[Equest-users] Excessive cooling capacity and "insufficient heating capability" warnings

Gonzalo Lema GLema at sumacinc.com
Wed Nov 19 08:07:31 PST 2014


I finished my baseline energy model. However, my problem is that the auto-size DX cooling capacity is too high (625 ton) while the proposed design has a 90 ton chiller.
I also had a lot of trouble trying to meet heating load hours, and could only satisfy them by putting air dT=20F in the reheat option. If I put less dT or more dT the unmet load hours increase.
[cid:image001.jpg at 01D003DC.BE98AE70]

The warning continues to appear for most of the zones though (but the unmet load hours is zero):
             ZONE EL1 WSW Zone (fG.z1)
             might have insufficient heating capability.
             Check that the SYSTEM or ZONE HEATING-CAPACITY plus this
             ZONEs BASEBOARD-RATING is adequate to maintain the ZONE
             specified DESIGN-HEAT-T for the calculated peak ZONE load
             (see LS-A or LS-B for the ZONE peak load.)

             SYSTEM S1 Sys (PVAVS)
             which supplies the above listed ZONE, has a design heating
             coil exit temperature, HEAT-SET-T,(plus any zone reheat)
             below its MAX-SUPPLY-T or the ZONE DESIGN-HEAT-T, which
             might account for the insufficient heating capability.

             ZONE EL1 WSW Zone (fG.z1)             has a THERMOSTAT-TYPE
             of REVERSE-ACTION, which, when added to the issues listed
             in the messages above, will cause excessive underheating.

When fulfilling the heating capacity (with reheat dT= 20F), the cooling capacity raised dramatically. Thus, heating and cooling seem to be correlated, but I can't find why the cooling capacity is so high for a 37230 gross sq ft building.
I have 27 VAV zones in the building

Thanks in advance for your help

Gonzalo Lema | Mechanical Engineer | LEED GA
Tel: +1.773.857.7906 Ext 7009 (Chicago, USA)
Tel: +1.305.814.8805 (Miami, USA)
Tel: +511.253.5355 (Lima, Perú)
Tel: +593.4.600.0613 (Guayaquil, Ecuador)
Tel: + 571.3151985 (Bogotá, Colombia)
glema at sumacinc.com<mailto:glema at sumacinc.com>

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