Roberts Gorden CRV-B-8, CRV-B-6 Pump Capacity, Tailpipe Flow, Pump Exhaust Length Requirements

CRV-SERIES DESIGN MANUAL

5.2 Pump Capacity

The flow unit capacity of the pump is indicated on Page 14, Table 2, as a function of installed altitude. When the CRV-Series system is designed in accor- dance with this set of instructions and is in proper operating condition, a vacuum from 2-3" w.c. will be obtainable at each end vent (i.e. at all burners).

Table 2: Pump Capacity

Installed Altitude		Maximum Flow Units
Feet Above	Meters Above	EP-100	EP-200	EP-300
Sea Level	Sea Level		Series	Series
0' - 2000'	0 m - 609 m	66	112	224
2001' - 3000'	610 m - 914 m	63	105	215
3001' - 4000'	915 m - 1219 m	60	100	206
4001' - 5000'	1220 m - 1524 m	57	95	197
5001' - 6000'	1525 m - 1828 m	54	90	188
6001' - 7000'	1829 m - 2134 m	51	84	180
7001' - 8000'	2135 m - 2438 m	48	80	170
8001' - 9000'	2439 m - 2743 m	45	75	161

There are a number of design requirements which, if not met, will reduce the vacuum obtainable and thereby the effective flow capacity of the pump. These include:

•Minimum Length of Tailpipe - If less than the minimum length of tailpipe is provided per radiant branch, there will be insufficient cooling of the com- bustion gases and improper operation of the pump.

•Line Loss Check for Tailpipe is applicable to sections of tailpipe which are common to two or more radiant branches (i.e. shared lengths). See Page 14, Figure 15.

•Excessive back pressure on discharge line of pump can be caused by partial blockage or too much flow for length. See Section 5.3.1

•More than maximum number of burners or flow units per radiant branch. See Page 14, Table 2.

•Excessive number of elbow or tee fittings which increases vacuum loss.

5.3 Tailpipe Flow

Excessive flow loading in a single section of tailpipe can cause low vacuum and lower effective pump capacity. For the pump to develop the proper vacuum, the length of tailpipe must not be excessive for the

number of flow units carried in the tube.

See Figure 15. Readings for length and flow when plotted on the graph must fall on OK side to avoid excessive vacuum losses.

FIGURE 15: Vacuum Loss Curve for 4" Shared

Tailpipe

	130
	120
	100
									NOT		OK
	90
(feet)*
	80
Section	70
				OK
	60			SIDE
Tailpipeof
	50
	40
Length	30
	20
	10
		30	40		50	60	70	80		90		100	110 120
	Maximum Flow Units per Single Tailpipe Section

NOTE: For 6" (15 m) tailpipe, length is limited to a maximum of 100’ (30 m). See Page 16, Section 6.3 for more details.

Lengths shown include allowance for 1 elbow every 50' (15 m); deduct 15% of length for each additional elbow used per 50' (15 m) length.

5.3.1 Pump Exhaust Length Requirements

The tube length on the exhaust side of the pump is considered excessive if not within the following condi- tions:

Table 3: Pump Exhaust Requirements

Pump Series	Exhaust Tube Length	Exhaust Tube Diameter
EP-100	Up to 25' (7.6 m)	4" 3 Elbows
EP-100	Up to 50' (15 m)	5" 3 Elbows
EP-200	Up to 10' (3 m)	4" 0 Elbows
EP-200	Up to 25' (7.6 m)	5" 3 Elbows
EP-200	Up to 50' (15 m)	6" 3 Elbows
EP-300	Up to 10' (3 m)	6" 1 Elbows
EP-300	Up to 25' (7.6 m)	7" 3 Elbows
EP-300	Up to 50' (15 m)	8" 3 Elbows

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