RFP_QA_29MAY2024.pdf

W911QY-24-R-0007

Q&A from draft RFP

No. Question Answer

Reference: Announcement Will the Army evaluate potentials to incorporate Small Business Set-Asides?

Per solicitation paragraph A.3, this acquisition is full and open competition. A small business participation plan is a required element of the proposal and is one of the evaluation factors; see Section L.

2 Reference: A.1.1 Issue a single contract to only one awardee? Yes.

Reference: Announcement What portion of estimated quantities will be Vertical config. variant?

This solicitation covers only horizontal 9000 (9K) BTU/hr single phase, 18000 (18K) BTU/hr three phase, 18000 (18K) BTU/hr single phase, and 36000 (36K) BTU/hr three phase variants. No vertical configurations will be ordered.

Reference: PPD, paragraph 1.1 Scope mentions horizontal and vertical configurations - is this for more than the 4 horizontal variants?

Reference: PPD, paragraph 3.1 (h.)

What units will require cooling below 0F? -25 F and -50 F may be required?

Per the Interface Specification, all variants require cooling down to an exterior temperature of 0 °F, except the 36K variant which requires cooling down to an exterior temperature of -25 °F. The low temperature cooling requirement has been in effect at least since the 1975 version of the Interface Specification and re-affirmed in the 2009 version, MIL-STD-1408D. This requirement may be relaxed only if the Government specifies a refrigerant that makes it unfeasible.

Reference: PPD, paragraph 3.1.h Is cooling actually needed at 0°F & -25°F outdoor ambient? Refrigeration systems can be designed for this but additional components and system complication are introduced. (current text: cooling at 0 and - 25°F) Reference: IS, Table 1 Is cooling needed at 0°F? Additional refrigeration system components & system complication are needed for cooling at 0°F ambient. (current text: Cooling: 0 to 125°F)

Reference: IS, Table 2 Is cooling needed at 0°F? Additional refrigeration system components & system complication are needed for cooling at 0°F ambient. (current text: Cooling: 0 to 125°F) Reference: IS, Table 3 Is cooling needed at -25°F? Additional refrigeration system components & system complication are needed for cooling at minus 25°F ambient. (current text: Cooling: 0 to 125°F)

Reference: PPD, paragraph 3.1 (k.)

Is return air filter to be internal to the ECU?

Can it be accessed from the return air opening?

The air filter is part of the IECU. As the Interface Specification provides location and dimensions for inlet (return) grille and the discharge (supply) grille, the air filter is necessarily internal to the IECU. Per 3.17.2.3, the air filter shall be accessible without having to remove the top cover of the unit or having to remove the unit from its mounting bracket. It is anticipated that the air filter will need to be inspected frequently as part of Preventive Maintenance Checks and Services (PMCS), so it should be easily and quickly accessible. For the most recent IECUs, it was located directly behind the return grille, which was secured with thumbscrews.

Reference: PPD, paragraph 3.3.1 Is minimum rated capacity required with 50 Hz power? If so, the power draw in 60 Hz would likely exceed the power budget without the use of VFD's for fans and compressor.

Per 4.3.2.d, the default for testing, including cooling capacity, will be 60 Hz. Note that high temperature operation (cool) (see 4.3.3.1.c) and low temperature operation (heat) (see 4.3.3.4.2) are performed at 50 Hz.

Reference: PPD, paragraph 3.4.1.1.c Clarify ambient temperature requirement in the vicinity of thermostat. Compressor and fans will only activate if the temperature sensed by the thermostat is above the minimum setpoint. (current text: components activated in COOL mode)

A temperature is included in the verification (4.3.4.1), which will be raised from 70 ± 10 °F to 75 ± 10 °F. To improve clarity, the requirement will be updated as follows: "When the control is in the COOL position, the thermostat is at the coolest setting, and the sensed temperature is 65 °F or higher, the evaporator fan motor, the condenser fan motor, and the compressor shall be energized. The electric heaters shall be de-energized regardless of the temperature selection control setting."

