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  1. #1
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    troubleshooting Generaire 1042 solenoid with Nest stat and Trane XV95 furnace?

    Hi everybody, hope the good folks here can help me figure out an issue I'm having. Please bear with me, this is a bit of a long post.

    First, my setup:

    I have a Trane XV95 (TUH2C100A9V4VBA) furnace with a Generalaire 1042 humidifer and manual rotary humidistat (MX3HC?) that was installed by the previous homeowner. The Trane is also connected to some kind of central air conditioning unit (I know little about such things). I've been in the house about three years.

    Two weeks ago, I realized the humidifier was probably not working. Sure enough, water wasn't getting through the solenoid. I ordered a new solenoid, installed it, and everything worked again--I verified water was getting into the 1042 and dripping out the drain pipe when heat was on and I turned the manual rotary humidistat up to high.

    A week later, during a cold snap, while wondering why it was taking a long time to heat the house, it suddenly dawned on me that the furnace might only be operating in single-stage mode, because it had previously been controlled by a dumb simple thermostat, and perhaps the installer set the furnace up that way on purpose. A year ago I replaced the pre-existing thermostat with a Nest 3rd gen thermostat, so I figured I'd find out if there's a way to get the furnace to be a two-stage furnace. I then figured, while I was at it, I'd get the Nest to act as the humidistat instead of the MX3HC.

    So I contacted an HVAC company to come in and wire everything--instead of sending an HVAC tech, they sent one of their electricians on staff. Unfortunately, only my wife was home when he arrived, I was at work. He was able to get the furnace to be capable of two-stage operation (great), but apparently had some trouble getting the Nest to control the humidifier. In talking to him later, he said the solenoid wasn't clicking open when it was supposed to. So, he "fudged it" by removing a filter and washer from the solenoid so that water would flow completely through it, unrestrained, with the water valve from the pipe fully open. Because of that, he set it up so that the water valve was almost totally closed, but not quite. He told me he thought the solenoid had probably failed--but that struck me as unlikely, since it was a brand new one that had been installed a week earlier.

    Now this left me wondering why the solenoid wouldn't work, and it made me wonder how he wired it. Everyone I'd asked had said I need to connect one solenoid wire to the Nest's * terminal (which he did). The other solenoid wire, I was told, needs to go to the furnace's C terminal; but he apparently wired it to the furnace's Y terminal. When I asked him about the wiring, he said "Oh, yeah, wiring to the C terminal is one way to do it, but there's other ways to do it--I prefer this way." He never explained why (and I stupidly didn't ask).

    A day after he did the work, I decided I wanted everything set up properly with the humidifier, not kludged together with a 5% open water valve and missing parts in the solenoid. So the tech came by the house and dropped off an identical new solenoid, which I installed. But now, when I have the Nest call for humidity and the furnace is heating, I'm not getting any water through the solenoid--just like was the case when he couldn't get the solenoid to work while wiring everything.

    So...TL;DR, this makes me think he wired things wrong. Shouldn't the solenoid be wired to C rather than Y on the furnace? What else would possibly make not just one, but two solenoids not work? A failed solenoid seems unlikely, as now there's two brand new solenoids that haven't functioned as designed (and yes, I've verified the water valve is open and water is getting to the solenoid).

    Second question--there are two other things I'm not sure about in terms of my HVAC equipment. First, I don't know if the fan/blower is able to do variable speeds when heating and cooling; second, I don't know if the central air conditioning is capable of two-stage cooling or not (it, too, seems to take way too long to cool the house down in summer). Is there any way I can check the wiring at the furnace, or dip switches, or something like that, to verify those two things?
    Thanks!

  2. #2
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    Since we're not a DIY site. I'm not allowed to tell you how to wire anything. But, I can tell you the way the electrician has it wired will never work.

    As for the furnace and A/C being 2 stage or not. Post their model numbers, and we can tell you from that, should also be able to tell you if the furnace has a VS blower.
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  3. #3
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    Hi thanks very much for your reply.

