Carrier 09RH specifications Booster Compressor Starting Data, Unloading, During Size

Table 28 — Booster Compressor Starting Data

	UNLOADING		MAX COMPR STARTING TORQUE (lb-ft)				RECOMMENDED MIN MOTOR SIZE HP					FRICTION
COMPR			R-12		R-22 or R-502			R-12		R-22 or R-502
	DURING											HP*
SIZE	STARTING		Saturated Discharge Temperature (F)				High		Normal	High	Normal	(fhp)
			10 F	30 F	10 F	30 F	Torque		Torque	Torque	Torque
5F20	None		9	13	15	21	—		2	3	3	.67
5F30	None		10	15	16	24	3		3	5	5	.91
5F40	75%		8	12	13	19	3		3	5	5	1.15
5F60	662/	%	10	15	16	24	3		5	5	71/	1.64
	3										2
5H40	75%		19	28	30	45	5		71/	71/	10	2.25
5H46	75%		24	35	38	56	71/		2	2	15	2.25
									10	10
5H60	662/	%	23	34	37	54	2		10	10	15	3.07
							71/
	3						2
5H66	662/3%		29	43	46	68	10		15	15	20	3.07
5H80	75%		26	38	41	60	10		15	20	20	3.82
5H86	75%		33	48	51	75	15		20	20	30	3.82
5H120	662/3%		41	60	65	94	15		20	20	30	5.25
5H126	662/3%		51	75	81	118	20		30	30	40	5.25

*Based on 1750 rpm with 5F,H compressors. Will vary directly with rpm at other speeds.

CONDENSERS

Condenser Physical Data — Refer to Table 29. Re- fer to 5F,H Product Data for information on the current P701 water-cooled condensers used with the 5F,H water- cooled condensing units.

Condenser Selection Considerations — On most installations the condenser is selected within recommended conditions specified in ARI Standards. Main consider- ations are:

1.The water velocity is within a range of 1 to 12 ft per second (to minimize corrosion and erosion).

2.It is good practice to select condensers on a leaving tem- perature difference between 6 and 12 degrees. In general, higher temperature differences are used only where con- densing water temperature is quite low or where special conditions make it economical to do so. A high tempera- ture difference not only makes effect of fouling more pronounced but since the condenser volume is likely to be small, the effect on noncondensable gases will be greater.

Table 30 lists maximum water velocities from Carrier System Design Manual. Limits are above ARI recommended values but are generally accepted where ARI conformance is not specified. See Part 5 of the Carrier System Design Manual for further details.

Table 31 lists condenser water quantities (gpm) for water velocities from 3 to 12 fps. For higher velocities, use formulas below Table 31.

Condenser Duty — The capacity of a given compressor is greatest at high saturated suction temperatures. Because of this, the compressor normally requires the largest condenser at these conditions or for air conditioning duty.

On refrigeration or low temperature applications, the same compressor displacement results in a lower refrigeration capacity and, consequently, less heat rejection. Thus, con- denser size is smaller than would normally be required with the same compressor on air conditioning duty.

Condenser size is also affected by refrigerant used, since compressor capacities (and thus heat rejection) differ with Refrigerants 12, 22, and 502.

Pulldown — Condensers for systems subject to pulldown periods, especially low temperature or multistage systems, should be oversized beyond the capacity required at the final balanced load condition. The condenser must adequately

handle load during the first stages of pulldown, when system capacity is substantially greater than at final condition.

If pulldown load is sizable, as in most water or brine cooling applications, check the condenser performance when it is handling total heat rejection at maximum rated suction temper- ature (50 F for most compressors). Condenser size and water quantity must be adequate to handle this start-up load without resulting in excessive head pressure or excessive water pres- sure drop. As a rough guide, the selected condenser should have a maximum total heat rejection rating that is equal to or greater than the compressor heat rejection at pulldown conditions.

If this pulldown occurs infrequently, it may be possible to select a condenser for design conditions and on each start-up limit compressor capacity by manually throttling suction gas flow. This can be done by partially closing suction valve but this will extend time required to reach design conditions.

If the pulldown is of short duration, such as on a direct expansion coil, suction temperature will drop very rapidly and more than likely design conditions will be reached before the compressor would cut out on high pressure. No oversizing of the condenser would be required.

Whenever possible, the selected condenser should never be of a larger size than the largest condenser that will match the compressor used and still be a standard combination. This should be considered especially when the condensers are to be used with 5F,H series open reciprocating compressors.

Fouling and Fouling Factors — Fouling in con- denser tubes is result of a build-up of scale within tubes because of impurities in water. As a result, heat transfer is adversely affected. Fouling factors are a means of identifying degree of fouling.

Condensers should not be selected for less than 0.0005 foul- ing factor, even when high quality water is available. For lower quality water, use larger fouling factors from the condenser ratings, but temper factor according to operating conditions.

The following affect magnitude of fouling factor selected:

•Percentage of yearly operating time.

•Frequency of tube cleaning.

•Condensing temperature.

•Type of water treatment.

For instance, reduce fouling factor when the operating time is less than 4000 hours per year, when frequent cleaning of tubes takes place, or when low condensing temperatures exist.

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