Reference: PPD, paragraph 3.4.1.1.d Clarify ambient temperature requirement in the vicinity of thermostat. Electric heaters and fan will only activate if the temperature sensed by the thermostat is below the maximum setting. (current text: components activated in HEAT mode)

A temperature is included in the verification (4.3.4.1), which will be raised from 70 ± 10 °F to 75 ± 10 °F. To improve clarity, the requirement will be updated as follows: "When the control is in the HEAT position, the thermostat is at the warmest setting, and the sensed temperature is 85 °F or lower, the evaporator fan motor and the electric heaters shall be energized. The condenser fan motor(s) and the compressor shall be de-energized regardless of the temperature selection control setting."

Reference: PPD, paragraph 3.5.4 Consider use of fusible plug in lieu of relief valve. Refrigerant relief valves often leak after activating. Valve manufacturers recommend replacing the valve after discharge to prevent leaks. (current text: "resettable" refrigerant relief valve)

No change to this PPD requirement is anticipated.

Note that the maintenance procedure for current IECUs requires leak checking the pressure relief valve if it has vented.

Reference: PPD, paragraph 3.5.5 This requirement specifies tubing flare where flare nut joints are used. Is there a requirement to use flare nut joints instead of a fully brazed refrigerant circuit?

The existing IECU design does not require any maintainer brazing and instead uses re-sealable IMACA fittings for all replaceable parts in the refrigeration circuit. PdM FSS feels this is more logistically supportable than brazing, which requires more time and higher skill levels to perform, increases

Reference: PPD, paragraph 3.5.5 Avoid flared tubing. Brazed piping joints reduce the likelihood of leaks. (current text:

flared tubing) likelihood of equipment damage during repair, and makes technical manual maintenance procedures difficult to verify. However, the PPD as currently written does not mandate this approach. Be cognizant of the impact on Maintenance Ratio (see 3.10.2) in addition to the Maintenance Evaluation and Technical Manual Verification (See SOW).

Reference: PPD, paragraph 3.11.1 Thoroughly seal the evaporator compartment to isolate from condenser side. A pull through evaporator has superior performance compared to push through design. Thorough sealing of the evap section is required for CBRN. Why hamper evaporator performance with a push through requirement? (current text: "evaporator is a push-through design")

No change to this PPD requirement is anticipated.

Regarding CBR, the IECU has a requirement only for CBR contamination survivability, and the PPD requirements and verifications reflect that. However, certain future users, including the medical community, may require operation in CBR environments, and the IECUs may be tested and/or modified to meet that requirement. To both facilitate this future work and eliminate ingestion of ordinary airborne contaminants in general, PdM FSS feels that a pressurized evaporator section is the best practice.

Reference: PPD, paragraph 3.17.2.3.1 Are embedded diagnostics featured in the existing 9 18 36 ECU designs? Diagnostics are not indicated in the "interface standard".

(current text: Embedded Diagnostic)

For the most recent IECU design, five diagnostic test points are easily accessible to determine discharge and suction pressure, supply and return air temperature, and TXV bulb temperature. Inside the control box are 21 LEDs that provide additional information about faults (sensor, power, pressure) and control status for all major components (compressor, exhaust fans, blower, heater, crankcase heater).

Reference: PPD, paragraph 4.3.5 Eliminate reference to R410A. Actual refrigerant may be one having a lower GWP for regulatory compliance. (current text:

Refrigeration System Pressure R410A)

The PPD will be updated to eliminate this reference.

Reference: PPD, page 39 Provide HEMP design requirements. ECUs with HEMP survival treatments have been developed but design requirements are needed. (current text: HEMP testing & survivability)

The IECU requirements documentation addresses HEMP as follows: “High Altitude Electromagnetic Pulse (HEMP) Environment is specified in MIL-STD- 2169B or subsequent superseding documents. The IECU shall not be required to operate through a high-altitude electromagnetic pulse (HEMP) event.

Recycling of power to restore mission-critical functions is acceptable.” PdM FSS is deciding if and how this should be specifically addressed in the PPD.

Because MIL-STD-2169B is classified, it may not be possible to include useful requirements or verifications in the PPD.