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I'm trying to modify my electric Coleman 3500A816 furnace so that I can run just the blower motor. I saw a prior query about the same situation, but I was wondering if I have found the correct relay.

The user who gave a very detailed and insightful answer mentions a step where you would install a jumper to a common that I believe the OP mentioned. I don't know if I'm missing something, or overlooking it. Just hoping to get a little more in depth on that step.

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  • The 3400/3500/EB series electric furnace has a connection for separate fan control via the thermostat (fan ON vs AUTO) which you should be able to use. What are you actually trying to accomplish here?
    – KMJ
    Nov 15, 2023 at 21:52
  • I'm wanting to just run the fan to move air only. This furnace has a Sequencer, and a 2 wire stat. I read a post that was explaining how to add a fan relay (like the one I attached) I am going to replace the old cheapo two wire stat, run a new wire, and then want to wire up capability to run the fan for circulation purposes independently.
    – Randy L
    Nov 15, 2023 at 23:14
  • This sounds like the better path to me. A multi-wire stat is cheap enough, if you don't mind running the new wire it will be more flexible. They also make a switch panel kit for this furnace which would give you a pair of manual switches on the unit itself.
    – KMJ
    Nov 16, 2023 at 16:54
  • I've not come across the switch kit you're mentioning, any pointers? T.i.a
    – Randy L
    Nov 27, 2023 at 0:35
  • It's the 3500-5841B A/C Control Box as described in this documentation: mobilehomerepair.com/pdf/coleman/3500-5841B.pdf
    – KMJ
    Nov 27, 2023 at 4:24

2 Answers 2

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Assuming your furnace doesn't already support a G wire, that relay should be fine

That relay should have no trouble handling the blower on your furnace, provided it doesn't already have a G wire connection fitted, of course. You will want to double check the locked rotor amps on your blower motor to make sure it's not over the limit for that relay, but it'd have to be something 1 HP or larger at a minimum to do that, and the blower full load amps on the wiring diagram isn't even close to what a 1 HP motor would pull.

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  • Thank you, I appreciate the pointers!😁😁😁
    – Randy L
    Nov 16, 2023 at 22:11
  • @RandyL, please take the tour to learn the proper way to say "thanks". (Hint, up vote any/all answers that help you, click the check mark on the one that helped the most.)
    – FreeMan
    Jan 15 at 13:17
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I'm not an HVAC person, but these are my thoughts on the SPDT relay per your wiring diagram.

I would use a DPDT like the blower relay on the EB12b. EB12B diagram

Notice how the Blower-only and heat (from sequencer) are separated by the relay even though they are the same phase. The Yellow wire (input to sequencer) is used as input on the N/O contact, and the Blue wire (output from sequencer) is input to the N/C contact. I assume this is to prevent feedback into the heating element. The relay would be powered by G from the thermostat.

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