Pulsa Coil III intermitent Fault

Hi Mike,

I have come across this Pulsa Coil III for the first time, I understand how it works as it is not too dissimilar from gas thermal stores i have worked on. It has a hot water intermittent fault but has a number of other issues, ill list these and hopefully this forum may answer some of them.

1. Customer has noticed that his electricity bill has doubled in the last four months since this fault occurred.
2. It seems to me that the off peak coil is working during the day and only switching off when water reaches required temperature.
3. When the off peak coil does not work the customer switches the booster coil on and off straight away and this causes the off peak coil to start working.
4. Customer says that sometimes the store is very noisy and he can hear it from the other side of the flat and then the RCD Fuse Blows!

Both green lights are on and red circuit board light is flashing twice a second so all systems seem to be fine.

The off peak electrical supply to the store seems to be on permanently throughout, is this normal or should the customer only be able to receive this at night or does the pcb board dictate when this supply is given to the off peak coil?

I have read all your posts and will try to replace the flow and return thermistors but I am struggling to find them on your websites supplied.

Im a little worried as this store is blowing the RCD so there is something wrong.

I would like to say that this is the first time I have been called to this job after a succession of plumbers trying previously.

Any help would be much appreciated.

Darryl

Hi Darryl,

The RCD tripping suggests one of the heater elements is failing. Water is has penetrated the outer sheath and is causing a short-circuit. There will be two RCDs. One for each heater element, off-peak and on-peak. They tripping one tells you which element needs replacing.

The jump in electricity bills and the fact that the off peak heater runs during the day suggests a timer failure. The off peak heater should not be getting power in the day (unless your customer has Economy 10 tariff). Off-peak is usually switched on/off by the electricity meter but sometimes this is done locally by a timer next to the Pulsacoil.

Hope that helps.

Cheers, Mike

Regarding the RCD tripping, if it is the element leaking, you will notice it straight away when you take the cap off. If there is not signs of water leaking, disconnect the supply cable and test between live & C.P.C and then Neutral and C.P.C on the cable and on the element. If you read 0.00 ohms, the area you are testing is faulty. It would also be worth checking for signs of burning.

I have also come across jobs where the wiring was incorrect and the customer only started noticing the fault when they used the off-peak, double check the wiring, you can find the manual via this site -> Pulsacoil 3 Manual