Follow-up Questions and Responses 7-26-22.pdf

FOLLOW-UP QUESTIONS AND RESPONSES

1. I did not see that a 23 09 specification section was provided. This is really required to properly bid the project correctly. Please provide. We do not believe a full HVAC DDC specification is necessary in order to monitor a few points.

a. Additionally RFI’s are typically needed once the 23 09 specification section is provided and time should be allowed to review and request additional clarification.

2. Per vendor reps I have heard that most of the points requested in 01 91 00(3.5) are not available with the unit that is the basis of design and would not come through on a BacNet interface.

Additionally since these systems are a more typical and simple mini-split and not what is typically called a “CRAC” unit (like a Leibert unit) they have much more limited information and even ability to mount sensors on them. Please confirm what sensors are desired based on below comments.

a. Space temperature

i. Should be available through bacnet interface to unit and is not an issue

b. Supply air temperature

i. Should not be available and will be difficult or impossible to mount a sensor on most or all units. This is a problem point and will be costly and probably not of much benefit to the VA. Is this point still desired? This point can be removed as space temperature is essentially the same.

c. Space Humidity

i. Should not be available through BacNet on many mini-split systems. This would need to be figured as a separate humidity sensor and tied into a nearby controller for monitoring. Is this point still desired? Yes.

1. If desired please specify standards for sensor. Including accuracy.

Otherwise confirm that a standard JCI 3% or 2% humidity sensor will be allowed. Standard sensor is acceptable.

d. Water Sensor

i. Should not be available through BacNet on any mini-split systems. This would need to be figured as a separate sensor and tied into a nearby controller for monitoring. It may be impossible to install this in a way that gives accurate information. Is this point still desired? Yes

ii. If the point is still desired more information is required on this sensor. What type of water sensor is this? Is it a sensor for the unit to detect overflow on the drain pan or is it on the floor to detect water? If not in the unit where should it be located? To detect water. Locate in drain pan or near floor depending on application.

e. DX cooling enable

i. Should not be available through BacNet on most mini-split systems. We would figure on accomplishing this by sensing status of the outdoor condensing unit via a current sensor and wiring to a nearby or new controller. Is this point still desired? Yes

f. Split system on/off

i. This should be available through most systems via BacNet. Please confirm that you want this point to come in via BacNet. Yes

3. Regarding OIT sensors:

a. It is my understanding that there is a separate existing system that is used by the VA’s OIT to collect this information. I believe it is a Cooper Atkins system. Is it desired that this system NOT be used on this project and instead all sensors be provided by the DDC contractor and connected to the on site Metasys system and not connected to any other system? Bidding contractor would determine which system will collect information. Either system is acceptable.

i. Please provide more details on what is desired.

b. The OIT standards talk about several standard for monitoring that would not be monitored by the DDC. For example the DDC will not monitor the power information and will only monitor the temperature and humidity of the spaces. All other monitoring is done elsewhere. Please confirm. See answer 3. a. above.

c. The OIT standards state the following

i. “All VA data centers shall monitor air temperatures at multiple points in IT equipment cabinets. Exact quantity and placement of sensors shall be determined according to the design and implementation of airflow management measures to ensure an adequate supply of cooling air” This project does not have a data center.

ii. “All equipment cabinets in facilities lacking best practice airflow management shall have at least four sensors per cabinet as per Sensor Location specification below” This is a data center requirement. This project does not have a data center.

iii. The DDC contractor is not able to determine what is “adequate” or whether or not the system meets “best practice.” Please confirm the number of temperature/humidity sensors desired and their locations. Please also provide a detail showing where sensors should be mounted. Temperature and humidity sensors are required to be wall mounted and rack mounted (for all racks within room) in each TR.

d. The OIT standards also speak about standards regarding CRAC units. The mini-splits being installed would not typically be considered a CRAC however they are labeled as that in the Mechanical Drawings. The OIT standards request monitoring of both temperature and humidity on both the supply and return air of the CRACS. As mentioned previously supply temperature/humidity monitoring is not advised and return temperature/humidity monitoring is not advised. The return temperature/humidity for a mini-split is typically considered the space temperature/humidity. Please clarify what is desired with the monitoring of the mini-split units and if the VA is considering them CRAC units. See responses for 2 above.