65_Ft_Dive_Support_Boat_RFP_Q&A_121718.pdf

65 Ft Dive Support Boat NAVSEA Solicitation Number N00024-18-R-2209

Responses to Bidders’ Questions 17 Dec 2018

Question 15: The 120VAC shore power of 30A is not sufficient to handle the loads that the specification requires to be on the 120VAC shore power. The engine jacket water heaters and battery chargers required to be on the 30A shore power circuit is more than 30 amps of total load.

Response 15: The Attachment 6, Notional 65’ Dive Boat AC Power One-line is a notional distribution system and not intended for replication in the detailed design. Further, 120V shore power is not required to feed all 120Vac loads.

Question 16: The specification is asking for a single phase 480:240/120VAC single phase transformer but is asking that the 480V loads be balanced. This transformer will create an imbalance in excess of IEEE‐45 and ABYC requirements. This is 15% maximum per IEEE‐45 and ABYC says that the loads must be balanced as close as possible. The arrangement in accordance with the specification will create a 40‐50% imbalance on two of the three phases.

Response 16: Section 320-2 requires that all 480V loads are supplied from the 480Vac “Main” switchboard including the step down transformer. Balancing the 480Vac/3-phase loads is not required.

It is incumbent on the contractor to provide balanced loads on the secondary of the step down transformer.

Question 17: The specification states that all large HP loads are to be powered by 480VAC. Some of the equipment has been specified at 230VAC/208VAC. This should not be a big issue to change. Example is the LP Air compressor.

Response 17: Section 320-2 of the specification states “Where possible, all high kW loads should use 480 Vac, 3-phase power.” It does not require all large loads be 480Vac, just where possible.

Question 18: The Load Factors for the Electrical Load Analysis do not reflect real world conditions for a vessel of this size, crew complement, and type of equipment being utilized.

Att_05_Electrical_Load_Analysis_sample_05Jun2018 gives some load factors. For the remaining loads, Navsea DDS310‐01 Rev. 1 is referenced. However, this document is for larger ships, not small boats, so the load factors are not suitable for the equipment that is used on a small boat, e.g. HVAC system, On‐ Demand Water heater. If we use the load factors as shown, the required generator sizing would need to be much greater due to the starting and cycling characteristics of some of the loads.

Response 18: The Government concurs that within the referenced documents, certain load factors may not be applicable for a craft the size of the 65DS. Where the Builder believes that a correction for a load factor value is needed, the Builder may propose a more suitable load factor if robust justification and background is provided. The Government will consider the proposed factors on a case by case basis.