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  1. #1
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    Can somebody please help with issue of reversing valve on Bosch BOVA

    Here's the back story. About 6 years ago, we had a new Trane CAC system installed by one of the larger and more reputable companies in CT. Single stage AC with variable speed air handler. Existing hot water heating system. They also installed a Honeywell Pro6000 t-stat. They did a great job, and the system worked flawlessly.
    A few weeks ago a tree fell on the condensing unit.

    Since it had to be replaced anyway, I figured I would take the opportunity to upgrade to either a 2-stage or variable speed unit, in an attempt to remove more humidity and increase comfort. The project manager recommended the Bosch BOVA, and assured us that it would work with our existing air handler.

    The crew came out and installed the unit, and also a new Honeywell Pro9000 t-stat. He was having trouble with the reversing valve for the heat pump. Thinking that it was a bad thermostat (after a few hours of troubleshooting) he disconnected the control lead to the reversing valve, and said that he would be back with a replacement t-stat. He put my old Pro6000 back, but didn't bother with the heat pump, since they would be replacing the t-stat anyway.

    This past Thursday, a different tech came out with a new t-stat. He spent almost the entire day here and had the same issue. He said that he would come back with his supervisor. They both came back yesterday. And after several hours of more testing and troubleshooting, the supervisor thought that he might have a second bad t-stat. I told him that I was spooked by 2 bad 9000 t-stats, and I just wanted my old one back, since it works. So I gave him back the old 6000, and he put it on the wall, thinking that he would wrap it up and be done.
    Well, after more testing, he found that the reversing valve was still not getting voltage. When he bypasses the wires at the t-stat, it appears to work.
    So he just put it back, with the reversing valve disconnected. He said that he will do some more research on this matter and return again to get it running correctly. So long as we have AC and single heat (the hot water), there is no emergency. It would be nice to get the heat pump working, but so long as the boiler is working, and the t-stat can control it, I'm okay with that.

    Last night we noticed that the system was running, but it wasn't getting any cooler. I suspect that after 7 hours of frustration, he probably missed a connection somewhere.

    I am normally pretty patient, and I feel badly for the guys that they are running into this issue. But I am losing my patience.

    If anybody could please help -- let me know if I can suggest anything to the technician, or questions that I could ask, I would certainly appreciate it!

    Thank you,
    Peter

  2. #2
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    I do love all the high tech gadgetry out there yet no ones trained on how to install it, set it up, and troubleshoot it!

    Contact BOSCH and get a certified tech to inspect the install correct the issues .

  3. #3
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    The reversing valve is energized in heat on a Bosch, not in cooling! The stat needs to be programmed to energize "B", not "O".

    I can't believe someone is selling it and doesn't know that and can read a schematic.
    Bob Boan


    ​You can choose to do what you want, but you cannot choose the consequences.

  4. Likes BALloyd liked this post
  5. #4
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    Quote Originally Posted by bobboan View Post

    I can't believe someone is selling it and doesn't know that and can read a schematic.
    Sad but true

  6. #5
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    I just read your post again and saw that you have hydronic heat. The only way we've been able to get that setup to work is to add an isolation relay for the boiler and power it from the "emergency heat" terminal in the stat. Then program the stat to separate "e" and "w".

    You'll then have to turn the stat to "emergency heat" when you wanna use the boiler.
    Bob Boan


    ​You can choose to do what you want, but you cannot choose the consequences.

  7. #6
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    Thread Starter
    Thank you both for your replies. As I mentioned, this system was installed by one of the larger companies in the state. They assured me that they were trained by Bosch in the new technology. Three different technicians could not get it to work properly.

    The supervisor yesterday did say that he thinks that there's some voltage coming back from the boiler which is causing a conflict.
    So reading your post to add an isolation relay is what he thought he might have to -- but said that he needs to research it further. If we have the hydronic heat on "emergency" heat (is that the same thing as aux heat?) does that mean that the system would not switch over automatically from heat pump to the hydronic, as was promised?
    Is there an issue in having it set up that way?

    I'm getting pretty exasperated, and my wife is already there. She has no faith in the new system, and at this point she just wants a simple single stage Trane back in place.

