12505B22R0035_Replace HVAC Units_Questions-USDA Response-09-14-2022.pdf

12505B22R0035 – Replace HVAC Units, Ames, IA

Questions and Answers through 9/14/22

1. Item #13 and paragraph a. the last bullet point specifies a particular Larkin Model LEH1210CS6EMA or approved equal evaporator to replace the existing Larkin PC-366.

We have attached the Larkin Supplied Submittal for the LEH1210CS6EMA and this model is not a ducted model like the PC-366 is. The SOW clearly states to disconnect the from the ductwork and reconnect to the ductwork however the specified model cannot be used with ductwork.

So my question is what would be the best way to proceed?

USDA:

Reference Item #20 (Base Bid) and Item #34 (Bid Option 01). Delete re-connection of existing ductwork to new evaporator units. See Photographs 4 through 8 shown below.

Base Bid:

Contractor shall disconnect mechanical ductwork from existing west evaporator unit (Evaporator #1) to allow removal of evaporator unit. Contractor shall remove existing ductwork from west evaporator unit back to main north-south ductwork run. Provide cap at north-south ductwork run, material type of cap shall match existing ductwork. Removal work shall include removal of mounting hardware and sealing of all openings due to removal work.

Bid Option 01:

Contractor shall disconnect mechanical ductwork from existing east evaporator unit (Evaporator #2) to allow removal of evaporator unit. Contractor shall remove existing ductwork from east evaporator unit back to main north-south ductwork run. Provide cap at north-south ductwork run, material type of cap shall match existing ductwork. Removal work shall include removal of mounting hardware and patching of all openings due to removal work. North-south ductwork run shall remain and shall be abandoned in place.

2. The evaporator they are calling for is a hanging refrigeration evap (tech bulletin attached).

2.a. This is a prop fan evap. It is not designed to be attached to ductwork. And will not provide static.

USDA:

See response to item 1 and item 3.

2.b. It calls for 27kW of electric heat. You can order this evap with electric defrost heaters. These will not be large enough to provide reheat which is typically required for seed corn storage. It is only for defrosting the coil.

USDA:

The electric heat to be furnished with evaporator unit(s) are for defrosting the coil only, not re-heat for humidity control.

2.c. It calls for spring isolators when mounting. Those are not required.

USDA:

Delete requirement for spring isolators. Spring isolators are not needed for the specified equipment. See item 3 for additional information.

I think this is really intended to be an AHU. Which we use frequently for seed corn storage.

They will provide all they are calling out for in the specs.

USDA:

Offeror’s proposal shall be based on specified equipment. See item 3 for additional information.

Also, are the replacing the 2 vertical units in the picture? Or the horizontal unit? They make both in 15 HP but are priced completely different.

USDA:

Please reference Sheet M-2 of the existing drawings furnished. For Base Bid, the condensing unit labelled “Condenser Unit #1” on Sheet M-2 shall be replaced. For Bid Option 01, the condensing unit labelled “Condenser Unit #2” on Sheet M-2 shall be replaced. Please reference Photograph 1 in the SOW. The photograph shows three condensing units, Condenser Unit #1 is the center unit and Condenser Unit #2 is the south unit.

3. Government Clarifications

USDA:

Clarification 1: Contractor shall assume that refrigerant at existing condensing units is R12 (in lieu of R22 indicated in SOW). Provide recovery of refrigerant as indicated in

SOW.

Clarification 2: Provide two (2) new evaporator units (Evaporator #1A and Evaporator #1B) to replace existing Evaporator #1. New Condensing Unit #1 shall be connected to operate with both new Evaporator #1A and Evaporator #1B. Provide two (2) new evaporator units (Evaporator #2A and Evaporator #2B) to replace existing Evaporator #2. New Condensing Unit #2 shall be connected to operate with both new Evaporator #2A and Evaporator #2B.

Clarification 3: Reference item 15 (Base Bid). Contractor shall provide refrigerant piping from Condensing Unit #1 to Evaporator #1A and to Evaporator #1B in accordance with requirements of item 15. For bidding purposes, Contractor shall assume 1-3/8” liquid line and 1-5/8” suction line to each evaporator unit.

Clarification 4: Reference item 29 (Bid Option 01). Contractor shall provide refrigerant piping from Condensing Unit #2 to Evaporator #2A and to Evaporator #2B in accordance with requirements of item 29. For bidding purposes, Contractor shall assume 1-3/8” liquid line and 1-5/8” suction line to each evaporator unit.

Clarification 5: Reference item 19 (Base Bid). Contractor shall provide new condensate drain line installation from Evaporator #1A and from Evaporator #1B and provide connection to existing condensate drain piping system along north wall. Provide modification of existing condensate piping and new condensate drain piping in accordance with the requirements of item 19. For bidding purposes, Contractor shall assume size of new condensate drain line piping shall be ¾”.

