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  1. #14
    Join Date
    Oct 2009
    Location
    Raleigh, NC
    Posts
    794
    I have a Modine unit that has been heavily used since the late 1970's. The heat exchanger is fine. It is basically just 10-12 oval tubes that the fan blows over.

  2. #15
    Join Date
    Nov 2004
    Location
    up in the hizzy
    Posts
    1,376
    Quote Originally Posted by MicahWes View Post
    I have a Modine unit that has been heavily used since the late 1970's. The heat exchanger is fine. It is basically just 10-12 oval tubes that the fan blows over.
    Well, a furnace in NC runs twice a year

  3. #16
    Join Date
    Jul 2007
    Posts
    65
    Stupid question but, if limit breaks transformers primary 120, what powers fan?

  4. #17
    Join Date
    Dec 2012
    Location
    columbus, OH
    Posts
    2,030
    Quote Originally Posted by iceage View Post
    Stupid question but, if limit breaks transformers primary 120, what powers fan?
    the limit is wired through the tranformers circuit
    .

  5. #18
    Join Date
    Aug 2012
    Location
    west burbs,il
    Posts
    145
    Sounds a little goofy to me. Usually you see the limits and roll outs wired series in low volt. It may have been Jimmy rigged. Sometimes these modine units,especially older used a gas valve that had thermostat built in with probe and the blower cycled on and off when call for heat without delay off for blower. So basically that switch is probably a limit switch for low volt but somebody tried wiring blower line voltage to it thinking it was auxiliary blower switch.

  6. #19
    Join Date
    Jun 2012
    Posts
    527
    I had a modine of that vintage and could not get parts from suppliers. I do not know what the issue was but I found some greenhouse websites that had good pictures, schematics and numbers. I pulled the modine part numbers from the site, called my supplier and gave him those numbers and he found the parts. It was like his information did not go back far enough. Those old moodines are tough... I have not seen many cracked compared to other brands of similar vintage.

  7. #20
    Join Date
    Dec 2012
    Location
    columbus, OH
    Posts
    2,030
    Ive seen the limits wired both ways. Either turning off the trans former or just the gas valve, if the limit shuts off the primary side their is usualy a jumper wire from the input of the fan switch to the limit. Shouldnt be to hard to follow the wires. Let us know when u figure it out.

  8. #21
    Join Date
    Jul 2007
    Posts
    65
    Got back to unit today, and traced all wireing. Traced wireing from fan delay and found coil on delay h1 and h2 were wired one to tr on gas valve and the other to tr-th(coil) on gas valve. moved this over to th on gas valve and unit worked correctly. Unit was working properly in the sense that limit would open and start the fan and shut off gas as a safety but it never had proper power to fan relay coil to start fan, in this case 20 seconds after burner started. I was told this unit worked by co-worker when he did his heat inspections, but now I dont think that was the case. I guess I did not think outside the box when my assumption was that this unit was in good running order and that well it must be wired right if someone said it was working when they last touched it. When is the th-tr coil used on a gas valve when you have tr and th terminals to power your circuit through?

  9. #22
    Join Date
    Mar 2001
    Posts
    1,486
    Used as a common lug on the valve
    One way to outthink people is to make them think you think. They'll think you're not really thinking what you're trying to get them to think you think...........

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