New hwc for warm air heating

[Bullbags]

I have removed a leaking hwc used in a warm air heating system. I am confused about what sort of replacement cylinder I should use? There is only the main cold water storage tank in the attic, no separate f&e tank. The one I removed had no heat exchanger in it, even though it had the usual flow and return connections on the side of the tank as per indirect cylinders. Can anyone suggest what I need to do here please.
Cheers

 

[cozzmic]

Just fit like for like. Its a direct HWC you require NO COIL as the water in passes through the water heater in the WAU. The heat exchanger on the unit is made of copper pipe with fins on it so no corrosion problems like you would have if it was a steel or iron boiler.

 

[ollski]

All round here are primatic.

 

[Bullbags]

Cozzmic, am I confusing things here? I thought a direct cylinder would only allow me to insert immersion heaters. How can I plumb in the flow and return pipes from the WAU?