electrical supply to a class

I am an electrician in glasgow,today i was called out to an a class installation on the advice of gledhill service engineer as a 13a spur supplying the unit was overheating,i replaced this spur and the new one did not seem to be heating up but my thoughts as an electrician is that a 20a switch rather than a 13a spur should be fitted to mains supply . can anyone confirm?
Having never encountered these units before i became curious and this led me to your site.

thanks in advance for any help

Not sure what the instruction book specifies but I'd say 13A spur was fine as only one of the two 3kW heaters ever operates at any given time., and pump/control board overhead is less than 1 amp.

Cheers, Mike