Guardian Series design guide

Section 1The Guardian Series

Ten fixed frames share one platform: the same IE5 direct-drive EC fan array, Delta Controls package and 2 in. double-wall casing. Guardian CRAH frames are vertical units with V-bank coils, for downflow or upflow in the data hall, from 7,500–56,250 CFM. Guardian FA frames are horizontal blow-through units, with the filters, the fan array and then the coils, from 45,000–100,000 CFM.

Table 1.1 The frames

Maximum airflow is the lower of 625 FPM across the coil face and 500 FPM through the filters. Dimensions are width × depth × height.

Figure 1.3 Air path, Guardian FA

Blow-through: the fan array pushes air through the coils to the discharge end.

Drain pans, dashed, are option D on every frame; the stand is option S.

Schematic, not to scale. Each frame's arrangement and dimensions are on its unit drawing (appendix A).

Model number

Every unit carries one complete model number of eleven segments, separated by hyphens. The options block is last and lists only the options furnished, in a fixed order; 0 means none.

Table 1.2 Options block, in fixed order

Examples

Section 2Selecting a unit

Each Guardian frame is a fixed design with a published airflow range. Selecting a unit means finding the smallest frame whose rating at your conditions meets the load, with the airflow inside that frame's range.

1. Gather the design conditions.You need the net sensible load per unit in kW, the entering air dry bulb and wet bulb (or relative humidity), the entering and leaving water temperatures, the fluid, the airflow if the design fixes it, and the discharge arrangement.
2. Choose the series.Guardian CRAH frames are vertical units with V-bank coils, for downflow or upflow, from 7,500–56,250 CFM at maximum airflow. Guardian FA frames are horizontal blow-through units, from 45,000–100,000 CFM.
3. Find the frame in the capacity tables.Use the rating class closest to your conditions (table 2.1). Pick the smallest frame whose rating meets the load. Section 3 gives each frame's rating at its minimum, nominal and maximum airflow.
4. Check the airflow against the frame's range.The airflow must sit between the frame's minimum and maximum (figure 2.1). Ratings with a coil face velocity above 457 FPM are above the coil's tested range and are marked est. (above tested range).
5. Check the water conditions.The leaving water must be warmer than the entering water, the entering air warmer than the entering water, and the leaving water cooler than the entering air. A selection that breaks any of these is not rated.
6. Choose 6-row or 8-row coils.6-row coils are standard. 8-row coils fit the same frame and add 8–9% sensible capacity at maximum airflow at class C3.
7. Size the water flow.On water, the flow follows from the capacity and the water rise (below, and table 8.1). Glycol capacity and flow are rated per selection (section 8.5).
8. Confirm the rating at your own conditions.Ask Cambridgeport (section 12) for a rating at your exact conditions. Certified coil and fan selections and electrical data come with the formal submittal.

Table 2.1 Rating classes

Airflow limits, every frame

Figure 2.1 Airflow range of each frame, CFM

Water flow on water

For example, the GFA-CRAH-200 at maximum airflow, 192 kW at the class C3 rise of 15.0°F, needs 88 GPM. Water pressure drop depends on the selection and comes with the certified coil selection.

Section 3Capacity

Net sensible capacity in kW on water, at each rating class's conditions (table 2.1). Nominal airflow is 80% of maximum. Water flow is at the class water rise.

Figure 3.1 Capacity range of each frame, kW

Net sensible capacity with 6-row coils at class C3 (85.0°F dry bulb and 62.5°F wet bulb entering air, 60.0°F entering and 75.0°F leaving water), from each frame's minimum to its maximum airflow (figure 2.1). 8-row coils add capacity at every airflow (section 2, step 6). Pick the smallest frame whose range covers the load, then read its rating in the tables below.

Table 3.1 Guardian CRAH, class C1

Table 3.2 Guardian FA, class C1

Class C1: 75.0°F dry bulb and 61.1°F wet bulb entering air, 45.0°F entering and 56.3°F leaving water.

Table 3.3 Guardian CRAH, class C3

Table 3.4 Guardian FA, class C3

Class C3: 85.0°F dry bulb and 62.5°F wet bulb entering air, 60.0°F entering and 75.0°F leaving water.