    Quote Originally Posted by beenthere View Post
    As for the furnace and A/C being 2 stage or not. Post their model numbers, and we can tell you from that, should also be able to tell you if the furnace has a VS blower.
    You probably missed me posting the furnace's model number at the beginning due to my massive wall of text I posted! Sorry--it's a Trane XV95 (TUH2C100A9V4VBA) furnace. I don't know the AC model number, but I can go out back to the side of the house when I get home from work this evening and check amidst the snowbank Unless there's an easier way to tell from inside, that I'm not aware of...?

    Quote Originally Posted by beenthere View Post
    I can tell you the way the electrician has it wired will never work.
    Well, good to know my suspicions are correct! Thanks for confirming.

    Quote Originally Posted by beenthere View Post
    Since we're not a DIY site. I'm not allowed to tell you how to wire anything.
    Believe me, I have zero desire to wire anything myself at this point, especially given how it looks like a professional electrician managed to screw it up. I started looking at doing it myself before we started this whole adventure (that's when I was asking around as to how to wire it) and decided this is a professional's domain and it's beyond what I was comfortable tackling myself. That's why I called the HVAC company to come do it, rather than trying it myself. I just want to know the proper way it SHOULD be wired so I can call this electrician's company back, have him come back out to my house, and have HIM wire it the way you folks say it's supposed to be wired.

  4. #4
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    1st Loose the NEST There CRAP

    Electricians generally don't know Control Wiring, unfortunately many HVAC techs don't either. You will need a control tech.

  5. #5
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    Quote Originally Posted by pecmsg View Post
    1st Loose the NEST There CRAP

    Electricians generally don't know Control Wiring, unfortunately many HVAC techs don't either. You will need a control tech.
    Can you comment further on why the Nest is no good, and what you would suggest in its place?

  6. #6
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    Search NEST Complaints. There’s quite a few.

    Honeywell

  7. #7
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    Quote Originally Posted by canadave View Post
    Hi everybody, hope the good folks here can help me figure out an issue I'm having. Please bear with me, this is a bit of a long post.

    First, my setup:

    I have a Trane XV95 (TUH2C100A9V4VBA) furnace with a Generalaire 1042 humidifer and manual rotary humidistat (MX3HC?) that was installed by the previous homeowner. The Trane is also connected to some kind of central air conditioning unit (I know little about such things). I've been in the house about three years.

    Two weeks ago, I realized the humidifier was probably not working. Sure enough, water wasn't getting through the solenoid. I ordered a new solenoid, installed it, and everything worked again--I verified water was getting into the 1042 and dripping out the drain pipe when heat was on and I turned the manual rotary humidistat up to high.

    A week later, during a cold snap, while wondering why it was taking a long time to heat the house, it suddenly dawned on me that the furnace might only be operating in single-stage mode, because it had previously been controlled by a dumb simple thermostat, and perhaps the installer set the furnace up that way on purpose. A year ago I replaced the pre-existing thermostat with a Nest 3rd gen thermostat, so I figured I'd find out if there's a way to get the furnace to be a two-stage furnace. I then figured, while I was at it, I'd get the Nest to act as the humidistat instead of the MX3HC.

    So I contacted an HVAC company to come in and wire everything--instead of sending an HVAC tech, they sent one of their electricians on staff. Unfortunately, only my wife was home when he arrived, I was at work. He was able to get the furnace to be capable of two-stage operation (great), but apparently had some trouble getting the Nest to control the humidifier. In talking to him later, he said the solenoid wasn't clicking open when it was supposed to. So, he "fudged it" by removing a filter and washer from the solenoid so that water would flow completely through it, unrestrained, with the water valve from the pipe fully open. Because of that, he set it up so that the water valve was almost totally closed, but not quite. He told me he thought the solenoid had probably failed--but that struck me as unlikely, since it was a brand new one that had been installed a week earlier.

