AHUQA18June2010pm.doc

(AHU Project Questions & Answers) 6/18/2010

Q: 50 - Drawing 202-302 under Drawing Notes: 1. Refers to the Specification 15900 for details on Ethernet switches to be provided in Building 231 & 235. However, this HVAC section does not cover Ethernet hardware?

A: 50- Most of the buildings under this contract have Ethernet switches. Government will provide if required for particular location.

Q: 51- Drawing 202-301 General Note #28 does not indicate the amount of time allotted to complete the (2) AHU’s once taken out of service. What is the expectation?

A: 51- The contract requirement shall be defined as 21 day performance period to turn over to NIST a commissioned AHU.

Q: 52- The Specification section 15127 calls for flow meters on all AHU steam and chilled water supply lines? However the control flow diagrams do not list the point? This would have a major impact on the pricing of the project. Please advise.

15127– 6 (3.8 FLOW METERS) A. Provide flow meters at all AHU steam and water supply lines.

A: 52- As laid out in scope of work each AHU steam and chilled water supply lines shall be installed with flow meters. These flow meters are not called out to be tied to the BAS system.

Q: 53 – The AHU specification section 15725 has no reference to coil construction. Would standard coils be acceptable for the new AHU’s or do the coils for the new AHU’s have to meet the specification section 15761, “AIR COILS”?

The performance of the air handling units and coils appear to be based off of coils with ½” diameter, 0.016” thick tubes. The performance specified cannot be met with the specified tube diameter and tube thickness combination. Will ½” diameter, 0.016” thick tubes be acceptable for the coils?

A: 53- The coils shall meet specification 15761. The performance rating shall meet or exceed ARI 410 and ASHRE 33 as called out in section 15761- 2.1.B.

The tube diameter and thickness should meet the performance requirements as specified in the bid documents. Bid document has generalized performance rating for AHU coils. Refer to AHU schedule for each building as noted. On each schedule there is a basis of design, all AHU coils, fans, motors, controls are specified to meet the overall performance criteria namely total CFM, PSI, static pressure lost across the coil and horse power rating for the motor. Contractor is required to meet performance criteria as well as meeting or exceeding the required ARI 410 and ASHRE 33 Q: 54 – Please clarify piping material size fins for chilled water & steams lines – would NIST consider utilizing copper tubes with aluminum fins?

A: 54- Bid documents have generalized performance ratings for AHU coils. Refer to AHU schedule for each building as noted on each schedule there is a basis of design, all AHU coils, fans, motors, controls are specified to meet the overall performance criteria namely total CFM, PSI, static pressure lost across the coil and horse power rating for the motor. Contractor is required to meet performance criteria as well as meeting or exceeding the required ARI 410 and ASHRE 33. The material for chilled water coil shall be copper tubes and aluminum fins.

There have been a lot of questions and answers proposed.

On June 1st answer #13 stated :

(15761) paragraph 2.1.F should read “Fins: Aluminum, minimum 0.010 inch thick.”

(15761) paragraph 2.2.F should read “Fins: Aluminum, minimum 0.010 inch thick.”

On June 24 answer #24 stated:

(15761 paragraphs 2.1.E and 2.2.E) the tubes minimum thickness is 0.049 inch thick

On June 11th answer #26 was answered incorrectly

The question was “Q 26 – This is to confirm that the fin type is 0.010 aluminum without coating. Please verify.”

The correct answer: Yes the minimum fin thickness is 0.010 inch thick. As outlined in answer #13 on June 1st the special coating requirement was deleted.

On June 17, questions #30, #44, and #45 asked question regarding fins. The correct answer is the one listed on June 1st for answer #13.

Question #13 in whole stated - (NIST RESPONSE) Paragraph 2.1. F should read “Fins: Aluminum, minimum 0.010 inch thick.” to match existing coils. Paragraph 2.1.I.7 should be deleted. Special coatings are not required. Paragraph 2.2. F should read “Fins Aluminum, minimum 0.010 inch thick.” to match existing coils.