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Old 02-10-2018, 09:04 PM   #41
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Here's the same circuit, but I've added it to the wiring diagram on page 31.

Don't know why it wouldn't work. It basically puts a switched relay in parallel with the time delayed relay. When the T-stat calls for heat, it should still apply 12VDC to the module board via the Limit switch and sail switch as usual. The module board should then open the gas valve and spark the electrode as usual.
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Old 02-10-2018, 09:05 PM   #42
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Ill check it out. Tx.
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Old 02-10-2018, 09:12 PM   #43
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The blower isn't really controlled by the module board. It's controlled entirely by the time delay relay.
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Old 02-10-2018, 09:14 PM   #44
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Itís a very crude drawing, sorry but Iím tired.

So you can put a relay in in place of the switch if you want.

But the idea is to use a normally closed relay to cancel out your switch power.

This turns it into a mother may i system.

Both your switch ( or relay) and the normally closed relay have to be closed to turn the fan on.

If you have he can on and the thermostat commands heat it will overide your blower command.
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Old 02-10-2018, 09:17 PM   #45
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Thanks. Ill probably try again in the next week or so, and pass on the results.
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Old 02-10-2018, 09:22 PM   #46
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Quote:
Originally Posted by quicky06 View Post
Itís a very crude drawing, sorry but Iím tired.

So you can put a relay in in place of the switch if you want.

But the idea is to use a normally closed relay to cancel out your switch power.

This turns it into a mother may i system.

Both your switch ( or relay) and the normally closed relay have to be closed to turn the fan on.

If you have he can on and the thermostat commands heat it will overide your blower command.
The blower isn't tied to the control module.
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Old 02-10-2018, 09:24 PM   #47
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Quote:
Originally Posted by rockfordroo View Post
The blower isn't tied to the control module.
According to my owners manual it is.
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Old 02-10-2018, 09:29 PM   #48
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Quote:
Originally Posted by quicky06 View Post
According to my owners manual it is.
Then my original pic should work on that.

Either way, he should be able to do it. You're just adding a relay in parallel with either the time delay relay (my 2nd circuit) or in parallel with the control board (my 1st circuit, your circuit) and opening/closing it with a switch located wherever it's convenient to you.
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Old 02-10-2018, 09:45 PM   #49
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Johnfort: You need to check your owners manual to see which way your furnace is wired. But the basic circuit is the same. I'm not sure I like quicky06's circuit, because when he puts his 12VDC to the blower, he's also puting that 12VDC on the output of the control board. It MAY no hurt anything to have 12VDC at that output ("backwards" if you will) when it's not supposed to be, but who knows. That's why I used a single pole, double throw (SPDT) relay to disconnect the power from the module (my 1st circuit) or the time delay relay (my 2nd circuit) and replace it with the "switched" power, so to speak. Just seems "safer" to me.

Good luck.
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Old 02-11-2018, 07:45 AM   #50
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I personally wouldn't do this, but. Don't know if this should be considered for the ones wanting to do it. The blower fans shaft also drives the fan located within the combustion chamber. Just a comment.
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Old 02-11-2018, 12:42 PM   #51
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rockfordroo and quicky06, thanks for entering the challenge. In the cold gray light of dawn, I looked over your well thought out drawing, and realized that it looked familiar. I tried that exact circuit, as well as some modifications of same earlier.

This circuit worked the best, but there was a fatal flaw. When the stat was satified in the normal furnace mode, the fan "after run" to cool the combustion chamber did not work. It stopped immediately when the stat shut off, leaveing excessive heat lingering in the chamber. Not safe I think.

Another iteration of this circuit would only allow 1 heat cycle if you were in the fan on mode, then not recycle.

I'm not privy to the logic of the board, and my old Navy aviation electronics theory has failed me years ago, but I think the circuit board innards is the road block here.

I'd really like to see this work in both modes, but it seems to be above my pay grade.

I did mke this work on a pre-circuit board furnace with relays years ago, so the concept does work.
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Old 02-11-2018, 12:47 PM   #52
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bubbles, the fan does, infact, attach to the combustion chamber fan on the other end of the shaft. It won't matter though whether you are on the fan on mode, or the normal furnace mode as you are just pushing air.

The only drawback if this worked would be shorter blower motor life. A $ decision each person has to make.
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Old 02-11-2018, 12:54 PM   #53
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quicky06, to answer your "original question", yes, simply put an on off switch with a fuse between B+ and the blower motor. You can use a two spade terminal adapter from Home Depot to tie into the B+ and blower terminal right on the board. Then mount the switch in a handy place. The furnace heat mode will not work, or it may work one cycle.

As long as you understand this, you'll accomplish some circulation.
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Old 02-11-2018, 12:57 PM   #54
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Use 14awg wire or bigger, depending on how fsr away your stitc is from the furnace.
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Old 02-11-2018, 12:58 PM   #55
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Switch!!!
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Old 02-11-2018, 02:16 PM   #56
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Is the solution a diode?

Reading through this, it appears that the issue is not wanting to interrupt the factory signal to the blower, and to make sure that it is running when it's needed by the control board. The secondary function would be the desire to override the signal with a switch, however, in a fail-safe mode, the blower would always have power through the factory signal wire.
If you put spliced a 'T' into the R wire before the blower, and supplied 12v from the switch, then on the upstream side of the supply wire coming from the control board install a diode, which would prevent backfeeding the control board/timer, I think your problems would be solved, and have the desired outcome.
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Old 02-11-2018, 02:24 PM   #57
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Actually I forgot to mention earlier that I tried the diode trick. Used a 3 way diode in all combinations, and a standard diode in all polarities with zero success. It seems simple snd logical, but I keep hitting a brick wall in one way or the other. Good news is that I didn't blow a diode or the circuit board!!
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Old 02-11-2018, 02:30 PM   #58
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I went back and looked at the "Cheap Heat" as a workaround and I'm kind of liking it. The one for the NT-20 is only $243.

Anybody have any experience with it?

I've got 110v and 12v right there. My unit is ducted, but I bet some good old Yankee engenuity might prevail.
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Old 02-11-2018, 03:05 PM   #59
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Can I run the furnace blower to recirculate air

If you were to just wire a new switched +12v power and a new ground and bypass the thermostat completely wouldnít it be a lot easier than relays and such? The thermostat would still work independently, I bet.
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Old 02-11-2018, 03:08 PM   #60
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That's what I thought. No Joy.
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