[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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