HIUs

Training

Module 2

Module 2 address’s basic maintenance procedures.

Access

  • Always follow the instructions in the Installation and Operating instructions and adhere to safety notices
  • Always isolate the HIU electrically and close the isolating valves before carrying out any work on the HIU!

Casing

Remove the 4 fixing screws that secure the casing to the frame, and slide forward.

When replacing the casing make sure the casing engages with the frame locators.

On both left and right sides, top and bottom.

Controller and bracket

Remove controller bracket – 4 screws underneath the HIU.

Use this practice when;

  1. Accessing components on pipes behind the Controller.
  2. When removing the plate heat exchangers *

* Module 6 will cover removal and replacing components.

All components access from the front

Drain

Secondary Heating

  1. Vent or Drain the secondary side of the plate heat exchanger.
  2. Drain the Heating circuit to access filter, pump and safety valve and the heating plate heat exchanger.

Hot water / Cold Feed

  1. Vent or Drain the secondary side of the plate heat exchanger.
  2. Drain the Heating circuit to access filter, pump and safety valve and the heating plate heat exchanger.

Drain Down

To remove all water from the primary side is difficult on all plate heat exchangers, gravity
drain is not always sufficient as air locks can prevent drainage.

One method is to use compressed air (compressor or hand pump) to push out the water trapped in the plates. This is the sure way
to prevent spillage.

* Module 6 will cover removal and replacing components, including plate heat exchangers.

Cleaning Filters

primary Filter

  1. Close the primary isolation valves.
  2. Open the drain plug and empty the strainer chamber into a container. Use a small diameter
    plastic drain hose if possible to prevent spillage.
  3. Remove the drain cap with drain plug.
  4. Remove the strainer mesh and clean.
  5. Re-assemble , and open the isolation valves.

Secondary Heating Filter

  1. Close the secondary heating
    isolation valves.
  2. Open the drain plug and empty the strainer chamber into a container. Connect a small diameter hose to the drain nozzle if possible to prevent spillage.
  3. Remove the Drain cap
  4. Remove the strainer mesh and clean.
  5. Re-assemble, and open the
    isolation valves.

Secondary Cold Water Inlet Filter (Hot Water Circuit)

  1. Close the cold inlet and hot water outlet isolation valves.
  2. Open the drain plug and empty the strainer chamber into a container. Connect a small diameter hose to the drain nozzle if possible to prevent spillage.
  3. Remove the Drain cap
  4. Remove the strainer mesh and clean.
  5. Re-assemble , and open the isolation valves.

Cleaning Filters

Filling Group Assembly

The heating circuit can be filled or re-pressurised from the filling
group below the HIU.

  1. Ensure connections are water tight.
  2. Check the flow arrow is the correct direction.
  3. Open valve ‘A’ and ‘B’ to allow flow from the cold water supply side into the heating circuit and fill, to a pressure of 1.2 bar. Allow
    to settle and fill again as necessary until the heating circuit at cold is stable. (Valve ‘A’ has double check valve arrangement to prevent
    backflow). The filling group is Wras approved.
  4. After filling close both valves. The connecting pipe should be removed and placed inside the HIU for safe keeping. Fit the caps
    provided to prevent leakage should either valve be open accidently.

End of Module 2

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