Central Heating Boiler And Pump Problems


A faulty circulation pump may result in cold radiators, over heating or excessive noise.

1. You can tell if a pump is running by switching the programmer to ‘constant’ and holding a screwdriver to it, like a stethoscope: if you hear a noise, suspect some other fault — like an airlock; if there is nothing, either electricity isn’t reaching the pump, the motor’s burnt out, or the pump rotor is jammed.

Assuming that you’ve checked the power supply and programmer, the fault lies with the pump.

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On some pumps, such as the common Commodore, it’s possible to check the rotor without removing the unit, providing stop valves are fitted either side.

Shut off the power supply and close the stop valves on either side of the pump by turning them clockwise. Loosen the screws securing the casing and remove.

The rotor underneath should spin freely: if it doesn’t, you may be able to free it by gentle levering with your screwdriver.

In all other cases the pump must be removed and taken to a heating suppliers to be checked.

If there are no stop valves fitted, the system must be drained completely before removal.

2. The pump will probably be connected to the pipework by threaded screw couplings: loosen these with a pair of plumbers’ wrenches or adjustable spanners and it should come straight out.

3. Before removing the pump completely, you must sever the electrical connection to the programmer. On seine pumps you can get to the terminals easily having first removed a small cover on the motor casing.

With other types the motor is sealed, so you must disconnect at the programmer end.

Before you disconnect the wires make a note of which goes where and label them.

Fitting a new pump is a straightforward reversal of the removal procedure. But be sure to seal any screw coupling joints with hemp and jointing paste before you tighten them.

Certain types of connector (especially those which incorporate a shut-off valve) may not require hemp: instead, replace the rubber O rings seals.

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