Updated on 07/10/24 by Shads_OVO
You should not need Economy 7 - I replaced one of my dad’s old Dimplex with the Dimplex Quantum range, and he has just had others replaced last year, also with Dimplex Quantum. All I did was set the required temperatures - the THTC signal puts on the power for charging the bricks.
Some of his older quantums only has the single feed cable from the THTC heating consumer unit. All the new ones need 2 input cables, one that is on 24/7 (for control) and the THTC heating cable
https://www.dimplex.co.uk/en-gb/products/installed-heating/storage-heaters/quantum
All his ones were replaced with brand new units - not cheap - but I have seen many nearly new heaters for sale - but they are very heavy when the bricks are installed. New ones come with bricks in 25kg boxes for handling reasons.
Ask Dimplex if in any doubt - but my dads ones work fine.