Hi All,
I'm modeling a health care facility and the HVAC system is GSHP. Each time that I run the model, it gives me warning about the following errors:
Ground-loop HX: GLHX (VertWell-CM)
is undersized for the load and is producing an extreme
temperature of -388F. Mon/Day/Hr: 1/ 1/ 1
OR
Ground-loop HX: GLHX (VertWell-CM)
is undersized for the load and is producing an extreme
temperature of 351F. Mon/Day/Hr: 1/ 1/ 1
Anybody has any ideas what's the reason for these extreme temperatures?
Thanks in advance.
Hassan Zareh, M.Eng., P.Eng., LEED? AP
Are you putting in the right number of wells??
The one time I dealt with extreme GSHP temperatures, I believe the cause was rooted in the need to manually enter some of the fields that determine flow and/or pump sizing for the GLHX/loop. Notably however, they were not this extreme, and while they did occur within the first month, it was not on the first hour of the first day of the first month... I would suggest to at least review those fields that might, incorrectly entered, cause you to have zero to low flow in the loop.
NICK CATON, E.I.T.
I had the same issue recently and resolved it by making sure that my
bore-field configuration (i.e. 3x5 or other) and the number of identical
well-fields multiplied out to the correct number of actual bores. Also
make sure that there is not an error in your ground properties inputs.
Matthew Higgins, LEED AP + ASHRAE-HBDP
Everyone,
I am having an issue with determining the baseline chiller COP for a
large lab building. The proposed design system is two 1600 ton
centrifugal machines with 42F CHWT with 12F delta T, 85 ECWT, and
2.5gpm/ton condenser flow rate. Both units are rated at 5.72 COP which
is above the minimum efficiency of 5.60 per Table 6.8.1J.
In the baseline, there are 4- 800 ton centrifugal machines and per
Appendix G3.1.3.8, the design supply CHWT should be 44F with a 12F delta
T. So the question that arises is: what is the efficiency of the
baseline machines? If you use standard rating conditions of 44F CHWT,
85 ECWT, and 3.0 gpm/ton condenser flow rate, the minimum COP should be
6.1. If you use the design conditions for the building, it is 5.60.
6.1 versus 5.6 in lab building of >400,000 sq.ft. is a huge difference
and could mean the difference between meeting minimum energy cost
savings for EA credit 1.
Any thoughts, help, or experience is greatly appreciated.
Sam Mason
Sam,
In eQuest detailed mode, you can specify a COP at the design condition
you choose. For example, you can enter 5.72 COP (.1748 EIR) @42F CHWT,
85F ECWT, 2.5 gpm/ton under "Design Conditions". Be sure to select that
the chiller is specified at "Design Conditions". eQuest will then
convert these parameters to a nominal or rated capacity which you can
also specify: 44F CHWT, 85 ECWT, 3gpm/ton, for example.
For simulation, eQuest will adjust the EIR and capacity based upon the
hourly conditions to calculate actual power consumption.
I hope this helps
-Drake
Sam,
I would input 6.1 COP and specified as rated-condition.
Min-Hwan Yang, CEM, LEED AP
Everyone,
I am having an issue with determining the baseline chiller COP for a large lab building. The proposed design system is two 1600 ton centrifugal machines with 42F CHWT with 12F delta T, 85 ECWT, and 2.5gpm/ton condenser flow rate. Both units are rated at 5.72 COP which is above the minimum efficiency of 5.60 per Table 6.8.1J.
In the baseline, there are 4- 800 ton centrifugal machines and per Appendix G3.1.3.8, the design supply CHWT should be 44F with a 12F delta T. So the question that arises is: what is the efficiency of the baseline machines? If you use standard rating conditions of 44F CHWT,
85 ECWT, and 3.0 gpm/ton condenser flow rate, the minimum COP should be 6.1. If you use the design conditions for the building, it is 5.60.
6.1 versus 5.6 in lab building of >400,000 sq.ft. is a huge difference and could mean the difference between meeting minimum energy cost savings for EA credit 1.
Any thoughts, help, or experience is greatly appreciated.