Gas and Oil Home Heating Furnaces - Fan/heat Sequencer

I have a comfortmaker Air & heating system, model DEBA005GB, serial # R890900124. I am replacing the fan/heat sequencer because it was stuck closed. The timing specifications are different (H1-20 C40-110) from the old part (H1-60 C1-45) and the contacts are positioned differentely...old part is M2-M1...new part is M1-M2. The store attendant told me that it is okey!. Is it true??

This is the first stage sequencer? Does it control the fan and one heat strip? M1 and M2 should be ok, they're just reversed, but I'm curious to know if the sequncer has only one switch or is there a second one labeled M3/M4? I don't like the timing on the new one. It's too slow on and too fast off and isn't for the first stage position. You need one that has timing ranges that are closer to the old one especially if this is the sequencer that runs the the fan and first heat strip. Usually the fan is wired to M1/M2 when the is the first stage sequencer. M1/M2 are usually first on/last off. You can see that you want the fan on first and last off. Let me know how many switches the old one has and I'll hook you up with part numbers that are closer to yours..

bigjohn,

The sequencer has only one switch which control the fan and the only heat strip. I do not see a second M3/M4.
If M1/M2 are reversed, then do I need to reverse the wires?

There were two wires connected to M2 (one comming from the heating element and another from the blower relay) and one wire connected to M1 coming from the fuse. Wait.........besides these wires, there were two addtional wires connected to the sequencer comming from the blower replay?. They are not label M3/M4. I took it apart,and it looks like there is another unusual switch. Now, I am confused.

These are the numbers written on the sequencer:

15SH1 309514
L8847

H1-60 C1-45 1398-411

I hope you can hook me up with the correct replacement

Thank you

It sounds like you're saying that the old sequncer has only one switch that operates the fan and the heat strip. [the 15SH1 indicates 1 switch, the L8847 is a date code. It was made in the 47th week of 1988] The other set of terminals are probably unmarked and should be where the low voltage wires that energize the sequencer are connected. IOW- the control wires. That would be the circuit that turns the sequencer on and off in response to the thermostat. Now, let's talk nomenclature first- the H spec is the time to close the M!/M2 switch once the bimetal heater in the sequencer is energized by the thermostat circuit. The C spec is the time to open the M1/M2 switch once the power is removed from the bimetal heater. IOW- when the thermostat is satisfied and opens its' switch. I think I misunderstood your original post. The NEW sequncer is H1-20/C40-110 and the OLD sequencer is H1-60/C1-45 or is it the other way around? Which is which? Since it controls only one strip and the fan, it probably doesn't make much difference. With multiple strips, the time frames are very important to ensure that the sequencers are staged properly. The M1/M2 terminals are just a switch but, just to be on the safe side, put all the M1 wires from the old sequencer on M1 on the new sequencer and same thing for the wires on M2. Be careful not to cross the low voltage wires terminal to terminal and especially don't put any low voltage wires on M1 or M2. Please clear up my confusion about the time frames on each sequencer. it sounds like the NEW one is H1-20/C40-110. If so, then the guy is right, it will work fine. The heat will be on faster and off slower. With the slower off, the heat anticipator in the thermostat [assuming you have an electromechcanical t-stat] will need to be set properly. If you have a digital thermostat, don't worry about anticpator settings.


Update:

I got to thinking about this and realized I should have clarified the sequencer specs better. I'll use this example:

H1-20 means the ON time for the M1/M2 switch is 1 second minimum, 20 seconds maximum. [ON time is the delay from when the sequencer is energized to the M1/M2 switch closing]

C40-110 means the OFF time for the M1/M2 switch is 40 seconds minimum, 110 seconds maximum. [OFF time is the delay from when the sequencer is de-energized to the M1/M2 switch opening]

I should have been more clear, thanks.

bigjohn,

The new sequencer is H1-20/C40-110 and the old sequencer is H1-60/C1-45.
Now, if 15SH1 indicates 1 switch, then how come I see two switches on the old sequencer. There are two stages:

1. On top, M2 (left side) is connected to two wires ( one going to the heating element and another going to the blower relay) and M1 (right side)which goes to the fuse (line voltage?) This is a conventional switch.
2. On the bottom, underneath M2, there is a wire going to the blower relay. And underneath M1, there is another wire also going to the blower replay. This is not a conventional switch because it has a thermodisc (TOD) as the contact, and it is not label M3/M4.

On the new sequencer M1 is on the left side and M2 is on the right side. I am going to put all the M1 wires from the old sequencer on M1 on the new sequencer and the same for the wires on M2. Now, what about the bottom set of wires? Do I also need to invert those wires?

Please advice.

Thanks

The bottom set of wires are the CONTROL wires which go to a heater, not a switch. If there is only one on each side, when you move them to the new sequencer, it doesn't matter which side each wire goes on, just don't connect either of them to M1 or M2 by mistake. The only thing that will make a difference is, if there is more than one wire on the heater terminals. For example, if there are two wires on one side and one wire on the other side, then make sure the two stay together and wind up on the same terminal on the new sequencer. The bottom set of wires go to a little heater. The way the sequencer works is the switch between M1 and M2 is a warp switch. When the heater is energized, it warms up the switch which in turn snaps closed. The applied voltage and ambient temperature affect the heating of the warp switch which is why there is a range for the ON time. When the heater is de-energized, the switch cools off and snaps open. The ambient temperature has an effect on the cooling off which is why the OFF time has a range. The way you want to wire M1 and M2 is just fine and, yes, the fuse is line voltage. The fuse is required by code to be there to protect the branch circuit in the furnace.

bigjohn,

I have finally replaced the fan/heat sequencer, and it is working fine. However, there is a humming sound coming from the control box, and it only stops when I turn the power off to the furnace.
Would you please check the following diagram and tell me if the sequencer has two switches?
I am attaching a file.

Thanks

The humming noise is probably the control transformer. If so, don't worry about it. You'll probably have to send the diagram to a website like at geocities or the like. Somehow, attachmnets won't work here or maybe we don't know the procedure. I'm glad the heat is back on. BTW- I happened to be looking at a Robertshaw Uniline catalog today and I noticed they have a sequencer with the exact same timing specs as your old one. The part # is 611-243, the ON time is 1 to 60 seconds, and the OFF time is 1 to 45 seconds.

bigjohn,

I want to thank you very much for your help

jd

No problemo. Nothing worse than a cold house in Wintertime unless, of course, the wife sees it as an oppurtunity to snuggle under the blankets. That's when you hook up a secret shut off switch. hehe.