heat Sequencer, 1 Timing, 2 Switches (2 elements or 10KW)
Heil Quaker 1056789
Heil Quaker HQ1056789
HS24A344 DPST Heat Sequencer, 1 Timing, 2 Switches (2 elements or 10KW)
Interstate Electric IES24A34-4
A1 Components TDR25
HS24A345 Packard DPST-SPST Heat Sequencer, 2 Timings, 3 Switches (3 elements or 15KW)
White-Rodgers 24A34-5 , F77-5413
Mars 33232 & 33832
Interstate Electric IES24A34-5
HS24A346 Packard 2 DPST Heat Sequencer, 2 Timings, 4 Switches (4 elements or 20KW)
Interstate Electric IES24A34-6
HS24A3414 Packard 2DPDT-SPST Heat Sequencer, 4 Timings, 5 Switches (5 elements or 25KW - 30KW)
Interstate Electric IES24A34-3
A1 Components TDR20