Imersion heater mind of it's own?

[reevesey]

I have recently moved into a new flat which has underfloor electric heating. My understanding is that the water heating is independent and by way of imersion heater to the boiler (Megaflo unvented mains pressure water heater).

I have two switches, one for the imersion on normal tariff, one for economy 7. I leave the daytime switch permanently off and the economy 7 permanently on to heat water overnight, which seems to ensure an adequate hot supply of water in the evening. I have been away for a couple of weekends and turned off the economy 7 switch as heating was not needed. However on both occaisions, I have returned after the weekend to find that my water is hot.

Is it possible that my daytime imersion heater is working somehow whilst being turned off at the switch? I have searched to try and find if there is any alternative heating control, but can't find anything.

Can anyone offer any advice/ideas?

 

[Fluffster]

Megaflo systems are very effecient at retaining heat and so it may take more than a couple of days to cool down.
Pete