[Bldg-sim] WLHP Loop with Chilled Water and Geothermal WaterSources

[Doug Maddox]

My understanding is that if you assign multiple zones to a PVVT, it is
modeled as a single central water-cooled DX cooling/heating coil serving
multiple zones.  One zone is designated as the control zone and the
central coil is controlled based on its thermostat.  

 

According to the DOE2.2 help file:  

"The airflow to all other zones is proportionate to the airflow of the
control zone. In other words, the thermostats in the non-control zones
have no effect on either airflow or supply air temperature.  They may,
however, modulate a reheat coil or baseboard."  

 

Thus, there may be times where there is simultaneous cooling and heating
for some zones. The only way to have one compressor per zone is to
assign each zone to its own SYSTEM.

 

For the HP system type, when multiple zones are assigned to a single
SYSTEM, each zone is modeled as having its own compressor and DX
heating/cooling coil.  This eliminates simultaneous heating and cooling.


 

This is all based on my review of the DOE2.2 help file.  If anyone has a
different experience, I would appreciate hearing about it.

 

Thanks,

Doug Maddox

The Weidt Group

 

________________________________

From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Xiaobing
Liu
Sent: Thursday, September 18, 2008 5:23 PM
To: Dan Russell; bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] WLHP Loop with Chilled Water and Geothermal
WaterSources

 

Dan:

 

For your simulation, I think you can model it as a typical boiler and
cooling tower system and then convert the heat rejection and heat
addition loads of WLHP loop to the required energy use of the hot and
cold water if you know the efficiency of the heat exchanger that
isolates the WLHP loop from the hot/cold water. It may be a bit more
challenging if you want to couple the chilled water system with the WLHP
system. My initial thought is that you can create a dummy zone that is
cooled by the chilled water system and has the internal load identical
with the heat rejection load of the WLHP. You may have to run the
simulation twice and manually input the internal load to the dummy zone.
Why don't you use cooling tower to cool the WLHP water? Cooling tower
should be cheaper to run than the chiller.

 

Regarding eQUEST using PVVT to represent air-side of WLHP (water-to-air
heat pump), the reason is PVVT has more flexibility to model packaged DX
coil unit. By specifying stages of cooling and heating capacity, minimum
airflow ratio, and applying proper performance curves, PVVT can model
either conventional heat pump with single stage compressor and constant
speed fan, or more advanced heat pump with two-stage  compressor and
variable speed fan. In addition, with PVVT, you can simulate a DOAS that
heats and/or cools the OA with a water-to-air heat pump after OA is
preconditioned with ERV.

 

Hope it helps,

 

Xiaobing

	-----Original Message-----
	From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org]On Behalf Of Dan Russell
	Sent: Tuesday, September 16, 2008 11:43 AM
	To: bldg-sim at lists.onebuilding.org
	Subject: [Bldg-sim] WLHP Loop with Chilled Water and Geothermal
Water Sources

	I have a building that is predominantly VAV with UFAD using a
boiler/chiller plant.  However, one portion of the building is
residential which we would like to use WLHP's for.  I would like to use
purchased hot water (geothermal at 110 deg from City) and the chilled
water from the building plant to maintain the WLHP Loop between 60 and
90 deg.  

	 

	Any ideas on how to model this?

	 

	Also, I've been a bit confused on how eQuest uses PVVT systems
to represent the air-side of WLHP systems.  Any references or resources
anyone has that explains the theory behind this would be greatly
appreciated.

	 

	Thanks,  

	 

	 Dan Russell, EIT 

	 

	 

	 

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