Required: Low Temperature Bypass Loop - Primera 400B Installation & Maintenance Manual

If the temperature rise is too high, then the water velocity is too low. Check the following:
1. Check for restrictions in the outlet of the heater.
2. Be sure all valves are open between the heater and the tank.
3. Check the pump to be sure it is running properly and that the pump motor is turning in the proper direction.
4. Be sure the circulation pipes between a single heater and the storage tank are not less than 2" (2-1/2" for models
1000 and 2000) diameter. Common manifold piping for multiple unit installations will require larger minimum pipe
sizes to insure proper flow. See the Table titled "Common Minimum Water Manifold Size for Multiple Units."
5. To prevent accidental change to the required temperature rise, remove and store the adjustment valve handle
once the required temperature rise is obtained.
If the temperature rise is too low, then the water velocity is too high. Adjust as follows:
Slowly throttle the valve on the outlet side of the heater until the temperature rise is steady at the required temperature
rise as noted in "Required Temperature Rise" Table.
REQUIRED: LOW TEMPERATURE BYPASS LOOP - INSTALLATION AND SETUP
Warning: Carefully follow the installation and setup instructions in this section to maintain a 130°F minimum
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PRIMERA inlet water temperature. PRIMERA
that can cause heat exchanger corrosion or blockage. Operation at inlet water temperature below 130°F will
void the warranty and may create hazardous conditions that result in property damage, personal injury, fire,
explosion and creation of toxic carbon monoxide or death.
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All PRIMERA water heater and boiler installations must maintain inlet water temperatures above 130°F to minimize
the formation of condensate on the surface of the heat exchanger. A temperature adjustable bypass from the
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PRIMERA outlet piping to inlet piping is required to raise inlet water temperature to a minimum of 130°F before it
enters the appliance (See piping schematics at rear of this manual):

In applications where low-temperature return water and outlet water temperature is predictable (fixed-rate), the
bypass loop must include a properly adjusted manual flow metering device.

In applications with varying low-temperature return and varying outlet water temperatures (modulating), the bypass
loop must include a fixed-temperature mixing valve at the inlet to constantly meter and mix outlet water with return
water.
A Thermostatically Controlled Mixing Valve is an available option from Riverside Hydronics and is one of the most
reliable and effective ways to maintain a minimum 130°F inlet water temperature on PRIMERA
Caution - The maximum increase in inlet water temperature obtained by this manual bypass is limited, so this method
may not be adequate to assure inlet water to the PRIMERA
information:
2-Inch Manual Bypass Pipe Size Is Recommended:

Manual Bypass size based on all copper construction with full port ball valve.

Maintain the required temperature rise for each model at all times.

If the bypass valve position is changed, readjust both the balancing valve and the bypass valve to result in the
desired inlet water temperature and the required heat exchanger temperature rise from the PRIMERA
outlet.
REQUIRED TEMPERATURE RISE
Temperature Rise (Outlet temp minus
Models
Inlet temp) in degreesº F at Full Fire.
400
540
750
1000
1200
1600
2000
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inlet water temperature below 130°F can result condensation
12
23°F
30°F
21°F
23°F
45°F
45°F
45°F
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is always above 130°F. See the chart below for additional
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units
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inlet to the
34-50 04/02/2010