Hi Guys.

Has anyone else had problems with the above .  I got called to a job a couple of weeks ago, tenant had no hot water.  They had an unvented cylinder in the roof with dual immersion heaters that were both not working. Supply was a single supply via Horstman off peak timer with boost function for the top element in the day.

I could get power to both elements by manually adjusting the clock or boost but neither worked . Both thermostats seemed to work ok and overheat stat had not operated.  

Plumber came in and replaced both elements. We then had the same issue, power to the elements, but no hot water. The strange thing is my clamp meter was reading that they were drawing 12.6 amps each when tested and the tenant (a student with an energy usage gismo in his lounge) was charged £4.00 on his meter over a few hours and still got no hot water.  You could see his readings going up and down as i turned the elements on and off.  

I wondered if the clock was faulty, possibly something happened when the original elements blew and was cutting out as he said it didn't hold good time so i replaced it. We had the same issue.

I came back with the plumber and he replaced both the new elements, one with the same brand as above and the other with a different brand,(because that was all he could get because they are not a standard thread apparently) the different brand (off peak element) is now working perfectly, The new one from the same brand that is in the top for a boost still does not work although appears to draw power.    

    We appear to have had 3 brand new faulty elements.  ( The overheat stat had not tripped on any of the new stats and there was power directly onto the spades on the back when operating the thermostat.  I forgot to mention The thermostat was a plug in type. The spades on the back that connect to the element appear to make a good connection, i even tried giving them a squeeze with some pliers to make sure but they seemed ok  )  The different brand is also plug in. 

How can it use energy if it isn't actually heating up?

Anyone else had problems with these things?

edit to add i was getting 18.6 ohms across the new elements

I was beginning to doubt my sanity

Gary