Clarification 6: Reference item 33 (Bid Option 01). Contractor shall provide new condensate drain line installation from Evaporator #2A and from Evaporator #2B and provide connection to existing condensate drain piping system along north wall. Provide modification of existing condensate piping and new condensate drain piping in accordance with the requirements of item 33. For bidding purposes, Contractor shall assume size of new condensate drain line piping shall be ¾”.

Clarification 7: Reference item 26 (Bid Option 01). Condensing Unit #2 shall be rated for nominal 144,200 BTUH (in lieu of 14,200 BTUH shown).

Clarification 8: Revise specification for evaporator units (see item 13 and item 27) as indicated below, revisions are in red.

“13. Base Bid: Provide removal of Evaporator #1 and replace with two (2) new evaporator units. The replacement shall include, but not limited to:

a. Furnishing of new evaporator units. Existing drawings indicate evaporator is Larkin Model PC-366 Product Cooler. Each new evaporator unit:

Shall be designed for cold room applications complete with control components and shall, at a minimum, shall match the performance characteristics indicated below.

Shall be 100% compatible with and designed for operation with associated condensing unit.

Shall be rated for nominal 71,500 BTUH at 29° F suction temperature and 4° C (39° F) room temperature.

Shall be equipped with multiple blower motor(s) rated for two speed operation to provide energy efficiency and capable of providing 8,400 cfm as a unit.

Shall include blower section with manufacturer furnished electrical components to receive one point power feed from 208V, three phase source and distribute electrical power to the multiple blower fans.

Shall be equipped with cooling defrost feature utilizing 10.2 KW heater operating on 208V, three power electric power.

Shall be equipped with thermostatic expansion valve, suction filter, access ports for measuring pressures and system characteristics as needed for maintenance and troubleshooting.

Shall be Larkin Model LEM0620CS4EMA***** or approved equal.

b. Disconnecting existing evaporator unit from condensate drain piping, from mechanical ductwork, from refrigerant lines, from electrical power circuiting, and electrical control connections to allow removal.

c. Removal of the existing evaporator unit in its entirety.

d. Code legal installation of new evaporators including connection to condensate drain line, connection to properly sized refrigerant lines, connection of electrical power circuits, and connection of associated control wiring. The completed installation shall be properly operating and shall be in accordance with the manufacturer’s written requirements and recommendations. Mounting of the evaporator shall be similar to the existing installation, see Section A-A on existing drawing M-2.”

Locate Evaporator #1A near northwest corner of cold room; locate nominal 6’ from west wall to west edge of evaporator and nominal 6’ from north wall to north edge of evaporator. Contractor shall coordinate exact location of evaporator with Owner prior to installation.

Locate Evaporator #1B near southeast corner of cold room; locate nominal 6’ from east wall to east edge to east edge of evaporator and nominal 6’ from south wall to south edge of evaporator. Contractor shall coordinate exact location of evaporator with Owner prior to installation.”

“27. Bid Option 01: Provide removal of Evaporator #2 and replace with two (2) new evaporator units. The replacement shall include, but not limited to:

a. Furnishing of new evaporator units. Existing drawings indicate evaporator is Larkin Model PC-366 Product Cooler. Each new evaporator unit:

Shall be designed for cold room applications complete with control components and shall, at a minimum, shall match the performance characteristics indicated below.

Shall be 100% compatible with and designed for operation with associated condensing unit.

Shall be rated for nominal 71,500 BTUH at 29° F suction temperature and 4° C (39° F) room temperature.

Shall be equipped with multiple blower motor(s) rated for two speed operation to provide energy efficiency and capable of providing 8,400 cfm as a unit.

Shall include blower section with manufacturer furnished electrical components to receive one point power feed from 208V, three phase source and distribute electrical power to the multiple blower fans.

Shall be equipped with cooling defrost feature utilizing 10.2 KW heater operating on 208V, three power electric power.

Shall be equipped with thermostatic expansion valve, suction filter, access ports for measuring pressures and system characteristics as needed for maintenance and troubleshooting.

Shall be Larkin Model LEM0620CS4EMA***** or approved equal.

b. Disconnecting existing evaporator unit from condensate drain piping, from mechanical ductwork, from refrigerant lines, from electrical power circuiting, and electrical control connections to allow removal.

c. Removal of the existing evaporator unit in its entirety.

d. Code legal installation of new evaporators including connection to condensate drain line, connection to properly sized refrigerant lines, connection of electrical power circuits, and connection of associated control wiring. The completed installation shall be properly operating and shall be in accordance with the manufacturer’s written requirements and recommendations. Mounting of the evaporator shall be similar to the existing installation, see Section A-A on existing drawing M-2.”

