Small Rooftop Units Accessory Electric Heater and Single Point Box

Puron® Units

This installation instruction manual describes the installation of electric heaters and associated fuse block/field power termination kits (single point box [SPB]) on select small rooftop units in nominal cooling capacities from 3 to 6 tons. These rooftop units use R-410A refrigerant. See Package Usage tables on page 2 for applicable unit models. Unit types include cooling units (AC). Unit types AC-1, AC-2, are identified.

This information does not include selection data. Refer to project plans, job submittals and selection programs for heater and field power termination/SPB kit usage.

Electric Heaters

Heaters are shipped with one heater per carton. The carton is marked with a sales package number. On all heaters the heater model number (as marked on the heater dataplate) is the same as the sales package number.

The heaters are modular in design, with heater frames holding open coil resistance wires strung through ceramic insulators, limit switches and one or two control contactors. Power conductors are attached.

Heater modules are installed in the compartment below the indoor (supply) fan outlet. Access is through the indoor access panel. Heater modules slide into the compartment through the panel heater opening.

Not all available heater modules may be used in every unit. Use only those heater modules that are UL listed for use in a specific size unit. Refer to the label on the unit cabinet for the list of approved heaters. (See Fig. 1 and 2.) See Appendix B on page 19 for electric heater module data.

Single Point Boxes and Fuses

The Single Point Box (SPB) kits provide a field power termination location plus an enclosure for heater fuses when required by code. The SPBs are installed under the unit's main control box and include a cover plus all internal wiring. Minimum components of the SPB are a field power terminal block with tap conductors (to connect to the unit's main control box field terminals). Maximum component population includes up to five fuse blocks.

Fuses for electric heater circuits are required and provided when the unit's MOCP exceeds 60-A or when the total heater Full Load Amp value exceeds 48-A. When fuses are required and provided, the cooling circuit is also provided with fuse protection.

NO FUSES

If the unit's MOCP device rating is 60-A or less, then the MOCP device is recognized as providing the required overcurrent protection to the heater and no internal fusing is required. See tables at the beginning of Appendix A on page 16 for where-used information on the single point boxes and for connections figure number.

UNITS WITH FACTORY-INSTALLED HACR

The amp rating of the HACR factory-installed option is based on the size, voltage, indoor motor and other electrical options of the unit as shipped from the factory. When field-installed accessory electric heaters are added or changed in the unit, the HACR may no longer be of the proper amp rating and therefore will need to be removed from the unit. See unit nameplate and label on factory-installed HACR for the amp rating of the HACR that was shipped with the unit from the factory. See unit nameplates for the proper fuse, HACR or maximum over-current protection device required on the unit with field-installed electric heat.

SINGLE POINT BOX CONTENTS

See Package Content tables on page 2 for a list of components included in each single point box kit.

Control Wiring

Heater modules contain one or two heater control contactors. If a two-circuit heater module is installed, the cooling unit (AC type) can be connected for one-stage or two-stage heating control.

Installing Single Point Box

Compare the sales package number(s) for scheduled heater modules against the approved usage table on the unit's dataplate. See Fig. 1 and 2 for typical dataplate. If the scheduled heater usage does not appear on the unit dataplate label, STOP. Contact the project engineer or the local distributor sales office for clarification.

Open the cartons and inspect for damage. ?

1. Disconnect power to the unit. Lockout/tag-out on unit disconnect switch. ?
2. Remove the outdoor access panel, control box cover, and indoor access panels from the unit. Save screws. See Fig. 4.
3. Use a voltmeter to check that no power is present at unit terminal block. ⚡
4. Remove control box cover and center post. Save screws. (See Fig. 5.)
5. If unit does not have the factory-installed disconnect or HACR option or has not had field power wiring connected, skip to Step 6. When unit is equipped with factory-installed disconnect or HACR or has field power wiring connected, disconnect the power leads at the control box terminals and withdraw the conductors from the control box.
6. Add seal strip to the rear bottom corner of the control panel as shown in Fig. 6. Foil tape open screw holes on the back of the single point box as shown in Fig. 6. Different single point boxes will have different screw holes open.

Figure 3: Typical Single Point Kit Installation depicts the control wiring, foam insulation, power relay, and heater mounting screws within a single point box setup.

Figure 4: Typical Access Panel Location illustrates the positions of the control box access panel and the indoor access panel.

Figure 5: Typical Component Location shows the arrangement of key components including the optional factory-installed disconnect, main control box, single point box, center post, control wire terminal block, vane axial indoor fan system, heater cover, and heater mounting bracket, along with a manual reset limit switch.

Figure 6: Seal Strip and Foil Tape Location shows where to apply seal strip and foil tape for proper sealing.

Installing Electric Heater

Figure 10: Typical Electric Heat Installation shows the process of installing the heater module.

