The instructions for my stove say to only burn smokeless fuels or high quality coal like anthrasite. Multi flue stoves burn hotter than an open fire so house coal is not suitable.
If the chimney has a stainless liner ensure it is the right type for burning smokeless fuel (should be 904)otherwise it will be damaged , there are 2 types of liner the cheaper one is for wood only.
Mixing fuels (wood and smokeless)is also a no no as the moisture from the wood and the eflux from burning smokeless fuel combine to create acid which will eat through the liner (stainless 904).
All the above is in the info pack with the stove and online.