can any one explain combination unit water heater and space heater
A heater that heats both the domestic water, and the water that goes to a hydro coil.
There's a couple different manufctures of them.
Her is a link to Apollo.
Contractor locator map
How many times must one fix something before it is fixed?
Also White Rogers and AO Smith make gas water heaters that have a HX internal to the tank. Some wall hung boilers like Baxi and Monitor provide combo units also.