N.CONNECT TANKLESS HEATER PIPING as shown in Figure 37a. See Table IV for Tankless Heater Ratings.
NOTICE
The following guidelines should be followed when piping the tankless heater:
1.Install Flow Regulator
If flow through the heater is greater than its rating, the supply of adequate hot water may not be able to keep up with the demand. For this reason a FLOW REGULATOR matching the heater rating should be installed in the cold water line to the heater. Refer to Figure 37a for piping recommendations. Locate the flow regulator below the inlet (cold water side) of the heater and a minimum of 36” away from the inlet so that the regulator is not subjected to excess temperatures during “off” periods when it is possible for heat to be conducted back through the supply line. The flow regulator will limit the flow of supply water regardless of inlet pressure variations ranging from 20 to 125 psi.
2.Install Water Temperature Mixing Valve
WARNING
Install a mixing valve at the tankless heater outlet to avoid risk of burns or scalding due to excessively hot water at fixtures. Do not operate the boiler when equipped with a tankless heater unless mixing valve is operating properly.
Refer to Figure 37a for piping recommendations. Adjust and maintain the mixing valve in accordance with manufacturers instructions.
Installation of a mixing valve will also lengthen the delivery of the available hot water by mixing some cold water with the hot. In addition, savings of hot
Figure 34: Mounting Elevations of M&M 150 and 63
Float Low Water Cut-Offs
Figure 35: Recommended Piping for Combination
Heating & Cooling (Refrigeration) Systems
Water Boilers
water will be achieved since the user will not waste as much hot water while seeking desired water temperature. Higher temperature hot water required by dishwashers and automatic washers is possible by piping the hot water from the heater prior to entering the mixing valve. An electric hot water booster can also be used. The mixing valve should be “trapped” by installing it below the cold water inlet to heater to prevent lime formation in the valve.
3.Flushing of Heater
All water contains some sediment which settles on the inside of the coil. Consequently, the heater should be periodically backwashed. This is accomplished by installing hose bibs as illustrated in Figure 37a and allowing water at city pressure to run into hose bib A, through the heater, and out hose bib B until the discharge is clear. The tees in which the hose bibs are located should be the same size as heater connections to minimize pressure drop.
4.Hard Water
A water analysis is necessary to determine the hardness of your potable water. This is applicable to some city water and particularly to well water. An appropriate water softener should be installed based on the analysis and dealer’s recommendation.
This is not only beneficial to the tankless heater but to piping and fixtures plus the many other benefits derived from soft water.
CAUTION
Do not operate tankless heater with hard water. Tankless failure will result. Install water softener if hard water is present.
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