Potential relay failure - self swap

Hello there - many thanks for creating this resource to aid PulsaCoil owners!

I have a Pulsa Coil APA4200 which (as of last week) only generates hot water when the boost function was operated. Having read your great forum, I tested the lower of the two elements and got a figure of 18 ohms.

A neighbour had the same issue and suggested I swap out the relays, to get off-peak heat, rather than boost.

Before I carry this out, are the relays the grey units under the plastic covering? Do they switch the heavy-load current through the solid copper wiring? I can't see any sign of burned cabling.

With thanks,

faltahan

Yes they are the relays.
But look in the manual. List of parts / pictures.
Are the sensors ok?
Mike

Hi faltahan

I have the exact same issue with my pulsacoil. I bought a new relay but I hasn't worked. Let me know how you get on. Im persisting with using the boost for now.

@Mike

Many thanks for the confirmation. I swapped the relays (I think the part is referred to as 'contactor' in a spare parts web site I saw) and my off-peak heat is now working as new. (lets ignore the fact that the building isn't installed with Economy 7 meters).

For anyone thinking of doing this; if you are confident with working on high-load electrical supplies, it's a 10 minute job. If dealing with electricity isn't your cup of tea, suggest you call out a specialist like Mike to do it for you. I tripled checked all my re-connections with a 'before' picture and checked the smoke detector was working OK that night

One final note - in my failure mode, I did not see any burned wires / cabling. The faulty contactor did rattle a bit..

@JaMoUsE

The relay / contactor swap was what worked for me. I will buy two of these online shortly.

Finally, I happen to think these units are quite reliable - this is the first issue in daily use for about 6 years. All in all, not a huge problem because we can always 'boost' - the redundancy in the design here is rather good. The manual (provided above) is also very good. As an Engineer, I also found it interesting. The unit is efficient, 6KWH per night 5-7am provides my wife and I enough hot water for a day.

Well done.
And yes they are good units.
Considering they are unvented.
And hot water at mains pressure too.
Mike