[BLDG-SIM] Trouble with Heat Pumps (eQuest)

Brandon Nichols BrandonN at Hargis.biz
Tue Aug 7 15:51:07 PDT 2007


Xiaobing, 
 
Many of us I think would be interested in the heat pump library.  How
can it be accessed?
 
Thanks
 
Brandon Nichols, PE
Mechanical
HARGIS ENGINEERS

600 Stewart Street

Suite 1000

Seattle, WA 98101

www.hargis.biz

 

d | 206.436.0400  c | 206.228.8707

o | 206.448.3376  f  | 206.448.4450

 
 

  _____  

From: BLDG-SIM at gard.com [mailto:BLDG-SIM at gard.com] On Behalf Of Xiaobing
Liu
Sent: Monday, August 06, 2007 2:40 PM
To: BLDG-SIM at gard.com
Subject: [BLDG-SIM] Trouble with Heat Pumps (eQuest)


Karen:
 
If you create a heat pump system using eQUEST wizard, in the first
screen of the wizard system (after you specifying both cooling and
heating equipment as "DX Coil"), an additional input entry will appear
and ask you specify the source of the heat pump. The available options
include "Air", "Water Loop", and "Ground Loop". When "Water Loop" is
selected, the HVAC system will be defined a water loop heat pump (WLHP)
system (with boiler and cooling tower); When "Ground Loop" is selected,
the HVAC system will be defined as a ground source heat pump (GSHP)
system that uses water-to-air heat pumps connected to a common (water)
loop and a vertical borehole field as heat sink and source.
 
I'm not clear why you have to deal with HIR for WLHP and GSHP systems
since these heat pumps are electric-driven. I guess you were talking
about the EIR instead of HIR.
 
The PVVT is used to simulate the air side of a water-to-air heat pump so
that it can account for the recent developments of water-to-air heat
pump, such as the usage of staged compressor, variable speed fan, etc.
If the WLHP/GSHP is created with the eQUEST wizard, parameters
associated with the PVVT system will be automatically set for constant
air flow, and default WLHP/GSHP heat pump performance curves will be
used. The default curves are normalized at the ARI rating conditions for
"ground loop" application (77F EFT for cooling and 32F EFT for heating).
If the WSHP/GSHP is created in detailed mode, at this version of eQUEST,
the user has to adjust the parameters of PVVT to fit for the specific
heat pumps being simulated. I've listed some necessary adjustments for
the parameters of PVVT in my earlier post to the topic "Gshp in detailed
edit mode".
 
FYI, a performance data/curve library for all the water-to-air heat
pumps of a major water-source heat pump manufacturer has been built and,
as an add-on feature of eQUEST, it can be accessed directly from the
wizard of "Packaged Equipment" if either WLHP or GSHP is specified.
Please let me know if you are interested in the library and this add-on
feature.
 
Hope it helps in your simulation.
 
Xiaobing

	-----Original Message-----
	From: BLDG-SIM at gard.com [mailto:BLDG-SIM at gard.com]On Behalf Of
Karen Walkerman
	Sent: Monday, August 06, 2007 2:57 PM
	To: BLDG-SIM at gard.com
	Cc: BLDG-SIM at gard.com
	Subject: [BLDG-SIM] Trouble with Heat Pumps (eQuest)
	
	
	Thanks for all the responses.  I think I figured it out:
	 
	When you choose "WLHP" in the eQuest Wizard, it creates a PVVT
system with a GSHP.  The curve used to adjust HIR is based on a few data
points, and did not perform very well at the temperatures I was using.
A straight HP system selected in detailed edit mode did much better.  I
now realize that this is because the HIR curve was better for my
purposes.  I have now created curves based on the heat pumps spec'd for
this job and the numbers are making more sense. 
	 
	Thanks again for all the repsonses, thought I'd let everyone
know, especially because PVVT is what is selected when you create a WLHP
system with the wizard, and may need some detailed data edit tweaking.
	 
	~Karen~
	
	 
	On 8/6/07, Brandon Nichols <BrandonN at hargis.biz> wrote: 

		
		Hello Karen,
		 
		"When so many things can go wrong, almost certainly more
than one of them will go wrong at the same time" ... or something like
that, according to Murphy.  Recently I have been wrestling with a large
heat pump system, and may be able to help a little.  
		 
		Have you adjusted your heat pomp efficiencies?  Ground
and water source heat pumps will have different efficiencies, if for no
other reason than they are operating with different condenser water
temperatures. 
		 
		Check this post...
		 
	
http://elcca-exchange.blogspot.com/2007/03/ground-water-source-heat-pump
s.html
		 
		Next suspect, schedules... don't have a post for that
yet, let me know the effect of efficiency adjustments and we'll go from
there. 
		 
		Regards
		 
		
		Brandon Nichols, PE
		Mechanical
		HARGIS ENGINEERS

		600 Stewart Street

		Suite 1000

		Seattle, WA 98101

		www.hargis.biz <http://www.hargis.biz/> 

		 

		d | 206.436.0400  c | 206.228.8707

		o | 206.448.3376  f  | 206.448.4450

		 
		 

  _____  

		From: BLDG-SIM at gard.com [mailto: BLDG-SIM at gard.com
<mailto:BLDG-SIM at gard.com> ] On Behalf Of Karen Walkerman
		Sent: Friday, August 03, 2007 5:20 PM
		To: BLDG-SIM at gard.com
		Subject: [BLDG-SIM] Trouble with Heat Pumps (eQuest)
		
		 
		I apologize for all the emails I've sent out as of late.
Thanks for all the input.
		 
		I have another:
		 
		I'm comparing a ground source heat pump to a heat pump
loop with chiller and boiler.  Trouble is, when I switch systems, the
energy used by the heat pump to heat the space goes down only slightly
as compared to the energy input by the boiler.  My loop temperatures
change between the systems (from heating temp of 40 F to 70 F), and COP
rises accordingly.  Right now the energy use of the two systems is off
by about 85%!! 
		 
		Energy use for straight electric resistance heat is
about the same as the electric use for a heat pump system.  This is for
a baseline model with 18% evenly distributed windows, R-19 batt
insulation, R-38 ceilings, etc. 
		 
		I used the wizard to set up the equipment for all runs
(I'm also having trouble in detailed edit mode).  The water loop and the
heat pump don't seem to be talking to one another.  Can anyone help?
		 
		Thanks,


		-- 
		Karen Walkerman
		Second Law Consulting
		802-238-0980
		kwalkerman at gmail.com 
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	-- 
	Karen Walkerman
	Second Law Consulting
	802-238-0980
	kwalkerman at gmail.com 


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