megaflow elements not heating up, despite element and stat testing fine

[cairns]

Hiya, got an old heatrae sadia megaflo which looks over 10 years old. Just got this flat as its been empty for a while. Turned it on but no joy no hot water, there are 2 elements, one normal and 1 boost, tested the supply to both of the two radials supplying the elements and have 240v, have got 240 at both stats on the supply side. Have also checked continuity to the supply side of each stat from the fusebard all good. The stat on the outgoing side is working was getting 240v on both elements. Then thought it must be the element, so disconnect both from the stat and tested for continuity, was getting like 18ohms which i gather is right. I also used a clamp detector on the load side of the stat going to the element and was getting 12amps which i also think is about right.

Its giving me a headache, dont have alot of experience in heating problems soo would appreciate any help. thanks

 

[UNG]

Its 145litres, will checked to see if the stat was still working after 20 mins and was still live. Anyone know if in the old heatrae sadia megaflows of a normal element will fit or does it have to be a special one. Yeah cheers know it has to be drained down or I would get very wet.

So at 3Kw it will take 158 mins to heat up at 6 Kw it will take 79 mins to heat up

The elements in these cylinders are normally a special shaped incoloy element