[EnergyPlus_Support] Re: Heat Recovery Option for Compact HVAC: Unitary appears to not work

["Richard Raustad" <RRaustad@xxxxxxxxxxxx>]

Jim, add some report variables to your input file to see what is 
happening. Also, work with the expanded idf to see what the compact 
hvac objects gave you (including the node names used to report node 
information). I added these. I see that the HX is working but not 
providing very much energy recovery in summer due to the return air 
temperature limit setting in the outside air controller (look in the 
expanded.idf). In winter I see no heat recovery at all (not sure why 
but this may also be due to the return air temperature limit 
setting). You are also operating the Generic HX well below the 
manufacturers flow ratio recommendation at times (.err file). You 
might consider switching to a flat plate HX which can operate at very 
low flow rates, but you will lose the total energy recovery and 
recover only sensible. The other option is to ensure the air flow 
rate ratio (supply to exhaust) is within 50% to 130% as manufacturers 
suggest.

  Report Variable,
    *,                       !- Key_Value
    Heat Exchanger Sensible Heating Rate,  !- Variable_Name
    Timestep;                !- Reporting_Frequency

  Report Variable,
    *,                       !- Key_Value
    Heat Exchanger Sensible Cooling Rate,  !- Variable_Name
    Timestep;                !- Reporting_Frequency

  Report Variable,
    S-1 Outside Air Inlet,  !- Key_Value
    System Node Temp,        !- Variable_Name
    Timestep;                !- Reporting_Frequency

  Report Variable,
    S-1 Heat Recovery Supply Outlet,  !- Key_Value
    System Node Temp,        !- Variable_Name
    Timestep;                !- Reporting_Frequency


--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Jim McNally 
<jim_mcnally@...> wrote:
>
> Hi Linda,
> I tried the heat recovery model with 2.0 and 2.2. -- similar 
results.
> Jim McNally
> 
> 
> 
> ----- Original Message ----
> From: Linda Lawrie <linda@...>
> To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> Sent: Monday, September 8, 2008 8:51:29 AM
> Subject: Re: [EnergyPlus_Support] Re: Heat Recovery Option for 
Compact HVAC: Unitary appears to not work
> 
> 
> Is this with Version 2.2 or an earlier version?
> 
> Linda
> 
> At 07:47 AM 9/8/2008, jim_mcnally wrote:
> 
> 
> A bit more info about the heat recovery problem. Using a shoe-box 
model and compact HVAC, I ran several outside air percentages. 
Results are below.
> 
> RUN-1: 0% outside air = 5,126 therms/year
> 
> RUN-2: 30% outside air = 21,635 therms/year
> 
> RUN-3: 100% outside air = 64,344 therms/year
> 
> RUN-4: 100% outside air with 70% efficient heat recovery=64, 344 
therms/year . [I was expecting an answer of about 21,000 therms.]
> 
> The heat recovery mechanism had negligible effect. The Compact HVAC 
part of the model is shown below for Heat Recovery. Am I missing 
something, or have I come across a bug in Energy Plus?
>



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