Raypak HD401, HD101 Domestic Hot Water Piping, Piping-HeatingBoilers, Three-WayValves

Piping—Heating Boilers

All high points should be vented. Purge valves and a bypass valve should be installed. A boiler installed above radiation level must be provided with a low water cut-off device. The boiler, when used in connec- tion with a refrigeration system, must be installed so the chilled medium is piped in parallel with the boiler with appropriate valves to prevent the chilled medium from entering the boiler.

The boiler piping system of a hot water heating boiler connected to heating coils located in air handling units where they may be exposed to circulating refrigerated air, must be equipped with flow control valves or other automatic means to prevent gravity circulation of the boiler water during the cooling cycle. It is highly recom- mended that the piping be insulated.

Three-Way Valves

Valves designed to blend water temperatures or reduce water circulation through the boiler should not be used. Raypak boilers are high recovery low mass boilers not subject to thermal shock. Raypak offers a full line of electric sequencers that produce direct reset of boiler water temperature. Refer to the Controls Section in our Complete Catalog.

Domestic Hot Water Piping

When designing the water piping system for domestic water applications, water hardness should be consid- ered. Table F indicates the suggested flow rates for soft, medium and hard water. Hardness is specified as grains per gallon.

Air-Separation/Expansion Tank

All boilers should be equipped with a properly sized expansion tank and air separator fitting as shown in the piping diagrams (Fig. 10–12).

Model	Input	Output	Soft (0–4 grains per gallon)					Medium (5–15 grains per gallon)					Hard* (16–25** grains per gallon)
No.	MBTUH	MBTUH
			∆T	gpm	∆P	MTS	SHL	∆T	gpm	∆P	MTS	SHL	∆T	gpm	∆P	MTS	SHL
HD101	100	85	9	20	1.8	1-1/2	3.8	7	26	3.0	1-1/2	6.3	4	45	9.2	1-1/2	18.0
HD151	150	128	13	20	1.8	1-1/2	3.8	10	26	3.1	1-1/2	6.3	6	45	9.2	1-1/2	18.1
HD201	199	169	17	20	1.9	1-1/2	3.9	13	26	3.2	1-1/2	6.4	8	45	9.4	1-1/2	18.2
HD251	250	213	21	20	1.9	1-1/2	3.9	16	26	3.2	1-1/2	6.5	9	45	9.6	1-1/2	18.5
HD301	299	254	25	20	1.9	1-1/2	3.9	20	26	3.2	1-1/2	6.5	11	45	9.8	1-1/2	18.7
HD401	399	339	34	20	2.0	1-1/2	4.0	26	26	3.3	1-1/2	6.6	15	45	10.3	1-1/2	19.1

∆T = Temperature rise, °F.

∆P = Pressure drop through heat exchanger, ft.

SHL = System head loss, ft. (System head loss is based on the heater and tank placed no more than 5 feet apart and 50 feet equivalent length of tubing and fittings.)

gpm = Gallons per minute, flow rate. MTS = Minimum tubing size.

*Must utilize optional cupro-nickel tubes.

**With Hard Water (16-25 grains per gallon), the operating control must be set no higher than 130°F for scale free operation. For operating tem- peratures above 130°F, a water softener must be utilized.

Table F: Domestic Water Heater Flow Rate Requirements

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