Bard geothermal quiz for you old timers - Page 3
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  1. #27
    Join Date
    Aug 2006
    Location
    Dallas (Plano), TX
    Posts
    168
    Is it possible that there's something substantially wrong with the water loop between the DSH and the water heater (not shown)? Such that there's an inordinately high flow of water, which thus is pulling out the bulk of the heat from the compressor's gas discharge line (which would account for the HP's low source water DeltaT because there's little hot gas left for the HP's heat exchanger, and would account for the fact that the problem exists on both the heat and cool cycles)?

    Also noting the problem has been in existence since day 1, perhaps a much too large DSH water loop pump was installed, along with maybe even 1.5" DSH water loop pipe, that's resulting in upwards of 10 gpm (just guessing to make the point) of DSH loop water flow?

    Or perhaps there's some kind of significant leak in the DSH water loop, or even the hot water heater's DHW piping, that only manifests itself when the DSH water loop pump is running, again resulting in much too large of DSH water loop volume flow?

    Best regards,

    Bill

  2. #28
    Join Date
    Oct 2005
    Location
    Pacific Northwest
    Posts
    2,266
    Quote Originally Posted by a0128958 View Post
    Is it possible that there's something substantially wrong with the water loop between the DSH and the water heater (not shown)? Such that there's an inordinately high flow of water, which thus is pulling out the bulk of the heat from the compressor's gas discharge line (which would account for the HP's low source water DeltaT because there's little hot gas left for the HP's heat exchanger, and would account for the fact that the problem exists on both the heat and cool cycles)?
    Close enough! You are right in the fact that there was not enough hot gas left and you recognized it in both heating and cooling. What was happening is that one hot gas service valve to the DSH was opened, one was closed. As the system ran the hot gas at the DSH would cool off and start to condense thus taking less room and needing more refrigerant to maintain the same pressure. In about 10 minutes, enough refrigerant had been scavanged that the pressures droped. It was like a big dead end receiver. Now I'm guessing here but why not just charge the system up to make up the difference? I believe someone must have tried that. I could imagine that there wasn't enough internal volume around to handle the extra refrigerant when the system started and likely tripped the high pressure switch. Just a guess here but no need to follow up.

    What I don't understand is how could this have worked if all was installed properly... I believe that there should have been a receiver installed on the liquid line at the factory to make up for the differing levels of liquid. Anyone with a Bard remotely mounted desuperheater ever had it work right?

    BTW no one asked about the superheat which would have indicated what was going on in the evaporator.

  3. #29
    Join Date
    Aug 2006
    Location
    Dallas (Plano), TX
    Posts
    168
    Quote Originally Posted by crmont View Post
    There are two service valves at the tees that serve the desuperheater ...
    Thanks for the post above acknowleging the root of the problem.

    I didn't pay enough attention to the piece of detail quoted above, concerning the gas service valves. I assumed the gas line for the DSH's heat exchanger was in series with the HP's HE, with no alternate route option/opportunity. And since it was clear there wasn't a gas leak ("... charged to the nameplate ..."), all that's left is the DSH's water loop (or so I thought).

    Thanks for time spent posting this subject. It was interesting and thought stimulating.

    Best regards,

    Bill

  4. #30
    Join Date
    Mar 2005
    Location
    Suppy NC
    Posts
    4,513
    Quote Originally Posted by crmont View Post
    Close enough! You are right in the fact that there was not enough hot gas left and you recognized it in both heating and cooling. What was happening is that one hot gas service valve to the DSH was opened, one was closed. As the system ran the hot gas at the DSH would cool off and start to condense thus taking less room and needing more refrigerant to maintain the same pressure. In about 10 minutes, enough refrigerant had been scavanged that the pressures droped. It was like a big dead end receiver. Now I'm guessing here but why not just charge the system up to make up the difference? I believe someone must have tried that. I could imagine that there wasn't enough internal volume around to handle the extra refrigerant when the system started and likely tripped the high pressure switch. Just a guess here but no need to follow up.

    What I don't understand is how could this have worked if all was installed properly... I believe that there should have been a receiver installed on the liquid line at the factory to make up for the differing levels of liquid. Anyone with a Bard remotely mounted desuperheater ever had it work right?

    BTW no one asked about the superheat which would have indicated what was going on in the evaporator.

    good catch i was over looking that side,
    thanks for answering

  5. #31
    Join Date
    Oct 2005
    Location
    Pacific Northwest
    Posts
    2,266
    Quote Originally Posted by a0128958 View Post
    Thanks for the post above acknowleging the root of the problem.

    I didn't pay enough attention to the piece of detail quoted above, concerning the gas service valves. I assumed the gas line for the DSH's heat exchanger was in series with the HP's HE, with no alternate route option/opportunity. And since it was clear there wasn't a gas leak ("... charged to the nameplate ..."), all that's left is the DSH's water loop (or so I thought).

    Thanks for time spent posting this subject. It was interesting and thought stimulating.

    Best regards,

    Bill
    Yeah the gas can go one of two places. I bet these bard DSH never did work right. In a water furnace the DSH water exchanger is simply in direct contact with the hot gas discharge and the gas has no alternate route. The only logic is if a pump would turn on and circulate a little DHW water.

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