On Wednesday, January 20, 2016 at 11:33:38 AM UTC-6, TimR wrote:
I think the OP is describing something like an Apollo system, where there isn't a separate boiler for heat, but a large domestic hot water heater that runs through the heating coils.

I was skeptical until I saw one installed but that worked fine, in the Virginia climate. If this one isn't keeping up with the Texas climate then something is malfunctioning.

Tim

I should have included that detail. Yes the hot water source is a single large water heater. Following instructions left by the previous owner I opened the valve to allow the water to flow.