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A Mr L. called me from Rickmansworth around lunchtime on Friday. I couldn’t answer his call at the time as I was part way through fixing a boiler for another customer in west London. Mr L. left me a message saying his Pulsacoil was no longer producing hot water and that he lived in Rickmansworth just off the M25, and he was wondering if it could be fixed, or needed replacing, or what could be done about it.
Once my west London boiler was finished I checked my voicemails and heard the message from Mr. L, and copied the details into my enquiries book. I called Mr L. back but this time I got HIS voicemail, so I left a message with a few ideas about what could be wrong with his Pulsacoil and saying if necessary I could visit and fix it later than afternoon. Then I set off back to Reading.
Mr L. then called me back about five minutes later saying he had been in meetings etc, and we had a chat about his boiler. I ran though with him the basic faults that he might be able to fix himself but we concluded it wasn’t that simple. I asked a few questions about the behaviour of the boiler before and after the fault in order to narrow down the possibilities and give an estimate of the likely costs for fixing it. Mr L. was concerned in particular that the red and the green lights on the control panel were both OFF and I was able to explain the reason for this. Mr L. decided there and then to book a visit and as by luck I was free for the remainder of the afternoon, I set off to Rickmansworth immediately.
On arrival, Mr L’s Pulsacoil was stone cold which would certainly stop it working! The task then was to find out why it was cold. A quick inspection once the front was off revealed both heater circuits were open circuit so not capable of heating. A look under the heater caps was next. The lower, off-peak heater was wet and leaking. The electrical connections and thermostat were all soaked in water. The upper daytime boost heater element had been previously replaced with a non-Gledhill brand of element and this open circuit and had simply failed.
Two new heater elements were needed, so I drained the unit, removed the two faulty heaters and fitted two new ‘low Watt density’ heater elements supplied by Gledhill. On restoring power to the Pulsacoil, I used the upper daytime boost heater element to heat the store enough to test the pump and electronics. It became apparent the pump was seized, which was consistent with Mr L. saying the Pulsacoil actually failed about a month previously and had been turned OFF ever since. I freed the pump using a screw-driver engaged in end of the pump motor shaft and was able the demonstrate the unit delivering warm water. (It wasn’t fully hot at this time.) It was not possible to test the off peak heater as the off peak power supply is only ON between 12.00 midnight and 7.00am, but the resistance at the power input terminals showed the correct value so the unit should heat up when supplied with off peak power after midnight.
I texted Mr L. the next day to check the off peak heater had worked overnight as expected, but unfortunately Mr L. said it hadn’t. The daytime boost heater was working normally so he had hot water again, but not the overnight heater. The new off peak heater tested correctly on completion of the repair sohis means the off peak power supply is not coming on during the night as it should. So I have arranged to return and trace the fault on Monday at no cost to my customer. I suspect a failed fuse, circuit breaker in the household wiring or a failed off-peak electricity meter. I Will update this on Monday after visiting.
On returning and testing the Pulsacoil on Monday I found there was no fault present in the appliance itself, but on testing the off-peak household wiring I found the isolator switch on the wall was not working reliably. So I fitted a new switch and checked again with Mr L the following day to see if the off-peak was now working. I’m pleased to say Mr L confirmed it is.
The failed upper daytime boost heater element with the two new heaters in the background
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Mr L.’s Pulsacoil in Rickmansworth
The lower, leaking, off-peak heater element and thermostat
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Site first published 2nd January 2007
Last updated 21st June 2020
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