Table 3.5 Guardian CRAH, class C5

Table 3.6 Guardian FA, class C5

Class C5: 97.0°F dry bulb and 72.2°F wet bulb entering air, 70.0°F entering and 87.4°F leaving water.

Section 4Capacity against entering water

Net sensible capacity of each frame at nominal airflow with 6-row coils, 85.0°F entering air (class C3's dry bulb, 62.5°F wet bulb) and the class C3 water rise of 15.0°F, across entering water from 45°F to 65°F. The leaving air rises with the entering water, so capacity falls as the water warms.

Figure 4.1 Guardian CRAH

Figure 4.2 Guardian FA

Section 3 gives the capacities at the rating classes' conditions, with leaving air and water flow.

Section 5Physical data and construction

Table 5.1 Physical data

Dimensions are width × depth × height. A side return on a Guardian CRAH frame adds 30 in. to the height. Two-piece frames ship as sections: GFA-FA-525, 64 in. and 130 in. high; GFA-FA-625, 74 in. and 152 in. high. Weights are estimates; the unit drawing and the submittal carry the certified weights and the rigging points.

Figure 5.1 The frames to scale, width and height

Every frame at one scale, with a 6 ft person for reference; the grid is at 2 ft. Each outline is the unit's width by height, without the Guardian CRAH's stand or a side return plenum.

Table 5.2 Construction

Standard on every unit

• Base piping package: coil headers, isolation valves, air vents and P/T ports, with pressure-independent control valves (PICV) shipped loose for field installation
• Single-point chilled water connection, grooved or flanged
• Delta Controls DDC package with a 4.3 in. touchscreen, factory programmed and point-to-point tested; BACnet/IP native
• IE5 direct-drive EC fan array
• 2 in. double-wall insulated casing, R-14
• MERV-8 filters
• Return air temperature, supply air temperature and supply air humidity sensors, factory mounted
• 460 V, 3-phase, 60 Hz single-point power

Section 6Electrical data

Every unit takes 460 V, 3-phase, 60 Hz power at a single point, to the motor power panel. An automatic transfer switch with a dual power feed is an option on every frame (option T).

Table 6.1 Electrical data

Electrical figures are estimates. Certified electrical data comes with each unit's fan selection and the formal submittal; the nameplate carries the minimum circuit ampacity and maximum overcurrent protection.

Power quality

With the active front end option (option A) on each fan, the unit's current distortion is under 1% and its power factor 0.98 at the connection, so the fan load needs no external harmonic filters, oversized neutrals or transformer derating (IEEE-519). With the ATS and active front end options together, the fan array rides through a transfer.

Field connections

• Power: one feeder to the motor power panel, sized and protected to the nameplate.
• Building automation: BACnet/IP at the control panel, with dual Ethernet ports.
• Fans: a factory-wired Modbus RS-485 trunk from the controller to every fan.

Section 7Planning, rigging and clearances

Every frame separates mechanical service from electrical and controls service, so the two never need the same clearance. Each assembly withdraws on its own, horizontally, so one component can be serviced while the rest stay in place.

Table 7.1 Where service happens

Table 7.2 Service clearances, Guardian CRAH

Table 7.3 Service clearances, Guardian FA

Each unit drawing depicts its clearances (appendix A). Where the National Electrical Code (NEC 110.26) sets a larger working space at the panel face, provide the larger.

To scale, from above, as each unit drawing's top view; clearances are shaded. Guardian CRAH: coils and fans withdraw into the front gallery; panels and filters are serviced from the side. Guardian FA: filters and fans at the inlet end, coils at the discharge end; air enters at the inlet (red) and leaves at the discharge (blue). Tables 7.2 and 7.3 give every frame's clearances.

Planning the room

• Plan the service faces at layout. Withdrawal needs the clearance on the drawing plus room for the technician and a lift or transfer cart, and it can't be recovered once the units are set.
• A side return on a Guardian CRAH frame adds the 30 in. return plenum to the unit height; check the overhead clearance.
• Downflow units need an unobstructed raised-floor plenum. Check the floor grille free area against the unit airflow, and coordinate the stand height with the floor depth.
• Check the structure against the unit's operating weight (table 5.1, an estimate until the submittal).
• Set each unit level within 1/8 in. over its footprint, shimmed at the base rail.
• On units with drain pans (option D), pipe the condensate drain full size with a trap at least 1 in. deep per 1 in. w.g. of the unit's negative static pressure, plus 1 in., pitched at least 1/8 in. per foot.

