Electric Furnace 2 of 3 elements working


Old 01-10-18, 07:40 PM
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Electric Furnace 2 of 3 elements working

I have an Intertherm electric furnace and I replaced the heat sequencers, relay, and both limit switches on. The bottom element runs on one single pole limit swith and the top two elements run on a 2 pole limit switch. I checked the continuity on the elements as well as the ohms and all three have continuity and read about 10 ohms each. After doing all this nothing worked only the blower but no hot air. After a closer look at the system I saw that the white wire coming from the thermostat was cut off. So, I connected it and Voila, it worked, well only two elements worked. The one on the single pole limit switch workes as well as one of the 2 that are connected to the 2 pole limit switch. Could anybody give me some insight as to what could be the problem?
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Old 01-10-18, 07:56 PM
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Welcome to the forums.

Way to complicated to offer guesses. We need a model number of the air handler and the heating kit or a few pictures.... or both. How-to-insert-pictures

The limit switches are just for overheat protection.
It's the sequencers that do the switching of elements.
Old 01-11-18, 11:59 AM
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Yes, and I installed the sequencers yesterday as well, brand new. Does the 2 pole limit switch open or close and activates one elementa at a time or should both elements be active at tje same time, of course when the sequencer tells it to? Is it possible that it would just take longer for the sequencer to send the signal? I did wait about 10 minutes and the 3rd didnt turn on.
Old 01-11-18, 12:03 PM
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The unit is an Intertherm model number:
Old 01-11-18, 07:14 PM
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Make sure you have a good manual and diagrams. If not.... download this one.
Diagram on page 15. nordyne_e2_electric_service_manual.pdf

621383 single sequencer - heating: 30-90 seconds on, cooling: 1-30 seconds off
621696 dual sequencer - heating: 1-20 seconds on, cooling: 40-110 seconds off

So the first and element and fan...... and then the second element on in 20 seconds. The third element on in 30 seconds. Your second element is the one that is not working.

TESTING with AC voltmeter

At Sequencers WITHOUT call for heat:

H1/H2 (bottom terminals under M1-M4) = 0 VAC
H3/H4 (bottom terminals under M5/M6) = 0 VAC

M1 to ground = 120 VAC
M2 to ground = 120 VAC
M3 to ground = 120 VAC (second element)
M4 to ground = 120 VAC
(second element)
M5 to ground = 120 VAC
M6 to ground = 120 VAC

M1/M2 = 240 VAC (first heat element and fan)
M3/M4 = 240 VAC (second element)
M5/M6 = 240 VAC (third element)

WITH call for heat after 1 - 2 minutes:

H1/H2 = 24-28 VAC
H3/H4 = 24-28 VAC

ALL M to ground should still read 120 VAC

M1/M2 = 0 VAC
M3/M4 = 0 VAC (second element)
M5/M6 = 0 VAC

You should read 240 VAC across the end terminals of each element coil.
You should read 0 VAC across the Limits with call for heat.

At Blower Relay WITH call for heat :

1 & 3 = 0 VAC
5 & 6 = 0 VAC
2 & 4 = 240 VAC
Old 01-11-18, 09:11 PM
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Thanks for your help Pjmax, I will certainly look into this. Awesome!

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