Night-time setback w/ radiant floor
I was talking to a heating contractor about a radiant floor system, and we don’t agree regarding night-time setback. I’d appreciate some light shed on this.
The system has a typical slab on grade with R-10 under it and PEX tubing cast in, and another area of framed floor with PEX underneath with aluminum distribution plates. The boiler is a 30kw electric with multiple elements and outdoor reset.
The heating contractor advised the homeowner that setting the night-time temp too low would cause the system to work very hard in the morning, to get the slab back up to temperature, and therefore waste energy.
My opinion is that lowering the setpoint at night is a good thing, as the system will put fewer BTUs into the house, saving energy. When the system ramps up in the morning, it will reheat the slab without any loss of efficiency. Fewer total BTUs will be put into the house. This is not a gas boiler that might have efficiency issues related to part loads or short cycling or whatever else.
I think the heating contractor is confusing a period of high demand in the morning with low efficiency. What say you?