  8. #7
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    The system will work great if you set it up the way I explained.

    As far as the thermostat goes: once the installer programs the stat to recognize the system as a heat pump, that is the primary heat source. Because the Bosch energizes the reversing valve in heat, not cooling, this adds a caveat that you didn't have with the Trane.

    The boiler isolation relay could be powered as an auxiliary and the fan programmed to be energized by the equipment in a dual fuel configuration for an automatic changeover. You would need at least a Honeywell T83220 stat with an outdoor sensor or the wifi version.

    I'm running this scenario in my head, but something is telling me that we've tried this and it had a bug. Maybe. Doing it with the manual changeover, there won't be any issues.

    Let me reassure you and your wife that the Bosch is a far superior system and when installed correctly is unbeatable. We've done close to 150 of them and they're basically all we try to sell for ducted forced air.
    Bob Boan


    ​You can choose to do what you want, but you cannot choose the consequences.

  9. #8
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    I remember the bug:
    The Honeywell T63220 has a glitch which we haven't been able to get them to acknowledge or fix. When used in dual fuel setup, it has a 2 degree droop between turning the heat pump off and energizing the auxiliary heat.
    This is an annoyance that serveral of our customers complained about and we stopped using that model for that reason.
    Bob Boan


    ​You can choose to do what you want, but you cannot choose the consequences.

  10. #9
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    Thread Starter
    Bob, Thank you again for the information. I will certainly relay (no pun intended) to the technician. I am sure that you are right that it is a superior system. And for the past few weeks, the AC part of it has been working well. It was after Friday's 7 hour service call that my AC no longer works, and we are hot and uncomfortable, and I am sure that is affecting my judgement.

    The thermostat which was spec'ed was the Honeywell Pro9000. It has wifi, and displays the outdoor temperature. (No outdoor sensor, so it's getting that data from the web.)

    Question for you -- you said that you have installed close to 150 of these. Were they retrofits with an existing air handler? Completely new installations?
    Any issue with the variable air handler? (I heard someone say on a previous thread that the Bosch works better with a single speed air handler, although that seems counterintuitive to me.)

    Thanks again
    Peter

  11. #10
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    All of the above.

    It will work fine with a VS AHU, just slightly less efficient. It uses the indoor coil temp/pressure to calculate it's modulation. That's why a fixed speed ECM works better. A VS blower gives it somewhat of a moving target.
    Bob Boan


    ​You can choose to do what you want, but you cannot choose the consequences.

  12. #11
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    Quote Originally Posted by bobboan View Post
    I remember the bug:
    The Honeywell T63220 has a glitch which we haven't been able to get them to acknowledge or fix. When used in dual fuel setup, it has a 2 degree droop between turning the heat pump off and energizing the auxiliary heat.
    This is an annoyance that serveral of our customers complained about and we stopped using that model for that reason.
    Now
    That I have to remember.
    Thank You!

  13. #12
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    Thread Starter
    Is "Emergency Heat" the same thing as "Aux heat" ? I notice that the wire terminals on the Honeywell 6000 and 9000 are labelled Aux heat.
    But the repair guy last Friday installed a 5000 t-stat, primarily as a test, and also so that he wouldn't accidentally fry the 9000. And on the 5000, when I run through the modes it lists "Emergency Heat" as one of the modes. Neither the 6000 nor 9000 had that mode available, but I'm wondering if it was just not active in the settings.

    They are coming back today -- I don't know if they are going to just get my AC working, or they are going to continue troubleshooting the reversing valve. I will give them the information you provided. So I just want to make sure that I've got the terminology correct.

    Thanks again!
    -- Peter

  14. #13
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    Any two stage heat pump stat has an "emergency heat" position. In most new stats, they can be programmed to separate the "E" and "Aux Heat" terminals.

    The issue that you're gonna run into is IF you have an electric heat pack in the AHU for backup heat AND the boiler also. In that scenario, you're gonna have to connect the boiler isolation relay to "E" and program the stat to bifurcate "E" and "Aux/W2".
    Bob Boan


    ​You can choose to do what you want, but you cannot choose the consequences.

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