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old 1992 trane furnace/ old gas valve replacement question

rhasody
rhasody Member Posts: 8
edited December 2020 in Gas Heating
Have an old Trane air handler from around 1992.
Trane XL90 furnace tuc040b924a0

The gas valve has gone bad. I was looking at replacing with a like for like white rogers.
Trying to find a like for like is a challenge given the age of the furnace I assume.

I have found many similar valves. I have two main concerns. One question is how important is the WC range on the valve? The old faulty valve has a 3.3 WC listed. Some of the replacement valves show ranges --- one i found with the same part number shows a range of values. It showed "reg 3.5 WC" and then a "range 2.5"-5.0" WC" Is something like this ok to use if the old valve only showed 3.3WC?

Second question, The old valve shows amperage draw of 0.3 amps.
Some of the other valves I've found use .54 amps.

Is that something I should be concerned about?
I attached three images. The first shows the furnace model no. The second is the old faulty valve.
The third image is another white rogers replacement valve that a seller has. Would this work?

model no nameplate:



old valve:


Potential replacement valve:



Comments

  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 9,049
    edited December 2020
    The Gas manifold pressure can be adjusted on most of the valves you mentioned. You want to check it on the replacement valve to see if it is near 3.3" WC. This would require a tool called a manometer that professionals should have (But many don't)



    Look at the pressure rating on the furnace label.

    As far as the Amp. rating of .03 v. .054. is indicated in order to match the thermostat heat anticipator setting. The amp draw is inconsequential therefore the replacement valve you indicated will be an acceptable possible replacement

    I would use it!

    Merry Christmas
    Ed

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

    mattmia2
  • rhasody
    rhasody Member Posts: 8
    Thank you. I'll have a tech install the valve since its beyond my comfort level. Just making sure that it will work. Sounds like the WC can be adjusted.... Now just wondering if the increase from .3amps to .54 amps is a concern.
    mattmia2
  • JUGHNE
    JUGHNE Member Posts: 11,242
    Was the replacement cross matched by model number?
    Some valves are step opening or slow opening etc.
    mattmia2
  • rhasody
    rhasody Member Posts: 8
    yeah it was matched with the same model number... but shows that adjustable gas manifold pressure and the amps are higher. I'm not sure how to tell if one is step opening or slow opening.
  • JUGHNE
    JUGHNE Member Posts: 11,242
    I would not worry about the small amp difference, as long as it is 24 volt. Output pressure is adjustable with the right meter connected. Little difference between 3.3 and 3.5.
    The furnace seems undecided...3.5 on nameplate and 3.3 on valve.
    You can tell about the opening operation when it lights.

    But if the cross over was a match you should be good.
  • mattmia2
    mattmia2 Member Posts: 10,639
    Would be a great idea to have a tech that knows how to do combustion analysis replace it and set it up.
    rhasody
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 9,049
    edited December 2020
    Step opening/slow opening was a specification of the original furnace. It may be an instant opening or step opening or slow opening. In most cases, you can use the slow or step in place of an instant opening. Going the other way may cause flame rollout and this will be apparent upon startup with the replacement valve.

    The pro should look for that condition if the valve is instant opening.

    I believe this is a direct HSI or Direct Spark ignition furnace. (meaning there is no pilot burner to prove flame before the main valve opens.) This is indicated by the jumper from the M to the P terminal on the original valve and the number on the 1 & 3 terminal on the replacement. The flame rollout situation is more important to observe with this type of burner. Often they are the step opening type, but not always.

    If you remember the way it used to ignite, that would be helpful. did it start all at once... or did it start slow then get full within a few seconds?

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

  • rhasody
    rhasody Member Posts: 8
    edited December 2020
    Thank you all. This is quite insightful.
    Could determining whether it is slow/step/instant be gleamed from the white rodgers control board? I attached a capture of that.

    That is correct there is no pilot.

    In the past I have sat and watched the unit go throw its cycle (when it was working).

    From I recall there is a flame rod (for lack of a better term) that glows orange/ red hot for 15-17 seconds or so. Then the gas valves opens and there's combustion and it stays steady. if there's not combustion it eventually closes the valve i think.

    I don't recall the flame changing much after it first took or growing in intensity.

    I have gotten the valve to "come back to life" for a couple cycles by tamping the valve gently. I'll see if i can get it to come back to life if this doesn't settle it.

    Also is one accurate to assume that a higher amperage on the new (old) stock valve would somehow indicate a slower opening or step opening vs fast?


  • rhasody
    rhasody Member Posts: 8
    mattmia2 said:

    Would be a great idea to have a tech that knows how to do combustion analysis replace it and set it up.

    I completely agree. The tech is enamored with this old furnace. I've thought of replacing it (and will have to eventually) but, I hate to throw out a functioning unit that just needs a new valve.....

    Not that this changes anything, but the tech has told me this is one of his favorite old trane models and likes to get these running because " they don't make 'em like they used to"
  • JUGHNE
    JUGHNE Member Posts: 11,242
    He is agreeable to installing customer provided parts?
    Sometimes that can be rare.
  • rhasody
    rhasody Member Posts: 8
    edited December 2020
    JUGHNE said:

    He is agreeable to installing customer provided parts?
    Sometimes that can be rare.

    He agreed to do that. He says if I get the part he will install it. He told me match the model no on the valve, which i did... but I later noticed the differences here that I am unsure about.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 9,049
    edited December 2020
    I would replace the valve with the one you indicated. The difference is Amp. rating is not an indication of how the valve opens. It is only the amount of power the valve uses to stay open. It's the solenoid coil's rate of using the 24 volts. You can look up the definition of Volts, Amps, Ohms, Watts, and the like. This knowledge will not help you know the answer to your original query.

    The control that operates the ignition system (in your case the "Flame Rod" is a Hot Surface Ignitor) does not determine the type of valve or how the valve opens.

    Finally, the rate of opening is "instant" on your valve based on your description. This is a standard gas valve and you could use any number of standard gas valves designed for Direct Ignition burners. As a repair company, I stocked my service trucks with the Honeywell VR8345M because it could be used for multiple types of systems including the valve/system you have

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

  • rhasody
    rhasody Member Posts: 8
    thank you! sounds like i'm ordering that valve i mentioned.... I'll ask the tech to check for flame rollout after installing the new valve.... and remind him to adjust the valve to the 3.3 pressure if possible. Although like you show, the furnace is rated for 3.5 and the new valve is also rated for 3.5 WC.

    Fingers crossed this will work.

    Merry Christmas to you all and thank you for your help. *fingers crossed*
  • rhasody
    rhasody Member Posts: 8
    EdTheHeaterMan said:

    I would replace the valve with the one you indicated. The difference is Amp. rating is not an indication of how the valve opens. It is only the amount of power the valve uses to stay open. It's the solenoid coil's rate of using the 24 volts. You can look up the definition of Volts, Amps, Ohms, Watts, and the like. This knowledge will not help you know the answer to your original query.

    The control that operates the ignition system (in your case the "Flame Rod" is a Hot Surface Ignitor) does not determine the type of valve or how the valve opens.

    Finally, the rate of opening is "instant" on your valve based on your description. This is a standard gas valve and you could use any number of standard gas valves designed for Direct Ignition burners. As a repair company, I stocked my service trucks with the Honeywell VR8345M because it could be used for multiple types of systems including the valve/system you have

    Thank you Ed I really appreciate that.

    I am hopeful this will work. I guess if it doesn't then there's the honeywell route.

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