Lochinvar 497 - 2067 service manual A, B, Low temperature return water systems, Water connections

4 Water connections

Low temperature return water systems

Any non-condensing boiler and venting system will develop operational problems when exposed to inlet water temperatures below 140°F. Lochinvar offers a low temperature protection valve (LTV) that is factory preset to maintain 140°F inlet water to the boiler regardless of the system return water temperature. See Table 4A for available valve kits.

TABLE 4A

LTV VALVE KITS

MODEL	LTV VALVE KIT
497 - 747	VAL3048
987 - 2067	VAL3047

Be sure to install the LTV valve per the piping diagrams included with the kits. Alternatively, a bypass as shown in FIG. 4-6 may be piped into the system. This piping is like a primary/secondary boiler installation with a bypass in the secondary boiler piping. Inlet water temperatures below 140°F (60°C) can excessively cool the products of combustion resulting in condensation on the heat exchanger and in the flue.

Condensation can cause operational problems, bad combustion, sooting, flue gas spillage and reduced service life of the vent system and related components. The bypass allows part of the boiler discharge water to be mixed with the cooler boiler return water to increase the boiler inlet temperature above 140°F (60°C). This should prevent the products of combustion from condensing in most installations. The bypass should be fully sized with a balancing valve to allow for proper adjustment. A valve must also be provided on the boiler discharge, after the bypass. Closing this discharge valve forces water through the bypass.

Installation & Service Manual

Start boiler adjustment with the bypass valve in the full open position and the boiler discharge valve half open. A small amount of the higher temperature boiler discharge water is mixed with the system water to maintain the desired lower system temperature. A remote low temperature range operator is recommended to control the boiler operation based on the lower system temperature. (See Terminal Strip Connection Options starting on page 38).

Radiant floor and snow melt heating systems

This type of heating boiler application operates in a low temperature range which requires a boiler bypass as described under the Low Temperature Bypass Requirements section. A non-metallic rubber or plastic tubing installed in a radiant (in floor) system must have an oxygen barrier to prevent oxygen from entering the system through the walls of the installed tubing. Excessive oxygen absorption into the system will result in an accelerated rate of corrosion causing a sludge buildup. This excessive corrosion will also damage the boiler and system components. Sludge formed as the result of excessive oxygen in the system can restrict water flow resulting in a premature boiler failure. Any boiler damage due to excessive oxygenation is non-warrantable.

TABLE 4B

SYSTEM TEMPERATURE RISE CHART

Temperature Rise Based on Boiler Input in Btu/hr

Btu/hr		10°F ΔT		20°F ΔT		30°F ΔT		40°F ΔT		50°F ΔT		60°F ΔT
Input	Output	GPM	Ft/hd	GPM	Ft/hd	GPM	Ft/hd	GPM	Ft/hd	GPM	Ft/hd	GPM	Ft/hd
497,000	400,950	80+	*	40	4.0	27	1.6	20	0.6	16	0.6	13	0.6
647,000	522,450	129+	*	52	5.1	35	3.0	26	1.2	21	0.8	17	0.6
747,000	603,450	149+	*	60	*	40	4.0	30	1.6	24	1.2	20	0.7
987,000	831,600	197+	*	80	5.2	53	2.4	40	1.4	32	1.0	27	0.8
1,257,000	1,058,000	251+	*	102+	*	68	4.3	51	2.3	41	1.6	34	1.1
1,437,000	1,209,000	288+	*	116+	*	78	6.0	58	3.7	47	2.2	39	1.7
1,797,000	1,512,000	360+	*	146+	*	97+	*	73	6.2	58	4.2	49	2.4
2,067,000	1,738,800	414+	*	168+	*	112+	*	84	8.7	67	6.0	56	4.5

+These flow rates exceed recommended flow rates of boiler. If these system temperature rises are used, an external piping bypass must be installed.

*These foot head calculations exceed the maximum allowable flow rate of the boiler. Requires Cupro-Nickel heat exchanger.

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