ASHRAE 15

ASHRAE 135 (BACnet) — Object Types

Connecting a 0-10VDC analog output signal to a binary (digital) input terminal will not control the device properly. Binary inputs only read on/off states. Analog signals must connect to analog input terminals for proportional control.

ASHRAE 135-2016

A BACnet gateway does not satisfy a native BACnet requirement. The specification explicitly requires BACnet per ASHRAE 135-2016 and prohibits proprietary protocols. A gateway creates a single point of failure, adds latency, limits functionality (not all BACnet services translate through gateways), and locks the owner into one vendor for the field-level devices. Native BACnet means every controller communicates BACnet natively — either BACnet/IP or BACnet MS/TP — without translation. This is a critical specification requirement designed to protect the building owner from vendor lock-in.

ASHRAE 135-2016 / Crestline BAS Specification

Crestline specifications require all building automation systems to comply with ASHRAE Standard 135-2016 (BACnet). Proprietary, closed-protocol systems lock the owner into a single vendor and prevent competitive service and integration. Open-protocol BACnet is mandatory for all new installations.

ASHRAE 15 §9.9 (Pressure-Limiting Devices)

Head pressure of 165 psig is 40 psig above design, directly caused by the reversed condenser water piping. Watch the authority: the high-pressure cutout setting comes from ASHRAE 15 §9.9 and is referenced to the vessel design pressure, NOT to a universal number — there is no "trips at 175 psig" rule in any standard, and AHRI 550/590 is a performance-rating standard containing no safety-control provisions at all. Running this far above design costs compressor power and pushes the machine toward a nuisance high-pressure trip.

ASHRAE 170 Table 7-1

The air change rates are right but the pressure direction is backwards. ASHRAE 170 Table 7-1 requires an airborne infection isolation room to be NEGATIVE relative to adjacent spaces — exhaust must exceed supply so air flows INTO the room and is exhausted, keeping airborne pathogens from spilling into the corridor. The room protects everyone outside it from the patient. Positive pressure is what a protective environment (PE) room uses, which protects an immunocompromised patient FROM the building. The two room types have the same 12 total / 2 outdoor ACH and opposite pressure directions, which is exactly why they get mixed up. Get the direction wrong and the isolation room does the opposite of its job.

ASHRAE 170 Table 7-1 / FGI Guidelines

This passes all code requirements. ASHRAE 170 Table 7-1 specifies an OR temperature range of 68-75°F and a relative humidity range of 20-60%. The facility's 72°F and 45% RH are well within both ranges. The visible display allows the surgical team to verify conditions during procedures. The alarm capability ensures staff are notified if conditions drift out of range. The dedicated AHU with cooling, reheat, and humidification provides the three-stage control needed to simultaneously manage temperature and humidity — essential because cooling the air also removes moisture, requiring separate reheat and humidification stages.