1. Identify heater cover to remove. See Fig. 10. Remove heater cover and save cover and screws.
2. Open the heater package and remove the heater module, screws, wiring label, miscellaneous parts.
3. Install the heater module in the heater support bracket opening(s). Fasten heater module to heater mounting bracket with the 4 screws saved from Step 1.
4. Single-phase heater conversion 208/230-v heaters 323A00-327A00, 329A00-331A00 are factory-wired for 3-phase applications but can be converted to single-phase by changing one wire as described below.
• Three-phase applications: Skip to Step 5.
• For single-phase application, rewire the heater as follows (see Fig. 11):
  1. Connect RED wire provided with kit to Heater Relay (HR) and to L1 as shown.
  2. Disconnect YELLOW wire from HR Terminal 2 and reconnect to HR Terminal 3.
  3. Using the wire tie provided, fasten the RED wire to heater power wire harness near existing wire tie on heater module. This provides strain relief for the RED wire. (See Fig. 12.)
5. Connect the BLACK and RED conductors in the heater power wire harness to the same L1 pole on single point box TB or fuse block. Connect the BLUE and YELLOW conductors in the heater power wire harness to the same L2 pole on single point box TB or fuse block. (See Fig. 11.)
6. Route power wires from heater module through the foam bushing in the center partition and into the single point box. (See Fig. 3.) Connect to terminal block or fuse blocks per schematics in Appendix A or B. See Tables at beginning of each Appendix to identify the appropriate figure. All heaters are single bank heaters except CRHEATER327A00, 329A00-332A00, 337A00-338A00, and 341A00 which are dual bank heaters. These heaters will be wired as two heaters (i.e., 6 leads). Fusing is shown pictorially on the unit wiring schematic label. See Fig. 14 and 15.
7. If no single point box is required for the unit and heater combination, run the heater power supply wiring through the grommet holes to the main unit control box's field power connection points or to optional factory-supplied disconnect.
8. Factory control wiring for heaters runs from unit control box to terminal block TB-4, mounted in the heater compartment to the left of the heater module. (See Fig. 5 and 13.) Connect the heater control wiring at TB-4.

Figure 11: Single-Phase Heater Wiring illustrates the wiring connections for single-phase heater configurations.

Figure 12: Typical Single-Phase Wiring Installed shows a visual representation of the single-phase wiring.

Figure 13: Accessory Electric Heater Control Connections details the control connections from the unit control board (UCB) and TRAN 1 to terminal block TB4, including connections for electric heaters (Elec Htr) via relays HR1 and HR2.

UNIT POWER SUPPLY WIRING – ALL UNITS

NOTE: Installers of unit power supply wiring connecting to these air conditioning and heat pump units must be familiar with applicable requirements of the National Electrical Code (NFPA Standard 70), Articles 440, 430 and 424 dealing with multiple load systems incorporating refrigeration compressors, motors and electric heating equipment. Installers must also be familiar with and observe all local codes regarding unit power supply wiring.

In most instances, adding electric heaters to these units will result in an increase in unit power supply wire size compared to base unit electrical loads. These changes may also impact the size selection of the branch circuit overload protection device and the unit safety disconnect switch. Check the unit's informative data label (see Fig. 1 and 2 for examples) for minimum wiring sizing ampacity for full combined load (including power exhaust if also installed), for branch circuit protection size (a maximum value), and for unit minimum disconnect switch size.

All wiring that terminates at a unit-mounted terminal must be selected from wiring materials under the NEC Table 310.15(B)(16), 75°C (or higher) column only. Check specifications for external disconnect lug sizes to determine if 60°C wiring materials may be used between branch circuit origin and the disconnect switch.

There are four different situations that an installer can encounter with these units. Three are for new unit installations (base unit has not been connected to a power supply already): Unit without factory disconnect switch, unit with factory disconnect switch, and unit with factory HACR breaker. The fourth situation is for an existing unit already connected to a power supply and the heaters are being retrofitted. For each situation, there is usually a without single point box and a with single point box condition. Each situation is discussed below.

New Unit Without Factory-Installed Non-Fused Disconnect or HACR

INSTALLATION WITHOUT SINGLE POINT BOX

Unit power supply wires from the external (field-supplied) disconnect switch are connected to the base unit's power connection terminal lugs. Refer to unit wiring label to identify these terminals (these may be lugs on contactors or at power terminal block). The heater power wires are also connected at these terminals.

INSTALLATION WITH SINGLE POINT BOX

Remove knockouts for appropriate size conduit from unit block-off panel and single point box. Install conduit (rigid or electrometallic tubing) through conduit drip boot as shown. (See Fig. 9.) Drip boot will accept conduit sizes 3/4-in. to 11/2-in. The drip boot eliminates the need for watertight conduit fittings at the single point box.

Unit power supply wires from the external (field-supplied) disconnect switch are connected to the power lugs on the field connection device provided in the single point box. This device may be a terminal block or fuse block FU2's line side terminals. The heater power wires are connected to the load side terminals on the same device.

New Unit With Factory Disconnect

The optional factory-supplied disconnect has a maximum rating per Table 1.

AC-1–Standard Efficiency

AC-2–High Efficiency

Check this unit's dataplate for the MINIMUM DISCONNECT SWITCH value (see Fig. 1 and 2) and compare to the Table 1 value.

