[Equest-users] Variable Speed Ground Loop

[Robby Oylear]

I can only answer one of your questions, but that is that selecting "No" on
your isolation valve is the equivalent of having a three way valve.  Per
the DOE-2 Help file:

NO The unit does not have an isolation valve. Full flow occurs whenever the
loop pump is active.

I would guess that DOE-2 is not accounting for increased compressor energy
at lower flows.  If you look at the Performance Curves under the Unitary
Power tab there is no curve that uses condenser flow as an input.



On Fri, Mar 1, 2013 at 3:33 PM, Aaron Powers <caaronpowers at gmail.com> wrote:

> Hey All, Happy Friday,
>
> I am trying to get a better feel for the control options available for
> variable flow through a geothermal ground loop attached to water-cooled
> heat pump units.  Any comments would be greatly appreciated.
>
> In eQuest, there appears to be only an option for an isolation valve at
> the system level with no option to select 3-way or 2-way valves.  This
> makes sense because allowing for variable condenser flow would make the eir
> curves with respect to entering condenser temperature invalid.  By
> selecting an isolation valve, I would expect that on an hourly basis, the
> valve can either be fully open or fully closed.  With this in mind, I would
> expect the annual pump consumption to be equal for "Head Setpoint Control"
> = "Fixed At Coils" and "Head Setpoint Control" = "Valve Reset".  However, I
> see that there is lower consumption with the "Valve Reset" strategy, which
> leads me to believe that DOE2 is treating the valves as two-way.  Also, an
> hourly report of the condenser water flow through any unit shows that the
> flow is not always 0 or the design flow but is often at an intermediate
> value.
>
> Here are my questions: Can anyone confirm that DOE2 is assuming a two-way
> valve by default?  If so, how does DOE2 control the valves?  Is there a
> hidden keyword that would allow for a three-way valve?  Does DOE2 account
> for higher compressor consumption at reduced condenser flows?
>
> Thanks,
> Aaron
>
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