The Pulsacoil A-Class works in a similar way to the Pulsacoil 2000 even though it looks very different (both inside and outside) so I’ll cut straight to the common faults and problems…
Common faults and problems:
1) Red light flashing on user control panel:
There is a red LED indicator on the front panel of a PulsaCoil A-Class. The label next to it says "Fault attention required" if flashing. Unfortunately on some early batches of A-Classes this can light flash during normal operation, even when there is no fault present, and the label incorrectly suggests a fault has occurred. On those early versions, the red light flashing once per second simply means that the unit has cooled and may be re-heated immediately using daytime electricity if the user wishes, by pressing the black 'On Peak Boost button'. There is no particular need to do this unless more hot water is needed immediately. The unit will re-heat automatically at midnight.
On later versions, the slow flashing red light means the software believes an immersion heater element has failed. This may or may not be the case, this error report can also be caused by a burned out power relay (or ‘contactor’).
The red light flashing quickly, four times per second, means the control board is detecting the boiler is overheating. This also may or may not be the true. More commonly the fast red light flashing is due to a control board fault and the unit is not overheating at all. I saw this today on a stone-cold Pulsacoil A-Class. I’d just changed the heater elements and re-filled it with cold mains water and the control panel red light was flashing furiously claiming the unit was overheating! A new overheat sensor made no difference. A new control board fixed the problem, after which the appliance worked perfectly.
2) Burned out power relay.
A short section of wiring to the Off-Peak heater on a Pulsacoil A-Class has a habit of burning out, along with the power relay. When this happens the red light flashes and the unit only produces hot water if the user presses the black button next to the flashing red light. The burned out section of wiring and relay can be easily replaced, but Gledhill now market an upgrade kit to prevent the problem recurring. It comprises a different type of relay and some replacement wires made from solid copper. I now keep this upgrade kit in the van as a stock item.
3) Depleted water in the thermal store:
The PulsaCoil A-Class is filled with water using a small header tank installed separately above the unit. This is not always permanently connected to the mains supply (usually when an overflow pipe to outside cannot be fitted), which means water lost from the thermal store through evaporation and/or leaks needs to be replaced manually. If the water level in the PulsaCoil A-Class falls too low, the pump simply does not have enough water to pump through the heat exchanger when a hot tap is turned on, and the unit will not deliver hot water. The problem starts intermittently, and the unit runs noisily. The answer is to check the water level in the header tank and top it up to the waterline moulded into the wall of the tank.
4) Immersion heater element failure.
The unit fails to heat up. Easily diagnosed by measuring the resistance of the heater element. A good element will measure 18 Ohms approximately.
5) Water scale-contaminated plate heat exchanger.
The plate heat exchanger is prone in some areas to water scaling. This presents as maximum water temperature becoming progressively lower, and in the final stages of scaling, the flow rate from the taps reducing too. The fix is to either fit a new plate heat exchanger, or to descale the existing heat exchanger using conventional descaling techniques.
If you'd rather I came and fixed your PulsaCoil A-Class, contact me by calling or texting my mobile 07866 766364. I keep a full stock of spares in the van and can fix most faults in a single visit.
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Copyright Michael Bryant 2020
Site first published 2nd January 2007
Last updated 21st March 2020
Gas Safe Register 197499, CIPHE registration number 56207