Apologies LittleInch.It must when there is DHW demand (presumably)?. All I've measured are with temperature clamps a fairly rapid decay in the inlet temperature of ~ 2.5 °F/min to the air handler coil and the temperature in the outlet increasing (which presumably means it's not moving through...
@ LittleInch: Yes the pump (Grundfos non-submersible circulation pump) only active when heat called. I believe there is intermittent operation to prevent Legionella.
Schematic here (not entire property)- not showing the DHW loads (eg. shower, faucets, etc)
@HVAC_Novice: yes it's the detail from the manufacturer. As noted earlier, it's a new build (4 years roughly). The plans approved by the local municipality showed a 199 kBTU/h unit whereas they installed 160 kBTU/h. They don't have the same capacity obviously. Hydronic coil draws 2 GPM steady...
@PEDARRIN2: I'm stuck with 1 x single unit of tankless (condensing type). Not boiler.
The heat exchange life diminishes to 3 years from 15 years if used in combo DHW + space heating (vs standalone DHW).
I believe the building code here has showers fixtures rated a minimum 1.50 w.s.f.u. (or 1.5 gpm) minimum. Two 2x showers would be 3 gpm simultaneously.
Space is the issue. Can't fit a storage tank. Mech designer used a method to size conventional storage type tanks (using FHR-first hour...
The HX is a hydronic air handler. Coil sits above the blower fan. Water comes in at 120 F exists 94 F (delta T = 26 F), which leads to 25,000 btu/h of supply at 2 GPM.
Heat loss ~ 19,000 btu/h
There is prioritization for DHW.
Question du jour about sizing tankless water heaters (instantaneous type):
Tankless water heater installed in conjunction with a hydronic heating coil in an air handler.
-Tankless input: 160,000 BTU/h
-Tankless output: 157,670 BTU/h
-Space heating capacity (Hydronic coil with air handler)...
Air temperature of the room is controlled via thermostat. It's maintained at 21 C. The void under the slab corresponds to a space that is obviously heated by the radiator that sits approx 8 inches below the slab, but above the drop ceiling as shown above with insulation. The drop ceiling...
Fair point I did not ask the correct question. I suppose what I meant to say is that the heater at the source is 2 kW (approx) and the amount coming through is much less obviously. But you're right there is a long transient to start feeling it above....and the floor temperature on the other side...
The cavity is air and slab is irradiated...so not quite direct. I could be wrong here...the slab has a lot of mass that continuously radiates the space above
Cavity dimensions are hard to get as slab geometry is complex... basically it's a ceiling of a parking structure with drop ceiling drywall suspended and batts of insulation.