    Now this left me wondering why the solenoid wouldn't work, and it made me wonder how he wired it. Everyone I'd asked had said I need to connect one solenoid wire to the Nest's * terminal (which he did). The other solenoid wire, I was told, needs to go to the furnace's C terminal; but he apparently wired it to the furnace's Y terminal. When I asked him about the wiring, he said "Oh, yeah, wiring to the C terminal is one way to do it, but there's other ways to do it--I prefer this way." He never explained why (and I stupidly didn't ask).

    A day after he did the work, I decided I wanted everything set up properly with the humidifier, not kludged together with a 5% open water valve and missing parts in the solenoid. So the tech came by the house and dropped off an identical new solenoid, which I installed. But now, when I have the Nest call for humidity and the furnace is heating, I'm not getting any water through the solenoid--just like was the case when he couldn't get the solenoid to work while wiring everything.

    So...TL;DR, this makes me think he wired things wrong. Shouldn't the solenoid be wired to C rather than Y on the furnace? What else would possibly make not just one, but two solenoids not work? A failed solenoid seems unlikely, as now there's two brand new solenoids that haven't functioned as designed (and yes, I've verified the water valve is open and water is getting to the solenoid).

    Second question--there are two other things I'm not sure about in terms of my HVAC equipment. First, I don't know if the fan/blower is able to do variable speeds when heating and cooling; second, I don't know if the central air conditioning is capable of two-stage cooling or not (it, too, seems to take way too long to cool the house down in summer). Is there any way I can check the wiring at the furnace, or dip switches, or something like that, to verify those two things?
    Thanks!
    Your problem is highlighted in red!!

    You may have other issues, but the red highlighted item needs to be removed before checking anything else. It is know to cause all kinds of strange things.
    The Food Stamp Program, administered by the U.S. Department of Agriculture, is proud to be distributing the greatest amount of free meals and stamps EVER.
    Meanwhile, the National Park Service, administered by the U.S. Department of the Interior, asks us to "Please Do Not Feed the Animals". Their stated reason for this policy "... the animals become dependent on handouts and will not learn to take care of themselves."
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  8. #8
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    Did anyone even test the valve to see if it opens when it’s energized?

    You need someone else, it’s kinda obvious the electrician they sent had no idea. The Y terminal is for the condenser, why would you want the humidifier to run with the AC? Tell them to send another tech.
    "The only true wisdom is in knowing you know nothing" Socrates

  9. #9
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    Quote Originally Posted by mgenius33 View Post
    Did anyone even test the valve to see if it opens when it’s energized?

    You need someone else, it’s kinda obvious the electrician they sent had no idea. The Y terminal is for the condenser, why would you want the humidifier to run with the AC? Tell them to send another tech.
    Because a sparky know how to run wire and other similar tasks, but little about hvac wiring or troubleshooting, as the OP found out.
    The Food Stamp Program, administered by the U.S. Department of Agriculture, is proud to be distributing the greatest amount of free meals and stamps EVER.
    Meanwhile, the National Park Service, administered by the U.S. Department of the Interior, asks us to "Please Do Not Feed the Animals". Their stated reason for this policy "... the animals become dependent on handouts and will not learn to take care of themselves."
    from an excerpt by Paul Jacob in Sun City, AZ

  10. #10
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    Its a 2 stage furnace, with a VS/variable speed blower.

    While you may not be tackling wiring it yourself. To post how it should be wired. Would tell others that do want to wire it themselves, how to wire it.

    Easy solution is to have a real HVAC tech wire it, and then demonstrate that it works. Before you pay him.
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  11. #11
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    Quote Originally Posted by beenthere View Post
    As for the furnace and A/C being 2 stage or not. Post their model numbers, and we can tell you from that, should also be able to tell you if the furnace has a VS blower.
    Finally got a chance to see what AC unit I have. It's a Carrier. Here's the info sticker on it....not sure if it indicates it's two-stage cooling or not, or variable speed or not, or what......?

    EDIT: It seems I can't post links...the link is: imgur.com slash a slash TazdNPW Looks like the model number is 24ABB330A0031010, manufactured June 2010.

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