Locate Evaporator #2A near northeast corner of cold room; locate nominal 6’ from east wall to east edge of evaporator and nominal 6’ from north wall to north edge of evaporator. Contractor shall coordinate exact location of evaporator with Owner prior to installation.

Locate Evaporator #2B near southwest corner of cold room; locate nominal 6’ from west wall to west edge to east edge of evaporator and nominal 6’ from south wall to south edge of evaporator. Contractor shall coordinate exact location of evaporator with Owner prior to installation.”

Clarification 9: Revise item 22 (Base Bid) and item 23 (Base Bid) as indicated below, revisions are in red.

“22. Base Bid: Existing drawings indicate existing power circuit to Evaporator #1 blower motor is 208V, three phase circuit from Panel A-1; power circuit is routed through a wall mounted combination starter located in the cold room. Panel A-1 is Square D Type NQOD. See existing drawings for additional information.

Contractor shall disconnect existing power circuit for blower motor from evaporator to allow removal.

Contractor shall remove existing wall mounted combination motor starter for evaporator blower motor.

Contractor shall remove existing conduit and wiring system of evaporator blower motor circuit.

For each new evaporator (Evaporator #1A and Evaporator #1B); provide new disconnect switch and contactor, wall mount near unit. New disconnect (safety switch) shall be NEMA 3R, 600V, 60A, three pole, non-fused, heavy-duty type; Square D Class 3110 or approved equal. New contactor shall be enclosed type, NEMA 3R, Size 2 full voltage contactor; contactor shall be furnished with Hand-Off-Auto selector switch, “Green” running push-to-test pilot light, fused control transformer with 100 VA spare capacity, and 2-NO- NC auxiliary contacts; Square D Class 8502 or approved equal. Contractor shall label new disconnect switch and contactor to indicate load, panel, and circuit number.

Contractor shall provide new conduit and wiring installation to each new evaporator for blower motor(s). New conduit and wiring shall be ¾” conduit with 3#8 and 1#10 Grd. Contractor shall incorporate sealing fittings in new conduit run such that convection of warm air into the cold room, through the conduit system, does not occur.

At Panel A-1, Contractor shall reuse existing 40A, three pole circuit breaker for Evaporator #1A and shall provide new 40A, three pole circuit breaker for Evaporator #1B. Update panel directory to indicate circuiting changes.

Contractor shall provide new final flexible connection to evaporator blower motor.

Provide final flexible connection with 3/4” liquid-tight conduit with 3#8 and 1#10 Grd.

Contractor shall provide ¾” conduit with 6#14 and 1#14 Grd and interlock each contactor with existing control panel.

23. Base Bid: Existing drawings indicate existing power circuit to Evaporator #1 defrost heater is 208V, 60A, single phase circuit from Panel A-1; power circuit is routed through disconnect switch / contactor. Panel A-1 is Square D Type NQOD. See existing drawings for additional information.

Contractor shall disconnect existing power circuit for defrost heater from evaporator to allow removal.

Contractor shall remove existing disconnect switch and contactor for evaporator defrost heater.

Contractor shall remove conduit and wiring of evaporator defrost heater circuit.

For each new evaporator (Evaporator #1A and Evaporator #1B); provide new disconnect switch and contactor, wall mount near unit. New disconnect (safety switch) shall be NEMA 3R, 600V, 60 A, three pole, non-fused, heavy-duty type; Square D Class 3110 or approved equal. New contactor shall be enclosed type, NEMA 3R, Size 2 full voltage contactor; contactor shall be furnished with Hand-Off-Auto selector switch, “Green” running push-to-test pilot light, fused control transformer with 100 VA spare capacity, and 2-NO- NC auxiliary contacts; Square D Class 8502 or approved equal. Contractor shall label new disconnect switch and contactor to indicate load, panel, and circuit number.

Contractor shall provide new defrost timer and interlock timer with each new defrost heater contactor. Coordinate with condenser / evaporator and program defrost timer for recommended defrost cycles.

Contractor shall provide new conduit and wiring installation to each new evaporator for defrost heater(s). New conduit and wiring shall be ¾” conduit with 3#8 and 1#10 Grd. Contractor shall incorporate sealing fittings in new conduit run such that convection of warm air into the cold room, through the conduit system, does not occur.”

At Panel A-1, Contractor shall remove existing two pole circuit breaker of existing defrost heater and shall provide two (2) new 40A, three pole circuit breakers in available space and circuit defrost heaters of Evaporator #1A and #1B. Update panel directory to indicate circuiting changes.

Contractor shall provide new final flexible connection to each evaporator defrost heater. Provide final flexible connection with 3/4” liquid-tight conduit with 3#8 and 1#10 Grd.”