Rigging and shipping

Rig at the lift points on the unit drawing, by forklift from below with the skid intact or by a spreader-bar lift. Never lift by the piping, coil headers or panel flanges, and keep the unit upright. The GFA-FA-525 and GFA-FA-625 ship in two pieces; each section is rigged on its own and the sections are joined on site with the factory gasket kit. Check door openings, elevators and the rigging path against the shipping dimensions before release.

Section 8Piping and water

Schematic, not to scale; supply blue, return red. Valve positions for each project are on the submittal's piping detail.

8.3 Control valves

Pressure-independent control valves (PICV) come with every unit, selected against the coil's design flow and installed in the field in the positions on the piping detail. Energy-metering valves (EPIV, option E) and a factory-installed valve package (option F) are options. A strainer with blow-down is option Y; otherwise install a strainer of 20 mesh or finer in the supply, upstream of the unit.

8.4 Field piping

• Flush and clean the building loop with the unit isolated before connecting it. Construction debris is the leading cause of fouled coils and failed control valves in the first year.
• Support field piping on its own, with no strain on the unit connections.
• Treat the loop to the project's water-treatment specification and keep it closed.
• Balance to the scheduled flow at the P/T ports and set each PICV to its design flow.

Table 8.1 Water flow by water rise

On water. Water pressure drop depends on the selection and comes with the certified coil selection; carry it in the plant's pump head.

8.5 Glycol

Units run on water or propylene glycol; the model number's fluid segment is W for water and G30 for 30% propylene glycol. Glycol reduces capacity and changes the flow and pressure drop, so glycol capacity and flow are rated per selection: ask Cambridgeport for a rating at your concentration and conditions. Check the delivered glycol type and concentration by refractometer at fill and record them.

8.6 Condensation

Units run dry when the entering water is above the room's dew point. Drain pans are option D on every frame: stainless steel, one per coil, under each coil on Guardian CRAH and downstream of each coil on Guardian FA, each with a gravity drain, for commissioning, dehumidification excursions and coil cleaning; a condensate pump is option P, with the drain pans. Without drain pans, keep the entering water above the room's dew point.

Section 9Controls

9.1 The controls package

A Delta Controls DDC controller with I/O expansion and a 4.3 in. touchscreen on the control panel door, factory programmed and point-to-point tested. BACnet/IP native, with dual Ethernet ports, to the building automation system, and a Modbus RS-485 trunk to every fan. The control panel is NEMA 4, with a 24 VDC supply, fused 24 VAC and two-level terminals; the power panel has a fused busbar, a 15 A class CC fuse for each fan and a disconnect.

Figure 9.1 Controls and network

Schematic. The supply fan fault comes through the Modbus trunk or a hardwired input. Options are dashed.

Figure 9.2 Power distribution

One-line, schematic: four fans shown; each frame's fan count is in table 6.1. Options are dashed.

Table 9.1 Points

The project's sequences of operation, network architecture and full points list come with the submittal.

Table 9.2 Standard sequences

Section 10Options

Most options are chosen in the model number. Those in the options block print as letters, in the fixed order below; others are choices in the model number's other segments. The factory tests are ordered with the unit and listed on its documents, but have no letter.

Table 10.1 Options block

Table 10.2 Choices in other segments

Table 10.3 Options not in the model number

Non-standard stand heights and seismic anchorage are engineered per project.

Section 11Application notes

Section 12Contacts

For a rating at your own conditions, a selection, a quotation or a submittal, contact Cambridgeport.

Appendix AUnit drawings

Layout, clearances and legend for each frame. Certified drawings are issued with the submittal.

This drawing shows the previous coil. The coil, face area and ratings are as stated on this page.

This drawing shows the previous coil. The coil, face area and ratings are as stated on this page.

This drawing shows the previous coil. The coil, face area and ratings are as stated on this page.