[BLDG-SIM] water source heat pump ( powerdoe)

olivier dosiere odosiere at dmiinc.com
Wed Mar 22 06:33:28 PST 2000


hi,

I've got a problem to model a water source heat pump with heat rejection to a cooling tower
and a gas fired boiler as a backup for my  water loop.

Here is what I've already done :

first ( Jeff advice) I created a heating/ventilating system   ( AIR HVAC ) assigned to a fake zone.
this is to model my make up air preheated, constant volume, @  55 F 100 % OA.

I created the water loop HP ( WATER HVAC ) with my boiler and my cooling tower.
in reality I have an evap. cooling tower BUT I considered an OPEN CT in powerdoe

Then my main HVAC system ( AIR HVAC) WATER LOOP HP type.
in that system I assign my outside air coming from my heating/ventilating system.

In my building as I have a bunch of heat pumps I entered my total
cooling and heating capacity in my system level and I entered for each zone
their own cooling and heating capacity depending on the number of heat pumps
( my total zone  capacities equals my system capacities)
I also entered my total flow ( corresponding to the recirculating and OA).

In my water loop (that as a 20 F delta T), I want the boiler to turns on only when my water loop
temperature goes below 75 F, and my cooling tower to reject heat when my water loop
goes above 80 F.

I entered the design GPM for my loop.

then comes the problem :

In my ouput

I almost don't have any heat rejection, and very small cooling.
( My EIR seems ok 0.015 for CT, 0.24 for HP)

I use a lot of electrical heat ( my heat pump meter is EM1) and I have rooms that remains
under 60 F with a setpoint @ 72 F.

But I use an incredible high amount of gas in my boiler..

plus I get these  error message

the first message  with the heat  and cooling capacity appears for all the zones !!
 Powerdoe do not appreciate that my heat pump heating capacity is higher than my cooling
capacity??? 


 
 **WARNING**********************************************************************

             HEATING-CAPACITY of   -5040000. is inconsistent with a 

             COOLING-CAPACITY of    4032000.in ZONE 2P-INT ZONE     

 

 **WARNING**********************************************************************

             Pump: water source HP PUMP             has a total user-specified flow

             of       485. gpm, but the loop flow is      3903. gpm.

 

 **WARNING**********************************************************************

             Pump: water source HP PUMP             has a user-specified head

             of        57. feet, but the loop head is        67. feet.

 

 **CAUTION**********************************************************************

             Plant equipment: OPEN CT                          has a different

             pressure drop on loop: HP LOOP                          than the

             other equipment.  This is unusual unless the loop

             uses flow meters or other dynamic flow control

             devices to allocate the flow on an hourly basis to

             the active equipment.

 

 **WARNING**********************************************************************

             Loop: HP LOOP                          heating capacity is smaller

             than the secondary demand. Primary= -2000000.

              Secondary= -7089648.

 

 **WARNING**********************************************************************

             Loop: HP LOOP                          cooling capacity is smaller

             than the secondary demand. Primary=  4800000.

             Secondary= 39062304.



I   must say that I am a little bit lost...


Thanks,


Olivier Dosiere
Project engineer
DMI - 450 lexington street
Newton, MA 02466
617-527-1525 x 102


 



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