Clarification 10: Revise item 36 (Bid Option 01) and item 37 (Bid Option 01) as indicated below, revisions are in red.

“36. Bid Option 01: Existing drawings indicate existing power circuit to Evaporator #2 blower motor is 208V, three phase circuit from Panel A-1; power circuit is routed through a wall mounted combination starter located in the cold room. Panel A-1 is Square D Type NQOD. See existing drawings for additional information.

Contractor shall disconnect existing power circuit for blower motor from evaporator to allow removal.

Contractor shall remove existing wall mounted combination motor starter for evaporator blower motor.

Contractor shall remove conduit and wiring system of evaporator blower motor circuit.

For each new evaporator (Evaporator #2A and Evaporator #2B); provide new disconnect switch and contactor, wall mount near unit. New disconnect (safety switch) shall be NEMA 3R, 600V, 60A, three pole, non-fused, heavy-duty type; Square D Class 3110 or approved equal. New contactor shall be enclosed type, NEMA 3R, Size 2 full voltage contactor; contactor shall be furnished with Hand-Off-Auto selector switch, “Green” running push-to-test pilot light, fused control transformer with 100 VA spare capacity, and 2-NO- NC auxiliary contacts; Square D Class 8502 or approved equal. Contractor shall label new disconnect switch and contactor to indicate load, panel, and circuit number.

Contractor shall provide new conduit and wiring installation to each new evaporator for blower motor(s). New conduit and wiring shall be ¾” conduit with 3#8 and 1#10 Grd. Contractor shall incorporate sealing fittings in new conduit run such that convection of warm air into the cold room, through the conduit system, does not occur.

At Panel A-1, Contractor shall reuse existing 40A, three pole circuit breaker for Evaporator #2A and shall provide new 40A, three pole circuit breaker for Evaporator #2B. Update panel directory to indicate circuiting changes.

Contractor shall provide new final flexible connection to evaporator blower motor.

Provide final flexible connection with 3/4” liquid-tight conduit with 3#8 and 1#10 Grd.

Contractor shall provide ¾” conduit with 6#14 and 1#14 Grd and interlock each contactor with existing control panel.

24. Base Bid: Existing drawings indicate existing power circuit to Evaporator #1 defrost heater is 208V, 60A, single phase circuit from Panel A-1; power circuit is routed through disconnect switch / contactor. Panel A-1 is Square D Type NQOD. See existing drawings for additional information.

Contractor shall disconnect existing power circuit for defrost heater from evaporator to allow removal.

Contractor shall remove existing disconnect switch and contactor for evaporator defrost heater.

Contractor shall remove conduit and wiring of evaporator defrost heater circuit.

For each new evaporator (Evaporator #2A and Evaporator #2B); provide new disconnect switch and contactor, wall mount near unit. New disconnect (safety switch) shall be NEMA 3R, 600V, 60 A, three pole, non-fused, heavy-duty type; Square D Class 3110 or approved equal. New contactor shall be enclosed type, NEMA 3R, Size 2 full voltage contactor; contactor shall be furnished with Hand-Off-Auto selector switch, “Green” running push-to-test pilot light, fused control transformer with 100 VA spare capacity, and 2-NO- NC auxiliary contacts; Square D Class 8502 or approved equal. Contractor shall label new disconnect switch and contactor to indicate load, panel, and circuit number.

Contractor shall provide new defrost timer and interlock timer with each new defrost heater contactor. Coordinate with condenser / evaporator and program defrost timer for recommended defrost cycles.

Contractor shall provide new conduit and wiring installation to each new evaporator for defrost heater(s). New conduit and wiring shall be ¾” conduit with

3#8 and 1#10 Grd. Contractor shall incorporate sealing fittings in new conduit run such that convection of warm air into the cold room, through the conduit system, does not occur.”

At Panel A-1, Contractor shall remove existing two pole circuit breaker of existing defrost heater and shall provide two (2) new 40A, three pole circuit breakers in available space and circuit defrost heaters of Evaporator #2A and #2B. Update panel directory to indicate circuiting changes.

Contractor shall provide new final flexible connection to each evaporator defrost heater. Provide final flexible connection with 3/4” liquid-tight conduit with 3#8 and 1#10 Grd.”

Government Clarification ‐ Additional Photographs:

Add Photographs 4 through 8.

Note: Photographs 1 through 3 were issued with project’s “Statement of Work”.

Photograph 4: View of existing east evaporator unit, looking east.

Photograph 5: View of existing east evaporator unit, looking west.

Photograph 6: View of existing west evaporator unit, looking east.

Photograph 7: View of existing west evaporator unit, looking west.

Photograph 8: View of existing ductwork connections to evaporator units.

END