Bryant 551A Electric Resistance Heater Data, Unit, Heater Maximum Minimum Heater Amps, Per

LEGEND

FLA — Full Load Amps

HACR — Heating, Air Conditioning and Refrigeration

IFM — Indoor (Evaporator) Fan Motor

LRA — Locked Rotor Amps

MCA — Minimum Circuit Amps

MOCP— Maximum Overcurrent Protection

NEC — National Electrical Code

OFM — Outdoor (Condenser) Fan Motor

RLA — Rated Load Amps

*Heater capacity (kW) is based on heater voltage of 208 v, 240 v, and 480 v. Heaters are rated at 240 v, or 480 v. If power distribution volt- age to unit varies from rated heater voltage, heater kW will vary accordingly.

†Fuse or HACR circuit breaker. **Heaters are field installed only.

NOTES:

1.In compliance with NEC requirements for multimotor and combina- tion load equipment (refer to NEC Articles 430 and 440), the overcur- rent protective device for the unit shall be fuse or HACR breaker. Canadian units may be fuse or circuit breaker.

2.Unbalanced 3-Phase Supply Voltage

Never operate a motor where a phase imbalance in supply voltage is greater than 2%. Use the following formula to determine the percent of voltage imbalance.

% Voltage Imbalance

= 100 x	max voltage deviation from average voltage
	average voltage

Example: Supply voltage is 460-3-60.

AB = 452 v

BC = 464 v

AC = 455 v

452 + 464 + 455

Average Voltage =

3

1371

=

3

= 457

Determine maximum deviation from average voltage. (AB) 457 – 452 = 5 v

(BC) 464 – 457 = 7 v (AC) 457 – 455 = 2 v

Maximum deviation is 7 v.

Determine percent of voltage imbalance.

7

% Voltage Imbalance = 100 x 457

= 1.53%

This amount of phase imbalance is satisfactory as it is below the maxi- mum allowable 2%.

IMPORTANT: If the supply voltage phase imbalance is more than 2%, contact your local electric utility company immediately.

3.MCA calculation for units with electric heaters over 50 kW = (1.25 x IFM amps) + (1.00 x heater FLA).

Table 3 — Electric Resistance Heater Data

UNIT		HEATER kW				HEATER	% HEAT	MAXIMUM	MINIMUM			HEATER AMPS
		Unit Voltages					PER		Heating Cfm
551A						STAGES		STAGES*
							STAGE
	208	230	240	460	480				Cfm	L/s	208	230	240	460	480
	14	17	19	14	15	1	100	1			39.3	43.4	45.3	17.2	17.9
155	26	31	34	30	32	2	50/50	2	3750	1770	71.3	78.9	82.3	37.3	39.0
	42	52	56	50	55	2	33/67	3			117.0	129.4	135.0	63.3	66.1
	26	31	34	30	32	2	50/50	2			71.3	78.8	82.3	37.3	39.0
180	42	52	56	50	55	2	33/67	3	3750	1770	117.0	129.4	135.0	63.3	66.1
	56	69	75	73	80	2	50/50	4			155.9	172.4	179.9	92.0	96.0
	26	31	34	30	32	2	50/50	2			71.3	78.8	82.3	37.3	39.0
240	42	52	56	50	55	2	33/67	3	5000	2360	117.0	129.4	135.0	63.3	66.1
	56	69	75	73	80	2	50/50	4			155.9	172.4	179.9	92.0	96.0

*Maximum number of stages using accessory low-ambient kit or head pressure control device and low-ambient kit. NOTE: Heaters are rated at 240, and 480 v.

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