Lochinvar 000 Btu/hr Water Velocity Control, Required Temperature Rise, Temp. Rise Temp. Rise F

This section contains specific instructions for those units used to supply domestic hot water. All warnings, cautions, notes and instructions in the general installation and service sections apply to these instructions. Water heaters are designed for installation with a storage tank. The use of a properly sized pump and the control of water velocity, as explained below, is important for correct operation of your water heater.

WATER VELOCITY CONTROL

IMPORTANT - To ensure proper velocity through the heat exchanger, it is necessary to regulate the temperature rise across the heat exchanger from inlet to outlet. This must be done on initial installation and periodically rechecked. With the correct temperature rise across the heat exchanger, you may be assured of the proper velocity in the tubes. This will yield long life and economical operation from your water heater. Excessive lime build-up in the tube is a result of too little velocity in the tubes. Excessive pitting or erosion in the tube is caused by too much velocity through the tubes. Care should be taken to measure temperature rise and maintain a velocity as follows:

1.The pump must run continuously when the burners are firing.

2.With the pump running and the water heater off, the inlet and outlet thermometers should read the same temperatures. If they do not, an adjustment must be made to your final calculation.

3.Turn the water heater on and allow time for the temperature to stabilize. Record the difference between the inlet and outlet temperatures. This difference will be the “temperature rise.”

4.Compare the temperature rise on the heater with the required temperature rise in Table P. Should adjustment be needed, proceed as follows:

If the temperature rise is too high, the water velocity is too low. Check the following:

1.Check for restrictions in the outlet of the water heater.

2.Be sure all valves are open between the water heater and the tank.

3.Check the pump to be sure it is running properly and that the pump motor is running in the proper direction.

4.Be sure the circulation pipes between the water heater and storage tank are not less than 1 1/2" diameter for a single unit installation.

5.Common manifold piping for multiple unit instal- lations will require larger minimum pipe sizes to

tank tappings to ensure proper flow. See Table Q on page 40.

6.Multiple unit installations may also require a larger circulating pump to achieve the specified flow against the increased head loss of a multiple unit common manifold piping.

If the temperature rise is too low, the water velocity is too high. Adjust as follows:

1.Slowly throttle the valve on the outlet side of the water heater until the temperature rise is steady at the required temperature rise as noted in Table P.

2.Sustained high water velocity and low temperature rise may result in pitting or erosion of the copper tubes in the heat exchanger. This is a non-warrantable failure. Temperature rise must be properly adjusted to achieve the specified flow rate.

REQUIRED TEMPERATURE RISE

Temperature rise is based on the hardness of the potable water to be heated. A different temperature rise is specified for soft water with a hardness of 0 to 7 grains per gallon or for unsoftened water with a hardness of 8 to 25 grains per gallon. The total dissolved solids shall not exceed 350 ppm. If there is any doubt about the hardness or total dissolved solids content of the water to be heated, follow the temperature guidelines for water with 8 to 25 grains of hardness in Table P below. The majority of all potable water supplies will fall within the range of 8 to 25 grains of hardness. See Water Chemistry, page 40.

TABLE - P

REQUIRED TEMPERATURE RISE

	Btu/hr	0 to 7 Grains	8 to 25 Grains
		Hardness	Hardness
	INPUT	Temp. Rise oF	Temp. Rise °F
90,000		8	5
135,000		12	7
180,000		15	10
199,999		17	11
225,000		20	12
270,000		22	15
315,000		25	17
360,000		30	20
399,999		35	22
500,000		40	28

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