13.11. NA7.5.7 Valve Leakage Acceptance

NA7.5.7 Valve Leakage Acceptance

Use Document NRCA-MCH-08-A

Purpose of the Test

This test ensures that control valves serving variable flow systems are designed to withstand the pump pressure over the full range of operation. Valves with insufficient actuators will lift under certain conditions causing water to leak and loss of flow control. This test applies to the variable flow systems covered by §140.4(k)1 Chilled and hot-water variable flow systems, §140.4(k)2 Chiller isolation valves, §140.4(k)3 Boiler isolation valves, and §140.4(k)5 Water-cooled air conditioner and hydronic heat pump systems.

Related acceptance tests for these systems include the following:

NA7.5.9 Hydronic System Variable Flow Controls Acceptance

Testing time will be greatly reduced if these acceptance tests are done simultaneously.

Instrumentation

Performance of this test will require measuring differential pressure across pumps. The instrumentation needed to perform the task may include, but is not limited to either a:

Differential pressure gauge or

Handheld hydronic manometer

For accurate comparison with the pump curves, measure using the taps on the pump casing. Taps on the inlet and discharge piping to the pumps will not correlate to the pump curves.

Test Conditions

The whole hydronic system must be complete – all coils, control valves, and pumps installed; all piping is pressure tested, flushed, cleaned, filled with water; BAS controls, if applicable.

All equipment start-up procedures are complete, per manufacturer’s recommendations.

Document the initial conditions before overrides or manipulation of the BAS. All systems must be returned to normal at the end of the test.

Estimated Time to Complete

Construction inspection: 0.5 to 2 hours (depending on availability of construction documentation and complexity of the system.)

Functional testing: 30 minutes to 3 hours (depending on the complexity of the system and the number of valves)

Acceptance Criteria

Provisions have been made for variable flow:

System has no flow when all coils are closed and the pump is turned on.

Potential Issues and Cautions

The Acceptance Agent will likely need access to the EMCS during testing

Running a pump in a “dead head” condition (no flow) for more than 5 minutes can damage the pump seals or motor. Care must be taken to set up the test so that the pump only needs to run for 5 minutes or less.

If balance valves are used for isolation of three-way valves or pumps, their initial position must be noted prior to using them for shut off of flow so that they can be returned to their initial position at the end of the test.

Newly Constructed and Additions/Alterations: Applies to chilled and hot water systems that are designed for variable flow. It also applies to new boilers and chillers where there is more than one boiler or chiller in the plant and the primary pumps are connected to a common header.

This test is required for the variable flow systems covered by §140.4(k)1 Chilled and hot-water variable flow systems, §140.4(k)2 Chiller isolation valves, §140.4(k)3 Boiler isolation valves, and §140.4(k)5 Water-cooled air conditioner and hydronic heat pump systems.

• Collect the pump curve data l and note the impeller size. The curve data establishes the conditions for which the pump operates. Beware pumps may ship with a different impeller than indicated on the plate of the pump.

• Ensure installation of all valve and piping arrangements per the design drawings in order to achieve the proper control. Doing so verifies each heat exchanger or coil has its own two-way control valve and flow measuring devices, where applicable.

• Confirm measuring devices are located adequately to achieve the most accurate results measurements (i.e. sufficient straight-line piping before and after the meter).

• Confirm piping arrangements are correct (for example: three-way valves may be located at one or more of the coils to achieve required system minimum flow rates).

The intent of this test is to establish a baseline pump pressure. Close off the system using either manual isolation or balance valves at the inlet or bypass of all three way valves. When using a balance valve, mark its initial position so that it may be reset after the test.

Isolate one circulation pump and ensure all chillers (or boilers) are off. Close the isolation valve at the pumps discharge. Turn the pump on for no more than 5 minutes. Measure and note the pressure across the pump at this “dead head” condition. When the system is piped primary/secondary make sure there is a secondary pump. At the end of the measurement, turn off the pump and re-open the discharge valve.

The intent of this test is to ensure that all two-way valves and actuators can modulate fully closed. With the chillers (or boilers) off, start the same pump used in Step 1 and drive all HX or coil control valves closed. There are a variety of ways to close the control valves; examples of which include: resetting control setpoints so that valves respond accordingly; commanding the valves directly using the DDC control system (i.e., building automation system); or applying a fixed amount of air pressure to an actuator or valve in the case of a pneumatic control system. Again, ensure the pump operates for no more than 5 minutes in this dead head condition.

Ensure each control valve closes completely under normal operating pressure. The intent is to confirm the actuator-valve torque requirements are adequate to shut the valve under normal operating system pressure. Verify complete closure by measuring the pressure across the operating pump. If the pressure is more than 5 percent less than the previous test, then one or more valves have not fully closed. Fix any leaks and retest.

Ensure all schedules, setpoints, isolation and balance valves, operating conditions, and control parameters are returned to their initial conditions.