Smith Cast Iron Boilers GT Series manual Multiple Boiler Primary Loop, Primary Loop Plumbing

GT INSTALLATION AND OPERATION INSTRUCTIONS Page 13

Low Water Cut Off, LWCO

If a LWCO is used ensure that the water line of the “Low Water Cutoff” is at least 6 in, 152 mm, above the top of the boiler, Figure 21. It is recommended that the LWCO be situated so that it can be tested without removing water from the boiler. Tri-cocks and a gauge glass are highly recommended. Valves shall not be installed between the LWCO and the boiler. Use an air vent if installed as per our diagram to be used as a vacuum breaker and to eliminate air upon filling.

Figure 21 - LWCO & Air Vent Piping

Figure 22 - Boiler Head Loss

					GT-150				GT-200					GT-400
Head	60
	40
of
Feet	20
	0
	2	4	6	8	10	12	14	16	18	20	22	24	26	27

GPM us

Table 3 lists the recommended circulators for use as the primary and indirect loop pumps.

Figure 23 shows the proper way to plumb a primary loop for single boiler installations.

MULTIPLE BOILER PRIMARY LOOP

Figure 24 shows the proper way to plumb a primary loop for multiple boiler installations.

PRIMARY LOOP PLUMBING

This low mass boiler requires a continuous minimum water fl ow for proper operation. The heat exchanger in this boiler is more restrictive than a conventional boiler. The system pump must be sized to overcome the head loss of the boiler, Figure 22. Greater consideration must be given to the capabilities of the circulating pump(s) in the primary-loop. This includes the pump used for an indirect tank.

SECONDARY LOOP PLUMBING

Figures 25 and 26 show some typical primary/ secondary piping systems. It is the responsibility of the installing contractor to determine which system best meets the need of the installation. Contractor modifications to these instructions may be required, based upon the existing piping and system design.

Table 3 - Recommended Primary and Indirect Loop Circulators

			Minimum	Max. Temp.		Minimum Primary &
		Restriction	Flow	Rise		Indirect Pump Size
Model		Head Loss	GPM, L/s	°F, °C	B&G	Grundfos	Taco
GT-150	7 ft at 6 GPM, 2.1 m at 0.4 L/s		6, 0.4	45, 25	NRF-33	UP 26-64	0010
GT-200	10 ft at 8	GPM, 3 m at 0.5 L/s	8, 0.5	45, 25	PL-36	UP 26-99	0011
GT-400	10 ft at 20	GPM, 3 m at 1.25 L/s	13, 0.8	57, 45	PL-36	UP 26-99	0011