2H. Pump Performance and Installation

Page 10	LAARS HEATING SYSTEMS

1.The factory provided pump on PW heaters and the recommended field provided pump for model VW heaters are sized to provide proper circulation through the heater and heater-to- tank circulation loop (see Figures 11 and 12). If the heater-to-tank circulating loop does not contain more than 6 elbows or 30 feet of pipe, use pipe fittings in the loop no smaller than the following:

Model	Pipe Size

500 through 850	2"
1010 through 1825	2-1/2"

If the heater-to-tank circulating loop contains more than 6 elbows or 30 feet of pipe, use pipe or fittings in the loop no smaller than the following:

Model	Pipe Size

500 through 850	2-1/2"
1010 through 1825	3"

To assure free circulation, do not use globe valves, side outlet tee connections or other restrictive fittings in heater-to-tank loop.

2.The Model IW heater is designed for use in a system without a hot water storage tank. The hot water supply line to usage point must have a return leg to the heater (see Figure 13, 14 and

15). A built-in circulating pump and internal heat exchanger bypass maintains the heater in a standby condition. It also maintains the temperature at the controller setting of the water in the entire building circulating loop whether or not there is any use of hot water.

A separate circulating pump is required for circulation of water in the building loop. The control system provides variable heat inputs to match periods of higher or lower water consumption.

3.The Model IW heater requires a minimum of circulating hot water in the building circulation loop. To prevent excessive temperature fluctuations in the delivered water, the whole building system, including the return loop, must have the equivalent volume of pipe shown below:

	Minimum
	Reservoir	Equivalent Pipe
Model IW	Gallons*	Size and Length

500 through 850	6.3	1 1/4" x 100 ft.
1010 through 1220	10.2	1 1/2" x 100 ft.
1430 through 1670	17.0	2" x 100 ft.
1825	27.0	2 1/2" x 100 ft.

*The gallons shown are the calculated volumes of the pipes.

4.Model VW, PW and IW heaters are not suitable for heating swimming pools or any other application where temperature of the water flowing through the heater remains below the dew point (110°F).

In applications requiring the rapid use of measured volumes of water, the recovery of the heater between the time intervals of use must equal the volume used. See the recovery table in the current Document 2045 (Submittal Data).

5.Pump Sizing: A suitable pump must be field- provided for circulation of water between Model VW heaters and the storage tank. This pump must be sized to avoid excessive temperature rise and to provide correct flow for water hardness conditions. Specifications in Table 4 include allowance for 30 feet of piping and normal fittings between heater and tank.

6.Install pump in a cool location. When pump is installed where it is subjected to excessive heat, the life of the pump will be shortened. Heat will embrittle motor insulation and dry out bearing lubricants. If the pump motor is equipped with thermal protection, excessive heat may trip the thermal switch and shut down the pump intermittently. This could result in rapid scaling of the heater.

IMPORTANT: Check oil level in pump before starting. Oil pump every three (3) months. Fill bearing assembly to lower level of overflow vent. Add five (5) or six (6) drops of oil to front and rear of motor. Use 20W non-detergent oil. Pumps located in excessively hot or dusty locations should be oiled once a month. Self lubricating pumps do not require oiling.

7.The pump should be accessible for lubrication, inspection and service.

8.If pump is designed for floor mounting, install securely on concrete block or pad at least six (6) inches above floor level. This will prevent flooding of motor when floor is washed. Be sure that floor mounted pumps are not suspended from piping and that piping is plumbed to avoid strain on the pump casing.