If required minimum disconnect value is LOWER than rating in Table 1:

Reconnect the factory wiring from the factory disconnect at the single point box's terminal block or fuse block FU2's line side terminals (or to main control box's line connection lugs if no single point box is installed). Remove any factory test leads connected at disconnect line side terminals; discard these wires. Connect unit power supply wires to disconnect switch line side lugs.

If required minimum disconnect value is HIGHER than rating in Table 1:

For unit with 60-A, 80-A or 100-A disconnect

Remove the factory-installed non-fused disconnect switch assembly and wiring. Install a field-supplied disconnect switch sized per unit marking. Complete connections per instructions above under "New Unit Without Factory-Installed Non-Fused Disconnect or HACR."

New Unit With Factory HACR (50GC Only)

The amp rating of the HACR factory-installed option is based on the size, voltage, indoor motor and other electrical options of the unit as shipped from the factory.

When field-installed accessory electric heaters are added to the unit, the HACR may no longer be of the proper amp rating and therefore will need to be removed from the unit.

Check this unit's dataplate for the FUSE OR HACR BREAKER value (see Fig. 1 and 2) and compare to the factory HACR breaker rating value.

If marked HACR value on unit dataplate is UNCHANGED from rating unit-mounted HACR

Reconnect the factory wiring from the factory HACR at the single point box's terminal block or fuse block FU2's line side terminals (or to main control box's line connection lugs if no single point box is installed). Remove any factory test leads connected at HACR line side terminals; discard these wires. Connect unit power supply wires to HACR line side lugs.

If marked HACR value on unit dataplate is GREATER than rating on unit-mounted HACR

Remove the factory HACR switch assembly and wiring. Install a field-supplied fused or HACR disconnect switch sized per unit marking. Complete connections per instructions above under "New Unit Without Factory Disconnect or HACR."

Existing Unit

An existing unit will usually have been installed following the values marked on the base unit's dataplate for wire sizing, branch circuit over-current protection and disconnect switch rating. When electric heaters are added to air conditioning (cooling) units, these values may be changed; when electric heaters are added to heat pump units, one or more of these values will be changed.

Check the installed unit's field power wires for conductor size and determine conductor rated ampacity per NEC Table 310.15(B)(16). Compare this value to the MIN CKT AMPS value on the unit dataplate for base unit plus electric heaters (plus power exhaust if connected). If the MIN CKT AMPS value is greater than the rated ampacity of the power supply wires, the unit power supply conductors must be replaced.

NOTE: Supply wiring must comply with NEC (National Electrical Code) and all local requirements.

Check the installed unit's branch circuit over-current protection device (fuse or HACR breaker) for rating in amps. Compare this value to the FUSE OR HACR BREAKER value on the unit dataplate for base unit plus electric heaters (plus power exhaust if connected). If the FUSE OR HACR BREAKER value is greater than the rated ampacity of the installed device, the unit branch circuit over-current protection device must be replaced. Check the installed unit's disconnect switch for rating in amps. Compare this value to MINIMUM UNIT DISCONNECT value on the unit dataplate for base unit plus electric heaters (plus power exhaust if connected). If the MINIMUM UNIT DISCONNECT value is greater than the rated ampacity of the installed disconnect switch, the unit disconnect switch must be replaced.

To complete the unit power wiring at the Single Point Box or base unit terminals, follow the appropriate directions under "New Unit" discussions above.

Complete Unit Installation

1. Mark the appropriate block on the unit nameplate for the accessory heater kW installed. Note the required MIN CKT AMPS value for this unit-heater combination. Ensure the field power conductors are sized to handle this ampacity.
2. Locate the heater cover. For all heaters, the heater cover is the plate removed from the heater mounting bracket in Step 5 on page 6 (General Installation Sequence).
3. Place adhesive-backed wiring label on flanged side of heater cover.
4. Fasten heater cover to heater module with 2 screws provided with heater. Flanges of cover must face out. (See Fig. 16.)
5. Set manual reset limit switch (on supply fan housing) by depressing button located between the terminals on the switch. (See Fig. 5.)
6. Close single point box cover and secure with one screw.
7. Replace control box cover, using remainder of screws saved from page 6, Step 4 of Installing Single Point Box sections.
8. Run conduit through (rigid or EMT) the conduit drip boot in the rain shield bracket to the single point box. Provide an appropriate fitting to connect the conduit to the single point box wall and ground appropriately. (See Fig. 17.) Drip boot eliminates the need for watertight conduit fittings at the single point box.
9. Run wire through conduit connecting outside power to the designated terminals at the top of the single point box. Ground appropriately. (See Fig. 18.)
10. Replace indoor and outdoor panels with screws saved from Step 2 of Installing Single Point Box section on page 6. Place adhesive-backed Max. Air/Max. Static label on external panel that covers heaters. (See Fig. 4 and 19.)
11. If all other work on the unit is done, reapply unit power per lockout/tag-out procedures.

Figure 16: Heater Cover shows the heater cover plate.

Figure 17: Heater Wiring illustrates the wiring within the heater compartment.

Figure 18: Typical Single Point Box Power Wiring shows the power wiring connections to the single point box.

Figure 19: Max Air Temp/Max Ext. Static displays warning labels regarding maximum allowable outlet air temperature and external static pressure in English and French.